View/Open - Calhoun: The NPS
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1. NAVAL POSTGRADUATE SCHOOL Monterey California THESIS DESIGN DEVELOPMENT AND TESTING OF AN ULTRAVIOLET HYPERSPECTRAL IMAGER by Erik O Johnson December 1996 Thesis Advisors D Cleary S Gnanalingam Approved for public release distribution is unlimited Thesis ds DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOO MONTEREY CA 93943 5101 REPORT DOCUMENTATION PAGE et 7 Public reporting burden for this collection of information is estimated to average 1 hour per response including the time for reviewing instruction searching existing data ources gathering and maintaining the data needed and completing and reviewing the collection of information Send comments regarding this burden estimate or any other aspect of this collection of information including suggestions for reducing this burden to Washington Headquarters Services Directorate for Information Operations d Reports 1215 Jefferson Davis Highway Suite 1204 Arlington VA 22202 4302 and to the Office of Management and Budget Paperwork Reduction Project 0704 0188 Washington DC 20503 I AGENCY USE ONLY Leave blank 2 REPORT DATE 3 REPORT TYPE AND DATES COVERED December 1996 Master s Thesis MITE AND SUBTITLE 5 FUNDING NUMBERS DESIGN DEVELOPMENT AND TESTING OF AN ULTRAVIOLET HYPERSPECTRAL IMAGER u 6 AUTHOR S Johnson Erik O 7 PERFORMING ORGANIZATION NAME S AND ADDRESS ES 8 PERFORMING Naval Postgraduat2. advancements in remote sensors have led to an effective technique for image data acquisition namely Hyperspectral Imagery HSI The HSI process is a form of 1maging spectrometry in which an image is obtained at many contiguous wavelengths 100 or more spectral bands with spectral resolution sufficient to distinguish features of interest e g molecular transitions in materials with spectral resolution on the order of 1 2 nm This technique generates a three dimensional image in which two of the dimensions contain spatial information and the third dimension contains spectral information To date some 45 hyperspectral sensor systems are either deployed or under development Most of these sensors detect radiation in the visible or far infra red 400 nm 15 um portions of the electromagnetic spectrum and only 2 of them detect radiation below 400 nm This research involved the design fabrication and testing of the first mid ultraviolet MUV hyperspectral imager built to operate in the MUN to visible 200 500 nm region of the electromagnetic spectrum This ultraviolet UV imager will extend the range of current hyperspectral imagers and enhance existing capabilities for exploiting the spectral signature of targets The UV spectrum can be divided into three regions namely the far ultraviolet FUV 100 200 nm MUV 200 300 nm and near ultraviolet NUV 300 400 nm Atmospheric transmission of radiation in the troposphere in bot
3. remir end of galvo send 56 ro en em set strobe active LOW send LS Byte send MS Byte set strobe inactive HIGH LIST OF REFERENCES Atkinson J D IV Implementation and use of a computational ray tracing program for the design and analysis of complex optical systems Master s Thesis Naval Postgraduate School Monterey California 1993 Cleary D D Private Conversation 1996 Cleary D D S Gnanalingam R P McCoy K F Dymond and F G Eparvier The middle ultraviolet dayglow spectrum J Geophys Res 100 9729 9739 1995 Electrim Corp EDC 1000HR Computer Camera Technical Manual 1992 General Scanning Inc M3 Scanner Driver User Manual 1992 Hamamatsu Photonics Characteristics and Applications of Microchannel Plates 1985 Hecht Eugene Optics 2nd ed Addison Wesley Publishing Co Menlo Park CA 1987 Hicks J D Design development and testing of the All reflection Michelson Interferometer AMI for use in the mid ultraviolet region Masters Thesis Naval Postgraduate School Monterey California 1995 Holst G C Electro Optical Imaging System Performance SPIE Press and JCD Publishing Winter Park FL 1995 Hymas H M A calibration of the Naval Postgraduate School middle ultraviolet spectrograph and a analysis of the OII 2470 C emission obtained by the middle ultraviolet spectrograph Master s Thesis Naval Postgraduate School Mo
4. 8255 from a C program would result in the output voltages shown in Table 2 27 Table 2 Example of PCDIO 48P Signal Transfer MSB LSB 1797 0 0 0 0 0 1 1 1 0000 Zu Port Address B7 BO A7 AO PORT PIN VOLTAGE NUMBER Vde A 0 a 5 A 0 A 2 SE A 3 0 A 4 0 A 5 0 A 6 0 A fi 0 B 0 5 B l 5 B 2 5 B 3 0 B 4 0 B 5 0 B 6 0 B 7 0 Scanning requirements for DUUVIS are driven by two factors the horizontal IFOV 1 12 mrad and the exposure time required for the CCD to collect the image The typical DUUVIS scan cycle would be to step the mirror 1 mrad pause save the image and repeat through the desired horizontal FOV A 16 bit binary word allows us to express integers ranging from 0 to 216 65 536 This implies that the minimum increment of movement for a scanner with a 60 total arc of travel 1s 60 65 536 degrees or 16 urad DUUVIS did not require 600 of rotation so our M3 galvanometer was tuned at the factory to set it s arc of travel to 10 Recalculation of the minimum increment of movement yields 20 65 536 degrees or 5 3 urad Actual positioning of the mirror would be in one mrad increments which translates to 188 bit increments in the C program controlling mirror position Upon receipt of the scanning equipment several additional components had to be fabricated First an adapter had to be designed to house the M3 scanner and allow for mating with both the telescope and the sun shade The adapter was des
5. J1 The EDD plugs into the backplane so as to form a T This leaves approximately 1 4 inch of clearance between the male connector P1 on the EDD and the backplane There isn t enough room to plug in a 90 connector if one were even available into P1 and still clear the backplane The M3 Scanner Driver User Manual furnished by General Scanning does not contain a schematic of the EDD nor does it outline a detailed procedure on how to connect the EDD to a digital I O card Initially this caused considerable amount of 31 confusion as to the function of J1 Time was growing short and no 96 pin female connectors were locally available so ingenuity was forced to take control Pin extenders were made by soldering IC socket pins See Figure 22 onto female connectors from a standard 25 pin D connector The extenders were insulated with heat shrink tubing and slipped onto the appropriate pins of P1 Proper alignment of the EDD with the backplane to allow the 25 pin extenders to pass through the correct holes on the backplane required a significant amount of patience Once the EDD was mated with the backplane the top of the chassis served to lock the pins in place Female socket connectors were then soldered onto the appropriate leads on the ribbon cable Each of the ribbon cable connectors was Figure 22 Pin Extenders for EDD Connector P1 then insulated with heat shrink tubing labeled and attached to the appropriate pin of J1 The last ite
6. as the host platforms improved so did the sensors The earliest remote sensing images were black and white photographs These were bi spectral in nature that 1s distinguishing features of an object were depicted by varying shades of gray resulting from different combinations of black and white Information obtained through literal interpretation of these black and white images was somewhat limited This is because the human eye is a multi spectral sensor which allows us to recognize a multitude of colors through combinations of three spectral bands namely red green and blue Unfortunately this remarkable color sensor is rather limited in its resolution of shades of gray At best a trained analyst can only distinguish about ten Since the initial data obtained from remote sensors was in the form of photographs Un which were interpreted by trained human analysts it was a natural progression to develop multi spectral sensors Color images obtained from early multi spectral sensors provided much more information than their black and white predecessors The next logical progression was to extend the sensor s range beyond the visible spectrum into the UV and infrared IR Today s multi spectral sensors have on order of 10 spectral bands which sample the electromagnetic spectrum at various points between the UV and IR regions These are considered to be broad band sensors since their spectral bands or channels are fairly wide ranging from a f
7. design fabricate and test the first MUV hyperspectral imager Design began with the NPS MUSTANG instrument MUSTANG s one dimensional detector was replaced with a two dimensional image intensified CCD The new two dimensional detector required an optical coupler to map the image from a circular aperture IIT down onto a rectangular detector area As a result of the optical coupler the new detector assembly was twice the length of it S predecessor Great care was taken in mounting the new detector assembly to preserve the integrity of the existing off axis telescope A servo controlled scanning mirror was then mounted to the front of the telescope Budget constraints required design and fabrication of a chassis to house the control circuitry for the scanning motor in addition to design and fabrication of special cabling to connect the EDD to the digital I O card Three power supplies were acquired to provide the proper voltages to the EDD A program for control of the instrument was written and compiled in Microsoft Visual C The first successful operation of DUUVIS occurred on 08 DEC 96 Unforeseen compatibility problems between Borland C and Microsoft C 8 0 resulted in schedule delays which precluded extensive testing of the instrument The only data obtained by DUUVIS to date is spectra from two calibrated UV source lamps B RECOMMENDATION FOR FURTHER RESEARCH There are two categories of software development associated with this effort soft
8. eise EP sy Pes CN ION 7TH e r t 1 ame nn E prt gg dar n Y Bel I e TI Se hed LI ya la bg A c I le A Finn 34 78 gw PANAS y JI ar 1 Le EE E rrirt a Lon s Bel HT EDD Backplane Wiring Schematic Taken from General Scanning 1992 Figure 25 program and some of the problems encountered during it s development are discussed herein There are three primary components which must successfully interact for DUUVIS to function namely the digital I O card the M3 scanner and the digital camera Program development was aimed at conquering each component individually prior to incorporating them into the main program The first component addressed was the digital I O card As mentioned in the previous section control of the mirror 1s accomplished by passing a 16 bit binary word to the PCDIO48 which in turn delivers a digital signal to the EDD card In decimal values 0 represents the limit of travel in one direction 109 32 768 represents the center of travel 0 and 65 536 represents the limit of travel in the opposite direction 10 Operation of the PCDIO48 in Mode 0 is pretty simple The base address of the I O card is 300 hex Addition of a 0 1 or 2 to the base address provides access to Port A B or C respectively To set the mode on the 8255 add a 3 to the base address and send an 80 hex This sets only the M
9. of application in mind B HYPERSPECTRAL IMAGERY As previously mentioned hyperspectral imagers split a portion of the electromagnetic spectrum into many distinct contiguous narrow channels whose widths are on the order of a few nanometers or less This allows for very precise spectral signature discrimination which broad band multi spectral imagers are incapable of providing Exactly which method 1s employed for conducting such a precise spectral signature analysis 1s the basis of a great deal of ongoing research The general consensus Is that literal interpretation of remote sensing imagery by trained human analysts is a thing of the past This is not necessarily bad since human interpretations are highly subjective and not perfectly repeatable Hyperspectral images contain a vast amount of precision data which lends itself rather nicely to digital processing An appreciation of the amount of information collected by a hyperspectral imager can be gained from the hyperspectral cube provided in Figure 2 This image was produced by Jet Propulsion Laboratory s Airborne Visible Infra Red Imaging Spectrometer AVIRIS instrument during an August 20 1992 overflight of Moffett Field on a NASA ER 2 plane at an Y 2 wg E gt s K Ao e DH w X LI n sh 7 Sen Ae sa p s in d D Y PS A EN P Ke ST Ze A Td S ETS f H Ca L P 5 pa i b Sei o or Y we A sf Ca 4 Cas Ts mes T v 3 pre si H Ya ee 2 e
10. problem was to retrofit MUSTANG with a two dimensional detector and install a scanning mirror at the entrance of the telescope Since both focal length and entrance slit would remain unchanged the new instrument DUUVIS Dual Use Ultra Violet Imaging Spectrograph would have the same instantaneous field of view IFOV as MUSTANG namely 2 3 in the vertical direction and 0 06 in the horizontal direction At any given instant of time a snapshot taken with DUUVIS would produce a very narrow sliver of a hyperspectral image As illustrated in Figure 7 below each sliver contains spatial information in the y direction and spectral information from 135 narrow channels in the z direction Once a snapshot is stored the scanning mirror is repositioned to obtain the next adjacent sliver and the process is repeated After the mirror has scanned through the entire field of view FOV all the slivers are combined into one image file and the instrument is ready to begin all over again The transformation of MUSTANG into DUUVIS was comprised of four main elements 1 Grating selection 2 Detector upgrade Figure 7 Method of Constructing a Hyperspectral Image with DUUVIS Data 13 3 Scanning mirror installation 4 Software development This chapter will elaborate on each of the aforementioned elements A GRATING SELECTION As previously mentioned DUUVIS is designed to operate in the Mid UV through visible portion of the electromagnetic
11. spectrum Unfortunately it is not possible for the instrument to cover the entire spectral range from 200 nm through 500 nm simultaneously and maintain the desired spectral resolution A sketch of the optical path through the spectrograph is provided in Figure 8 The spectrograph 1s configured such that the incident angle between the incoming light and the normal of the grating is 9 1 when phi 0 The instrument bandpass is a function of the separation distance between rulings on the grating and the detector aperture Detector position dictates that the minimum detectable wavelength is that which has an exit angle of approximately 10 and the maximum detectable wavelength is that which has an exit angle of 20 Rotating the grating so that it 1s no longer normal to the Ebert mirror causes the values of the minimum and maximum detectable wavelengths to change However the width of the bandpass remains roughly constant A more detailed description of this relationship 1s LS Entrance Slit Ebert Mirror Ne i Pd _ _ _r 6 EN 7 ya ene d Grating eo AZ m o ex NS Sa M nn p SE 2 1 b lt e A A AAN c i T al ER E n nr A A DON Ee n Tuy Cw x p Lambda min IL Detector oe Lambda max Figure 8 Optical Path Through DUUVIS Spectrograph 14 provided below Since the focal length of our in
12. unique identification of specific materials 3 Short wave Visible submarine mine detection in littoral waters A OBJECTIVES The objectives of the research described in this thesis were to design fabricate and test the first Mid Uv hyperspectral imager Design of the instrument was driven by two principal factors namely economy and size Limited funding resources encouraged maximum utilization of existing components Thus the NPS Middle Ultraviolet SpecTrograph for Analysis of Nitrogen Gases MUSTANG instrument was chosen to be the backbone of the new design Furthermore additional components required for MUSTANG s conversion were selected from commercial off the shelf COTS items The size limit was imposed by the ultimate goal of flying the instrument aboard one of the NPS Unmanned Aerial Vehicles UAV s during subsequent research B THESIS OUTLINE This thesis is divided into five chapters and one appendix The first chapter 1s the introduction Chapter two provides the background information for the design and development of the NPS UV hyperspectral imager These areas include an overview of hyperspectral imagery and the NPS MUSTANG instrument Details of the conversion of MUSTANG into a UV hyperspectral imager are provided in chapter three Chapter four discusses the data collected by the new hyperspectral instrument Conclusions and recommendations for future design improvements are contained in Chapter five The goal of this
13. work was to demonstrate the operation of the first UV hyperspectral imager by generating the first UV hypercube One appendix is included which contains a listing of the instrument control and data collection programs UJ II BACKGROUND This chapter provides a brief introduction to remote sensing and the progression from early imaging techniques to hyperspectral imaging Additionally it uses an example to provide motivation for development of a UV imaging spectrograph Finally it introduces the MUSTANG instrument which will be thoroughly investigated in follow on chapters A REMOTE SENSING It is often easier to observe measurable features of an item of interest from a considerable distance rather than close up For example it 1s easier to construct a map of a valley from an observation point high atop a mountain than from within the valley itself In the early days of remote sensing cameras were mounted on balloons and even kites to obtain aerial photographs of the land below The information gained from these photos proved extremely useful in a variety of applications ranging from locating armies to surveying unexplored territories The once mysterious Amazon River and it s surrounding rain forest which was impervious to the advance of civilization is now charted and open for development as a result of aerial surveying As technology improved airplanes and satellites served as the host platforms for the sensing equipment Just
14. 1 target identification and 2 battle damage assessment Additionally this instrument has dual use applications namely 1 redirection of jet aircraft to avoid the foreign object damage FOD hazards presented by volcanic ash clouds through analysis of the absorption of solar UV radiation by the sulfur dioxide SO gas associated with volcanic ash and 2 forest fire detection 15 NUMBER OF PAGES 70 16 PRICE CODE 20 LIMITATION OF ABSTRACT 14 SUBJECT TERMS Hyperspectral Imaging Ultraviolet Imaging Spectroscopy Remote Sensing Dual Use Support to Military Operations 19 SECURITY CLASSIFICATION OF 9 SECURIT CLASSIFICATION 18 SECURITY CLASSIFICATION OF OF REPORT THIS PAGE ABSTRACT Unclassified Unclassified Unclassified UL a D 5 FE VE NSN 7540 01 280 5500 Standard Form 298 Rev 2 89 Prescribed by ANSI Std 239 18 298 102 Approved for public release distribution is unlimited DESIGN DEVELOPMENT AND TESTING OF AN ULTRAVIOLET HYPERSPECTRAL IMAGER Erik O Johnson Lieutenant United States Navy B S University of La Verne California 1988 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN APPLIED PHYSICS from the NAVAL POSTGRADUATE SCHOOL December 1996 DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE S MONTEREY CA 93942 5101 VU ABSTRACT This research involved the dev
15. A UV IMAGING SPECTROGRAPH Figure 3 illustrates the vast amount of volcanic ash introduced into the atmosphere as a result of volcanic eruption during recent activity beneath Vatnaj kull glacier in Iceland While the eruption poses an 1mmediate threat to nearby land inhabitants it also commands the respect of aviators as the ash cloud presents a Foreign Object Damage FOD hazard to gas turbine engines Current procedure is to give the ash cloud an extremely wide berth sometimes entire continents are avoided Large savings in time and money could be achieved through the accurate identification or prediction of the safe ash cloud perimeter In addition to the lava ash etc one of the products of a volcanic eruption 1s SO In fact a strong correlation exists between the presence of volcanic ash and the concentration of SO This is evidenced by the data obtained from the Total Ozone Mapping Spectrometer TOMS an instrument on board the Nimbus 7 low earth orbiting satellite Krueger et al 1995 Nimbus 7 is in a polar sun synchronous orbit That is it crosses the equator every 26 degrees of longitude at local noon making approximately Figure 3 October 96 Eruption Beneath Vatnaj kull Glacier in Iceland Taken From the Nordic Volcanological Institute 1996 15 7 orbits day thus observing the entire earth once a day TOMS is a multi spectral instrument with six spectral bands ranging from 312 nm 380 nm originally designed to m
16. DAC cvcle TSHGC 3 x DA NOTE Address Setup amp Hold times aze identical ta these of Dono Epos dh fe fw NNN i res H CR AMA Als Ad o ROVER m a j TOYEL TEHON r TSS u STRCIE 5 Z Fog Pai e A P DODI 4 A o BZ e d rene r gt x ESC BHL DAL OUT a Figure 26 Bus Write Cycle Diagram Taken from General Scanning 1992 proprietary They do provide Linkable Routines which allow for slight modification of their programs to perform a variety of functions including saving images to disk in TIFF format The functions called out by the linkable routines are contained in various object files furnished by Electrim which have already been compiled in Microsoft C 8 0 The source code for control of the scanner was written in Borland C That version of C was chosen because it contains the outportb command which was referenced in General Scanning s sample program for scanner control After many painful hours of self study in compiling and linking the incompatibility of Borland C and Microsoft C became an insurmountable obstacle There was no way to determine Electrim s function protocols and the linkable routine for writing TIFF files would never suffice as written since it utilized only one file name as it was designed to terminate upon successful image storage After successfully writing a routine for generating sequential filenames a copy of Microsoft Visual C Ver 1 52c was
17. NO OO O n e ee a OCC E OO OFT OR er lL nmr Te rir dc m ttha S e wg e gees pg E 4 s je O O a ege 0 A O IO AK EM e s gt a O ORO O DO e ae ation elm eg D e e AO Co OO er 099090 t eee e e 86 1 Ee pue haa eun na rs ee MN la eo o e o errore ecc o sates oo doita e O VU d D 000 e c Pere et e e Ne s lt DENTEN E E E AA eias e e e e D IRONIA sv ee eee RO tia N A aM eee bet gt ee Bee Fi i igure 20 Scanning Mirror Adapter Partially Disassembled 4 TO da tear tbe e vr ni EV Sr DI Ce Ri ule ti Er d Ld Figure 21 EDD Chassis with Backplane 30 Table 3 PCIO 48 to EDD Wiring List Signal Name 8255 Port PCDIO48 P1 Backplane JI Address Pin Pin DO BO 31 A DI Bl 29 A2 D2 B2 27 A3 D3 BS 25 A4 D4 B4 25 AS DS BS 21 A6 D6 B6 19 A7 D7 B7 17 AN D8 AO 47 Ci D9 Al 45 C2 D10 A2 43 ES DAI A3 41 C4 DI A4 39 CS D13 AS DI C6 D14 A6 35 C7 D15 A7 33 C8 Al CO 15 Gis A2 13 C14 A3 C2 11 C15 A4 ES 9 C16 RESET C4 7 NOT USED STROBE es l A10 RD WR DIR ES 5 A12 E Viale N A 49 052 GND N A 50 A32 Although the wiring requirements listed in Table 3 seem pretty straight forward accomplishment of the task proved to be non trivial J1 and J2 on the backplane are 96 pin connectors configured as 3 columns of 32 rows with the center column not used The backplane only had a female connector for J2 No connector was provided for
18. SB of the control register of the 8255 HIGH with all other bits LOW which configures the 8255 for mode 0 operation with all output ports Every word passed to the PCDIO48 from the program automatically results in a corresponding digital signal being sent to the backplane through the ribbon cable Once the digital signal 1s present at J1 of the backplane the EDD must be directed to read it and convert it to a position command This direction 1s achieved by toggling the strobe Refer to the timing diagram in Figure 26 STROBE is a leading edge triggered control signal At program start RD WR 1s set LOW WRITE and remains at that value for the rest of the program Strobe Port C pin 7 is set LOW before a new digital signal 1s sent over DO through D15 Port B and Port A respectively all pins When STROBE goes HIGH again the EDD reads in the new digital signal on DO through D15 and converts it into a new position command Now the program is able to control the position of the scanning mirror At each position it must obtain an image and subsequently store it to disk This 1s where the real problems arise Electrim Corporation furnishes several programs to facilitate the use of their cameras However they keep the source code for manipulation of the CCD itself 36 Description Symbol Min Typ Max Units Corcel Setup TCVYSL LO n3 Data Setup TOV SH 20 A 2 af Suobe IBS TES TN LOU n amp Corbol Hold LS zn DE Cam Hele TSHIX 00 n amp
19. ST Defense Technical Information Center 8725 John J Kingman Rd STE 0944 Ft Belvoir Virginia 22060 6218 Dudley Knox Library Naval Postgraduate School 411 Dyer Rd Monterey California 93943 5101 Dr Anthony A Atchley Chairman PH Physics Department Naval Postgraduate School Monterey California 93943 5002 Dr D D Cleary Code PH CL Physics Department Naval Postgraduate School Monterey California 93943 5002 Dr S Gnanalingam Code PH GM Physics Department Naval Postgraduate School Monterey California 93943 5002 LT Erik O Johnson 592 Belden Ave Camarillo CA 93010 99 KEN m IO DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOO MONTEREY CA 93943 5101 nn mn TUTTI l
20. UUVIS detector assembly can be gained by viewing Figure 17 The shiny ring in the middle of the lens coupler was originally a knurled adjustment ring similar to those found on telephoto lenses When the telescope could no longer be machined the coupler was disassembled the ring removed and machined Putting a knurled finish on the ring subsequent to machining would require 1t to be clamped so tight in the chuck of the lathe that it might result in damage to the internal threads The solution to this problem was to cut longitudinal grooves in the ring They could be inserted without risking damage to thie internal threads and still provide enough texture to grip onto while adjusting the focus of the lens coupler assembly L Figure 17 Comparison of Installed MUSTANG top and DUUVIS bottom Detector Assemblies C SCANNING MIRROR INSTALLATION Several possibilities were considered for control of the scanning mirror Initially a motor and cam assembly was envisioned for positioning the mirror then the possibility of making the mirror shaft out of two way shape memory NiTi alloy sexy technology was considered Neither of these designs provided the accuracy required for this application Due to the position accuracy requirement and potential need for high speed slewing a servo controlled mirror assembly was finally chosen The MG series optical scanner a high speed galvanometer designed for advanced beam positioning commercially availabl
21. UUVIS spectrograph the incident cone of rays originating from that object strike the lens asymmetrically This causes an aberration known as astigmatism See Figure 31 In an off axis instrument there are two distinct focal lengths which cause the cone of rays to become elliptical The focal plane of our instrument is the tangential focal plane represented by F in the illustration in which the ellipse degenerates into a line This explains why our simulated 41 kaliii SURI 7 VUN m n O Se Figure 30 Pt and Hg Lamp Spectra Obtained During DUUVIS Scan of 0 9 FOV taken on 08 DEC 96 42 Circle of least contusion Primary imaze image Sagittal Optical plane system Figure 31 Illustration of Astigmatism Taken from Hecht 1987 point source appeared as a line on the detector Again this 1s good for spectroscopy but doesn t lend itself to imaging Seeking improved performance the mounting clamp for the lens coupler assembly was loosened and the entire assembly was moved back away from the spectrograph in an attempt to move the photocathode behind the tangential focal plane The result of this adjustment is shown in Figure 32 The point spread function was clearly reduced but further adjustment 1s necessary Figure 32 DUUVIS Snapshot of a Simulated Hg Point Source taken on 09 DEC 96 44 V CONCLUSION A SUMMARY OF FINDINGS The main objective of the research described in this thesis was to
22. ctive plane diffraction grating The grating separates the incident polychromatic light into it s monochromatic components which are directed back to the Ebert mirror and subsequently focused onto the detector area in the exit focal plane The instrument s original detector was a one Tete Plasma Coupled Device PCD a monolithic self scanning linear array of 512 p n junction photodiodes MUSTANG s output was in the form of a plot of intensity vs wavelength A typical spectrum of the instrument is shown in Figure 6 With a 1200 ruling per mm grating and a 25mm detector aperture MUSTANG had a band pass of 135 nm at a spectral resolution of approximately 1 nm Cleary et al 1995 MUSTANG s spectrograph provided 135 narrow spectral channels which would be ideal for hyperspectral imagery if the instrument could be modified to produce a two dimensional image 11 430 309 200 Intensity R F WM H AM A 2000 2200 240C 2600 EBOD 3000 3220 Wavelength A Figure 6 Typical Spectrum from MUSTANG Instrument Taken From Hymas 1994 IIl MUSTANG CONVERSION In an effort to minimize the cost of developing the NPS hyperspectral imager the decision was made to modify the existing MUSTANG instrument to enable it to function as an imaging spectrograph Additionally the stipulation was made that any new piece of hardware purchased for the conversion had to be a COTS item Simply stated the basic approach to the
23. der 1000 00 This created two major challenges 1 The necessity to marry products from the spectroscopy community one inch wide rectangular standard aperture with those from the photography community in which circular apertures are standard and 2 Ensuring that design requirements met the needs of both DUUVIS and AMI while maintaining complete interchangeability between the two instruments The detector is a charge coupled device CCD which is sensitive to visible light at wavelengths between 400 nm 1100 nm Since we re interested in wavelengths between 200 nm and 400 nm modifications were necessary to convert the incident UV light into visible light for the CCD A commercially available Image Intensifier Tube IIT performs that task quite nicely The image intensifier is a proximity focused channel intensifier tube with dual microchannel plates It was manufactured by BV Delft Electronische Producten DEP located in Holland The basic intensifier consists of a 17 quartz input window a photocathode two microchannel plates a phosphor screen and a fiber optic face plate for output A quartz window is used to allow UV light to enter the detector since glass 1s opaque at Mid UV wavelengths Incident light encounters an S 20 photocathode which converts incident photons into electrons S 20 the name of the coating on the photocathode is made from a multi alkalide compound known as Suprasil which among others contains cesium potassium sod
24. e School ORGANIZATION Monterey CA 93943 5000 REPORT NUMBER 9 SPONSORING MONITORING AGENCY NAME S AND ADDRESS ES 10 SPONSORING MONITORING AGENCY REPORT NUMBER II SUPPLEMENTARY NOTES The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Department of Defense or the U S Government 12a DISTRIBUTION AVAILABILITY STATEMENT 12b DISTRIBUTION CODE Approved for public release distribution is unlimited I3 ABSTRACT maximum 200 words This research involved the development of an ultraviolet UV hyperspectral imager A hyperspectral image is a three dimensional image in which two of the dimensions provide spatial information and the third provides spectral information In an effort to minimize the cost of this experiment the NPS Middle Ultraviolet SpecTrograph for Analysis of Nitrogen Gases MUSTANO instrument was modified to function as a hyperspectral imager This required the design fabrication and testing of hardware and software to coordinate the operation of a two dimensional charge coupled device CCD detector with a servo controlled scanning mirror Control and synchronization of scanning mirror and image collection was accomplished by software written in Borland C run from an Intel microprocessor based PC The benefits of a UV hyperspectral imager are primarily in the area of Support to Military Operations SMO There are two principal applications
25. e from General Scanning Inc proved worthy of the task The M3 scanner uses a moving magnet design which enables it to move at high speed over wide angles total range of 30 of travel with precise angular positioning Additionally the M3 maintains the low inertia rigidity and temperature control of moving iron devices while retaining the low inductance of a moving coil unit General Scanning located in Watertown MA was chosen based on their outstanding reputation for high quality scanning components and their twenty five plus years of experience in the field Again financial limitations added to the challenge Our budget did not allow purchase of the complete system with all necessary electronics contained in a Eurocard chassis Instead we purchased the M3 galvanometer a MgF coated UV sensitive Y mirror an electronic digital driver EDD with backplane and a six foot cable for connecting the galvanometer to the backplane with the understanding that we would have to furnish power to the EDD and provide the computer interface Dimensions for the Y mirror and M3 galvanometer are provided in Figure 18 While awaiting arrival of the scanner components computer interface requirements were identified Control of the M3 scanner is accomplished by sending a 16 bit binary word from a personal computer PC to the EDD The EDD then converts the digital input signal into an analogue output signal which repositions the galvanometer General Scan
26. e ozone layer and favorable atmospheric transmission below it allow for detection of weak target signatures emanating from artificial sources of MUV radiation with an extremely low probability of false alarm For example fluorescent lights are common in nearly all buildings and structures These lamps have a number of atomic Mercury emissions in the Middle UV It is possible that the scattering of this radiation near building openings such as doors or windows could be used for overhead detection of human activity or even battle damage assessment BDA The interest in the blue green 400 500 nm region of the visible spectrum is due to it s favorable transmission properties in water Figure 1 shows that light with wavelengths between 380 and 500 nm have the lowest coefficients for both absorption Si T z O 0 05 absorption coefficient a m ul d 1u9121j202 3ULISALOS O O 700 800 wavelength A nm Figure 1 Absorption and Scattering Coefficients vs Wavelength for Transmission in Pure Sea Water Taken From Mobley 1994 2 and scattering in pure sea water This is extremely beneficial in the area of submarine and mine detection in littoral waters To briefly recap the new NPS Mid Uv hyperspectral imager would have a bandwidth covering three principal regions with the following utilities 1 Mid Uv overhead detection of human activity BDA 2 Near UV observation of electronic transitions to aide in the
27. e passing FV 244 FH 753 AspcrXN 753 AspcrXD 4 AsperYN 244 AsperYD 3 buffer is already defined buffer will be loaded by highcaml procedure for write big TIFF proc fname image name filename tif extension in the filename is necessary retCode write TIFF fname FV FH buffer AsperXN AspcrXD AspcrYN AspcrYD print the return code cprintf r nThe return code is d r n retCode pou Se free buffer i m for position MA XPOS position gt 32766 0 position position 188 0 d galvo_send position for counter 1 0 counter lt 50 0 counter y Y J shutdown ctrlport return end of main void startup int ctrlport f l int modeO out cport x write model out 0x80 _outp ctrlport mode0 out cport BASE1 DEV lt lt 2 C x_write 0x0a _outp cport x write set RD WR to write LOW _outp cport x_write 0x80 set strobe inactive HIGH return y end of startup void shutdown int ctrlport f l int modeO 1n mode in O0x9b _outp ctrlport modeO 1n return end of shutdown void galvo send unsigned int position f l int aport bport cport x_write aport BASE1 DEV lt lt 2 A bport BASE1 DEV lt lt 2 B cport BASE1 DEV lt lt 2 C x_write 0x0a _outp cport x write amp 0x7f _outp bport position amp Oxff _outp aport position amp Oxff00 gt gt 8 _outp cport x write 0x80
28. e principle of operation is simple enough After the desired FOV has been determined the main program slews the mirror over to one end and begins to step it through the FOV in 1 mrad increments At each step the detector 1s exposed to the incident radiation for the appropriate amount of time after which it stores the image to disk as a TIFF file The cycle repeats for each step through the entire FOV In practice this process would continue until the entire area of interest were imaged For the sake of simplicity this discussion will only address one sweep through the entire FOV In an attempt to minimize start up time for the instrument this effort pushed the development of a program in C for instrument control This was the easiest path to compatibility with the equipment manufactures since most PC application software is written in C Saving the files in TIFF format for subsequent compilation into a multi dimensional array for data analysis is a cumbersome method of operation That bridge will have to be crossed at a later time The numerous bugs which surfaced during this experiment precluded software development beyond successful control of the instrument The actual program MSCNSCAN C is provided in the Appendix A general overview of the DO k kt ir e a bei Yn d Le bl le are Tit Pr 4 ee e a 2e OU PaM Ap Sa VER db 1 Figure 24 DUUVIS with Associated Support Equipment vf POAL Me
29. ecame the length of the reduced radius section at the front end of the lens coupler assembly The focal plane of the instrument was located 0 151 from the rear face of the spectrograph There was only 0 564 clearance between the back of the grating and the rear face of the spectrograph This implied the front of the lens coupler casing could not extend over 3 8 of an inch beyond the focal plane to allow for positioning of the grating Ideally the photocathode should have been positioned in the focal plane In reality the focal length 1 e the distance from the outer surface of the entrance window to the S 20 coating of the photocathode was 0 250 0 050 Assuming a 1 16 0 0625 0 005 minimum thickness for the retaining lip on the front of the casing the worst case scenario was that the front of the lens coupler casing would extend 0 519 beyond the focal plane This would clear the back of the grating by 0 045 less than 1 16 of an inch Figure 15 contains a block diagram of the lens LU Window Figure 14 Coverage of CCD Input Window by the Image From the Lens Coupling Device Taken from Hicks 1995 i While this decision was optimal for AMI it was less than optimal for DUUVIS 22 M STANDARD LEKS COUPLES ICRDSS HATCHED ARCA vc DEFTH OF PROFODZATHCIDE N CAME AS PRESENTI CZE CARE EX WITHO COVER Nage TT INTENSIFIES 3 921 3 420 i Figure 15 Block Diagram of the Lens Co
30. elopment of an ultraviolet UV hyperspectral imager A hyperspectral image 1s a three dimensional image in which two of the dimensions provide spatial information and the third provides spectral information In an effort to minimize the cost of this experiment the NPS Middle Ultraviolet SpecTrograph for Analysis of Nitrogen Gases MUSTANG instrument was modified to function as a hyperspectral 1mager This required the design fabrication and testing of hardware and software to coordinate the operation of a two dimensional charge coupled device CCD detector with a servo controlled scanning mirror Control and synchronization of scanning mirror and image collection was accomplished by software written in Borland C run from an Intel microprocessor based PC The benefits of a UV hyperspectral imager are primarily in the area of Support to Military Operations SMO There are two principal applications 1 target identification and 2 battle damage assessment Additionally this instrument has dual use applications namely 1 redirection of jet aircraft to avoid the foreign object damage FOD hazards presented by volcanic ash clouds through analysis of the absorption of solar UV radiation by the sulfur dioxide SO gas associated with volcanic ash and 2 forest fire detection TABLE OF CONTENTS MITAD IONE EC 1 i OJBJEC ES a A 33535 gt 553505U5U 5 3 c TAREIS QUICINE ee 3 de ee OCC LOIRE TEM 5 FO sese MM 5 c Jl AO TRAL A TERM 6 BE et
31. ew tenths of a micron up to several microns Images generated from spectral bands outside the visible region can no longer be literally interpreted Since the human eye is incapable of viewing UV or IR radiation false coloring must be applied to data from those spectral channels Additionally there are many algorithms which employ techniques of linear algebra to perform transformations on the data in different multi spectral bands to enhance their signal to noise ratio Various combinations of the bands are then examined until the characteristic of interest 1s exploited In addition to providing more information increasing the number of spectral bands opened the door to an even greater range of applications such as terrestrial land ecology bathymetry and geology Green plants for example use chlorophyll to absorb the visible light from the the sun but reflect radiation in the Near IR 0 7 um 2 5 um Sensors operating in this bandwidth will record a significant increase in reflectance around 0 7 um due to the presence of vegetation Incidentally a military application of this same phenomenon is detection of camouflaged objects such as artillery installations tanks and troops Today there are IR reflecting camouflage paints capable of deceiving broad band multi spectral sensors However these paints each have unique spectral signatures which could be exploited by an imaging spectrometer Hyperspectral imagers were designed with this type
32. gh an ash cloud in an experiment designed to provide an accurate assessment of the exact correlation between SO concentration and volcanic ash concentration Figure 4 SO and SO Absorption Lines Taken From Pearse and Gaydon 1963 D MUSTANG DESCRIPTION The NPS MUSTANG instrument is a 1 8th m Ebert Fastie spectrograph which has been flown on three separate NASA sounding rocket experiments to obtain information on nitrogen gases in the ionosphere MUSTANG s major components are illustrated in Figure 5 Incident light enters the off axis telescope where it is collimated by a series of baffles prior to striking a 1 8th m spherical mirror Reflected light from the telescope mirror is focused onto a 5mm by 140 um vertical slit After passing through 10 or 153 Veler Sohericol Miror Aperture ee Kor tego i N AR re er SCH y WAI MAA O A me Gg w ee ESPARTA lt LI UA MAA ee N A A Ad 7 S i 1 De A 1 d E E jn d i i gt N e ad Lo FT e EE e e eL d NP P 2m d y k G TU UE AR E 4 SA Le gt a NA PEA DER RR TO ee nenn SATA A aa AE A N N Si Xx ee 5 4 zz een Entic ce Sit 3 POS Na da pi Pa ST os Mo Sr n ee SE y OA Ec TS s IA 4 un ER NZ E he E IE 1 8 Meer Sphenco Vurer Jelecto Assemby Cie ON f Plone Grating Muro Figure 5 MUSTANG Instrument Taken From Atckinson 1993 the entrance slit the light is reflected off the 1 8 m Ebert mirror onto a refle
33. h the middle and near UV regions 1s mainly determined by scattering Rayleigh and Mie Transmissivity in these two regions is relatively high for path lengths up to tens of kilometers depending on wavelength In the stratosphere absorption by molecular oxygen can result in complete extinction of radiation in the FUV over a distance of less than ten meters again depending on wavelength Since our applications involve remote sensing this transmissive property of radiation in the FUV caused us to restrict the lower end of our instrument bandwidth to the MUV In the NUV solar radiation penetrates the earth s atmosphere providing natural illumination Radiation in this wavelength region is similar t visible light in that target materials are identified by their reflectance spectrum Although both the target and l background can be relatively bright at these wavelengths many materials experience electronic transitions in this region The advantage of operating in the NUV is that each transition observed aides in the unique identification of a specific material Most of the solar radiation in the MUV region is prevented from reaching the Earth s surface by the ozone layer at an altitude of 40 km A MUV sensor operating at an altitude below the ozone layer would observe almost zero natural background illumination Propagation of any MUV radiation existing between the ground and the ozone layer can still be appreciable The combined effects of th
34. he file retCode 99 initialize the return code keyboard check KEYBOARD CHECK ILength V 2 number of lines to display IWidth H number of pixels to display duvis duvis eo counter strl fcvt eoj counter ndig amp dec amp sign strcpy image name duvis strcat image name strl strcat image name str2 InitDAC base call only once at start SetBiasValue base BiasValue call to set bias voltage SetGain Value base 255 GainValue call to set gain voltage Allocate the image buffers for 120 1 lt V i if buffer i pixel far calloc size_t H sizeof pixel pixel far NULL cprintf n n rCannot allocate memory for buffer n r exit char 1 b Build display buffers from image buffers for 1 0 j 0 1 lt V i j 2 display buffer j display buffer j 1 buffer i 54 if init800 init 800 x 600 by 256 color VESA mode 103 cprintf r nVESA mode 103 not supported by display adapter rn AMA Read the camera and display image for 1 0 1 lt 4 1 i V Read the camera ignore keyboard interrupt highcam base refresh flag ab flag interlace flag field flag exposure time buffer keyboard check display 1mage display buffer ILength IWidth Set the VGA to character text mode set ch mode Save the last image as a TIFF file Assign values to the parameters of write TIFF befor
35. ift readout register to be processed by the computer as shown in Figure 12 Using an analog to digital A D converter the output is transformed into an 8 bit signal and is used for display or storage in a tagged image file format TIFF file for further analysis MUSTANG had a circular aperture IIT very similar to the one previously described However the one dimensional nature of 1t s detector did not require any further optical consideration The 25 mm diameter of the IIT matched quite well with the one inch horizontal width of the linear array allowing the fiberoptic output window of the IIT to be directly mated to the face of the PCD detector In the case of DUUVIS it became necessary to focus the two dimensional image produced by the 25 mm dia circular aperture IIT down onto the 8 67 mm by 6 59 mm rectangular sensing area of the CCD In the initial AMI configuration a high quality fiber optic taper with a demagnification ratio of 1 6 is used to transfer the image to the 11 millimeter cross diagonal face plate of Interline transfer vertical shift registers image column Be _ KE Video out horizontal shift Figure 12 CCD Data Output Circuit Taken From Walters 1990 20 the CCD chip Unfortunately the tapered fiber optic bundle generated an intolerable amount of distortion for the AMI application due to it s demagnification process Electro optical Services Inc located in Charlottesville VA was contracted to manufact
36. igned to position 28 the scanning mirror at a 45 angle to the optical centerline of the telescope This would minimize the vignetting effect of the scanning mirror The height of the galvanometer casing dictated that it should be mounted on top of the adapter Figure 19 shows the configuration of the scanning mirror adapter when fully assembled Close inspection of Figure 19 reveals a seam in the adapter at the base of the cylinder which houses the galvanometer barrel The scanning mirror is wider than the diameter of the galvanometer barrel making it necessary to remove the top of the adapter to attach the scanning mirror to the galvanometer shaft This 1s illustrated more clearly in Figure 20 The next items needed to be fabricated were a chassis to mount the EDD and backplane and ribbon cable to provide the connection between the 50 pin I O connector on the PCDIO48 P and the input to the EDD The chassis shown in Figure 21 was made in the student workshop out of excess material from discarded items A standard 50 pin ribbon cable was modified to make the connections shown in Table 3 nm g eent enc MEC AUD OR Figure 19 Scanning Mirror Adapter Completely Assembled 29 D D D s e o 0 7 090 0 oe e s o E e o NAO OC D our ee eee o e e s EE EE se P e zs 0 0 0 0 FI CCA MAS 0 0 090 0090 e e 0 e EA DIRE O SDA O OC a e H gt s 9 i lese e eap eoe ooo Bo te our
37. ine is displayed to the screen twice to give 488 lines total Define storage for display buffer line pointers pixel far display buffer V 2 display buffer pointers Define the passing parameters unsigned int AsperXN AspcrXD Aspcr YN AspcrYD numbers for aspect ratio unsigned int FV FH height amp width of the tiff image void cdecl main void d void startup int void shutdown int void galvo send unsigned int void clrscr char image name 12 duvis strl str2 tif fname double eoj counter int dec sign keyboard check ndig 0 unsigned int MINPOS MAXPOS ILength IWidth position retCode int ctrlport i J refresh flag ab flag interlace flag field flag long counter MINPOS 31452 0 MAXPOS 34460 0 MINPOS 24576 0 MAXPOS 40960 0 eoj counter 100 0 position 32767 0 ctrlport BASE1 DEV lt lt 2 P startup ctrlport for position 32767 0 position gt MINPOS position position 188 0 t j galvo send position for counter 1 0 counter lt 50 0 counter d for position MINPOS position lt MAXPOS position position 188 0 f t Flags galvo send position refresh flag 0 0 disables RAM refresh ab flag 0 0 disables anti blooming interlace flag 0 10 for interlace mode field flag 0 if interlace mode 0 for first frame 10 for second frame the return code is for checking the status of saving t
38. ing us to believe the bandpass is fairly close to the estimated value of 195 nm to 330 nm Also the bright line above the Pt spectra appears to be the strong Hg emission at 254 nm Figure 29 is an image of the same scene with Y D 500 tV Z 4 LU Sa m n rq in im E L a Ro SN A Vis E d wi e EN i gt r 4 NOS 2 300 su fe 7 o Ve pel ba e N i is n nm ch te z Gr p e E Gs t JR me fa Od E a i Au 3 Cat mr N f e 5 O o a Pris ape y p59 3 7 Li ri FI c3 ayi fol Zend Ste d E CP CARL ee E GIN Ot e JEU es H qe d FIT it cc 78 per 7 008 u a We H 5 d lt gt A KZ 1800 2000 2200 2460 7600 2300 3000 3200 34 Figure 28 Platinum Hollow Cathode Lamp Spectra Taken from Cleary 1996 Figure 29 DUUVIS Snapshot of Pt and Hg Lamp Spectra taken on 04 DEC 96 40 the 600 Lmm grating installed In the left two thirds of the image we observe a similar pattern to that of Figure 27 The bright lines in the right one third of the image are believed to be in the visible portion of the spectrum If this is true then we are observing a spectral bandpass which is approximately between 190 nm and 480 nm So far the images presented in this section have been static As previously mentioned software problems curtailed progress in the area of data analysis As a result there 1s no hyperspectral cube to display A feel f
39. ium and antimony The S 20 photocathode is sensitive to light with wavelengths between 200 nm and 520 nm Primary electrons emitted by the photocathode are directed to the microchannel plate MCP assembly Figure 10 is an illustration of a microchannel plate The MCP is comprised of millions of glass capillaries channels with an inner diameter of approximately ten um Each tube acts as an independent photo multiplier An electric potential 6000 Vdc 1s established across the MCP as seen in Figure 11 Incident primary electrons collide with the capillary walls and strip off electrons from the glass in the process These secondary electrons are accelerated by the difference in electrical potential across the MCP Accelerated secondary electrons collide with the capillary walls and strip off more electrons etc This cascading of electrons results in approximately 15 000 electrons at the output of the MCP for every single electron emitted by the photocathode The amplified electron beam is subsequently focused onto an aluminum screen coated with P 43 luminescent phosphor causing it to fluoresce rr CHANNELS SIP Figure 10 MCP Construction Taken From Hamamatsu Photonics 1985 18 PRIMARY CHANNEL WALL ELECTRODE ELECTRON 8 OUTPUT ELECTRONS Vo a Figure 11 Electric Representation of Electron Amplification Taken From Hamamatsu Photonics 1985 thereby emitting photons w th wavelengths between 535 nm to 555 nm Pho
40. m Y A 4 gt E i G A Zei i D ie x BILE 4 EP bl 24 LE p 1 r 4 2 i T T OB A iT A A i 5 gt 2 i T x sli E SA z OS AENA x ft Figure 2 AVIRIS Hypercube Taken From JPL 1994 7 altitude of 20 km 65 000 ft Although the hypercube is not a desirable format for data analysis it clearly illustrates the nature of a hyperspectral image Two dimensional spatial information is contained in the x y plane i e the top of the cube and spectral information 1s contained in the z direction AVIRIS has 224 spectral channels ranging from 400 nm to 2 5 um In Figure 2 spectral information 1s ordered such that the shortest wavelength is at the top of the cube and the longest wavelength at the bottom The two solid dark lines traversing the lower half of the cube represent the absorption of IR at 1 4 um and 1 9 um due to the presence of water molecules in the atmosphere Note the rectangular features located in the upper right corner of the cube s larger side They represent a marked response in the red portion of the visible spectrum around 700 nm to the presence of one centimeter long brine shrimp residing in an evaporation pond located in the far right corner of the top of the cube The ability to identify such minute features from an altitude of 65 000 feet boggles the mind however this 1s only the tip of the Iceberg regarding potential capability of a rapidly evolving technology C MOTIVATION FOR
41. ms to be acquired were power supplies Power requirements for the MG scanner are identified in Table 4 Table 4 EDD Power Requirements VOLTAGE CURRENT 18 Vdc 1 5 A continuous 3 A peak 18 Vdc 1 5 A continuous 3 A peak dro uc 1 5 A Max Three Hewlett Packard power supplies two HPE3615A s and one HP6216B were obtained and a connector cable was fabricated to plug into J5 on the backplane DUUVIS was completely assembled U t3 The final DUUVIS configuration is illustrated in Figure 23 The entire DUUVIS system including EDD backplane PC power supplies and associated cabling is shown in Figure 24 As mentioned previously the closest thing to a schematic available in the M3 Scanner Driver User Manual is illustrated Figure 25 D SOFTWARE DEVELOPMENT With DUUVIS completely assembled the only missing ingredient was the software to coordinate the operation of all it s individual components The amount of effort required to accomplish this task was by far the most underestimated aspect of the experiment If DUUVIS is to operate on a UAV in future experiments it must be able to function autonomously This requires hands off operation after initiation of a master program As previously mentioned all the individual DUUVIS components are advertised as being capable of operating in this manner Unfortunately there are many subtle barriers that are not readily apparent until the individual components begin to interact Th
42. ning provided guidance on selection of a compatible digital input output I O card for the computer as well as some programming suggestions written in C for galvanometer control 26 REFLECTIVE SURFACE 2498 6 345 2495 6 537 L 0007 A 1 872 093 42 423 7 421 si 1 362 si 2 56 12 34 S4 uw 67 56 3 05 1 380 C17 E y vraies REFERENCE DIAMETER Z COG 25 67 E 1 28 31 752 25 2 00 50 805 25 Figure 18 Y Mirror top and M3 Galvanometer bottom Dimensions Taken From General Scanning 1992 After thorough study of the sample General Scanning code a PCDIO48 P dual channel digital I O board was purchased from Industrial Computer Source in San Diego CA The PCDIO48 P contains two Intel 8255A 5 programmable peripheral interface integrated circuits IC s designed for use with Intel microprocessors DUUVIS uses an Intel 486DX2 50 microprocessor The 8255 has 24 I O pins constituting 3 I O ports and is capable of several modes of operation Our application calls for Mode 0 basic I O In this mode Ports A and B are utilized for transferring a 16 bit 2 byte binary word while Port C is used for control of the 8255 Each of the 8 pins or channels assigned to an I O port can be toggled individually The 16 bit word is comprised of two 8 bit words Port B passes the high order byte and port A passes the low order byte For example a decimal value of 1797 passed to the
43. nt angle of the incoming light with respect to the optical axis of the Ebert mirror then 0 4 amp represents the incident angle and 0 the exit angle The grating equation becomes n dsin9 dsin 04 d sin 6 0 sin b Q substituting the proper trigonometric identities n d sin 6 cosa cos 6 sin o sind cos amp cos sino m RC m el nh n d 2 singcosa solving for A we arrive at sin 777 Since this is an Ebert monochromator we are dealing with first order spectra therefore n 1 In our instrument is fixed at 9 1014 thus we can determine the grating angle d necessary to obtain the desired minimum detectable wavelength from sin 0 5064 Once 6 is known it can be substituted back into the grating equation to find the values for the corresponding minimum and maximum detectable wavelengths For example with a 1200 line mm grating at an angle of 6 3 Amin 193 nm Amax 328 nm and the instrument bandpass 1s 135 nm A significant increase in bandpass can be achieved by installing a 600 line mm grating Setting the grating angle at 3 0 we obtain Amax 200 nm Amax 476 nm with an instrument bandpass of 276 nm This increase in bandpass does not come without cost Spectral resolution 1s controlled primarily by the instrument dispersion and entrance slit width Instrument dispersion is controlled by among other things the grating ruling density Reducing the
44. nterey California 1994 Industrial Computer Source Model PCDIO Series Product Manual 1995 Jet Propulsion Laboratory AVIRIS in a nutshell ftp ophelia jpl nasa gov 1996 Klein M V T E Furtak Optics 2nd ed John Wiley amp Sons New York 1986 Krueger A J L S Walter P K Bhartia C C Schnetzler N A Krotkov I Sprod and G J 5 Bluth Volcanic Sulfur dioxide measurements from the total ozone mapping spectrometer instruments J Geophys Res 100 14057 14076 1995 Milton Roy Company Diffraction Grating Handbook 2nd ed 1994 57 Mobley C D Light and Water Radiative Transfer in Natural Waters Academic Press Inc New York 1994 Nordic Volcanological Institute NORDVULK Home Page http www norvol hi is 1996 Pearse R W B A G Gaydon The Identification of Molecular Spectra 3rd ed John Wiley amp Sons New York 1963 Richards J A Remote Sensing Digital Image Analysis An Introduction 2nd ed Springer Verlag New York 1993 Samson J A R Techniques of Vacuum Ultraviolet Spectroscopy John Wiley amp Sons New York 1967 Walters D L PH4050 Class Notes 1990 Wilson J J F B Hawkes Optoelectronics An Introduction 2nd ed Prentice Hall New York 1989 Wolfe W L G J Zissis The Infrared Handbook Office of Naval Research Department of the Navy Washington DC 1978 58 U Un INITIAL DISTRIBUTION LI
45. number of rulings by a factor of two causes a reduction in resolution by a factor of two as well There are three plane diffraction gratings currently available for DUUVIS these include 600 l mm 1200 l mm and 2400 l mm This grating assortment allows for extreme flexibility in tailoring the instrument to a variety of applications Table 1 provides a summary of capabilities based on grating ruling density Note that the bandpass and resolution are subject to 16 change while the number of spectral channels bandpass resolution remains fairly constant Two gratings were utilized during this experiment one had 1200 lines mm and the other 600 lines mm The 1200 l mm grating has a bandpass and resolution which match well with the challenges of SO analysis while the 600 l mm is better suited for rocket plume analysis Table 1 Summary of Capabilities Grating Density Instrument Bandpass Resolution nm Vmm nm 7 600 276 2 1 200 155 2 400 64 0 5 B DETECTOR UPGRADE The next step in MUSTANG s conversion was replacement of it s one dimensional PCD detector with a two dimensional detector Adhering to the economical restrictions described earlier the decision was made to adopt a detector which was already employed in the NPS All Reflection Michelson Interferometer AMI Hicks 1995 This detector is contained in a high resolution digital camera the EDC 1000HR produced by the Electrim Corporation and commercially available for un
46. obtained to be compatible with the Electrim object files One minor problem Visual C doesn t contain the outportb command so the _outp command had to be used for sending binary words to the digital I O card MSCNSCAN C listed in the Appendix is the program which finally proved successful in stepping the scanning mirror through a scene while collecting an image file at each position increment along the way Results obtained with this program are provided in the following chapter 38 IV DATA COLLECTION Two UV source lamps were used to conduct initial testing of DUUVIS a mercury Hg lamp with 5 spectral emission lines the strongest of which is at 254 nm and a platinum Pt hollow cathode lamp with 23 spectral emissions between 180 nm and 340 nm Hymas 1994 A wavelength calibration has not yet been conducted on DUUVIS thus the exact correlation between pixel and wavelength is unknown However the images contained herein do illustrate the two dimensional property of the DUUVIS detector in addition to exploiting some of the spectral features of the source lamps themselves This 1s illustrated in Figure 27 a static image taken with the 1200 l mm erating installed in the instrument In this image the two source lamps are separated in height The spectra along the bottom of the image 1s that of the Pt lamp Comparison of the spectral features contained in the image to those of Figure 28 show a nice correlation of the Pt spectra lead
47. of the photocathode to minimize aberrations associated with off axis optics 47 APPENDIX 49 Erik O Johnson Ti DEC 96 77 Program Name MSCNSCAN C RR A DS is This program controls the operation of DUUVIS through one complete n scan through it S FOV It contains commands obtained from the ei htfsamp c program provided by Electrim Corp to save images to disk SE in TIFF format It also contains the basic I O functions required by un the Electronics Digital Driver EDD to control the galvanometer for S DUUVIS scanning mirror It is based upon the sample code listed on Ki pages 44 thru 48 of the M3 Scanner Driver Users Manual by General Wi Scanning Inc Detailed descriptions of the functions called out in S this program are contained in the M3 Scanner Driver Users Manual and Ki in the source code for htfsamp c This program was compiled in Microsoft Visual C Ver 1 52 S pe gi EER K K KE E E E kE Ek k E kE E k kk kE k k SCENE SCAN FOR MICROSOFT VISUAL C include lt stdio h gt include lt stdlib h gt include lt conio h gt include lt dos h gt Finclude lt malloc h gt include lt math h gt include lt string h gt define BASE 0x300 Base address of IO board for define DEV 0x000 scanning mirror interface define A 0x0 define B Ox define C 0x2 define P 0x3 define BASE 0x360 Base address of camera must match camera addres
48. onitor ozone depletion by measuring the ratio of back scattered Earth radiance to incoming solar irradiance representative of UV absorption by the ozone layer As a result of TOMS contiguous spatial mapping of the earth in the Near UV it recorded strong absorptions in its shortest wavelengths due to SO in the volcanic plume during the 1982 El Chichon eruption Krueger et al 1995 Since then TOMS has been monitoring SO with it s four shorter spectral bands 312 5 317 5 331 2 and 339 8 nm to provide a continuous record of volcanism In the previous chapter the NPS UV imaging spectrograph was proposed as a dual use instrument meaning that 1t could support commercial applications in addition to it S support to military operations Providing accurate identification of safe ash cloud perimeters for civilian aircraft as a result of SO analysis is a prime example of such an application A strong portion of the SO absorption spectrum extends down to 260 nm see Figure 4 below This is well below the minimum detectable wavelength of the TOMS instrument Additionally there 1s an overlap of the SO absorption spectrum with the absorption systems of both ozone 300 nm 360 nm and sulfur monoxide SO 250 nm 285 nm which is difficult to discern with a multi spectral instrument A hyperspectral imaging system 1s necessary in this situation to properly sort things out Additionally the proposed NPS instrument is capable of actually being flown throu
49. or the dynamic properties of DUUVIS may be gained through Figure 30 a thru o To actually scan through a 2 5 FOV would require 88 snapshots In Figure 30 15 consecutive snapshots are presented thus illustrating the scanning capability of the instrument For this image a slight separation distance was introduced between the source lamps in both the horizontal and vertical directions As DUUVIS scans through a 0 9 FOV moving from left to right and top to bottom on the page we observe a very strong Hg signature in the first few frames The Hg begins to fade out around frame g and is completely gone by frame CN In similar fashion the Pt signature continues to grow stronger until it peaks out in frame o All the images presented thus far have been in the form of vertical spectral lines Although this is quite normal in spectroscopy it is not very desirable for imaging applications A simple test to obtain a feel for the instruments point spread function PSF was conducted by positioning the Hg lamp approximately two meters away from the entrance of DUUVIS sun shade A shroud was placed over the lamp and two pin holes where poked through it Initially we observed no difference that is we still Observed a vertical spectral line even from a point source After some consideration we realized this is a property of an off axis optical instrument When an object lies an appreciable distance off of the optical axis as is the case in the D
50. re was no other alternative An example of this is the mapping of the intensifier image down onto the detector Another example is the scanning mirror selection Ideally a larger mirror is desirable to eliminate vignetting The mirror currently installed in the instrument was one of only two mirror sizes which the manufacturer offered with a UV sensitive MgF coating A trade off analysis should be conducted to determine how much improvement could be gained by upgrading the current design and at what point does it become advantageous to design a new instrument from the ground up based on lessons learned from DUUVIS At the very least a compact power supply needs to be manufactured for the instrument to replace the bulky laboratory type power supplies currently in use prior to DUUVIS s first UAV flight Finally now that we have an instrument which extends the spectral range of the hyperspectral imagers currently in operation there should be a schedule for frequent data collection In the grand scheme of things DUUVIS is working it s way towards a volcanic ash cloud There are many opportunities right here in our own back yard that shouldn t be overlooked such as rocket plume spectra over at the NPS rocket engine test 46 facility A trip to the beach might prove interesting to see how well DUUVIS performs in the 400 nm to 500 nm portion of the visible spectrum Even in the lab more tests should be conducted to determine the optimum positioning
51. s define V 244 Lines per field define H 733 Bytes returned per line ESI define KEYBOARD CHECK 0 define DEFAULT EXPOSURE 100L 100 millisecond exposure define BiasValue 127 mid scale of bias range define GainValue 175 2 3 scale of gain range typedef unsigned char pixel one byte per pixel typedef pixel far far field field 1s a pointer to an array of pointers Linkable Routines Function Prototypes unsigned short int cdecl far h ghcaml unsigned int int int int int unsigned long int field int int cdecl far init800 void init vga to 800 x 600 void cdecl far display image field unsigned int unsigned int void cdecl far IntDAC unsigned int initialize D A converter void cdecl far SetBiasValue unsigned int unsigned int set bias D A converter void cdecl far SetGainValue unsigned int unsigned int set gain D A converter unsigned short int cdecl far write TIFF char unsigned int unsigned int field unsigned int unsigned int unsigned int unsigned int save image as a tiff file void cdecl far set_ch_mode set VGA to character mode HIGHCAMI argument definitions unsigned int base BASE base address of camera unsigned long exposure time value in milliseconds exposure time DEFAULT EXPOSURE for EDC 1000HR exposure control pixel far buffer V image buffer DISPLAY IMAGE argument definition Each l
52. strument is much greater than the separation distance between the rulings we assume the light rays to be parallel in both the incident and diffracted wavefronts As illustrated in Figure 9 the total difference in path length between two incident rays of light after reflecting off adjacent rulings in the grating is given by dsino d sin D where d is the separation distance between rulings is the incident angle and f is the exit angle When this difference in path length is equal to an integral multiple n of the wavelength of interest the reflected rays will be in phase and produce a spectral line of order n At all other angles there is some measure of destructive interference Therefore the diffracted beams will only exist at the angles D as prescribed by the grating equation n dsmo dsinp where n order number of the spectral line of interest A wavelength of the spectral line of interest o Incident angle of the incoming light onto the grating D Exit angle of spectral line of interest It was previously stated that rotation of the grating determined the minimum detectable wavelength How is that grating angle determined Suppose we rotate the grating normal incident wavefront diffracted wavefront Figure 9 Geometry of Diffraction Taken From Milton Roy Company 1994 15 grating so that it s normal is displaced by an angle amp while keeping amp constant We define amp to be the incide
53. tons are then directed to the output of the IIT via a 25 millimeter diameter fiber optic faceplate which preserves the spatial order of the image The incident UV light is thus converted into visible light within the CCD s sensitivity range The CCD utilized in the digital camera is a TI 241chip manufactured by Texas Instruments which consists of a two dimensional array 753 H x 244 V pixels of closely spaced metal oxide semiconductor MOS capacitors Incident photons have energies which exceed the bandgap energy of the silicon material of the MOS capacitor This causes them to be absorbed by the semiconductor material resulting in the formation of an electron hole pair Electrons are collected in energy wells generated by each of the MOS capacitors when their gates are positively biased 1 e during the integration portion of the operation cycle The amount of charge collected in each of these packets is proportional to the total integrated light flux incident upon an individual MOS capacitor during the measurement period Wilson and Hawkes 1989 Read out of the charge packets is accomplished by sequentially reversing the bias on the capacitors thereby transferring the stored charge from the image columns exposed to incident radiation to the vertical shift registers which are shielded from incident radiation During the scan period each charge packet is sequentially transferred from the vertical shift registers to E the horizontal sh
54. upler Assembly coupler assembly Inspite of the close tolerances and after numerous phone calls and facsimile exchanges an acceptable detector assembly was delivered in November 1995 Upon arrival of the new detector assembly the next challenge was to mount it onto the spectrograph while preserving the integrity of the off axis telescope This was a rather delicate operation A mounting clamp was designed consisting of two half shells which when bolted together provided support for the lens coupler in addition to providing a means for attaching it to the spectrograph The clamp was manufactured by the Physics Department Machinist and subsequently the painstaking process of fitting the lens coupler with the telescope began The mounting clamp located at the front of the DUUVIS detector assembly is shown at the top of Figure 16 which illustrates the size difference between the MUSTANG and DUUVIS detector assemblies Both the telescope and lens coupler were made of aluminum with fairly thin wall thickness If too much metal was removed from any given area the section being reduced would begin to tear and the integrity of the component would be violated An iterative cycle of disassembly machining reassembly and measurement was implemented to ensure just enough metal was removed from the right places The result of this process was a very precise fit to a tolerance of 0 001 An appreciation of the close fit between the telescope and the D
55. ure an optical coupler between the IIT and CCD Now the COTS requirement added to our challenge MUSTANG s direct coupling between IIT and PCD made for a very compact detector assembly Since the instrument was used in sounding rocket experiments MUSTANG s designers were pretty stingy with it s real estate See Figure 13 As a result there wasn t much clearance between the back of the off axis telescope and the detector assembly Naturally we desired the overall length of the DUUVIS detector assembly to remain consistent with that of MUSTANG in order to avoid having to build a new telescope Unfortunately the commercially available lenses under consideration for the new optical coupler possessed focal lengths which precluded matching detector assembly lengths and fabrication of lenses to meet that requirement were simply cost prohibitive There were other considerations as well Should the mapping of the IIT be fully contained in the detector or vice versa 1 e should the circle be contained within the rectangle or the rectangle be contained within the circle At that time the AMI experiment was in full swing so we decided on the circle in a square mapping to maximize the resolution of the fringes observed with the AMI Figure 14 Figure 13 The MUSTANG Instrument Telescope Spectrograph and Detector Assembly 21 illustrates the geometry of the mapping Once the mapping geometry was determined the most challenging dimension b
56. ware for control of the instrument and software to enable analysis of the data after 1t has been collected Numerous problems encountered during the development of the initial instrument control software precluded any progress toward data analysis In this experiment it was necessary for instrument control software to be developed first in order to obtain a working instrument Approaching the problem from the opposite end might prove to be more productive The premiere software on the market for analysis of 45 hyperspectral imagery is ENVI It is a very powerful software package that is written in the Interactive Data Language IDL IDL has the capability to control peripheral devices The instrument would operate much more efficiently if it could continuously download data to an ENVI file vice store each snapshot as a TIFF and subsequently combine files to make an image There is potential for very productive research in this area Before it can provide useful data the instrument must undergo a wavelength calibration Additionally the scanning mirror must be bore sighted to precisely determine it s FOV at the center position Finally sensitivity tests should be performed on the instrument prior to it s first UAV flight These three items could easily work into a thesis This initial cut at building a hyperspectral instrument was conducted on a shoestring budget There are several aspects of the design which were accepted mostly because the
57. y AMON FOR A UN IMAGING SPECTROGRAPH 8 BEN DE SCRIE TONT rn iii 10 TU Mil Del ING ONY NACH L EEN 13 As EAU SELECTION TEE e E iae 14 BEE BESTOTTERSERADET en nenne nie 17 aoe eo INNING MIRROR INSTALLATION nn rr m mmm I e Imm 26 EN PERS RED VEBOREMEN Eer 35 Los A A EU CIONI ecc 39 s CONC HUS No aT 45 A IIA SA A cC M 45 PARE CONMENDA TON FOR FURTHER RESEARCH ee NN SEELEN 45 APPEND aro E 49 MERECES TT HSL Ta TRIBUTION E LK cre eece he rtr mmm Im mIBR 59 Vil Vili AMI AVIRIS CCD COTS Cs Le DUUVIS EDD FOV FUV Hg IDL IFOV LSB MCP MgF MOS MSB MTF MUSTANG MUV NPS NUV OPD PSE Iu TIFF UAV UV LIST OF ABBREVIATIONS All Reflection Michelson Interferometer Airborne Visible Infrared Imaging Spectrometer Charge Coupled Device Commercial Off The Shelf Cesium Telluride Dual Use UltraViolet Imaging Spectrograph Electronic Digital Driver Field Of View Far Ultraviolet Mercury Interactive Data Language Instantaneous Field Of View Least Significant Bit Microchannel Plate Magnesium Fluoride Metal Oxide Semiconductor Most Significant Bit Modulation Transfer Function Middle Ultraviolet SpecTrograph for Analysis of Nitrogen Gases Middle Ultraviolet Naval Postgraduate School Near Ultraviolet Optical Path Difference Point Spread Function Platinum Tagged Image File Format Unmanned Aerial Vehicle Ultraviolet 1X I INTRODUCTION Over the past decade
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