Single-shot spectral imager
A single-shot spectral imager or imaging system which acquires multiplexed spatial and spectral data in a single snapshot with high optical collection efficiency and with the speed limited only by the readout time of the detector circuitry. The imager uses dispersive optics together with spatial light modulators to encode a mathematical transform onto the acquired spatial-spectral data. A multitude of encoded images is recorded simultaneously on a focal plane array and subsequently decoded to produce a spectral/spatial hypercube.
1. A multiplexing array spectral imager for simultaneously acquiring multiplexed spatial and spectral data from incoming light representing a scene, comprising:
a two-dimensional focal plane array (FPA) for capturing an image, the FPA defining a plurality of pixels;
a first optical system that creates a plurality of intermediate sub-images each representing at least part of the imaged scene;
a second optical system that includes a spectrally dispersive element and creates a spectrally dispersed image for each sub-image created by the first optical system;
a spatial light modulator (SLM) that receives the spectrally dispersed sub-images, the SLM defining a two-dimensional array of encoding sub-masks each containing a plurality of elements that either transmit, block or reflect some or all of the light that impinges on them to thereby accomplish a transform of the spectral data within the spectrally dispersed sub-images and create spectrally-encoded intermediate sub-images;
a third optical system that receives spectrally dispersed and encoded intermediate sub-images and includes a spectrally de-dispersive element, to spectrally de-disperse the intermediate sub-images and create a plurality of spectrally encoded sub-images that are imaged onto the FPA; and
a processing system that applies the inverse transform to the sub-images that were imaged onto the FPA, to produce a set of spectrally and spatially resolved images.
2. The multiplexing array spectral imager of claim 1 in which the second optical system comprises a first polychromator.
3. The multiplexing array spectral imager of claim 2 in which the first polychromator comprises one or more collimating lenses, one or more dispersive elements and one or more imaging lenses.
4. The multiplexing array spectral imager of claim 3 in which the first polychromator comprises a first lenslet array, a first dispersive element or a first array of dispersive elements, and a second lenslet array.
5. The multiplexing array spectral imager of claim 4 in which the first and second lenslet arrays each define at least N lenslets, where N equals the number of spectral bands in the acquired spectral image.
6. The multiplexing array spectral imager of claim 5 in which the third optical system comprises a second polychromator.
7. The multiplexing array spectral imager of claim 6 in which the second polychromator comprises one or more collimating lenses, one or more dispersive elements and one or more imaging lenses.
8. The multiplexing array spectral imager of claim 7 in which the second polychromator comprises a third lenslet array, a second dispersive element or a second array of dispersive elements, and a fourth lenslet array.
9. The multiplexing array spectral imager of claim 8 in which the third and fourth lenslet arrays each define at least N lenslets, where N equals the number of spectral bands in the acquired spectral image.
10. The multiplexing array spectral imager of claim 1 in which there are at least N spectrally dispersed sub-images, and the SLM defines the same quantity of sub-masks as sub-images.
11. The multiplexing array spectral imager of claim 10 in which each sub-mask contains a number of elements N equal to the number of spectral bands N defined by the imager.
12. The multiplexing array spectral imager of claim 1 in which the encoding sub-masks represent one-dimensional spectral Hadamard transforms in the form of Simplex or S-matrices.
13. The multiplexing array spectral imager of claim 12 in which the encoding sub-masks are transmission or reflection masks.
14. The multiplexing array spectral imager of claim 13 in which the masks have fixed transmission or reflection characteristics.
15. The multiplexing array spectral imager of claim 13 in which the masks are electronically controlled such that the modulation accomplished by the masks can be changed.
16. The multiplexing array spectral imager of claim 1 in which the SLM comprises an array of spectrally-varying filters that isolates the spectral Fourier components of the image in the sub-images.
17. The multiplexing array spectral imager of claim 1 further comprising a second FPA, and a fourth optical system that receives light reflected from the SLM and creates a plurality of encoded sub-images that are imaged onto the second FPA.
18. The multiplexing array spectral imager of claim 17 in which the encoding sub-masks represent one-dimensional spectral Hadamard or Hadamard-Walsh transforms.
19. The multiplexing array spectral imager of claim 17 in which spectral content received from all bands is simultaneously utilized.
20. A multiplexing array spectral imager for simultaneously acquiring multiplexed spatial and spectral data from incoming light representing a scene, comprising:
a two-dimensional focal plane array (FPA) for capturing an image, the FPA defining a plurality of pixels;
a first optical system in the light path that creates a plurality of intermediate sub-images each representing the imaged scene;
a spatial light modulator (SLM) that receives the intermediate sub-images, the SLM defining a two-dimensional array of encoding sub-masks each containing a plurality of elements that either transmit, block or reflect some or all of the light that impinges on them, to thereby accomplish a transform of the spatial data within the intermediate sub-images and create spatially-encoded intermediate sub-images;
a second optical system that receives the encoded intermediate sub-images and includes a spectrally dispersive element and creates a plurality of spectrally resolved sub-images that are imaged onto the FPA; and
a processing system that applies an algorithm to the sub-images that were imaged onto the FPA, to produce a set of spectrally and spatially resolved images.
21. A multiplexing array spectral imager for simultaneously acquiring multiplexed spatial and spectral data from incoming light representing a scene, comprising:
a two-dimensional focal plane array (FPA) for capturing an image, the FPA defining a plurality of pixels;
a first optical system that creates a plurality of intermediate sub-images each representing at least part of the imaged scene;
a second optical system that includes a spectrally dispersive element and creates a spectrally dispersed image for each sub-image created by the first optical system;
a spatial light modulator (SLM) that receives the spectrally dispersed sub-images, the SLM defining a two-dimensional array of encoding sub-masks each containing a plurality of elements that either transmit, block or reflect some or all of the light that impinges on them to thereby accomplish a transform of spectral data within the intermediate sub-images and create spectrally encoded intermediate sub-images;
a third optical system that receives the spectrally dispersed and encoded intermediate sub-images and includes a spectrally de-dispersive element, to spectrally de-disperse intermediate sub-images and create a plurality of spectrally encoded sub-images that are imaged onto the FPA; and
a processing system that applies the inverse transform to the sub-images that were imaged onto the FPA, to produce a set of spectrally and spatially resolved images, and a processing system that enhances the spatial resolution of the final image based on information contained in multiple sub-images acquired simultaneously.
22. The multiplexing array spectral imager of claim 21 in which the SLM comprises an array of interference filters designed to produce a modulated spectral transmission or reflection, comprising a series of sine waves of varying frequencies and spectral shifts representing a spectral Fourier series, such that the spectral component of each sub-image after the SLM represents a component of the intended spectral transform.
23. A multiplexing array spectral imager for simultaneously acquiring multiplexed spatial and spectral data from incoming light representing a scene, comprising:
a two-dimensional focal plane array (FPA) for capturing an image, the FPA defining a plurality of pixels;
a first optical system that creates a plurality of intermediate sub-images each representing at least part of the imaged scene;
a second optical system that includes a spectrally dispersive element and creates a spectrally dispersed image for each sub-image created by the first optical system in which the second optical system comprises a first polychromator comprising a first lenslet array, a first dispersive element or a first array of dispersive elements, and a second lenslet array, in which the first and second lenslet arrays each define at least N lenslets, where N equals the number of spectral bands in the acquired spectral image;
a spatial light modulator (SLM) that receives the spectrally dispersed sub-images, the SLM defining a two-dimensional array of encoding sub-masks each containing a plurality of elements that either transmit, block or reflect some or all of the light that impinges on them to thereby accomplish a transform of the spectral data within the dispersed sub-images and create spectrally-encoded intermediate sub-images, in which there are at least N dispersed sub-images and the SLM defines the same quantity of sub-masks as sub-images, in which each sub-mask contains a number of elements N equal to the number of spectral bands N defined by the imager;
a third optical system that receives spectrally dispersed and encoded intermediate sub-images and includes a spectrally de-dispersive element, to spectrally de-disperse intermediate sub-images and create a plurality of spectrally encoded sub-images that are imaged onto the FPA, in which the third optical system comprises a second polychromator comprising a third lenslet array, a second dispersive element or a second array of dispersive elements, and a fourth lenslet array, in which the third and fourth lenslet arrays each define at least N lenslets, where N equals the number of spectral bands in the acquired spectral image; and
a processing system that applies the inverse transform to the sub-images that were imaged onto the FPA, to produce a set of spectrally and spatially resolved images.