CS-100 manual
Contents
1. 27 Interface Operation If required data may be read back after each step by including a after each PO above RS232C or performing a read operation IEEE 488 Setting Parallelism The etalon parallelism may be set in the same way as setting Z Thus 12800P1PO lt CR gt Set Y PARALLELISM to 2048 HFFFP1PO lt CR gt Set X PARALLELISM to 1 l0 lt CR gt Close all latches Setting Response Time The response time may be chosen by setting individual bits of port N This function is enabled by clearing bit Ob to zero For example O D lt CR gt Disable local control enable external control N1 lt CR gt Set 0 2ms response time While bit Ob is zero the 0 2ms response time selected will be active Setting bit Ob to 1 again will enable the front panel controls and the response time will be as set by the RESPONSE TIME switch O 2 lt CR gt Enable local control disable external control Selecting response times via the interface with the front panel controls disabled front panel DISABLED indicator illuminated gives the possibility of choosing longer response times than are available from the front panel If more than one bit is set two or more response times can be selected and the result will be the sum of the individual responses Thus O DNC lt CR gt Selects 2 0ms 1 0ms e 3 0ms Selecting zero response time will result in an OUT OF RANGE indication and the CS100 will enter BALANCE mode Changing Mode2. Figure 2 3 CS100 Installation Drawing ET Series Il Etalons Chapter 3 ET Series Il Etalons This chapter describes the IC Optical Systems ET Series II Fabry Perot etalons and accessories General Description The standard ET range of fused silica FS etalons have clear apertures between 28mm and 140mm with matched surface qualities of 1 50 A 100 and 1 200 A 633nm before coating ET etalons are available in water free fused silica WF for use in the near infrared The ET28 and ET50 are also available in zinc selenide ZS for use out to 15um wavelength and in crystalline quartz CQ or magnesium fluoride MF for the ultraviolet Imaging The rear surfaces of the etalon mirrors are wedged by nominally 15 minutes of arc Optionally etalons are available with front and rear mirror surfaces polished optically parallel to each other This will eliminate ghost reflections which are displaced from the main image when the etalon is used for two dimensional spectral imaging Glass Reference Capacitor An optional glass reference capacitor is available Fabricated in the style of the gap sensing capacitance micrometers this will reduce the impact of changes in ambient temperature pressure and humidity on the capacitance bridge controlling the cavity spacing The parallelism channels are self compensating This option is available on the ET50 and larger etalons Sealed Cell For applications where the highest possibl
3. STEP 1 num ASC MIDS a 1 1 n 0 Characters A to F IF num gt 65 AND num lt 70 THEN n num 55 Characters a to f IF num gt 97 AND num lt 102 THEN n num 87 t A O Characters 0 9 IF num gt 48 AND num lt 57 THEN n num 48 Accumulate the result n amp 16 n amp n NEXT O n amp is now the integer equivalent of the HEX string HexToNumber amp n amp END FUNCTION RS232C and IEEE 488 Interface Definitions RS232C Interface Characters are transferred on the RS232C interface as 7 bits with odd parity and one stop bit Baud rate is 9600 Parity and baud rate can be selected by internal switches but it is advisable to contact IC 32 Interface Operation Optical Systems if this is required The signals used are shown in Table 5 7 Connector pin number Signal Input or Output 2 TxD Output 3 RxD Input 4 RTS Output 6 DSR Input 7 Ground Table 5 7 RS232 Interface Connector IEEE 488 Interface The IEEE 488 is a Talker Listener without extended address or controller capability The address can be set with an internal switch but it is advisable to contact IC Optical Systems if this is required The interface is supplied set to address 8 The interface recognises EOI as a data terminator but does not assert it during read operations 33 Interface Operation 34
4. 1 OFF MOUNTING HOLES THREADED Ha CE EP EOLI SPALED On PLO A IH TOP AMO BASE PLATES 2 Model Clear Aperture Diameter D Height H Mounting PCD M ET28 28 100 60 66 ET50 50 125 67 86 ET70 70 153 75 120 ET100 100 170 100 142 ET116 116 194 112 151 All dimensions in mm for guidance only Figure 3 1 ET Series II Mechanical Interfaces standard cells only 11 ET Series Il Etalons Electrical CONNECTORS Station Type Purpose Comments 1 LEMO ERA 1S 305 CLL BRIDGE DRIVES PINS1 2 3 4 2 LEMO ERA 00 250 CTL Y ERROR SIGNAL 2 LEMO ERA 00 250 CTL X ERROR SIGNAL 2 LEMO ERA 00 250 CTL__ Z ERROR SIGNAL 3 KUHNKE 50 704 GAS CONNECTOR 4 LEMO EGJ 2B 306 CLA PIEZO DRIVES Figure 3 2 Etalon Plug Block and Electrical Connections Care of Etalon Store the etalon in the instrument case provided when not in use Always keep in a clean dry environment Avoiding Condensation In preparing for use allow time for the etalon to reach ambient temperature This is particularly important to prevent condensation forming on the mirrors and to minimize distortions of the mirror surfaces due to temperature gradients in the glass Typically an ET28 or ET50 will require 1 hour to stabilize whereas an ET140 could take up to 6 hours 12 ET Series Il Etalons To prevent condensation forming when taking an etalon from a cold to
5. Null the meters exactly using the QUADRATURE BALANCE controls and verify that the plates are still aligned Turn the METER DISPLAY back to OFFSET The meters will not now read zero but will give an indication of how much correction is being applied in the three axes to achieve parallelism at the spacing required to transmit the fringe used for alignment Usually the X and Y meters will read O plus or minus 5V and the Z meter O plus or minus 2V Record the PARALLELISM and SPACING control settings and QUADRATURE BALANCE settings for future reference The etalon plates are now aligned parallel and will remain so while the CS100 is switched on To switch off gt gt Turn the MODE switch to BALANCE POWER to off When the system is to be used again with a given etalon ensure that the PARALLELISM SPACING and QUADRATURE BALANCE 17 Getting Started Response Time controls are as recorded for that etalon turn on power and set MODE from BALANCE to OPERATE The OPERATE indicator will illuminate and the etalon will be parallel as before It should be noted of course that this simple procedure will only work for etalons that are coated for use in the visible part of the spectrum It may not be possible to see any fringes at all with some ultra violet or infrared etalons For these etalons the users optical system and detector must be employed and the parallelism adjusted for minimum transmission peak width If a step i
6. TIME to 0 5ms on the black scale Turn on the power The yellow 15 Getting Started BALANCE indicator will illuminate The red POWER indicator mounted in the POWER switch will also illuminate within about 1 second The three meters may go off scale gt Turn the X COARSE switch to bring the X meter as close to zero as possible Turning the switch clockwise will move the meter needle from left to right Zero the meter using the X FINE 10 turn control gt Repeat using the Y and Z controls observing the Y and Z meters respectively gt Setthe METER DISPLAY switch to QUADRATURE ERROR gt Null the X meter using the X QUADRATURE BALANCE 10 turn control gt Null the Y and Z meters using the Y and Z QUADRATURE BALANCE controls respectively gt Set the METER DISPLAY switch back to OFFSET and re zero them if necessary using the respective COARSE and FINE controls gt Turn the MODE switch from BALANCE to OPERATE The yellow BALANCE indicator should go out and the green OPERATE indicator should come on after a delay of about 2 seconds gt Turn the METER DISPLAY switch to QUADRATURE ERROR and null any offset using the relevant QUADRATURE BALANCE controls gt Turn the METER DISPLAY switch back to OFFSET The meters should all read within about 1V of zero The CS100 is now controlling the etalon in its as supplied state The next procedure aligns the plates to be parallel Aligning the Etalon Using the o
7. The CS100 operating mode can be selected by changing bit Oa This duplicates the action of the front panel MODE switch but is only active when enabled by clearing bit Ob c f setting response time 28 Interface Operation O0 lt CR gt Set OPERATE mode O1 lt CR gt Set BALANCE mode O2 lt CR gt Mode selected by front panel MODE switch O3 lt CR gt Mode selected by front panel MODE switch Reading Status When a read operation is performed on the IEEE 488 interface or read data is requested by sending a character on the RS232C interface four characters are received followed by CR LF carriage return line feed The first character is the bit pattern on port Q which carries status information Bits Qa and Ob are the relevant ones bits Ac and Qd are undefined Bit Level Indication Qa 0 System in BALANCE mode Qa 1 System in OPERATE mode Qb 0 OUT OF RANGE indication Qb 1 Not out of range Table 5 6 Status Indication If an OUT OF RANGE state is indicated the system will have automatically entered BALANCE mode Reading Z Spacing The second third and fourth characters received during a read operation represent the bit pattern on ports R S and T This will be the same as the last word written to the Z Buffer but with the most significant bit Rd inverted Thus if Z had been set to 7FF the readback would be FFF Software Examples The program examples given here are written in MicroS
8. interface the character is sent Thus lt CR gt Causes four characters followed by a lt CR gt and LF to be transmitted from the CS100 to the users computer To read back this data from the IEEE 488 interface an interface read operation is performed If the LF character is not required at the end of the data a character may be transmitted as part of the initialisation sequence This is only valid for the IEEE 488 interface Note Although the IEEE 488 interface recognises EOI asserted with the last character sent to it as a data terminator it does NOT assert EOI when it sends data back to the computer The computer interface must therefore be set up to recognise Carriage Return or Carriage Return plus Line Feed as a data terminator Controlling the CS100 Port Functions The function of the various port bits is shown in Table 5 4 below 25 Interface Operation Bit Read Write Function ld Write Not used Ic Open Z buffer Ib Open Y buffer la Open X buffer Jd Write MSB Jc Jb Ja Kd Write Kc Write Data Word Kb Ka Ld Write Lc Lb La LSB Md Write Mc Not used Mb Ma Nd Write Select 2 0ms Response Time Nc Select 1 0ms Response Time Nb Select 0 5ms Response Time Na Select 0 2ms Response Time Od Write Not used Oc Ob Set LOCAL operation Oa Set OPERATE mode Pd W
9. 1 0 130 2 0 90 Table 4 1 Response Time and RMS noise It will be observed that it is possible to set a response time of 0 1ms using an infrared etalon with long range PZTs This response time Getting Started is not recommended however as the servo control loop may become unstable resulting in an audible oscillation from the etalon Such oscillation will result in the OUT OF RANGE indicator lighting and the system reverting to BALANCE mode To return to OPERATE mode gt Select a longer response time gt Turn the MODE switch from OPERATE to BALANCE and back to OPERATE CONTROL ET SERIES ETALON COMPUTER BRIDGE DRIVES ERROR IEEESSS OR SIGNALS zz RS2RC PIEZ INTERFACE Fe sinn E MIS ALIGNED FRINGES AUGNED Figure 4 1 Aligning the Etalon 19 Getting Started 20 Interface Operation Chapter 5 Interface Operation This section describes the operation and use of the CS100 RS232C and IEEE 488 interfaces Only one of the above interfaces specified at the time of purchase is incorporated in the CS100 The protocol for CS100 operation is similar for both interfaces Controllable Functions Write Operations Table 6 1 shows the functions that can be controlled by writing to the interface their argument ranges and equivalent function ranges The commands that have to be issued to implement these functions are detailed in the section entitled Controll
10. RANGE 0 2msec 0 1msec 0 5msec 0 2msec 1 0msec 0 5msec 2 0msec 1 0msec Table 2 1 Response Time for Standard and Long Range PZTs STANDARD LONG RANGE gt 1600nm msec gt 1600nm msec Table 2 2 Slew Rate for Standard and Long Range PZTs Interfaces Interface range and resolution are shown in Table 2 3 A full description of the use of interfaces are given in Chapter Parameter Value Range 1000nm Resolution 12 bits 0 49nm Non linearity of scan 0 05 Accuracy 0 5 Isb when calibrated Table 2 3 X Y and Z Interface Control Range and Resolution The CS100 Controller Drift and Noise Z Modulation Parameter Value Range 1000nm for 10V differential input Non linearity 1 Frequency Response dc to limit set by RESPONSE TIME see Table 3 5 Table 2 4 Z Modulation Specifications Response Time ms Frequency Response Hz 3dB point 0 2 800 0 5 320 1 0 160 2 0 80 Table 2 5 Response Time vs Frequency Response All displacements refer to relative etalon plate movement Parameter Value Noise Equivalent Displacement lt 10 pm Hz Temperature Coefficient 0 50 pm K Table 2 6 Electronic Noise and Temperature Coefficient of the Cavity The CS100 Controller Installation A schematic diagram of the CS100 is shown in Figure 2 3 520mm 153mm
11. User s Guide CS100 Controller and ET Series II Servo stabilized Interferometer System G O S 190 192 Ravenscroft Road Beckenham Kent BR3 4TW Tel 020 8778 5094 Fax 020 8676 9816 www icopticalsystems com Ce Electromagnetic Compatibility The CS100 Fabry Perot Etalon Control System conforms with the protection requirements of Council Directive 89 336 EEC relating to Electromagnetic Compatibility emissions by the application of the following EMC Standard BS EN 50081 1 1992 Emissions Standard Residential commercial and light industrial Class B level The CS100 relies for its operation on the detection of very small signals from its capacitance bridge As such exposure to interference fields as defined in BS EN 50082 1 1992 Immunity Standard Residential commercial and light industrial may cause the CS100 to revert from OPERATE to BALANCE mode Correct operation can be restored after removal of the field by switching to BALANCE and back to OPERATE and if required resetting the X Y and Z interface registers Immunity can be improved by use of extra shielding around the etalon cables Please consult IC Optical Systems for advice on use of the CS100 in high interference field environments Contents Chapter 1 Introduction What is the ET etalon System Operating E Drift and Noise Installation Introduction Chapter 1 Introduction This User s Guide describes the operation and use
12. a warm environment it is advisable to seal it in a plastic bag until it has reached ambient temperature Should condensation form on the front or rear surfaces of the mirrors allow it to disperse naturally as the system reaches ambient temperature Under no circumstances should condensation be wiped away as this may damage the optical coatings Cleaning Dust can be removed from the outer surfaces of the etalon with a filtered air blower Under no circumstances should the outer surfaces be wiped clean Stubborn dust particles may be removed with the corner of a folded lens tissue but do not wipe Solvents and other liquid cleaners must not be used under any circumstances The antireflection coatings on the outer surfaces of the sealed cell windows are durable and can be cleaned with a soft brush or a lens tissue slightly moistened in isopropyl alcohol ET Series Il Etalons Getting Started Chapter 4 Getting Started Connect the etalon to the CS100 rear panel connectors using the cable loom provided Take care when connecting the X Y and Z ERROR SIGNALS the connectors used for the three channels are identical so it is possible to cross over these connections Faulty connection of the error signals will do no damage but the system will not work correctly The capacitance micrometers are very sensitive and can be upset by electromagnetic interference It is good practice to route the etalon connection cables away fro
13. contained in Chapter 5 Z Modulation A two pin socket is provided on the CS100 rear panel to enable analogue control of the etalon spacing A plus or minus 10V differential input will produce plus or minus 1000nm of plate movement for standard ET Series Il etalons This input is intended for modulation of the etalon plate spacing for applications that 3 The CS100 Controller require differentiation of the transmitted line profile etc It is not intended as the prime means of scanning the etalon as the linearity is poor compared to that available from the RS232C or IEEE 488 interface It can of course be used for scanning if the non linearity can be tolerated Protection System will enter BALANCE mode and indicate OUT OF RANGE within 0 55 when driven out of range of the piezo electric transducers or when an oscillatory RESPONSE TIME is set Control Indicator Comments A PARALLELISM Fine 10 turn pot X amp Y B PARALLELISM Coarse switch X 8 Y C SPACING Fine Z D SPACING Coarse Z E QUADRATURE BALANCE X Y amp Z F RESPONSE TIME G BALANCE OPERATE Indicators show status H METER DISPLAY Selects Quad error offset l POWER With indicator J OUT OF RANGE Indicates X Y or Z bridges out of range K DISABLED Front panel controls disabled via interface Figure 2 1 CS100 Front Panel The CS100 Controller Specification CONNECTORS Type Purpo
14. e stability is required the ET Series Il etalon is available mounted in a sealed cell with high efficiency anti reflection coated windows This eliminates the impact of changes in environmental pressure and humidity on both the Capacitance micrometers and on the optical cavity length With a sealed cell the cavity can be stabilized to 1 part in 5 10 corresponding to a transmitted wavelength stability 10MHz ET Series ll Etalons Specification Installation Parameter Value Clear Aperture mm 28 50 70 85 100 116 150 Surface Quality 21 50 4 200 defined at 633nm Wedge Angle Zero 1 fringe or 10 15 arcmin nominal Mirror Spacing Specified by user in range 3um to 30mm Coatings User Specified Cavity Tuning Range 3um nominal gt 6um optional Operational Temperature Range 10 40C Storage Temperature Range 20C to 70C non condensing Response Time when used with CS100 Controller 0 2ms 2 0ms Table 3 1 ET Series II Etalon Specifications Mechanical Figure 3 1 shows a drawing for the ET Series Il etalon Tapped holes are provided in the cell end plates for mounting Use of Gas Connector A connector is provided with standard ET Series Il etalons to allow the user to flush the etalon with a dry gas such as oxygen free nitrogen to minimize the effects of changes of ambient humidity on the capacitance micrometers ET Series Il Etalons
15. inator The Carriage Return is not then required Thus 11 lt CR gt Sets port to 1 NO lt CR gt Sets port N to O If a contiguous sequence of ports is to be set only the first port designator need be transmitted Thus J12F lt CR gt SetsportJto1 Kto2 LtoF Commands and data can be combined into strings up to 31 characters long for example of a longer string I700010 lt CR gt Sets port to 7 J K and L to O and then to 0 To set or clear individual bits of a port the OR and AND functions can be used For example 1 lt CR gt Sets bit la to 1 and leaves the other bits unchanged O 3 lt CR gt Sets bits Oa and Ob to 1 and leaves the other bits unchanged 24 Interface Operation E lt CR gt Clears bit la to O leaving the others unchanged WARNING Do not write to the read ports Q to T This will set them to be write ports with unpredictable results Reading from a Port Ports Q R S and T are used to read back data from the CS100 These are set by default to be read ports but it is good practice to initialise them in the software This is done using the character for an RS232C interface or character for an IEEE 488 interface IQT lt CR gt Define read ports Q to T RS232C QT lt CR gt Define read ports Qto T IEEE 488 This initialisation sequence need only be performed once on CS100 power up or after pressing the CS100 rear panel Interface Reset switch To read back data from the RS232C
16. ing the CS100 The function ranges for the X and Y PARALLELISM and Z SPACING is given in nanometers nm of etalon plate movement the wavelength scan range corresponding to the Z SPACING range will depend on the absolute etalon plate spacing Function No of Bits Argument Range Function Range X Parallelism 12 2048 to 2047 1000nm Y Parallelism 12 2048 to 2047 1000nm Z Spacing 12 2048 to 2047 1000nm Response time 4 0 2ms 0 5ms 1 0ms 2 0ms Mode 1 0 1 BALANCE OPERATE Enable 1 0 1 ENABLE DISABLE Table 5 1Available Write Operations Read Operations The information that can be read back via the interface is shown in table 5 2 Function No of Bits Numeric Range Function Range Z Spacing 12 0 to 4095 1000nm Status 2 Mode out of range Table 5 2 Available Read Functions The Z SPACING word read back is the same as the Z SPACING word previously written to the interface offset by 2048 and can be used as an optional check of correct write read operation during 21 Interface Operation scans If Z SPACING is set as 2048 the read back will be 0 A written Z SPACING of 2047 will give a read back of 4095 The STATUS word contains two bits one indicating the current operation mode of the CS100 the other indicating an OUT OF RANGE state caused by setting too fast a response time or requesting too large a spacing change Communicating wi
17. latest models in a system which was first introduced in 1979 This guide describes CS100 systems with serial numbers 8035 and greater ET Series Il etalons with serial numbers of 879 or greater Introduction All CS100s and etalons are inter compatible using adapter cables available from IC Optical Systems Operating Principles The arrangement of capacitance sensors and piezoelectric PZT actuators to be found in ET and EC series etalons is shown schematically in Three piezo electric actuators a b c are used to tune the cavity while the capacitance sensors Cx Cy etc fabricated onto the mirror surface are used to sense changes in parallelism and cavity length Parallelism information is obtained by comparing Cx with Cx2 X channel and Cy with Cy gt Y channel Cavity length control is achieved by referencing Cz to a stable fixed reference capacitor Z channel al LU 1 Sr T a connector block Figure 1 1 Etalon Schematic The X and Y capacitance bridges can be un balanced by means of the front panel controls or the interface to compensate for differences in micrometer capacitor values when the plates are parallel Varying the balance will cause the plates to tilt so they can be accurately aligned Similarly the Z channel can be un balanced causing the plate spacing to vary enabling the etalon to be tuned to a particular wavelength The CS100 Controller Chapter 2 The CS100 Cont
18. m interference sources such as computer monitors and the RS232C or IEEE 488 interface cable Electromagnetic interference will cause the etalon plates to wobble resulting in movement of the fringes and modulation of the transmitted light intensity Balancing the Capacitance Bridges As supplied the plates of an ET Series etalon will not be exactly parallel typically there will be a manufacturing error of one or two fringes across the mirror diameter The etalon will be supplied with a table of settings for the CS100 front panel PARALLELISM SPACING and QUADRATURE BALANCE controls When these settings are used the etalon should be aligned parallel and ready for use However ageing effects will cause these settings to change with time and it will be instructive for the user to follow the full alignment procedure Initial optical alignment is best done either by eye for etalons which operate in the visible or using a remote viewer for etalons coated for the infrared There are two procedures to be followed to align the etalon if the settings are not known Once these have been followed a given CS100 etalon system can be switched on and used with no further set up The first procedure balances the capacitance bridges with the etalon in its un parallel as supplied state gt Set up the system as shown in the Figure 5 1 gt Referring to Figure 2 1 set the MODE control to BALANCE the METER DISPLAY switch to OFFSET and the RESPONSE
19. n plate spacing is requested either by turning the Z COARSE front panel control or via the interface the etalon plates cannot respond instantaneously The RESPONSE TIME switch gives some control over the time taken for the plate position to stabilise There are two scales for different types of etalon Etalons designed for use in the visible and ultra violet region of the spectrum will have response times given by the black scale Infrared etalons have higher sensitivity piezo electric actuators which produce a more rapid response from the servo control loop Their response time is given by the blue scale The times quoted are approximate and correspond to the time taken to reach 60 of the demanded step distance The settling time should be taken as three times this value A choice of response times is provided to give some control of the system noise If a rapid response time is selected the system bandwidth is increased and thus the total system noise will be increased Electronic noise will cause the etalon plates to make small amplitude random movements about their mean position which effectively broaden the instrumental profile or modulate the transmitted light Whether or not this is a problem depends on the specific application The following table gives the approximate total RMS noise in pico metres on the etalon plate position as a function of set response time Response Time ms RMS Noise pm 0 2 230 0 5 180
20. nd response time but not for scanning and setting parallelism Numbers are more useful for this but they must be converted into suitable strings for output Also the number must be offset coded These operations are handled by functions OffCode amp n amp and MakeString n amp described in the section Demonstration Subroutines see below To scan Z over the full range FOR n amp 2048 TO 2047 i amp OffCodes n amp Offset code the number aS MakeString i Turn it into a 3 character string aS 14 aS P1P0 Add buffer control characters CALL OutputString a Output the string NEXT n CALL OutputString I0 Close the buffers 30 Interface Operation Setting Parallelism The X and Y registers are set in the same way thus to set X to 1234 and Y to 56 Xvalues 1234 Arbitrary values for demonstration Yvalue amp 56 i amp OffCodes Xvalue amp a MakeString 14 a 11 aS P1PO Add buffer control characters for X CALL OutputString a Output the string i amp OffCodes Yvalues aS MakeString 14 aS 12 aS P1P0 Add buffer control characters for Y CALL OutputString a Output the string CALL OutputString I0 Close the buffers Demonstration Subroutines These are useful routines used in the above examples This one converts an integer into a three digit hex string FUNCTION MakeSt rings n amp Convert to a HEX st
21. of IC Optical Systems ET Series Il ambient temperature etalons with the CS100 control system What is the ET etalon System The servo stabilized Fabry Perot interferometer system comprises ET Series Il etalons and the CS100 control unit which stabilizes the etalon spacing and parallelism How does it work The CS100 is a three channel controller which uses capacitance micrometers and PZT actuators incorporated into the etalon to monitor and correct errors in mirror parallelism and spacing Two channels control the parallelism and the third maintains spacing by referencing the cavity length sensing capacitance micrometer to a fixed reference capacitor Because this is a closed loop system non linearity and hysteresis in the PZT drive are eliminated completely as of course are drifts in mirror parallelism and spacing The CS100 can be operated manually from front panel controls or under computer control using either the IEEE 488 RS232C or analogue interfaces How stable is it The CS100 will control the etalon spacing and parallelism to better than 0 01 of a free spectral range FSR Stability of the transmitted wavelength will depend on the ambient environment and can be as good as 1 part in 10 if the etalon is mounted in a stable environment such as a IC Optical Systems sealed cell which has been temperature stabilized Compatibility with earlier models The CS100 and ET etalons described in this User s Guide are the
22. oft QuickBasic but should be readily adaptable to other languages It is assumed that the user has a routine OutputString a that can transmit a character string a to the interface in use and a function InputString that returns a string read from the interface It is further assumed that if an RS232 interface is used OutputString a appends a carriage return character to a before transmitting it This is not required for an IEEE 488 interface 29 Interface Operation Initialisation This program fragment will set up the read ports zero the X Y and Z buffers and ensure that front panel controls are enabled RS232 CALL OutputString QT Set read ports CALL OutputString P0 Ensure buffers disabled CALL OutputString I7000P1P0 Open X Y and Z buffers set ports J K L to zero latch the data CALL OutputString I0 Close the buffers CALL OutputString 03 Balance mode but front panel has control IEEE 488 CALL OutputString QT Set read ports and inhibit LF transmission CALL OutputString PO Ensure buffers disabled CALL OutputString I7000P1P0 Open X Y and Z buffers set ports J K L to zero latch the data CALL OutputString I0 Close the buffers CALL OutputString 03 Balance mode but front panel has control Scanning Z Sending strings directly is an efficient method for initialisation and setting mode a
23. ptical set up of Figure 5 1 with a suitable spectral lamp or laser plus beam expander straight line fringes should be visible on the screen If the etalon plates are almost parallel the fringe spacing may be too much for a fringe to be visible In this case turn the Z FINE control until a fringe appears When the etalon plates are parallel the fringe will be expanded to fill the whole aperture Getting Started gt Set the METER DISPLAY switch to QUADRATURE ERROR gt Turn the Z FINE control backwards and forwards The fringe should move backwards and forwards in a_ direction perpendicular to its length Turn the X COARSE and FINE controls until the movement observed above is predominately along the Y axis For a definition of axis orientations see Fig 1 1 While doing this keep the meters within a couple of volts of zero using the relevant QUADRATURE BALANCE controls If any meter exceeds about 5V the OUT OF RANGE indicator may illuminate and the system revert to BALANCE mode If this happens turn the last turned control back a few positions and set back to OPERATE mode by turning the MODE switch to BALANCE and then back to OPERATE Turn the Y COARSE and FINE controls to expand the fringe until it fills as much of the aperture as possible Again keep the meters within a couple of volts of zero Keep adjusting the X and Y FINE controls until turning the Z FINE control causes the field to lighten and darken uniformly
24. ring If the number is not three digits long it is padded out with leading zero s First ensure number is in range ie n amp Buffer variable to prevent n amp being changed IF i amp lt O THEN i amp 0 IF i amp gt 4095 THEN i amp 4095 aS HEXS i amp IF LEN a 1 THEN b 00 as IF LEN a 2 THEN b 0 as IF LEN a 3 THEN b as akeStringS b END FUNCTION This offset codes an integer for output FUNCTION OffCode amp n offset binary code the input number n amp Check that it is in valid range ie n amp Buffer variable to prevent n amp being changed IF i amp lt 2048 THEN i amp 2048 IF i amp gt 2047 THEN i amp 2047 31 Interface Operation 16 16 2048 Offset 18 i amp XOR H800 Invert MSB OffCode amp i amp END FUNCTION The following function is useful for decoding strings read back from the CS100 FUNCTION HexToNumber a QuickBasic does not contain any functions for converting HEX characters into numbers so one must improvise via the ASCII code This general function converts a hexadecimal string a into a long integer Note Visual Basic can do this directly 1 LEN a Find the length of the string n amp 0 Initialise the output integer Find the code for each character in turn A zero will be inserted if the character is not recognised FOR i 1 TO 1
25. rite Not used Pc Pb Pa Enable X Y and Z buffer Qd Read Not Used Qc Qb OUT OF RANGE status bit Qa OPERATE status bit Rd Read MSB Rb Rc Ra Sd Read Sc Read Data Word Sb Sa Td Read Tc Tb Ta LSB Table 5 4 Port Bit Functions 26 Interface Operation Data Coding Data for X and Y Parallelism and Z Spacing is offset binary coded as shown in Table 5 5 Bit Pattern Hexadecimal Decimal 0111 1111 1111 7FF 2047 0111 1111 1110 7FE 2046 0000 0000 0001 001 1 0000 0000 0000 000 0 1111 1111 1111 FFF 1 1000 0000 0001 801 2047 1000 0000 0000 800 2048 Table 5 5 Offset Binary Coding Setting and Scanning Z To set Z SPACING the Z buffer must be opened the required value written into the data register formed by ports J K and L and the transfer to the buffer enabled by setting bit Pa Clearing Pa at the end prevents further changes in data coming through until required I47FFP1PO lt CR gt Set Z SPACING to 2047 To scan an etalon a sequence of numbers must be written to Z SPACING The users program would normally provide a pause between steps for data collection etc Thus to scan from 0 to 10 in steps of 2 the following data would be sent to the interface l4 lt CR gt Open Z register JOO0P1PO lt CR gt J002P1P0 lt CR gt J004P1P0 lt CR gt JOO6P1PO0 lt CR gt J008P1P0 lt CR gt JOOAP1PO lt CR gt l0 lt CR gt Close Z register
26. roller This section contains a general description and specification of the CS100 controller including the front and rear panel controls and user interfaces General Description The CS100 control unit contains the three axis capacitance bridge stabilization system which enables the parallelism and cavity spacing of the etalon to be servo stabilized lt also houses the PZT power supplies to drive the etalon along with front panel manual set up and scan controls and rear panel interfaces for computer control Manual Controls Figure 2 1 shows a schematic diagram of the CS100 front panel and Figure 2 2 the CS100 rear panel On the front panel are the controls for manual setting of the static and dynamic response of the etalon The X and Y PARALLELISM and QUADRATURE BALANCE controls allow the capacitance bridges to be balanced and the etalon mirrors aligned parallel the meters are switchable to display either the real or imaginary part of the imbalance signal Other manual controls include a selectable RESPONSE TIME and BALANCE OPERATE to switch from set up mode BALANCE to closed loop control OPERATE Interfaces On the rear panel are mounted the user interface IEEE 488 or RS232C by which the system can be computer controlled All the functions controllable manually from the front panel with the exception of the COARSE OFFSET and QUADRATURE BALANCE can be controlled via the interface A full description of the interface is
27. se Comments 1 LEMO PSA 0S 302 CLLC 37 Z MODULATION LEMO PSA 1S 305 CLLC 37 BRIDGE DRIVES PINS 1 2 3 4 LEMO PSA 00 250 CTLC 27 X ERROR SIGNAL LEMO PSA 00 250 CTLC 27 Z ERROR SIGNAL 2 3 4 LEMO PSA 00 250 CTLC 27 Y ERROR SIGNAL 5 6 AMPH 57FE 40240 20S INTERFACE CONNECTOR D1 IEEE OR AMPH 17D TYPE B FR A 25 S RS232 OPTIONAL 7 LEMO PSA 2S 306 CLLC 42 PIEZO DRIVES 8 BULGIN PF001 1 63 30 LINE I E C MAINS PLUG Figure 2 2 CS100 Rear Panel The following specification relates to a CS100 with serial number 8035 or greater controlling any standard IC Optical Systems ET Series etalon with 3m cables The CS100 Controller Front Panel X Y amp Z Set up Control Range The front panel PARALLELISM and BALANCE fine and coarse controls have the following ranges FINE COARSE 530nm 5000nm Response Times and Slew Rate RESPONSE TIME switch selects the following responses The STANDARD response time blue scale on the CS100 is for standard ET Series etalons The LONG RANGE response time black scales is appropriate to etalons fitted with long range piezo electric actuators See the section on Response Time in Chapter 5 for the definitions of standard and long range piezos Note A response time of O imsec available for etalons with long range piezos may cause system instability The system may enter BALANCE mode STANDARD LONG
28. th the Interface Commands and data are transferred between the interface and host computer as ASCII coded characters on the IEEE 488 RS232C bus The commands as described in this section are quite versatile but this versatility leads to a rather un friendly protocol There are examples given in section entitled Software Examples which should help to clarify their use Interface Organization The interface is arranged as 12 four bit ports labelled to T see Fig 6 1 Ports Q R S and T are set up for read operations data transfer from the port to the IEEE 488 RS232C bus and ports I J K L N O and P for write operations Port M is not used For discussion purposes the individual bits of the ports are labelled a to d a represents the least significant bit and d the most thus Id denotes the most significant bit of port I Data written to a port will stay there until overwritten It would perhaps be more conventional to label bits with numbers e O to 3 but this could lead to confusion with valid command strings such as 12 Ports J K and L are used to create a 12 bit word which is latched into the X Y or Z buffers depending on the contents of the port and bit Pa Bit Pa must be set to 1 to enable operation of the bits Bit la opens the X buffer Ib the Y and Ic the Z buffer Bit Id is ignored The ports are opened independently by the individual bits so setting bits la b and c to one will transfer the word on ports J K and L
29. to X Y and Z simultaneously This is useful for resetting the buffers to zero Ports N and O are used to control various CS100 operations as described in the section entitled Controlling the CS100 see below 22 Interface Operation PORTS BUFFERS fs Se _ x Parallelism m 0 EE Co TTL Dr Fr EEN E E E EEE K LEA AS a e m L ln N LE EEE BE BE EEE Ike Y Parallelisri RESPONSE TIME pS Spacing o STATUS Figure 5 1 Interface Organisation 23 Interface Operation Writing to a Port Commands and data are sent to the interface as character string on the IEEE 488 RS232C bus Some characters have different functions depending on interface type Table 4 3 shows the characters used Character ASCII Code Hex Function Oto 9 30 to 39 Data AtoF 41 to 46 Write Port designation Ito P 49 to 50 Read Port designation QtoT 51 to 54 Define read ports RS232 21 Define read ports IEEE 488 5 2A Read from port RS232 only 3F Logical AND to port 2B Logical OR to port 2F Carriage return end of data designation lt CR gt 0D Omit Line Feed at end of read data IEEE 488 only Table 5 3 Command and Data Characters To write to a port the port designator and data are transmitted followed by a Carriage Return Note the IEEE 488 interface recognises EOI asserted with the last character sent as a data term
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