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Image Based Prediction of Thermal Imaging Performance

This paper explores the prediction of thermal sensor performance prior to operation in specific scenes. It addresses applications relevant to space probes, electro-optical missiles, and medical probes. Building on previous research, the study focuses on high-quality thermal imagery by considering scene radiance, atmospheric transmittance, and noise handling. The authors, Saar Bobrov and Yoav Schechner, delve into techniques for effective simulation, signal processing, and noise reduction, aiming to improve the diagnostic capabilities of thermal imaging systems.

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Image Based Prediction of Thermal Imaging Performance

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  1. Image Based Prediction ofThermal Imaging Performance Saar Bobrov Yoav Y. Schechner Department of Electrical Engineering,Technion Acknowledgement: Rafael Ltd.

  2. The Problem • Predict sensor performance • Prior to operation • In specific scenes Bobrov & Schechner

  3. Applications • Space probes • Electro-optical missiles • Medical Probes Bobrov & Schechner

  4. Previous work • Performance based on imager characteristics • Ratches 75’; Wittenstein and Gal 03’ • Synthetic scenes • Wegner and Drake 00’; Toler and Grey 80’ • Image based/Example based: • Texture synthesis • Wei and Levoy 00’; Heeger and Bergen 95’ • Image analogies • Hertzman and Jacobs 01’; Drori and Cohen-or 03’

  5. Systems Introduction High quality Thermal Sight Simulation Hi-q imaging Hi-q Imaging parameters Scene radiance Low quality Missile seeker Lo-q imaging Lo-q Bobrov & Schechner

  6. From Photons to Gray Levels Scene Optical Assembly Photon Irradiance Photon Radiance Signal Processing Electronic Signal Gray level Image Detector Module Bobrov & Schechner

  7. Optical Assembly Lens Scanning mirror Body Cold filter Cold shield Bobrov & Schechner

  8. Atmospheric Transmittance

  9. Cold Shield Internal radiation Body Cold shield Internal radiation Detector Filter Internal radiation Bobrov & Schechner

  10. Optical Assembly Lens Scanning mirror Body Cold filter Cold shield Bobrov & Schechner

  11. Optical Functional Diagram Projection Blur Irradiance Photon Radiance Projected radiance Blurred radiance Photon irradiance Bobrov & Schechner

  12. Projection Scene radiance Detector Bobrov & Schechner

  13. Blur Optical PSF Bobrov & Schechner

  14. Irradiance Internal radiance Direct Reflected Camera body Scene radiance Detector Optics radiance Cold Shield Bobrov & Schechner

  15. From Photons to Gray Levels Scene Optical Assembly Photon Irradiance Photon Radiance Signal Processing Electronic Signal Gray level Image Detector Module Bobrov & Schechner

  16. Detector Circuit Integration switch Readout Output Photons Integration InSb Capacitor Bobrov & Schechner

  17. Detector Flow Diagram Photo- detection Crosstalk Photon irradiance Electron Flux Electron Flux Electric signal Readout Sampling Noise Electrons Bobrov & Schechner

  18. Photo-Detection Photons Electron Flux InSb Bobrov & Schechner

  19. Detector Flow Diagram Photo- detection Crosstalk Photon irradiance Electron Flux Electron Flux Electric signal Readout Sampling Noise Electrons Bobrov & Schechner

  20. Crosstalk Crosstalk PSF Photons Bobrov & Schechner

  21. Detector Flow Diagram Photo- detection Crosstalk Photon irradiance Electron Flux Electron Flux Electric signal Readout Sampling Noise Electrons Bobrov & Schechner

  22. Sampling Δxd α β Δyd Bobrov & Schechner

  23. Detector Flow Diagram Photo- detection Crosstalk Photon irradiance Electron Flux Electron Flux Electric signal Readout Sampling Noise Electrons Bobrov & Schechner

  24. Noise • Noise components: • Shot noise: • Residual Non-Uniformity Bobrov & Schechner

  25. Lo-q Non-Uniformity Bobrov & Schechner

  26. Hi-q Non-Uniformity Bobrov & Schechner

  27. Noise • Noise components: • Shot noise: • Residual non-uniformity • Excess noise • RMS noise amplitude: • Noisy image: Bobrov & Schechner

  28. Detector Flow Diagram Photo- detection Crosstalk Photon irradiance Electron Flux Electron Flux Electric signal Readout Sampling Noise Electrons Bobrov & Schechner

  29. From Photons to Gray Levels Scene Optical Assembly Photon Irradiance Photon Radiance Signal Processing Electronic Signal Gray level Image Detector Module Bobrov & Schechner

  30. Signal Processing Electric signal Median subtraction A/D Add Gray level image Bobrov & Schechner

  31. 255 I8bit(m,n) [Digital units] Vmin V (m,n) [volt] Vmax Analog to Digital Conversion Bobrov & Schechner

  32. Signal Processing Electric signal Median subtraction A/D Add Gray level image Bobrov & Schechner

  33. Median Subtraction • Omits large DC signal before A/D • Subtracts non-uniformity between detector elements Bobrov & Schechner

  34. Signal Processing Electric signal Median subtraction A/D Add Gray level image Bobrov & Schechner

  35. Line Add to Standard Format Detector Array 120 lines 240 lines Bobrov & Schechner

  36. Signal Processing Electric signal Median subtraction A/D Add Gray level image Bobrov & Schechner

  37. Problem • How does the scene look like??

  38. From Gray Levels to Photons Optical Assembly Hi-q image Photon Irradiance Photon Radiance Signal Processing Hi-q image Electronic Signal Grey level Image Detector Module Bobrov & Schechner

  39. Inversion Pitfalls • Deblurring Hi-q Image Lo-q Image … Hi-q Deblur … Simulated Scene … Lo-q Blur … Bobrov & Schechner

  40. Blur Frequency Response HHi-q HLo-q Bobrov & Schechner

  41. Deblur Operation 1/HHi-q HLo-q/HHi-q HLo-q Bobrov & Schechner

  42. Noise Handling • Hi-q image is noisy: • No inversion to noise • Adding Lo-q noise • Estimate Hi-q noise • Calculate Lo-q noise amplitude: Bobrov & Schechner

  43. Experiments Courtesy of Rafael Ltd.

  44. Hi-q Image Bobrov & Schechner

  45. Lo-q Image Bobrov & Schechner

  46. Simulated Image Bobrov & Schechner

  47. Lo-q Hi-q Simulation Bobrov & Schechner

  48. Hi-q Image Bobrov & Schechner

  49. Lo-q Image Bobrov & Schechner

  50. Simulated Image Bobrov & Schechner

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