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SIGGRAPH 2012 Computational Plenoptic Imaging Course - 3 Spectral Imaging

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SIGGRAPH 2012 Computational Plenoptic Imaging Course - 3 Spectral Imaging

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SIGGRAPH 2012 Computational Plenoptic Imaging Course - 3 Spectral Imaging

  1. 1. Spectral Imaging Ivo IhrkeSaarland University/MPI Informatik
  2. 2. The spectral data cube • spectrometer
  3. 3. Principle of Operation - Dispersiondisadvantage:• dispersion relation is nonlinearadvantage:• light efficient
  4. 4. Diffraction Grating Diffraction Order Percentage of transmitted Light– At center, no diffraction 0 25% 1 20.26%– For higher orders, diffraction is 2 10.13% 3 2.25% taking place 4 0% remainder 9.72% disadvantage: • low light efficiency advantage: • linear relation pixel pos. <-> wavelength
  5. 5. Diffraction-Based Systems– Diffraction-based example ->– Spectrometer calibration (all types)1. mapping pixel <–> wavelength2. relative intensity of wavelengths
  6. 6. The spectral data cube• Spatial Scanning • E.g. in satellite imaging (2D sensor) – Pushbroom scanning
  7. 7. Spatial Scanning • Generalized Mosaics [Schechner & Nayar] • linear filter • each pixel column filtered differently • rotational motion & registration to assemble image stack
  8. 8. The spectral data cube• Spectral scanning
  9. 9. Frequency Scanning • Michelson Interferometer with moving mirror - Fourier Transform Imaging Spectroscopy (FTIS)
  10. 10. Imaging SpectrometersThe quest for the instantaneous spectral data cube (4D Imaging)
  11. 11. Multiplexing - Image slicers[WiFeS – Wide FieldSpectrometer]
  12. 12. Multiplexing - Image slicers[SPIFFI - SPectrometer forInfrared Faint Field Imaging]
  13. 13. Fiber Optical cables (OKSI)300 “pixels”2D -> 1D reformatting
  14. 14. Multiplexing: Prism-Mask Based System [Du’09]
  15. 15. Computational Imaging SpectrometersThe quest for the instantaneous spectral data cube
  16. 16. CTIS –Computed Tomography Imaging Spectrometry • Original method [Descour’95] • Image a full diffraction pattern • Perform “CT” spectral image diffraction pattern
  17. 17. CTIS in graphics • HDR imaging for CTIS [Habel’12] (not snapshot due to HDR exposure stack)
  18. 18. CTIS in graphics • Spatial resolution 124x124, 54 bands [Habel’12]
  19. 19. CASSI – Coded Aperture Snapshot Spectral Imaging
  20. 20. CASSI – Coded Aperture Snapshot Spectral Imaging Implementation with prisms
  21. 21. CASSI – Coded Aperture Snapshot Spectral Imaging • Resolution: spatial ~200 x 200 pixels spectral ~30 bands projection reconstruction (stack) spectra
  22. 22. Spectral Transfer • Transfer low-res spectra to high res RGB image [Rump’10,Cao’11]
  23. 23. Applications
  24. 24. Applications • automatic white balancingSpatially uniform illuminationraw from RGB tungsten WB `greyworld WB spectral WB spectra Spatially varying illumination [Cao11]
  25. 25. Applications • improved tracking RGB – spectral – tracking lost tracking OK • real and fake skin detection [Cao11]
  26. 26. Applications • analyze / restore paintings [Calit]
  27. 27. Applications • Satellite-Based Remote Sensingvegetation mapping urban land use pollution monitoring [DigitalGlobe’10]
  28. 28. • Multispectral at Siggraph’12 – Kim, Harvey, Kittle, Rushmeier, Dorsey, O’Prum, and Brady “3D Imaging Spectroscopy for Measuring Hyperspectral Patterns on Solid Objects”, Monday, 3:45 - 5:35 – “Appearance” – Hosek and Wilkie, “An Analytic Model for Full Spectral Sky-Dome Radiance”, Wednesday 3:45-5:35 pm – “Physics and Mathematics for Light”

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