Dario Cabib, Amir Gil, Moshe Lavi. Edinburgh April 11, 2011

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1 New LWIR Spectral Imager with uncooled array SI-LWIR LWIR-UC Dario Cabib, Amir Gil, Moshe Lavi Edinburgh April 11, 2011

2 Contents BACKGROUND AND HISTORY RATIONALE FOR UNCOOLED CAMERA BASED SPECTRAL IMAGER OPTICAL CONFIGURATION AND FIELD USE DESIGN SPECIFICATIONS CONCLUSION

3 Background CI has been has a long history of remote sensing equipment development and commercialization: Vis/IR spectroradiometry and spectral imaging. 3

History of Spectral Imaging at CI Systems LWIR spectral imager

dual-mode spectral imager, based on a scanning Sagnac, for

spectral imager, based on a scanning Sagnac VIS, 256x256 pixels

4 History of Spectral Imaging at CI Systems LWIR spectral imager based on a fixed block Sagnac, uncooled FPA 640x480 SD-300 dual-mode spectral imager, based on a scanning Sagnac, for microscopy VIS-NIR 1Kx1K pixels SD-100 SpectraCube first staring spectral imager, based on a scanning Sagnac VIS, 256x256 pixels SI5000 MWIR spectral imager based on a fixed block Sagnac, 320x256 pixels 4

5 MWIR/LWIR Gas transmittance/emittance in the air 5

6 Motivation for this work There are unanswered LWIR applications of spectral imaging with affordable instrumentation Cooled 8-12µ arrays are prohibitively expensive for routine applications use Uncooled LWIR arrays are within reasonable price and unexploited in this field CI, as a commercial company, is attempting to develop an affordable LWIR SI product

7 LWIR applications Study of ambient temperature scenes Study of aerosol clouds Signature studies 7

8 Previous work Two academic groups are working on uncooled array based Long Wave IR spectral imagers : Paul Lucey et al., U. of Hawaii,. Sagnac interferometer with uncooled detectors for IR hyperspectral applications, SPIE 6565, Ingmar Renhorn et al., DRA Sweden, Demonstration of a Corner-cube-interferometer LWIR hyperspectral imager, J. Infrared Milli Terahertz Waves, 2009.

9 Spectral Imagers Instrumentation that provides calibrated spectra at each pixel of a scene X λ (x 1, y 1 ) λ n λ λ 1 λ 2 λ 3 λ 4 Y λ 9

10 Fourier Spectroscopy X1 X = X1 - X2 FPA INTERFEROGRAM X2 SPECTRUM FT INTENSITY Optical Path Difference [µm] WAVELENGTH [nm] 10

11 Pushbroom with interferometric design The interference pattern is superimposed on the FPA with the image of the scene. Scanning process acquires a frame every IFOV (Instantaneous Field of View) OPD 0 OPD Max 11

12 Sagnac Interferometer The angle of incidence of the incoming ray with the beamsplitter normal generates an OPD (Optical Path Difference) between the two coherent wavefronts which is proportional to this angle. 12

13 Optical Configuration Ray from scene Folding mirror 1 Telescope objective Axis of rotation for pushbroom scanning Beamsplitter plane Block interferomete r Folding mirror 2 Focusing optics Uncooled detector array 13

14 SI-LWIR LWIR-UC Design specifications Spectral range 8-14 µm Spectral resolution of 8 wavenumbers IFOV 0.5 mrad, 640 x 480 format FPA Field of View 18 0 x13 0 Widest cube horizontal Collection time for 18 0 x13 0 : <1 minute NESR (nw/cm 2 /sr/cm -1 ): Field and lab operation Calibrated spectral images 14

15 Field of View Response INSTRUMENT FOV 100 Normalized ang gular response ANGLE (de g.) 15

16 Optics MTF SYSTEM POLYCHROMATIC MTF Center and sagittal Pixel frequency: 40 cy/mm MTF Tangential SPATIAL FREQUENCY (CYCLES/MM.) Center: Tangential and Sagittal Vertical FOV edge tangential Vertical FOV edge sagittal FOV corner tangential FOV corner sagittal Detector limited behavior 16

17 Detector-with-window response Detector spectral response 100 Relative unit ts Wavelength (µ) 17

18 SolidWorks look Cross section Head mirror CCD for scene viewing Interferometer Camera Rotating stage for pushbroom operation 18

19 The way it looks

20 Conclusions CI is in the final stage of development of a new affordable LWIR spectral imager for unanswered LWIR applications of spectral imaging Unfortunately, I don t have yet measured performance results to show We hope to present them in a near future paper For more info on the present work, see the paper

New 3-5 µ wavelength range hyperspectral imager for ground and airborne use based on a single element interferometer

New 3-5 µ wavelength range hyperspectral imager for ground and airborne use based on a single element interferometer Dario Cabib, Amir Gil, Moshe Lavi, Robert A. Buckwald CI Systems Ltd., Industrial Park