Survey of Hyperspectral Imaging TechniquesCompared SystemsPoints of ComparisonBaseline – Scanning FilterBaseline – PushbroomGehm (Brady) – Multiplexed Pushbroom Gehm (Brady) – Multiplexed Pushbroom (2) Wagadarikar (Brady) – Single DisperserGehm (Brady) – Dual DisperserSingle/Dual Disperser ComparisonSingle/Dual Disperser ComparisonSingle/Dual Disperser ComparisonDescour – CTIS Mooney – Prism tomographic Gentry – ISIS Mohan (Raskar) – Agile Spectrum ImagingMohan (Raskar) – Agile Spectrum Imaging spectral selectivity Summary© 2009 The MITRE Corporation. All rights Reserved.Michael D. StennerOctober 30, 2009Survey of Hyperspectral Imaging Techniques© 2009 The MITRE Corporation. All rights Reserved.Compared Systems■ Baseline – Scanning Filter■ Baseline – Simple Pushbroom■ Gehm (Brady) – Multiplexed Pushbroom– “High-throughput, multiplexed pushbroom hyperspectral microscopy”■ Wagadarikar (Brady) – Single Disperser– “Single disperser design for coded aperture snapshot spectral imaging”■ Gehm (Brady) – Dual Disperser– “Single-shot compressive spectral imaging with a dual-disperser architecture”■ Descour – CTIS– “Computed-tomography imaging spectrometer: experimental calibration and reconstruction results”■ Mooney – Prism Tomographic– “High-throughput hyperspectral infrared camera”■ Gentry – ISIS– “Information-Efficient Spectral Imaging Sensor”■ Mohan (Raskar) – Agile Spectrum Imaging– “Agile Spectrum Imaging: Programmable Wavelength Modulation for Cameras and Projectors”© 2009 The MITRE Corporation. All rights Reserved.Points of Comparison■ Data volume■ Physical volume■ Architectural impact on acquisition time■ Computational reconstruction and scaling■ Photon efficiency (noise, sensitivity, etc.)■ Compression (Information efficiency)Caveats■ Many quantities (like physical volume and reconstruction scaling) depend heavily on the specific implementation. Interpret these results as expected limits.■ Data quality metric – there is none. Different techniques can be expected to produce different amounts and types of artifacts. These are discussed qualitatively herein.© 2009 The MITRE Corporation. All rights Reserved.Baseline – Scanning FilterxytunablefiltersensorSummary:• Data Cube: Nxx Nyx L• Volume: 1f * D2• Acquisition time: scanning.• Reconstruction: None• Photon Efficiency: 1/L• Compression: 1spectralspatialscan in λScan in λ using an electronically-tunable filter. Typically, the filter is based on either liquid crystals or acousto-optic principles.© 2009 The MITRE Corporation. All rights Reserved.Baseline – PushbroomxyslitgratingsensorSummary:• Data Cube: Nxx Nyx L• Volume: 5f * D2• Acquisition time: Mechanical motion is required between lines (resulting in photon dead-time) but object motion is treated stably.• Reconstruction: None• Photon Efficiency: 1/Nx• Compression: 1spectralspatialscan in xEach row on the sensor provides a spectrum at that y value. Scanning in x provides the other spatial dimension.© 2009 The MITRE Corporation. All rights Reserved.Gehm (Brady) – Multiplexed PushbroomxycodesensorgratingSummary:• Data Cube: Nxx Nyx L• Volume: 5f * D2• Acquisition time: Mechanical motion is required between lines.• Reconstruction: O(NxNy2L)• Photon Efficiency: ~1/2• Compression: ~1spectralspatialscan in y5 10 15510155 10 15510155 10 1551015code/decode orthogonality requires scene uniformity in y.by sliding code over scene vertically (or vice versa) one can mix rows to synthesize columns of uniform scene value.© 2009 The MITRE Corporation. All rights Reserved.Gehm (Brady) – Multiplexed Pushbroom (2)• Reconstruction: O(NxNy2L) = O(NxNyL x Ny)Every point in the data cube is a dot-product of length-Ny vectors.• Scanning options:• Scan scene over code for “continuous” pushbroom mode, requiring slightly more complex data re-mapping, or• Circularly scan code through the field stop for fixed-field capture• In prototype systems, resolution was set by code size to order 6x6 CCD pixels for processing/sampling convenience. The re-binning and digital aberration (smile) correction was not included in the reconstruction scaling.© 2009 The MITRE Corporation. All rights Reserved.Wagadarikar (Brady) – Single DisperserxycodesensorgratingSummary:• Data Cube: Nxx Nyx L• Volume: 5f * D2• Acquisition time: Mechanical motion is required between lines (if any).• Reconstruction: O((NxNyL)3), L1minimization• Photon Efficiency: ~1/2• Compression: 1/L to 1spectralspatialscan in y• Identical hardware to Multiplexed Pushbroom• Skip scan steps or don’t scan at all• Reconstruct via L1minimization• Reduced spatial information in single-shot mode – object pixels imaged to closed code addresses are completely lost© 2009 The MITRE Corporation. All rights Reserved.Gehm (Brady) – Dual DisperserSummary:• Data Cube: Nxx Nyx L• Volume: 9f * D2• Acquisition time: Snapshot• Reconstruction: O((NxNyL)3), L1minimization• Photon Efficiency: ~1/2• Compression: 1/L• Raw measured frames are spatially isomorphic with scene – each pixel is a spectral projection.Images removed due to copyright restrictions.Source: Gehm, M. E. et al. “Single-shot Compressive Spectral Imaging with a Dual-disperser Architecture.”Optics Express 15, no. 21 (2007): 14013-14027.© 2009 The MITRE Corporation. All rights Reserved.Single/Dual Disperser Comparison5 10 152468101214165 10 152468101214165 10 152468101214165 10 152468101214165 10 152468101214165 10 15246810121416scene after mask measuredsingledual© 2009 The MITRE Corporation. All rights Reserved.Single/Dual Disperser Comparisonscene after mask measuredsingledual5 10 152468101214165 10 152468101214165 10 15246810121416510152468101214165101524681012141651015246810121416© 2009 The MITRE Corporation. All rights Reserved.Single/Dual Disperser Comparisonscene after mask measuredsingledual5 10 152468101214165 10 152468101214165 10 152468101214165 10 152468101214165 10 152468101214165 10 15246810121416© 2009 The MITRE Corporation. All rights Reserved.Descour – CTISSummary:• Data Cube: Nxx Nyx L• Volume: 4f * D2• Acquisition time: Snapshot• Reconstruction: O(n3), FBPO(n2log n), Fourier• Photon Efficiency: 1• Compression: ~1• Inefficiently uses sensor; dead spaces required to avoid overlap.• Requires P > Nxx Nyx L pixels• Limited information
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