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Focus control device, focus control method, lens system, focus lens

1. 0 a 5 35 40 45 60 65 8 the image capturing apparatus 100 but also a touch panel on the display section 115 the operation input from a user may be received through the touch panel The memory ROM 150 is a non volatile memory that stores programs executed in the control section 130 and vari ous data The memory RAM 160 is a volatile memory that retains rewritable data and data which should be temporarily retained at the time of the operation of the control section 130 and is used as for example a work memory for the operation of the control section 130 The memory EEPROM 140 is a memory that retains data even while the power of the image capturing apparatus 100 is off and stores various setting conditions and the like The interface section 119 is connected to the interface section 201 on the side of the interchangeable lens 200 mounted on the image capturing apparatus 100 so as to communicate with the interchangeable lens 200 The inter face section 119 and the interface section 201 are examples of the communication sections described in the claims The control section 130 is a section that is formed of for example the CPU which executes the programs stored in the memory ROM 150 and the like and controls the respective sections of the image capturing apparatus 100 on the basis of each information stored in the memory 150 The control section 130 controls for example exposure white balance f
2. SECTION STORAGE 116 US 8 724 982 B2 Sheet 1 of 13 May 13 2014 U S Patent NY WOU NOud33 NOIL23S NOILOSS AYOWIN AMOWSW TOYLNOD 094 091 Ott 01 NOILOAS 1O41NOO SN31 0SC NOIL23S YOLOW NOLIO313Q NOILISOd NOOZ Ove M 91 NO1VH3N39 NOIL93S NOLLO313Q SAM O 148 CEC JOVYOLS 450 NOIL23S NOIL23S 101245 NOISYAANOO ONISSAQOUd ades des etos i 9NISS320Sd WLISIGOOTYNY WNSIS NOILO3S WNOIS WLI9Id QN 20 NNV AV laSI LEZ 126 L SH SuvNddvONMDINDSOVWW ii 00L 002 Sls U S Patent May 13 2014 Sheet 2 of 13 US 8 724 982 B2 10 121 y FIG 2A 200 FIG 2B 124 FIG 2C US 8 724 982 B2 Sheet 3 of 13 May 13 2014 U S Patent NOILISOd SN31 50304 TVA331NI NOILO313G I YVAN LSVYLNOO Ola U S Patent May 13 2014 Sheet 4 of 13 US 8 724 982 B2 FIG 4 y POETE TE SESA ELE 7 100 IMAGE CAPTURING CAPTURED 170 EVALUATED 131 APPARATUS MAGESIGNAL DETECTION VALUE IN FOCUS POSITION SECTION CALCULATION SECTION 132 DETECTION RANGE DETERMINATION SECTION 181 CONFUSION RANGE FOGAL DEPTH x DIAMETERLIMIT CALCULATION INFORMATION 5 NUMBER SECTION DETECTION DETECTION INTERVAL IN
3. depends on position of focus lens in accordance with detection range in which the focus lens is shifted in order to 51 Int CI g G03B 3 00 2006 01 detect the contrast of a captured image signal a detection 52 U S interval determination section that determines number of TSEC coop bodas tun tego 396 104 348 345 in detection interval focal depths which represents the num 58 Field of Classification Search ber of focal depths as the division units as a detection interval USPC 396 104 348 345 in the detection range in accordance with the calculated S sa lication file for complete arch hi sto number of in detection range focal depths and a focus lens PP P shift instruction section that instructs a lens section to 56 References Cited form a focus search which shifts the focus lens by specifying U S PATENT DOCUMENTS the detection range and the number of in detection interval focal depths determined as the detection interval 4 219 261 A 7 519 285 B2 yyy WEONGHEINS IMAGE CAPTURING APPARATUS ANALOG AD DIGITAL SIGNAL be Z CN L ANALOGIDIGITAL PROCESSING h PROCESSING CONVERSION SECTION SECTION SECTION 052 i 113 ZOOM POSITION i DETECTION t SECTION 8 1980 Rosner et al 396 147 4 2009 Ishii 396 102 212 260 18 Claims 13 Drawing Sheets 10 1 I 5
4. which are input in step S941 described above step 942 Further the focus lens shift calculation section 251 inputs the values of the number of in detection interval focal depths n and the circle of confusion diameter limit step S943 As the number of in detection interval focal depths n the value which is contained in the number of in detection interval focal depths 404 in the received focus search command 400 is input Further as the circle of confusion diameter limit the value which is stored as the circle of confusion diameter limit information 181 in the image capturing apparatus 100 is input In addition for example the value of the circle of confusion diameter limit which is first transmitted from the image capturing apparatus 100 at a predetermined timing is retained in the interchangeable lens 200 side and in step 943 the retained value may be input Further among the focus lens position P the aperture value F and the focal length f which are input in step S943 the aperture value F and the focal length f are fixed for a single focus search operation Therefore in the single focus search at the first time in step S943 the focus lens position P the aperture value F and the focal length f are input Then at the second time and thereafter only the focus lens position P may be newly input Then the focus lens shift calculation section 251 calculates the amount of lens shift Mv as described above on the
5. confusion diameter limit which is input from the main body of the image capturing apparatus and the number of focal depths which represents the specified detection interval This configuration provides an effect whereby it is possible to 0 30 40 45 55 4 calculate the amount of shift of the focus lens on the basis of respective values of the focus sensitivity the circle of confu sion diameter limit and the number of focal depths as the detection interval Further in the second embodiment it is preferable that whenever the focus lens is shifted to a new position on the basis of the calculated amount of shift of the focus lens the focus lens shift calculation section should calculate the amount of shift of the focus lens corresponding to the new position This configuration provides an effect whereby it is possible to calculate the amount of shift of the focus lens in which the focal depth changed by the focus lens position is reflected According to the embodiments of the invention there is a beneficial effect whereby it is possible to make constant the amount of change in contrast for each detection interval which is set in accordance with the single focus search under the autofocus control using the contrast mode BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a diagram illustrating an exemplary configuration of an image capturing system according to an embodiment of the invention FIGS 2A to 2C are diagrams
6. the information on the focal length f and the current aperture value is necessary for the calculation of the lens diameter D However the aperture value F can also be obtained by inputting a value which is retained as the aperture value information 343 in the inter changeable lens 200 In addition as will be described later in the embodiment of the invention the detection range which is determined in accordance with the first focus search is a range from the position corresponding to the farthest in focus distance to the position corresponding to the nearest in focus distance Accordingly the initial values of the farthest detection range distance and the nearest detection range distance Ay which are set in accordance with the first focus search are respectively the farthest in focus distance and the nearest in focus distance Example of Detection Interval Determination Processing Next a description will be given of detection interval deter mination processing executed by the detection interval deter mination section 134 of FIG 4 The detection interval is as described above an interval for each detection position in the detection range and as the detection interval is determined each detection position is also set Then the detection inter val which is determined by the detection interval determina tion section 134 is not represented by the physical position interval of the focus lens 221 but is represented by the n
7. Next the focus lens shift instruction section 135 generates for example the focus search command 400 shown in FIG 8A and transmits the command to the interchangeable lens 200 step S906 The focus lens shift instruction section 135 stores the value of the number of in detection interval focal depths n which is determined in step S920 described above as the number of in detection interval focal depths 404 at the time of generating the focus search command 400 Further the values of the farthest detection range distance and the nearest detection range distance corresponding to the detec tion range which is determined renewed in step 903 as the farthest detection range distance 402 and nearest detection range distance 403 In response to the transmission of the focus search com mand 400 the interchangeable lens 200 executes as will be described later the operation for shifting the focus lens 221 in accordance of a single focus search That is the focus lens 221 is sequentially shifted to the detection positions in the detection range Accordingly the detection section 170 cal culates the evaluated value from the image signal which is input for each detection position step S907 Then after the focus lens 221 reaches the detection end position the in focus position is calculated on the basis of the evaluated value obtained for each detection position passed hitherto step S908 Next for example the focus lens shift instructi
8. The focus control device according to claim 8 wherein the non overlapping ranges of the in detection range focal depths N include first second and third non overlapping ranges and wherein for the first range the number of in detection range focal depths N is OsN lt 20 and the number of in detection interval focal depths n is five for the second range the number of in detection range focal depths N is 20sN lt 100 and the number of in detection interval focal depths n is fifteen and for the third range the number of in detection range focal depths N is 100xN and the number of in detection interval focal depths n is twenty five 10 A lens system comprising communication circuitry that communicates with a main body of an image capturing apparatus in a state where the communication circuitry is mounted to the main body of the image capturing apparatus focus lens shift calculation circuitry that calculates a num ber of focal depths which represents a detection inter val as an amount of shift of a focus lens in response to receiving an instruction to shift the focus lens from the main body of the image capturing apparatus by speci fying a detection range in which the focus lens is shifted to detect a contrast of a captured image signal and the detection interval represented by the number of focal depths which are division units of the detection range and each of which is based on a corresponding posit
9. add ing such shift amounts Mv1 to Mvn the amount of lens shift Mv corresponding to the number of in detection interval focal depths n is obtained However in such a method of calculating the amount of lens shift Mv the calculation amount increases and thus the processing load increases For this reason in the embodiment of the invention in consider ation of satisfying both of an appropriate calculation amount and the calculation accuracy of the amount of lens shift Mv sufficient in practice the amount of lens shift Mv is obtained on the basis of the above described expression Example of Processing Procedure in Image Capturing Appa ratus The flowchart of FIG 10 shows an exemplary procedure of processing for the autofocus control executed by the image capturing apparatus 100 shown in FIG 4 The process in each step shown in the drawing is appropriately executed by any one ofthe functional blocks ofthe image capturing apparatus 100 shown in FIG 4 At the start of the autofocus control based on the contrast mode for example the in detection range focal depth num ber calculation section 133 assigns an initial value of 0 to a variable m representing the number of times the focus search operation is executed step S901 Next the in detection range focal depth number calculation section 133 acquires the lens information from the interchangeable lens 200 The lens information described herein is information used in the cal culation o
10. ap f _ D anlar f ar aw f That is the number of in detection range focal depths N can be obtained by integrating the minute focal depth Ad in the range from the position corresponding to the image plane distance B to the position corresponding to the image plane distance By Further in the above mentioned expression the inverses of the farthest distance and the nearest distance A respectively defined as a and a Cy and thereby the above mentioned expression can be rewritten as the following expression 30 35 40 45 50 55 16 Numerical Expression 3 D 1 ve crf S T u As can be seen from the above expression the number of in detection range focal depths N can be obtained on the basis of the circle of confusion diameter limit 6 the focal length f the lens diameter D and the farthest distance and the nearest distance A corresponding to the detection range Here it is preferable that the circle of confusion diameter limit should be acquired by reading the circle of confusion diameter limit information 181 stored in the image capturing apparatus 100 The focal length f can be acquired by inputting a value which is selected from the focal length table 330 in accordance with the current zoom position from the inter changeable lens 200 Further the lens diameter D can be obtained by the expression D f F based on the focal length f and aperture value F Accordingly
11. basis of the circle of confusion diameter limit and the focus sensi tivity e which are input as described above and the effective aperture value Fe corresponding to the focus lens position P step S944 First according to the procedure shown in FIG 12 in the single focus search by executing step S940 whenever shifting the focus lens 221 for each detection interval a new amount oflens shift My is obtained This is based on the change in the focal depth d the effective aperture value Fe and the focus sensitivity e according to the position ofthe focus lens 221 As described above the amount of lens shift Mv is calculated on the basis of the focal depth d the focus sensitivity and the number of in detection interval focal depths n There fore in accordance with step S940 of FIG 12 whenever the focus lens 221 is shifted a new focal depth d corresponding to a new focus lens position P after the shift is calculated and a new focus sensitivity is acquired Then on the basis of the new focal depth d and focus sensitivity e the amount of lens shift Mv corresponding to the new focus lens position P is calculated Through the procedure in the embodiment of the invention regardless ofthe shift ofthe focus lens position the amount of change in contrast is made to be a constant value corresponding to the number of focal depths n whereby it is possible to shift the focus lens for each detection interval Further gener
12. example the memory EE PROM 140 or the memory ROM 150 corresponding to FIG 1 The detection interval determination section 134 is a sec tion that determines the detection interval in the determined detection range on the basis of the number of in detection range focal depths N and the detection interval table 182 Although the detailed description of the detection interval table 182 will be described later the table has a structure in which each range of the number of in detection range focal depths divided in advance is associated with the number of focal depths corresponding to the detection interval That is the detection interval determination section 134 determines the detection interval on the basis of the number of focal depths The detection interval table 182 can be stored in the memory 140 or the memory 150 corresponding to FIG 1 In addition the detection interval table 182 is an example of the detection interval information described in the claims The focus lens shift instruction section 135 is a section that instructs the interchangeable lens 200 to shift the focus lens in accordance with the autofocus control based on the contrast mode The focus lens shift instruction section 135 gives an instruction to execute the focus search by specifying the detection range and the detection interval Further in response to obtaining the definitive in focus position by repeatedly performing the focus search a certain number of ti
13. illustrating an exemplary appearance of the image capturing system according to the embodiment of the invention FIG 3 is a diagram illustrating a brief overview of opera tions of autofocus control based on the contrast mode accord ing to the embodiment of the invention FIG 4 is a diagram illustrating a functional configuration example of the image capturing system FIG 5 is a diagram illustrating a concept of the number of in detection range focal depths FIGS 6A and 6B are diagrams illustrating an example of a method of calculating the number of in detection range focal depths FIG 7 is a diagram illustrating an exemplary structure of a detection interval table FIGS 8A and 8B diagrams illustrating exemplary struc tures of focus search commands FIG 9 is a diagram illustrating an exemplary structure of a focus sensitivity table FIG 10 is a diagram illustrating an example of a procedure of a process for autofocus control executed by the image capturing apparatus FIG 11 is a diagram illustrating an example ofa procedure of a detection interval determination process executed by the image capturing apparatus FIG 12 is a diagram illustrating an example ofa procedure of a process executed by an interchangeable lens in response to reception of the focus search command and FIG 13 is a diagram illustrating an example of a procedure of a lens shift calculation process corresponding to the detec tion interval executed by th
14. in focus posi tion is calculated at highest accuracy Accordingly no further focus search is necessary Therefore in this case the instruc tion is given to the interchangeable lens 200 so as to shift the focus lens to the in focus position which is calculated through the final in focus position calculation process step S908 step S910 In response to the instruction in the interchangeable lens 200 lens drive to shift the focus lens 221 to the designated in focus position is performed As a result it is possible to obtain a state in which the subject is in focus The flowchart of FIG 11 shows an exemplary procedure of the detection interval determination process indicated in step US 8 724 982 B2 21 920 of FIG 10 In addition in the description of the process shown in the drawing it is the premise that the detection interval table 182 has contents shown in FIG 7 First the detection interval determination section 134 determines whether or not the current variable m is the maxi mum value step S921 As described above in the embodi ment of the invention by repeatedly performing the focus search finally the final focus search is executed on the basis of the minimum detection interval However due to some factors there is a possibility of an operation state occurring in which it is difficult to set the minimum detection interval even when the focus search is executed a certain number of times or more which is original
15. is a section that calculates the evaluated value of the contrast by performing detection for extracting contrast components from the image signal in accordance with the autofocus control based on the contrast mode which is employed in the image capturing apparatus 100 The control section 130 performs on the basis of the evaluated value generated by the detection section 170 the autofocus control for shifting the focus lens 221 so as to achieve the in focus state In addition practically the detec tion section 170 may be provided as for example a single function which is executed by the digital signal processing section 114 Alternately it may be possible to adopt a con figuration in which at least a part of the signal processing function is executed by the control section 130 Exterior Configuration Example of Image Capturing System FIGS 2A to 2C are diagrams illustrating an exterior con figuration example of the image capturing system 10 accord ing to the first embodiment of the invention FIG 2A is a front US 8 724 982 B2 9 view illustrating an appearance of the image capturing system 10 FIG 2B is a rear view illustrating an appearance of the image capturing system 10 FIG 2C is a top view illustrating an appearance of the image capturing system 10 The image capturing apparatus 100 includes a flash light ing section 102 the imaging element 111 the display section 115 a shutter button 121 a mode dial 122 a up down r
16. may be determined in the following method That is the shift of the focus lens 221 based on the amount of lens shift Mv can be determined on the basis of whether or not the shift is repeated the number of times necessary therefor The necessary number of times can be obtained on the basis of for example the number of in detection range focal depths N and the number of in detec tion interval focal depths n in terms of N n In such a manner in the modified example the value of the number of in detection range focal depths N is changed in the detection range thereby performing the update In addition as described above in and after the second focus search it is possible to omit the process for calculating the number of in detection range focal depths N for each updated detection range Thereby it is possible to reduce the processing load on the image capturing apparatus 100 side In addition the configuration according to the embodiment ofthe invention can also be applied to for example an image capturing apparatus in which the lens and the main body are integrated In this case the data corresponding to the focus sensitivity table 310 may not be transmitted and received between the lens unit side and the main body sideofthe image capturing apparatus whereby it is possible to reduce the processing load on the autofocus control Further the embodiment of the invention shows an example for embodying the invention and as clarified in
17. the embodiment of the invention the matters in the embodiment of the invention respectively correspond to the specific mat ters in claims Likewise the specific matters in claims respec tively correspond to the matters which are referenced by the same names in the embodiment of the invention However the invention is not limited to the embodiment and may be embodied by modifying the embodiment into various forms without departing from the scope of the invention Further the processing procedures described in the embodiment ofthe invention may be understood as a method having a series ofthe procedures and may be understood as a program for causing a computer to execute the series of the procedures or a recording medium storing the program Examples of the recording medium include for example a CD Compact Disc an MD MiniDisc a DVD Digital Versatile Disc a memory card a Blu ray disc BD regis tered trademark and the like The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2010 122169 filed in the Japan Patent Office on May 28 2010 the entire contents of which are hereby incorporated by reference It should be understood by those skilled in the art that various modifications combinations sub combinations and 20 25 30 35 40 45 50 55 60 65 26 alterations may occur depending on design requirements and other factors insofar
18. the detection range is represented by how many focal depths d correspond thereto That is the number of focal depths d corresponding to the detection range is represented by the number of in detection range focal depths N The in detection range focal depth number calcu lation section 133 calculates as described above the number of in detection range focal depths N In the embodiment of the invention the number of in detection range focal depths N can be obtained by the follow ing method In FIG 6B the distance from the rear side prin cipal point Hr to the imaging plane Yr is indicated by x Regarding the minute variation Ax with respect to x how many focal depths d correspond thereto is calculated That is the minute focal depth Ad which is the focal depth corre sponding to the minute variation Ax is calculated The minute focal depth Ad can be obtained on the basis of the lens diameter D and the circle of confusion diameter limit 8 by the following expression Numerical Expression 1 Ad DAx x That is the minute focal depth Ad is obtained by dividing the minute variation Ax by a single focal depth Then the number of in detection range focal depths N can be obtained by the following expression In addition in the following expression f represents the focal length and e represents the circle of confusion diameter limit Numerical Expression 2 n f Addx bF D za 1 d 6 Jari x
19. the drawings whereby the interchangeable lens 200 can be mounted thereon or removed therefrom With such a configuration sometimes a user may interchange a plurality of interchangeable lenses 200 in the image capturing apparatus 100 in accordance with for example a photography situation or a photography pur pose The interchangeable lens 200 is an interchangeable lens unit which is mounted on the image capturing apparatus 100 through the lens mount mechanism not shown in the draw ings The interchangeable lens 200 includes a zoom lens 211 a zoom position detection section 212 a focus lens 221 a focus lens drive motor 222 a diaphragm mechanism 231 a diaphragm drive motor 232 a motor driver 240 and a lens control section 250 Further the interchangeable lens 200 includes a ROM 260 Read Only Memory and a RAM Random Access Memory 270 Further the interchangeable lens 200 includes an interface section 201 The zoom lens 211 is a lens that is shifted in a direction of the optical axis through electric drive or manual drive so as to adjust the focal length That is the zoom lens 211 is a lens which is driven back and forth relative to the subject in order to enlarge or reduce the subject included in a captured image Further the zoom lens 211 implements a zoom function In addition the first embodiment of the invention shows an example of drive of the zoom lens 211 based on the user s manual operation The zoom position dete
20. thereon Further according to a second embodiment of the inven tion a lens system includes a communication section that communicates with a main body of an image capturing appa ratus in a state where the communication section is mounted on the main body of the image capturing apparatus a focus lens shift calculation section that calculates the number of focal depths which represents a detection interval as an amount of shift of a focus lens in response to receiving an instruction to shift the focus lens from the main body of the image capturing apparatus by specifying a detection range in which the focus lens is shifted in order to detect the contrast of a captured image signal and a detection interval repre sented by the number of focal depths which are division units of the detection range and each of which depends on a posi tion of the focus lens and a focus lens drive control section that shifts the focus lens on the basis of the calculated amount of shift of the focus lens This configuration provides an effect whereby it is possible to shift the focus lens in accordance with the number of focal depths specified as the detection interval Further in the second embodiment it is preferable that the focus lens shift calculation section should calculate the amount of shift of the focus lens on the basis of a focus sensitivity which is specified on the basis of a focus lens position an aperture value and a focal length a circle of
21. to the detection interval table 182 step S922 Then it is determined which one of the range divisions divided in the detection interval table 182 corre sponds to the number of in detection range focal depths N referenced in step 904 of FIG 10 step S923 From the determination result if the number corresponds to the range division of Ns100 the variable n representing the number of in detection interval focal depths is set to 25 step S924 Further if the number corresponds to the range division of 20xN 100 the number of in detection interval focal depths n is set to 15 step S925 Further if the number corresponds to the range division of 0sN lt 20 the number of in detection interval focal depths n is set to 5 In such a manner in the embodiment of the invention on the basis of the detection range represented by the number of focal depths the detec tion interval represented by the number of focal depths is set step S925 Through the process from step S924 to step 926 the detection interval is set Example of Processing Procedure in Interchangeable Lens The flowchart of FIG 12 shows an exemplary procedure of processing which is executed by the interchangeable lens 200 in response to receiving the focus search command 400 In addition the process shown in the drawing is appropriately executed by any one of the functional blocks in the inter changeable lens 200 shown in FIG 4 The focus search command 40
22. 0 which is transmitted from the focus lens shift instruction section 135 of the image cap turing apparatus 100 is received by the focus lens shift cal culation section 251 in the interchangeable lens 200 step 5931 0 kay 5 35 40 45 50 55 60 65 22 In response to receiving the focus search command 400 first the control for shifting the focus lens 221 to the detection start position is executed step 5932 Hence the focus lens shift calculation section 251 refers to information contained in the focus search command 400 That is when the detection direction 405 represents the direction from the farthest detec tion range distance to the nearest detection range distance the farthest detection range distance 402 is determined as the detection start position On the other hand when the detection direction 405 represents the direction from the nearest detec tion range distance to the farthest detection range distance the nearest detection range distance 403 is determined as the detection start position Then the instruction of the focus lens drive for the determined detection start position is given to the focus lens drive control section 252 In accordance with the instruction the focus lens drive control section 252 executes the drive control and thereby the focus lens 221 is shifted to the detection start position Next the focus lens shift calculation section 251 executes the amount of shift of th
23. 81 from the image capturing apparatus 100 Further the effective aperture value Fe is an aperture value corresponding to the case where an object is located at a finite distance and is changed in accordance with for example the focus lens position P The effective aperture value Fe corresponding to the focus lens position P can be obtained by calculation In addition in the above expression for calculating the amount of lens shift Mv the term represents the focal depth d which can be obtained at the current imaging position In addition the term Fe d e represents the physical amount of shift ofthe focus lens necessary to shift the image plane by the focal depth d by a single focal depth Accord ingly the amount of lens shift Mv represents the physical amount of shift ofthe focus lens necessary to shift the image plane from the current imaging position by the number of focal depths n As described above the focus lens shift cal culation section 251 converts the number of in detection interval focal depths n into the physical amount of shift ofthe focus lens The focus lens shift calculation section 251 outputs the amount of lens shift Mv which is calculated as described above to the focus lens drive control section 252 The focus lens drive control section 252 performs the control for shift ing the focus lens 221 by the amount of lens shift Mv only in the designated detection direction Thereby the focus lens 221 is
24. OSITION YES END U S Patent May 13 2014 Sheet 13 of 13 US 8 724 982 B2 FIG 13 5940 LENS SHIFT CALCULATION PROCESSING INPUT FOCUS LENS POSITION P APERTURE VALUE F AND FOCAL LENGTH f INPUT NUMBER OF IN DETECTION INTERVAL FOCAL DEPTHS n AND CIRCLE OF CONFUSION DIAMETER LIMIT CALCULATE AMOUNT OF LENS SHIFT n Fed e US 8 724 982 B2 1 FOCUS CONTROL DEVICE FOCUS CONTROL METHOD LENS SYSTEM FOCUS LENS DRIVING METHOD AND PROGRAM BACKGROUND OF THE INVENTION 1 Field of the Invention The present invention relates to a focus control device in particular a focus control device which performs autofocus control by using a contrast mode a method therefor and a program which causes the focus control device to implement the corresponding method Further the invention also relates to lens system corresponding to such a focus control device a focus lens driving method for the lens system and a pro gram which causes the lens system to implement the corre sponding method 2 Description of the Related Art To perform an autofocus control a contrast mode is used If the contrast of a captured image is high this means that the blur in the captured image is low by the same amount and thus it can be assumed that this state corresponds to an in focus state The contrast mode is an autofocus control mode based on such an assumption Specifically in the contrast mode the con
25. TERVAL DETERMINATION TABLE SECTION FOCALLENGTH NEAREST N FOCUS DISTANCE FARTHEST IN FOCUS DISTANCE APERTURE VALUE F aS ae sk ya Ne hele ae Sanaa ne oma ale ole we Ce eee eee He ee ee ee ee ee ee ee ee ee ee ee ef ee eee INTERCHANGEABLE _ 390 INFOCUS 310 253 DISTANCE FOCUS FOCUS LENS SHIFT LENGTH REFERENCE TABLE SENSITIVITY CALCULATION TABLE TABLE SECTION SECTION FOCAL LENGTH TABLE i 343 Mv APERTURE VALUE 330 INFORMATION F 342 FOCUS LENS DRIVE FOCUS LENS POSITION CONTROL SECTION INFORMATION P 341 221 ZOOM POSITION INFORMATION 2 i a i a a i ee ee ew ew eee eee ee eee eee ins US 8 724 982 B2 Sheet 5 of 13 May 13 2014 U S Patent NOILISOd SN31911203 Gd rd d d 0 V GS NSH1d3Q 1v00439NvH Hlddd V903 NOILO313G NI dO YSEWNN JONVYMH NOILO313Q G 91 U S Patent May 13 2014 Sheet 6 of 13 US 8 724 982 B2 FIG 6A DETECTION RANGE FIG 6B CIRCLE OF CONFUSION DIAMETER LIMIT 6 U S Patent May 13 2014 Sheet 7 of 13 US 8 724 982 B2 FIG 7 182 NUMBER OF IN DETECTION RANGE IN DETECTION NSO FOCAL DEPTHS N FOCAL DEPTHS n U S Patent May 13 2014 Sheet 8 of 13 US 8 724 982 B2 FIG 8A 400 FARTHEST NEAREST NUMBER OF DETECTION IN DETECTION IN
26. TERvAL DETECTION RANGE RANGE DIRECTION DISTANCE DISTANCE FOCAL DEPTHS FIG 8B 400A 401 402A 403A 404 405 NUMBER OF DETECTION IN DETECTION NUMBER OF DETECTION HEADER REFERENCE IN DETECTION INTERVAL POSITION ROPE THS M FOCAL DEPTHS DIRECTION U S Patent May 13 2014 Sheet 9 of 13 US 8 724 982 B2 FIG 9 310 FOCUS SENSITIVITY e FOCAL DISTANCE f FOCUS LENS PTT TTT TTT T T tT TRA POSITION P APERTURE VALUE F N U S Patent May 13 2014 Sheet 10 of 13 US 8 724 982 B2 FIG 10 START ACQUIRE LENS INFORMATION E DETERMINE UPDATE DETECTION RANGE CALCULATE NUMBER OF IN DETECTION RANGE FOCAL DEPTHS N IS OPERATION EXECUTED ON THE BASIS OF MINIMUM DETECTION INTERVAL YES CONTROL IN FOCUS POSITION SHIFT S910 END U S Patent May 13 2014 Sheet 11 of 13 US 8 724 982 B2 FIG 11 920 DETECTION INTERVAL DETERMINATION PROCESSING IS CORRESPONDING RANGE OF NUMBER OF FOCAL DEPTHS N 20 lt N lt 100 S925 NUMBER OF IN DETECTION INTERVAL FOCAL DEPTHS n 15 NUMBER OF IN DETECTION INTERVAL FOCAL DEPTHS n 25 5926 NUMBER OF IN DETECTION INTERVAL FOCAL DEPTHS 5 U S Patent May 13 2014 Sheet 12 of 13 US 8 724 982 B2 FIG 12 CONTROL IN FOCUS POSITION SHIFT CORRESPONDING TO THE DETECTION START POSITION DOES IT REACH DETECTION END P
27. The focus lens shift calculation section 251 converts the detection interval based on the number of focal depths into a physical shift amount Hence the focus lens shift calculation section 251 specifies and selects one focus sensitivity e corresponding to the com bination of the focal length f the aperture value F and the focus lens position P from the focus sensitivity table 310 The focal length f is acquired by causing the reference table sec tion 253 which will be described later to select it from the US 8 724 982 B2 13 focal length table 330 Further the aperture value F is acquired by reading the aperture value information 343 The focus lens position P is acquired by reading the focus lens position information 342 In addition the exemplary struc ture of the focus sensitivity table 310 will be described later Next the focus lens shift calculation section 251 calculates the amount of lens shift Mv as will be described later on the basis of the value of the selected focus sensitivity e the value of the circle of confusion diameter limit 6 represented by the circle of confusion diameter limit information 181 which is input from the image capturing apparatus 100 side and the aperture value F The amount of lens shift Mv represents the physical amount of shift of the focus lens corresponding to the detection interval The focus lens drive control section 252 is a section that controls drive of the focus lens 221 and perfo
28. US008724982B2 United States Patent 10 Patent No US 8 724 982 B2 Ishiwata et al 45 Date of Patent May 13 2014 54 FOCUS CONTROL DEVICE FOCUS 2004 0165879 Al 8 2004 Sasaki etal 396 137 CONTROL METHOD LENS SYSTEM FOCUS 2005 0063693 A1 3 2005 Yoshibeet al 396 81 2005 0146790 7 2005 Liuetal 359 586 LENS DRIVING METHOD AND PROGRAM 2005 0271373 AL 12 2005 Tomita 396 103 2007 0103577 Al 5 2007 Misawa et al 348 333 01 75 Inventors Hisashi Ishiwata Tokyo JP Makibi TIE SIS Nakamura Tokyo JP FOREIGN PATENT DOCUMENTS 73 Assignee Sony Corporation Tokyo JP JP 2009 48126 3 2009 Notice Subject to any disclaimer the term of this cited by examiner patent is extended or adjusted under 35 U S C 154 b by 163 days Primary Examiner Clayton E Laballe Assistant Examiner Linda B Smith 21 Appl No 13 113 402 74 Attorney Agent or Firm Oblon Spivak 22 Filed May 23 2011 McClelland Maier amp Neustadt L L P 65 Prior Publication Data 57 ABSTRACT US 2011 0293256 Al Der 2011 A focus control device includes an in detection range focal erus depth number calculation section calculates number 99 Foreign Application Priority Data of in detection range focal depths as the number of focal 28 2010 JP c P2010 122169 depths which are divided as division units and each of which
29. ally at the time of driving the focus lens the image capturing apparatus specify the physical shift amount and gives an instruction to drive the focus lens In this con figuration under the image capturing system 10 shown in FIG 1 first the amount of lens shift Mv in the image capturing apparatus 100 is calculated Then by specifying the amount of lens shift Mv the instruction to shift the focus lens 221 is given to the interchangeable lens 200 However with such a configuration in order to calculate the amount of lens shift Mv of the focus lens 221 the data of the focus sensitivity table 310 is necessary for the image capturing apparatus 100 Alternately as the information which is substituted for the focus sensitivity table 310 for example information representing the focal depth for each focus position in the entire focus shift range is necessary Such information has a value which is unique for each lens unit Accordingly it is preferable to store the information in 0 5 30 40 45 50 55 65 24 the interchangeable lens 200 but in practice it is not prefer able to store the information in the image capturing apparatus 100 in which it is assumed that the lens is interchangeable Accordingly when the image capturing apparatus 100 is intended to calculate the physical amount of lens shift from the number of in detection interval focal depths n the com munication for inputting the focus sensit
30. aperture value the focal length the circle of confusion diameter limit and the farthest distance and nearest distance Further in the first embodiment it is preferable that the focus control device should further include a detection range determination section that as a single operation of the focus search is completed newly determines the detection range for the subsequent focus search In addition it is also preferable that the detection interval determination section should deter mine in accordance with the determined detection range the number of in detection interval focal depths associated with the detection range This configuration provides an effect whereby it is possible to determine the number of in detec US 8 724 982 B2 3 tion interval focal depths in accordance with each detection range which is newly determined Further in the first embodiment it is preferable that when the number of in detection interval focal depths determined as the detection interval is the predetermined minimum the focus lens shift instruction section should instruct the lens section to perform the final focus search by specifying the minimum of the number of in detection interval focal depths and instructs the lens section to shift the focus lens to an in focus position which can be calculated on the basis of the contrast detected through the final focus search This configu ration provides an effect whereby it is possible to perform the
31. apturing Sys tem FIG 4 shows a functional configuration example of the image capturing system 10 according to the embodiment of the invention It should be noted that in the drawing the elements common to those of FIG 1 are represented by the same reference numerals and signs The image capturing apparatus 100 shown in the drawing includes the detection section 170 an in focus position calculation section 131 a detection range determination section 132 an in detection range focal depth number calculation section 133 a detection interval determination section 134 and a focus lens shift instruction section 135 Further the image capturing appara tus 100 stores a detection interval table 182 and a circle of confusion diameter limit information 181 In addition as compared with the configuration of FIG 1 the control section 130 corresponds to the respective functions of the in focus position calculation section 131 the detection range determi nation section 132 the in detection range focal depth number calculation section 133 the detection interval determination section 134 and the focus lens shift instruction section 135 That is the respective functions are implemented by causing the control section CPU 130 to execute programs The detection section 170 is similarly to the description of FIG 1 a section that calculates the evaluated value of contrast by performing the detection on the captured image signal input from the d
32. as they are within the scope of the appended claims or the equivalents thereof What is claimed is 1 focus control device comprising in detection range focal depth number calculation cir cuitry that calculates a number of in detection range focal depths as a number of focal depths which are divided as division units and each of which is based on a corresponding position of a focus lens in accordance with a detection range in which the focus lens is shifted to detect a contrast of a captured image signal detection interval determination circuitry that determines a number of in detection interval focal depths which rep resents the number of focal depths as the division units as a detection interval in the detection range based on the calculated number of in detection range focal depths as compared to a plurality of predetermined ranges of in detection range focal depths of a detection interval table stored in memory and focus lens shift instruction circuitry that instructs lens cir cuitry to perform a focus search which shifts the focus lens by specifying the detection range and the number of in detection interval focal depths determined as the detection interval 2 The focus control device according to claim 1 wherein the in detection range focal depth number calculation cir cuitry calculates the number of in detection range focal depths based on an aperture value which is input from the lens circuitry a focal length whi
33. becomes high However the time necessary to detect the entire detection range increases and as a result the time necessary to obtain the in focus state also increases Accordingly in the related art there are existing configu rations in which as a user presses the release button halfway the detection interval is changed in accordance with the depth of field at the start timing of the autofocus control That is for example when a subject is near the depth of field is shallow Inthis case the detection intervalis changed to be narrow for example refer to Japanese Unexamined Patent Application Publication No 2009 48126 FIG 15 Thereby it is pos sible to increase the accuracy of focusing even under situation in which focusing is difficult since the depth of field is small On the other hand when the depth of field is large by setting a large detection interval it is possible to shorten the time necessary to reach the in focus state SUMMARY OF THE INVENTION In the related art in both cases where the detection interval is set to be large and is set to be small the amount of shift of 40 45 55 65 2 the focus lens corresponding to the detection interval is set to be constant However even when the detection interval is set such that the amount of shift of the focus lens is constant the amount of change in the contrast of the image for each detec tion interval is irregularly changed by the effects of focus sens
34. cal depths through the in detection range focal depth number calculation section 133 shown in FIG 4 will be described with reference to FIGS 6A and 6B First FIG 6A shows the focal length f Further FIG 6A shows the farthest detection range distance the nearest detection range distance Av Further FIG 6A shows image plane distances and respectively corresponding to the farthest detection range distance A the nearest detection range distance Ay The focal length f is equal to the distance from the front side principal point Hfto the front side focal point Ff and the distance from the rear side principal point Hr to the rear side focal point Fr The farthest detection range distance A is represented as the distance from the front side principal point Hf to the subject position Yf The nearest detection range distance A yis shorter than the distance from the subject position Yf to the front side principal point Hf The image plane distance corresponding to the farthest detection range distance is represented as the distance from the rear side principal point Hr to the imaging plane Yr The image plane distance corresponding to the nearest detection range distance A is longer than the distance from the imaging plane Yr to the rear side principal point Hr FIG 6B shows the circle of confusion diameter limit 5 The point light source which passes through the lens is in focus on the imaging p
35. calculated number of in detection range focal depths N that is the detection range Thereby when the detection range is large by setting a large detection interval it is possible to reduce the time necessary for the focus search Further as the detection range decreases the setting is made to also decrease the detection interval whereby it is possible to obtain the evaluated value with high accuracy Instruction of Focus Lens Shift Corresponding to Focus Search Next a description will be given of an operation example for the instruction of the focus lens shift which is executed in accordance with the focus search by the focus lens shift instruction section 135 When the detection interval deter mined by the detection interval determination section 134 that is the number of in detection interval focal depths is input the focus lens shift instruction section 135 generates for example a focus search command 400 shown in FIG 8A and transmits the command to the interchangeable lens 200 In addition a focus search command 400A shown in FIG 8B is a modified example which will be described later The focus search command 400 is formed to successively contain for example a header 401 the farthest detection range distance 402 the nearest detection range distance 403 the number of in detection interval focal depths 404 and a detection direction 405 In the farthest detection range distance 402 and the nearest detection range distan
36. ce 403 values of the farthest detection range distance and the nearest detection range distance Which correspond to the detection range determined by the detection range determination section 132 are respec tively stored On the basis of the farthest detection range distance 402 and the nearest detection range distance 403 the detection range is specified In the number of in detection interval focal depths 404 a value which represents the number of in detection interval focal depths n determined by the detection interval determi nation section 134 is stored In the detection direction 405 a value which represents the direction of shifting the focus lens in the focus search is stored The focus lens shift instruction section 135 instructs the interchangeable lens 200 to execute the focus search opera tion by transmitting the focus search command 400 based on the above structure Example of Processing of Calculating Amount of Lens Shift Corresponding to Detection Interval Next a description will be given of an example of process ofcalculating an amount of lens shift Mv ofthe focus lens 221 corresponding to the detection interval the process being executed by the focus lens shift calculation section 251 in the interchangeable lens 200 Inthe interchangeable lens 200 the focus search command 400 is input by the focus lens shift calculation section 251 The focus lens shift calculation section 251 calculates the amount of len
37. ch is input from the lens circuitry a circle of confusion diameter limit which is stored in the corresponding focus control device and a farthest distance and a nearest distance from and to respectively a principal point corresponding to the detection range 3 The focus control device according to claim 1 further comprising detection range determination circuitry that as a single operation of the focus search is completed newly determines the detection range for the focus search wherein the detection interval determination circuitry determines based on the determined detection range the number of in detection interval focal depths associ ated with the detection range 4 The focus control device according to claim 1 wherein when the number of in detection interval focal depths deter mined as the detection interval is a predetermined minimum number the focus lens shift instruction circuitry instructs the lens circuitry to perform a final focus search by specifying a minimum number of in detection interval focal depths and instructs the lens circuitry to shift the focus lens to an in focus position calculated based on a contrast detected through the final focus search 5 The focus control device according to claim 1 wherein the detection interval determination circuitry selects the num ber of in detection interval focal depths which can be asso ciated with the calculated number of in detection range focal depths based on de
38. ction section 212 detects the posi tion of the zoom lens 211 driven by the user s zoom operation and outputs the detection result to the lens control section 250 The focus lens 221 is a lens that is shifted in the direction of the optical axis through the drive of the focus lens drive motor 222 so as to adjust the focus That is the focus lens 221 is a lens used to bring the subject into focus to make the subject be in focus Further the focus lens 221 implements an auto focus function The focus lens drive motor 222 drives the focus lens 221 on the basis of the control of the motor driver 240 The diaphragm mechanism 231 adjusts the amount of inci dent light which passes through the zoom lens 211 and the focus lens 221 and supplies the adjusted light to an imaging element 111 The diaphragm mechanism 231 is driven by the diaphragm drive motor 232 so as to adjust the aperture of the diaphragm The diaphragm drive motor 232 drives the diaphragm mechanism 231 on the basis of the control of the motor driver 240 That is the zoom lens 211 and the focus lens 221 are a lens group that concentrates the light incident from the subject 20 25 30 35 40 45 50 55 60 65 6 and the light concentrated through such a lens group is inci dent on the imaging element 111 through the diaphragm mechanism 231 The motor driver 240 is a driver that drives the focus lens drive motor 222 and the diaphragm drive motor 232
39. d position In contrast if it is possible to obtain the com parison result that the current focus lens position is not beyond the detection end position it is determined that the focus lens position does not reach the detection end position In step S934 if it is determined that the focus lens position does not reach the detection end position the amount of lens shift Mv corresponding to the current focus lens position P is newly calculated step S940 Next the focus lens shift con trol based on the calculated amount of lens shift Mv 1s executed step S933 As described above as the result that the process of steps S940 and 5933 is repeatedly executed when it is determined in step S934 that the focus lens position reaches the detection end position the focus lens shift con trol which is performed hitherto in response to receiving the focus search command 400 is terminated The flowchart of FIG 13 shows an exemplary procedure of processing of lens shift calculation corresponding to the detection interval in step S940 shown in FIG 12 described above The focus lens shift calculation section 251 inputs the focus lens position P the aperture value F and the focal length f step S941 Next the focus lens shift calculation section 251 selects from the focus sensitivity table 310 the focus sensitivity e corresponding to the combination of the focus US 8 724 982 B2 23 lens position P the aperture value and the focal length f
40. e focus lens calculation process corresponding to the detection interval step S940 The lens shift calculation process is described in step 940 Next the control for shifting the focus lens is executed on the basis of the amount of lens shift Mv calculated in step S940 step S933 Hence the focus lens shift calculation section 251 instructs the focus lens drive control section 252 to shift the focus lens 221 by the amount of lens shift Mv which is calculated in step S940 In accordance with the instruction the focus lens 221 is shifted to the detection position at a distance of the amount of lens shift Mv away from the current detection position Next as the result that the focus lens 221 is shifted in step S933 described above the focus lens shift calculation section 251 determines whether or not the focus lens position reaches the detection end position step S934 The detection end position is one which is not determined as the detection start position in the farthest detection range distance 402 and the nearest detection range distance 403 in the focus search com mand 400 The focus lens shift calculation section 251 com pares the current focus lens position with the detection end position Then if it is possible to obtain the comparison result thatthe current focus lens position is the same as the detection end position or is beyond the detection end position it is determined that the focus lens position reaches the detection en
41. e interchangeable lens DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter the preferred embodiments hereinafter referred to as embodiments will be described Description will be given in order of the following items 1 First Embodiment Detection Interval Setting Based on Number of Focal Depths 2 Modified Examples 1 First Embodiment Internal Configuration Example of Image Capturing System FIG 1 is a block diagram illustrating an internal configu ration example of an image capturing system 10 according to US 8 724 982 B2 5 a first embodiment of the invention The image capturing system 10 includes an image capturing apparatus 100 and an interchangeable lens 200 The image capturing system 10 is realized by for example a digital still camera for example a digital single lens camera in which the lens is interchange able In addition by using the image capturing apparatus 100 a focus control device according to the embodiment of the invention is embodied Further by using the interchangeable lens 200 a lens section or a lens system according to the embodiment of the invention is embodied The image capturing apparatus 100 is an image capturing apparatus that generates image data captured image by cap turing an image of a subject and stores the generated image data as image content still image content or moving image content Further the image capturing apparatus 100 has a lens mount mechanism not shown in
42. earch command 400A shown in the drawing contains instead of the farthest detection range dis tance 402 and the nearest detection range distance 403 con tained in the focus search command 400 of FIG 8A the detection reference position 402A and the number of in detection range focal depths N The detection reference position 402A that is the refer ence position representing the position which is a reference in US 8 724 982 B2 25 the updated detection range may be set as for example the detection start position Alternately the reference position may be set as the center position the in focus position cal culated in step S908 in the detection range The number of in detection range focal depths 403A contains the value N which is obtained when the detection range updated in the current focus search is represented by the number of focal depths In the interchangeable lens 200 which receives the focus search command 400A the drive control of the focus lens 221 is executed in a procedure of the process as described in FIGS 12 and 13 However in step S932 for example the position which is indicated by the detection reference position 402A in the focus search command 4004 is set as the detection start position and the focus lens 221 is shifted Further the deter mination as to whether or not the focus lens position reaches the detection end position in step S934 may be not based on an actual position ofthe focus lens but
43. ed through the high pass filter HPF with prescribed characteristics Thereby the absolute value the differential absolute value of the amplitude correspond ing to the high frequency component of the luminance signal is detected That is by detecting the captured image signal the contrast component is extracted Then the value which can be obtained by integrating the detected differential abso lute value is the evaluated value The evaluated value can be obtained on the basis of the high frequency component ofthe luminance signal of the video signal and thus represents an intensity of contrast of the image FIG 3 shows a relationship between the evaluated value and the lens position of the focus lens the focus lens posi tion The drawing shows the operation ofthe focus search for acquiring the evaluated values V1 to V10 at 10 mutually different focus lens positions while shifting the focus lens from the near side to the far side relative to the principal point The focus lens positions at which the evaluated values V1 to V10 are acquired is the detection positions The range from the detection position at which the evaluated value V1 is acquired to the detection position at which the evaluated value V10 is acquired is the detection range After all the evaluated values in the detection range are acquired in such a manner for example by the interpolation calculation using these evaluated values the focus lens posi tion at w
44. emory 160 Further the image capturing apparatus 100 includes an interface section 119 Further the image captur ing apparatus 100 includes a detection section 170 In addition the digital signal processing section 114 the vertical driver 117 the timing generator 118 the operation section 120 and the detection section 170 are connected so as to be able to communicate with for example the control section 130 through the system bus 101 Further the memory EEPROM 140 the memory ROM 150 and the memory 160 RAM are connected so as to be able to communicate with the control section 130 and the like through the system bus 101 The imaging element 111 is a photoelectric conversion element that receives the light the incident light which is supplied through the zoom lens 211 the focus lens 221 and the diaphragm mechanism 231 so as to convert the incident light into an electric signal and supplies the converted elec tric signal to the analog signal processing section 112 Fur ther the imaging element 111 is driven by the vertical driver 117 In addition as the imaging element 111 it is possible to use for example a CCD Charge Coupled Device sensor a CMOS Complementary Metal Oxide Semiconductor sen sor and the like The analog signal processing section 112 performs the analog signal processing such as a noise removal process on the electric signal which is supplied from the imaging ele ment 111 at the timing of recei
45. er s manual operation The zoom operation is performed for example in a state where a pre scribed portion of the interchangeable lens 200 is held by user s hand For example when the zoom operation is per formed by the user s manual operation the zoom function is controlled in accordance with the manual operation whereby it is possible to enlarge or reduce the subject included in the capture image 20 25 30 35 40 45 50 55 60 65 10 Autofocus Control Based on Contrast Mode The image capturing system 10 according to the embodi ment of the invention employs the contrast mode as the auto focus control for automatically achieving the in focus state A basic operation of the autofocus control based on the contrast mode according to the embodiment of the invention is forexample as follows First the focus lens is sequentially shifted to a plurality of detection positions in the shift range the detection range of the focus lens which is set in accor dance with the focus control This operation can be consid ered as a search for the focus position the in focus position at which the in focus state is achieved and is thus herein referred to as focus search Then the evaluated value of the contrast of the image captured for each detection position is calculated In order to calculate the evaluated value for each detection position first the luminance signal component in the cap tured image signal is pass
46. f focal depths which are divided as division units and each of which is based on a corresponding position of a focus lens in accordance with a detection range in which the focus lens is shifted to detect a contrast of a captured image signal determining using the processing circuitry a number of in detection interval focal depths which represents the number of focal depths as the division units as a detec tion interval in a detection range based on the calculated number of in detection range focal depths as compared to a plurality of predetermined ranges of in detection range focal depths of a detection interval table stored in memory and instructing using the processing circuitry lens circuitry to perform a focus search which shifts the focus lens by specifying the detection range and the number of in detection interval focal depths determined as the detec tion interval 16 A focus lens driving method comprising communicating with a main body of an image capturing apparatus in a state where communication circuitry is mounted to the main body ofthe image capturing appa ratus calculating using circuitry a number of focal depths which represents a detection interval as an amount of shift of a focus lens in response to receiving an instruc tion to shift the focus lens from the main body of the image capturing apparatus by specifying a detection range in which the focus lens is shifted to detect a contrast of a capt
47. f the number of in detection range focal depths N and as described above includes the focal length f the in focus distance the farthest in focus distance and the nearest in focus distance and the aperture value F Subsequently the detection range determination section 132 executes the process of determining the detection range step S903 Here in step S903 corresponding to first focus search the range which corresponds to the farthest in focus distance and the nearest in focus distance acquired in step 902 is determined as the detection range Next the in detection range focal depth number calcula tion section 133 executes the process of calculating the num ber of in detection range focal depths N corresponding to the detection range which is determined in step S903 described above step S904 Then the detection interval determination section 134 determines the detection interval corresponding to the number of in detection range focal depths N which is calculated in step S904 described above step S920 Although the process of determining the detection interval in 20 25 30 35 40 45 50 55 60 65 20 step S920 will be described later with reference to FIG 13 the determined detection interval is represented as the number of in detection interval focal depths n For example in this step the in detection range focal depth number calculation section 133 adds an increment to the variable m step S905
48. focus lens shift for focusing after the focus search based on the number of in detection interval focal depths defined as the minimum Further in the first embodiment it is preferable that the detection interval determination section should select the number of in detection interval focal depths which can be associated with the calculated number of in detection range focal depths on the basis of detection interval information in which the numbers of in detection range focal depths are associated with the numbers of in detection interval focal depths thereby determining the number of in detection in terval focal depths corresponding to the detection interval This configuration provides an effect whereby by selecting the number of in detection interval focal depths which can be associated with the calculated number of in detection range focal depths on the basis of the detection interval information it is possible to determine the number of in detection interval focal depths as the detection interval in the detection range Further in the first embodiment it is preferable that the focus control device should further include a communication section that communicates with the lens section in a state where the lens section removable from a main body of the corresponding focus control device is mounted This configu ration provides an effect whereby it is possible to perform the instruction to shift the focus lens for each lens section mounted
49. fted in order to detect the contrast ofa captured image signal a detection interval deter mination section that determines the number of in detection interval focal depths which represents the number of focal depths as the division units as a detection interval in the detection range in accordance with the calculated number of in detection range focal depths and a focus lens shift instruc tion section that instructs a lens section to perform a focus search which shifts the focus lens by specifying the detection range and the number of in detection interval focal depths determined as the detection interval This configuration pro vides an effect whereby it is possible to set the detection interval on the basis ofthe number of focal depths as division units of the detection range Further in the first embodiment it is preferable that the in detection range focal depth number calculation section should calculate the number of in detection range focal depths on the basis of an aperture value which is input from the lens section a focal length which is input from the lens section a circle of confusion diameter limit which is stored in the corresponding focus control device and the farthest dis tance and the nearest distance from and to a principal point corresponding to the detection range This configuration pro vides an effect whereby it is possible to calculate the number of in detection range focal depths from respective values of the
50. h the compression process is not performed to the storage device 116 Further the digital signal processing section 114 performs a decompression pro cess on the compressed image data which is stored in the storage device 116 and supplies the image data subjected to the decompression process to the display section 115 In addition the digital signal processing section 114 can be embodied by a signal processing device as a DSP Digital Signal Processor The display section 115 is a display device that displays the image data which is supplied from the digital signal process ing section 114 The display section 115 displays for example the image data on which the digital signal process ing section 114 performs the image processing as a through the lens image Further for example the display section 115 displays the image data which is stored in the storage device 116 as a list image As the display section 115 it is possible to use for example a display panel such as an organic EL Electro Luminescence panel or an LCD Liquid Crystal Display The storage device 116 is a section that stores the image data on which the digital signal processing section 114 per forms the image processing Further the image data stored in the storage device 116 is supplied to the digital signal pro cessing section 114 In addition the storage device 116 may be built in the image capturing apparatus 100 and may be removable from the image capturi
51. her the in detection range focal depth number calculation section 133 also uses information on the focal length f the nearest in focus distance the farthest in focus distance and the aperture value F which are input from the interchangeable lens 200 A method of calculating the num ber of in detection range focal depths will be described later In addition regarding information on the focal length f the nearest in focus distance the farthest in focus distance and the aperture value F for example the respective current val ues at that time are transmitted from the interchangeable lens 200 side for each fixed time Such information is transmitted and received through the interface section 201 on the inter changeable lens 200 side and the interface section 119 of the image capturing apparatus 100 corresponding to FIG 1 The circle of confusion diameter limit information 181 is information that represents the value of the circle of confu an 0 jak 5 40 45 50 12 sion diameter limit The circle of confusion diameter limit is an eigenvalue of the image capturing apparatus 100 which is uniquely determined in accordance with the pixel size and the like of the imaging element 111 shown in FIG 1 In the image capturing apparatus 100 the circle of confusion diam eter limit information 181 is stored in advance at the time of manufacture The circle of confusion diameter limit infor mation 181 can be stored in for
52. hich is updated in step S903 of FIG 10 in and after the second focus search is represented by the farthest detection range distance and the nearest detection range distance That is on the basis of the physical distance relative to the lens the principal point the detection range is determined In contrast in the modified example the detection range which is updated in step S903 is represented by the number of focal depths N In this case step S903 in and after the second focus search is the following process That is in the number of in detection range focal depths N representing the detection range which is set at the previous focus search a value of the number of in detection range focal depths N which is smaller than the above is set in accordance with for example a prescribed algorithm In such a manner in step 5903 in and after the second focus search the new number of in detection range focal depths N is obtained by updating the detection range Hence it is possible to omit the process in step S904 In addition it is preferable that the detection inter val determination process in step S920 should be executed in the procedure shown in FIG 11 similar to the first embodi ment on the basis of the number of in detection range focal depths N corresponding to the newly updated detection range According to the modified example the focus search com mand 400A transmitted in step S906 of FIG 10 is shown in FIG 8B The focus s
53. hich the peak evaluated value Vpeak can be obtained is calculated The focus lens position at which the peak evaluated value Vpeak can be obtained is herein referred to as an in focus position Then the focus lens is driven so as to be shifted to the in focus position Thereby it is possible to automatically achieve the state in which the subject is in focus In addition in the drawing the number of the evaluated values to be acquired that is the number of the detection positions in the detection range is set to 10 However the number is set for the convenience of description in all respects and may be different in actual circumstances Fur ther in the embodiment ofthe invention as will be described later the number of the detection positions in the detection range can be changed Further in the embodiment of the invention until the definitive in focus position is obtained the focus search is repeatedly performed while changing the detection range Moreover in the embodiment of the invention each detec tion interval I is set as will be described later so as to make the number of focal depths d constant when the focal depth d is a single unit By setting each detection interval I in such a manner the amount of change in contrast which is obtained when the focus lens 221 is shifted for each detection interval Iin the detection range is made to be constant US 8 724 982 B2 11 Functional Configuration Example of Image C
54. ical system On the basis ofthis the focus sensitivity table 310 has a 3D table structure shown in FIG 9 Then the focus lens shift calculation section 251 inputs the focal length f in order to obtain the focus sensitivity e The focal length f is a value which is selected by the reference table section 253 from the focal length table 330 on the basis of the zoom position Z indicated by the zoom position infor mation 341 Further the value retained as the aperture value information 343 is input as the aperture value F Further the value retained as the focus lens position information 342 is input as the focus lens position P Then from the focus sen sitivity table 310 the value of the single focus sensitivity corresponding to the input combination of the focal length f the aperture value F and the focus lens position P Next the focus lens shift calculation section 251 calculates the physical amount of lens shift My of the focus lens 221 corresponding to the number of in detection interval focal depths n The amount oflens shift Mv is obtained on the basis of the effective aperture value Fe the circle of confusion diameter limit 5 the focus sensitivity e and the number of in detection interval focal depths n by the following expres sion The circle of confusion diameter limit 6 is acquired as described above by receiving the value which is stored as the circle of confusion diameter limit information 1
55. ight left operation button 123 a determination button 124 a can cel button 125 and a power switch 126 Further the inter changeable lens 200 includes the zoom lens 211 the focus lens 221 and the diaphragm mechanism 231 In addition the shutter button 121 the mode dial 122 the up down right left operation button 123 the determination button 124 the can cel button 125 and the power switch 126 correspond to the operation section 120 shown in FIG 1 Further the imaging element 111 the display section 115 the zoom lens 211 the focus lens 221 and the diaphragm mechanism 231 corre spond to the respective same named sections shown in FIG 1 Hence a detailed description thereof will be omitted herein In addition the zoom lens 211 the focus lens 221 the dia phragm mechanism 231 are built in the interchangeable lens 200 and the imaging element 111 is built in the image cap turing apparatus 100 Hence those are indicated by the dotted line in FIGS 2A to 2C The flash lighting section 102 irradiates the subject with rays on the basis of the control of the control section 130 shown in FIG 1 so as to increase light reflected light from the subject Thereby it is possible to capture an image even in a situation in which ambient illuminance is low The shutter button 121 is an operation member for per forming a shutter operation and allows a user to perform a full press operation or a half press operation thereon For examp
56. igital signal processing section 114 The in focus position calculation section 131 is a section that calculates the in focus position by executing for example interpolation calculation on the basis of the evalu ated value which is input from the detection section 170 The detection range determination section 132 is a section that determines the detection range for each single focus search In addition in the case of determining the detection range in and after the second focus search the detection range determination section 132 uses information on the in focus position which is calculated by the in focus position calcula tion section 131 in the previous focus search The in detection range focal depth number calculation section 133 is a section that calculates the number of focal depths the number of in detection range focal depths cor responding to the detection range which is determined by the detection range determination section 132 When the focal depth d is treated as a single unit the number of in detection range focal depths represents how many focal depths d cor respond to the detection range For example if a certain detection range corresponds to 10 focal depths d the number of in detection range focal depths is set to 10 The in detection range focal depth number calculation section 133 uses the circle of confusion diameter limit information 181 when calculating the number of in detection range focal depths Furt
57. ion of the focus lens and focus lens drive control circuitry that shifts the focus lens based on the calculated number of focal depths as the amount of shift of the focus lens 11 The lens system according to claim 10 wherein the focus lens shift calculation circuitry calculates the number of focal depths as the amount of shift of the focus lens based on a focus sensitivity which is specified based on a focus lens position an aperture value a focal length a circle of confu sion diameter limit which is input from the main body of the image capturing apparatus and the number of focal depths which represents the detection interval 12 The lens system according to claim 10 wherein the focal depths increase in value in correspondence with non overlapping focus lens positions which are respective increasing distances away from a first focus lens position 13 The lens system according to claim 10 wherein the detection interval is constant 14 The lens system according to claim 11 wherein when ever the focus lens is shifted to a new position based on the calculated number of focal depths as the amount of shift of the 25 40 45 55 60 65 28 focus lens the focus lens shift calculation circuitry calculates an amount of shift of the focus lens corresponding to the new position 15 A focus control method comprising calculating using processing circuitry a number of in detection range focal depths as a number o
58. itivity and the like This is a factor that decreases the accuracy in detection of the in focus position Specifically in accordance with the shift direction in the case of practical detection as the focus lens is sequentially shifted for each detection interval the amount of change in contrast is changed to increase Accordingly since the differ ences among detected values of the respective detection posi tions increases it becomes difficult to perform interpolation calculation for obtaining for example the position at which the contrast becomes the maximum at a high accuracy As a result it becomes difficult to obtain a desirable in focus state In addition in a case of adopting a configuration in which the detection interval is changed such a problem tends to arise when the detection interval is changed to be large The invention has been made in view of the above situation and addresses the issue of making constant the amount of change in contrast of each detection interval at time of setting the detection interval in the detection range According to a first embodiment of the invention a focus control device including an in detection range focal depth number calculation section that calculates the number of in detection range focal depths as the number of focal depths which are divided as division units and each of which depends on a position of a focus lens in accordance with a detection range in which the focus lens is shi
59. ivity table 310 from the interchangeable lens 200 is performed The focus sensi tivity table 310 has a 3D table structure as shown in FIG 9 and the data size is considerably large Hence the communi cation processing load increases and thus the speed of the autofocus control decreases Therefore in the embodiment of the invention from the image capturing apparatus 100 side the instruction to shift the focus lens 221 is issued on the based on the number of in detection interval focal depths n thereby obtaining the amount of lens shift Mv corresponding to the number of in detection interval focal depths n in the interchangeable lens 200 Thereby it becomes unnecessary to transmit or receive the focus sensitivity table 310 or information with a large data size substituted therefor between the image captur ing apparatus 100 and the interchangeable lens 200 For example as described above for the autofocus control in the embodiment of the invention the information which is input from the interchangeable lens 200 to the image capturing apparatus 100 includes the focal length f the nearest in focus distance the farthest in focus distance and the aperture value F When such information is transmitted and received it is possible to considerably reduce the communication load MODIFIED EXAMPLES Subsequently modified examples according to embodiment of the invention will be described In the first embodiment the detection range w
60. lane Yr and is imaged as a point However when the image plane becomes far from the imaging plane Yr the image of the light is formed as a circle This circle is the circle of confusion and the maximum circle of confusion which can be regarded as being in focus state as viewed by the human eye is referred to as the maximum permissible circle of confusion The diameter of the maximum permissible circle of confusion is the circle of confusion diameter limit The distance from the image plane Yr to the position cor responding to the maximum permissible circle of confusion is referred to as the focal depth d In addition the drawing shows the rear side focal depth which is on the rear side of the image plane Yr relative to the rear side principal point Hr However actually the front side focal depth is also present on the front side of the image plane Yr as a reference position Generally sometimes the distance of the front side focal depth and the US 8 724 982 B2 15 distance of the rear side focal depth are adjusted to each other and the adjusted distance may be referred to as the focal depth However in the embodiment of the invention for example only one front side or rear side focal depth is treated as the focal depth d Then in the embodiment of the invention first at the time of quantifying the detection range it is assumed that the distance as the focal depth d shown in FIG 6B is treated as a single unit Moreover
61. le when the shutter button 121 is pressed halfway the autofocus control and automatic control most appropriate for image capturing are performed Further when the shutter button 121 is pressed fully the data of image which is cap tured at the time of the full press operation through the auto focus control and automatic control most appropriate for image capturing is stored in the storage device 116 The mode dial 122 is a dial for setting the respective modes For example a bracket imaging mode an image display mode for displaying the image stored in the storage device 116 and the like are set by the operation of the mode dial 122 The up down right left operation button 123 is an opera tion button that is used when an item such as a button or an image displayed on the display section 115 is selected and moves the currently selected item corresponding to the pressed portion in directions of up down right and left The determination button 124 is a button that is used when the selection state of the respective items displayed on the display section 115 is confirmed The cancel button 125 is a button that is used to release the confirmation when the selec tion state of the respective items displayed on the display section 115 was confirmed The power switch 126 is a switch that changes the ON OFF state of the power to the image capturing apparatus 100 Further in the image capturing system 10 a zoom opera tion is performed by us
62. ly sufficient to set the minimum detection interval Accordingly in the embodiment of the invention in order to cope with such an abnormal operation a restriction is imposed on the number of times the focus search is executed in the following manner If it is determined in step S902 that the current variable m is the maximum value even when the focus search is executed a certain number of times or more the minimum detection interval is not yet set Therefore in this case the detection interval determination section 134 sets the number of in detection interval focal depths n to 5 through the detection interval determination process step S926 Thereby at the end stage of the focus search currently executed in step S909 of FIG 10 it is determined that the focus search is executed on the basis of the minimum detection interval That is the current focus search is regarded as the final focus search As described above in the embodiment of the invention the restriction is imposed on the number of times the focus search is executed Thereby the focus search is uselessly repeated a certain number of times or more and thus it is possible to make the maximum time necessary for the focus control be within a certain range In contrast if it is determined in step S921 that the variable m is not the maximum value normal detection interval deter mination process is executed Hence the detection interval determination section 134 refers
63. mes the instruction to shift the focus lens is also issued by specifying the focus lens position as the in focus position Next the interchangeable lens 200 includes a focus lens shift calculation section 251 a focus lens drive control section 252 and a reference table section 253 Such respective func tional sections are implemented by causing the lens control section CPU 250 shown in FIG 1 to execute programs Further the interchangeable lens 200 stores a focus sensitiv ity table 310 an in focus distance table 320 and a focal length table 330 These tables are stored in ROM 260 for example at the time of manufacture corresponding to FIG 1 Further the interchangeable lens 200 retains zoom position informa tion 341 focus lens position information 342 and aperture value information 343 Such information is updated in accor dance with the positions and the states of the zoom lens 211 the focus lens 221 and the diaphragm mechanism 231 in practical use and is retained in RAM 270 corresponding to FIG 1 The focus lens shift calculation section 251 is a section that calculates the physical amount of shift of the focus lens cor responding to the detection interval which is specified by the image capturing apparatus 100 the focus lens shift instruc tion section 135 In the embodiment of the invention the detection interval which is specified by the image capturing apparatus 100 is represented by the number of focal depths
64. ng apparatus 100 Further as the storage device 116 it is possible to use various media such as a semiconductor memory an optical recording medium a magnetic disk and a HDD Hard Disk Drive In addition as the optical recording medium it is possible to use for example a recordable DVD Digital Versatile Disc recordable CD Compact Disc a BD Blu ray Disc regis tered trademark and the like The vertical driver 117 is a section that drives the imaging element 111 on the basis of the control of the control section 130 The timing generator 118 is a section that gives an instruction of timings for respectively operating the analog signal processing section 112 and the A D conversion section 113 on the basis of the reference clock which is supplied from the control section 130 Specifically the instruction of the operation timing is performed for example by outputting the timing signal generated on the basis of the reference clock to the analog signal processing section 112 and the A D conver sion section 113 The operation section 120 is an operation section that has operation members such as buttons and switches for per forming various operations so as to receive an operation input from a user and outputs the contents of the received operation input to the control section 130 through the system bus 101 In addition by providing not only the operation members such as the buttons which are disposed on the exterior surface of
65. ns The nearest in focus distance means the shortest distance in the range of the distance from the subject which can be in focus Further the farthest in focus distance means the longest distance in the range of the distance from the subject which can be in focus The nearest in focus distance and the farthest in focus distance are changed in accordance with the zoom position Hence as described above the in focus distance table 320 is a table in which the in focus distances are associated with the zoom positions Z The focal length fis also changed in accordance with the zoom position Z The focal length table 330 is a table having a structure in which the focal lengths of the optical system in the interchangeable lens 200 are associated with the zoom positions Z The reference table section 253 is a section that refers to the in focus distance table 320 and the focal length table 330 That is the reference table section 253 selects and outputs from the in focus distance table 320 the in focus distances the nearest in focus distance and the farthest in focus dis tance which can be associated with the zoom position Z indicated by the zoom position information 341 Further the reference table section 253 selects and outputs from the focal length table 330 the focal length f which can be associated with the zoom position Z indicated by the zoom position information 341 0 pak 5 35 40 45 14 Calculation Example
66. ocus lighting a flash and the like Further for example at the time of capturing an image the control section 130 gen erates the control signal on the basis of the user s operation input from the operation section 120 and the image informa tion from the digital signal processing section 114 Then the generated control signal is output to the motor driver 240 the vertical driver 117 the timing generator 118 and the like so as to operate the focus lens 221 the diaphragm mechanism 231 and the like thereby controlling exposure white balance focus the flash and the like Further in a case of storing the image data on which the digital signal processing section 114 performs the image pro cessing the control section 130 outputs the control signal to the digital signal processing section 114 on the basis of the user s operation input from the operation section 120 Then the image data on which the digital signal processing section 114 performs the compression process is stored as a still image file in the storage device 116 Further in a case of displaying the still image file stored in the storage device 116 the control section 130 outputs the control signal to the digital signal processing section 114 on the basis of the user s opera tion input from the operation section 120 Then an image corresponding to the still image file stored in the storage device 116 is displayed on the display section 115 The detection section 170
67. of Number of In Detection Range Focal Depths First referring to FIG 5 a description will be given ofthe concept of the number of in detection range focal depths in the embodiment of the invention FIG 5 shows a detection range from a certain focus lens position P0 to P5 Here at the focus lens position the focal depth is d0 Accordingly the focus lens is shifted to the focus lens position P1 at a distance of the focal depth 40 away from the focus lens position The focal depth is changed in accordance with the focus lens position Here at the focus lens position P1 the focal depth is 41 larger than 90 Therefore the focus lens is shifted to the focus lens position P2 at a distance ofthe focal depth d1 away from the focus lens position P1 Thereafter likewise the focus lens is sequentially shifted to each of the focus lens positions P2 to P4 by each of the focal depths d2 to d4 As a result in FIG 5 the detection range is divided into five sections of the section from the focus lens position 0 to P1 the section from P1 to P2 the section from P2 to P3 the section from P3 to P4 and the section from P4 to P5 That is the detection range shown in FIG 5 is divided into five sections when the focal depths are treated as division units and thus corresponds to five focal depths Thus in FIG 5 the number of in detection range focal depths N is 5 Subsequently the method of calculating the number of in detection range fo
68. on section 135 determines whether or not the operation of the current focus search is based on the minimum detection interval step S909 The minimum detection interval corresponds to the minimum of the number of in detection interval focal depths n which can be determined Specifically on the basis of the detection interval table 182 shown in FIG 7 the number of in detection interval focal depths n corresponding to the minimum detection interval is 15 First if it is determined in step S909 that the focus search based on the detection interval which is larger than the mini mum detection interval the process from step S903 is executed again That is the focus search is executed again However in and after the second focus search the detection range determination section 132 executes the following pro cess as step S903 That is the in focus position which is calculated in step S908 on the basis of the previous focus search is set as a reference the center ofthe detection range In addition the detection range is set to be smaller than the previous detection range According to this as the focus search is repeated again and again it 1s possible to stepwise decrease even the detection interval which is determined by the detection interval determination process of step S920 Then when it was possible to obtain the determination result that the focus search is executed on the basis of the minimum detection interval in step S909 the
69. on the basis of the control of the lens control section 250 The lens control section 250 controls the respective sec tions the focus lens 221 the diaphragm mechanism 231 and the like constituting the interchangeable lens 200 The lens control section 250 is constituted by for example a CPU Central Processing Unit The ROM 260 is a section that stores unique information which relates to the respective members constituting the interchangeable lens 200 a program which will be executed in the CPU as the lens control section 250 and the like The RAM 270 is a section that is used as a work area when the lens control section 250 executes calculation processing The interface section 201 is a section that is for communicating with the image capturing apparatus 100 Next the image capturing apparatus 100 includes a system bus 101 animaging element 111 an analog signal processing section 112 and an A D Analog Digital conversion section 113 Further the image capturing apparatus 100 includes a digital signal processing section 114 a display section 115 and a storage device 116 Further the image capturing appa ratus 100 includes a vertical driver 117 a timing generator 118 an operation section 120 and a control section 130 Further the image capturing apparatus 100 includes a memory EEPROM Electrically Erasable and Program mable Read Only Memory 140 a memory ROM Read Only Memory 150 and a memory RAM Random Access M
70. ransitory computer readable storage medium storing computer readable instructions that when executed by a computer cause the computer to perform a method comprising communicating with a main body of an image capturing apparatus in a state where communication circuitry is mounted to the main body of the image capturing appa ratus calculating using circuitry a number of focal depths which represents a detection interval as an amount of shift of a focus lens in response to receiving an instruc tion to shift the focus lens from the main body of the image capturing apparatus by specifying a detection range in which the focus lens is shifted to detect a contrast of a captured image signal and the detection interval represented by the number of focal depths which are division units of the detection range and each of which is based on a corresponding position of the focus lens and shifting using the circuitry the focus lens based on the calculated number of focal depths as the amount of shift of the focus lens a 5 20 30
71. rms the drive control of the focus lens 221 according to the focus search at the time of the autofocus control For example the focus lens drive control section 252 drives the focus lens 221 to shift on the basis of the amount of lens shift Mv corresponding to the detection interval Further when the in focus position is des ignated the focus lens 221 is driven to shift to the in focus position Further as the aperture value is set in accordance with the user operation or the exposure control the focus lens drive control section 252 sets the aperture size of the diaphragm corresponding to the aperture value which is set by driving the diaphragm mechanism 231 Further the focus lens drive control section 252 detects the focus lens position whenever driving the focus lens 221 and updates the focus lens position information 342 In the embodiment of the invention the zoom position of the zoom lens 211 is configured to be manually changed The zoom position information 341 is updated whenever the zoom position is manually changed in such a manner As described above the zoom position is detected by the zoom position detection section 212 of FIG 1 The in focus distance table 320 is a table having a structure in which the combinations of the in focus distances the near est in focus distance and the farthest in focus distance are associated with the zoom positions Z The in focus distance is one of characteristics relating to the focus le
72. s shift Mv thereby acquiring the focus sensi tivity e corresponding to the current state ofthe optical system from the focus sensitivity table 310 FIG 9 shows an exemplary structure ofthe focus sensitiv ity table 310 As shown in the drawing the focus sensitivity table 310 has the structure of a 3D table in which one focus sensitivity is contained for each combination of the focal length f the aperture value F and the focus lens position P The focus sensitivity e represents the ratio ofthe amount of shift ofthe imaging plane the imaging position to the physi cal amount of shift of the focus lens As a specific example when the focus lens is shift from a certain lens position in the direction of the optical axis by 10 um the amount of shift of 20 35 40 45 65 18 the imaging plane is 1 um In this case the focus sensitivity is 0 1 That is the focus sensitivity is represented by the expression that e the amount of shift ofthe imaging plane the amount of shift of the focus lens The focus sensitivity e is changed in accordance with the focal length f Further the focus sensitivity e is changed in accordance with the aperture value F Moreover the focus sensitivity e is changed in accordance with the focus lens position P That is a single value of the focus sensitivity depends on the combination ofthe focal length f the aperture value F and the focus lens position P as the current state ofthe opt
73. shifted to the next detection position at a distance which corresponds to the number of focal depths n away from the current detection position US 8 724 982 B2 19 The focus lens drive control section 252 shifts the focus lens 221 by the amount of lens shift Mv which is newly calculated as described above Thereby the focus lens 221 is shifted to the next focus lens position the detection position at a distance corresponding to the number of in detection interval focal depths n away from the current focus lens position the detection position In addition the amount of lens shift Mv can be more accurately obtained That is first the amount of shift of the focus lens Mv1 necessary to shift the image plane by the focal depth d corresponding to the current focus lens position is obtained Next the shift amount Mv2 is obtained at the focus lens position P1 to which the focus lens is shifted from the focus lens position by the shift amount Mv1 Thereafter likewise the amount of shift of the focus lens Mvn which is necessary to shift the image plane by the focal depth d at the position to which the focus lens is shifted by a single focal depth each time is calculated and this calculation is repeated the number of times corresponding to the number of in detection interval focal depths n Thereby it is possible to obtain n shift amounts Mv1 to Mvn corresponding to the number of in detection interval focal depths n Then by
74. tection interval information in which the in detection range focal depths are associated with the in detection interval focal depths to determine the number of in detection interval focal depths corresponding to the detec tion interval 6 The focus control device according to claim 1 further comprising communication circuitry that communicates with the lens circuitry in a state where the lens circuitry is remov ably coupled to a main body of the focus control device 7 The focus control device according to claim 1 further comprising circuitry configured to store a reference table including US 8 724 982 B2 27 an in focus distance table portion in which combinations of in focus distances which include a nearest in focus dis tance and a farthest in focus distance are associated with corresponding zoom positions and a focal length table portion in which focal lengths of the focus control device are associated with corresponding zoom positions 8 The focus control device according to claim 1 wherein the detection interval table includes non overlapping ranges of the in detection range focal depths corresponding to respective numbers of in detection interval focal depths the number of in detection interval focal depths of the detection interval table increasing in correspondence with increasing different values of the respective non overlapping ranges of the in detection range focal depths of the detection interval table 9
75. trast of the cap tured image signal is measured detected while shifting a focus lens Then by shifting the focus lens to a position at which the measured contrast becomes the maximum it is possible to obtain a state in focus state in which a subject is brought into focus In a practical contrast mode the contrast is not continu ously detected from a detection range in which the focus lens is shifted but a plurality of detected values is obtained by performing detection at a plurality of detection positions which are separated from each other with intervals Then from such detected values a focus lens position at which the contrast becomes the maximum is obtained In such a manner in the contrast mode a predetermined interval a detection interval is provided for each detection position in the detection range As the detection interval increases the number of detection positions in the detection range decreases Therefore the time necessary to detect the entire detection range decreases However as the detection interval increases the amount of change in contrast for each detection position becomes large Hence the accuracy in detection of the position at which the contrast becomes the maximum becomes low In contrast when the detection interval becomes narrow the amount of change in contrast for each detection position becomes small Thus the accuracy in detection of the position at which the contrast becomes the maximum
76. um ber of focal depths The detection interval determination section 134 refers to the detection interval table 182 at the time of determining the detection interval One specific example of the detection interval table 182 is shown in FIG 7 In the detection interval table 182 shown in the drawing the range of the number of in detection range focal depths N is classified into 0 lt lt 20 20sN lt 100 and Ns100 In addition it is possible to respectively associate the ranges of the number of in detec tion range focal depths with 5 15 and 25 as the num bers of in detection interval focal depths n The detection interval determination section 134 selects from the detection interval table 182 the number of in detec tion interval focal depths n which can be associated with the number of in detection range focal depths N calculated by the in detection range focal depth number calculation section 133 For example the number of in detection range focal depths N of 50 is included in the range of 20sN lt 100 Therefore as the number of in detection interval focal depths n 15 which can be associated with the range is selected As described above by selecting the number of in detection interval focal depths n the detection interval is determined In such a manner the detection interval determination section US 8 724 982 B2 17 134 changes and sets the detection interval in accordance with the
77. ured image signal and the detection interval represented by the number of focal depths which are division units of the detection range and each of which is based on a corresponding position of the focus lens and shifting using the circuitry the focus lens based on the calculated number of focal depths as the amount of shift of the focus lens 17 A non transitory computer readable storage medium storing computer readable instructions that when executed by a computer cause the computer to perform a method comprising calculating a number of in detection range focal depths as a number of focal depths which are divided as division units and each of which is based on a corresponding position of a focus lens in accordance with a detection range in which the focus lens is shifted to detect a con trast of a captured image signal determining a number of in detection interval focal depths which represents the number of focal depths as the division units as a detection interval in a detection range based on the calculated number of in detection range focal depths as compared to a plurality of prede termined ranges of in detection range focal depths of a detection interval table stored in memory and instructing lens circuitry to perform a focus search which shifts the focus lens by specifying the detection range and the number of in detection interval focal depths determined as the detection interval US 8 724 982 B2 29 18 A non t
78. ving the instruction of the timing generator 118 The analog signal which is subjected to the analog signal processing in the analog signal processing section 112 is supplied to the A D conversion section 113 The A D conversion section 113 converts the analog signal which is supplied from the analog signal processing section 112 into a digital signal at the timing of receiving the instruc tion of the timing generator 118 and supplies the converted digital signal to the digital signal processing section 114 US 8 724 982 B2 7 The digital signal processing section 114 performs image processing such as black level correction white balance adjustment and y correction on the digital signal which is supplied from the A D conversion section 113 on the basis of the control of the control section 130 Then the digital signal processing section 114 supplies the image data which is subjected to the image processing to the display section 115 and the storage device 116 For example the digital signal processing section 114 performs a compression process on the image data subjected to the image processing and sup plies the image data the compressed image data subjected to the compression process to the storage device 116 In addi tion as a compression format it is possible to employ for example the JPEG Joint Photographic Experts Group for mat Further it is also possible to supply image data based on a RAW data format on whic

Focus control device, focus control method, lens system, focus lens

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