SIGGRAPH 2012 Computational Plenoptic Imaging Course - 3 Spectral Imaging
Post on 18-May-2015
3998 Views
Preview:
DESCRIPTION
Transcript
Spectral Imaging
Ivo IhrkeSaarland University/MPI Informatik
• spectrometer
The spectral data cube
disadvantage:• dispersion relation is nonlinearadvantage:• light efficient
Principle of Operation - Dispersion
Diffraction Grating
– At center, no diffraction
– For higher orders, diffraction is
taking place
Diffraction Order Percentage of transmitted Light
0 25%
1 20.26%
2 10.13%
3 2.25%
4 0 %
remainder 9.72%
disadvantage:• low light efficiencyadvantage:• linear relation pixel pos. <-> wavelength
– Diffraction-based example ->
– Spectrometer calibration (all types)
1. mapping
pixel <–> wavelength
2. relative intensity of wavelengths
Diffraction-Based Systems
The spectral data cube
• E.g. in satellite imaging
– Pushbroom scanning
• Spatial Scanning (2D sensor)
Spatial Scanning• Generalized Mosaics [Schechner & Nayar]
• linear filter
• each pixel column filtered differently
• rotational motion & registration to assemble image stack
• Spectral scanning
The spectral data cube
Frequency Scanning
• Michelson Interferometer with moving mirror - Fourier Transform Imaging Spectroscopy (FTIS)
Imaging Spectrometers
The quest for the instantaneous spectral data cube
(4D Imaging)
Multiplexing - Image slicers
[WiFeS – Wide Field Spectrometer]
[SPIFFI - SPectrometer for Infrared Faint Field Imaging]
Multiplexing - Image slicers
Fiber Optical cables (OKSI)
2D -> 1D reformatting
300 “pixels”
Multiplexing: Prism-Mask Based System
[Du’09]
Computational Imaging Spectrometers
The quest for the instantaneous spectral data cube
• Original method [Descour’95]
• Image a full diffraction pattern
• Perform “CT”
CTIS – Computed Tomography Imaging Spectrometry
diffraction patternspectral image
CTIS in graphics
• HDR imaging
for CTIS(not snapshot due to HDR exposure stack)
[Habel’12]
CTIS in graphics
• Spatial resolution 124x124, 54 bands
[Habel’12]
CASSI – Coded Aperture Snapshot Spectral
Imaging
CASSI – Coded Aperture Snapshot Spectral
Imaging
Implementation with prisms
• Resolution: spatial ~200 x 200 pixels
spectral ~30 bands
CASSI – Coded Aperture Snapshot Spectral Imaging
projection reconstruction (stack) spectra
• Transfer low-res spectra to high res RGB image [Rump’10,Cao’11]
Spectral Transfer
Applications
Applications
• automatic white balancingSpatially uniform illumination
[Cao11]Spatially varying illumination
raw from RGB tungsten WB `greyworld WB spectral WB spectra
Applications
• improved tracking
• real and fake skin detection[Cao11]
RGB – tracking lost
spectral – tracking OK
Applications• analyze / restore paintings
[Calit]
Applications• Satellite-Based Remote Sensing
[DigitalGlobe’10]
vegetation mapping urban land use pollution monitoring
• 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”
top related