Compressive spectral imaging via polar coded aperture
View Patent ↗Systems, methods, architectures, mechanisms and/or apparatus configured to provide a compressive spectral imager for estimating a spectral image of a rotating scene such as a target scene as viewed from a spinning munition.
1. A method for spectral imaging of a scene, comprising:
spatially coding and spectrally modulating an image of the scene using a polar coded aperture and a circular variable filter (CVF) of an imaging system rotating with respect to the scene;
detecting the spatially coded and spectrally modulated image of the scene with an array of sensors of the rotating imaging system;
collecting data from the array of sensors over time; and
estimating the spectral image of the scene from the data collected over time and a measurement matrix H determined in accordance with spatial coding and spectral modulation imparted to the image of the scene
wherein a total number of cells is S in 2 , with S out =2S in , R in ≈0.156S in , and R out ≈ 0.421S in such that R in S in +R out S out =S in 2 .
2. The method of claim 1 , wherein the measurement matrix H is further determined in accordance with one or more of a resolution of the array of sensors and a number of sensor measurements.
3. The method of claim 2 , wherein the measurement matrix H is modified to account for continuous motion.
4. The method of claim 1 , wherein the polar coded aperture comprises a polar shaped coded aperture with a rings-spoke structure configured to impart block-unblock coding to light passing therethrough.
5. The method of claim 4 , wherein a ring spacing of the rings-spoke structure is selected to provide cells of equal area.
6. The method of claim 4 , wherein an optimizing of shapes is provided by selectively using inner and outer sections.
7. The method of claim 4 , wherein the rings-spoke structure is configured to optimize a code pattern.
8. The method of claim 4 , wherein the polar coded aperture imparts a ring index and spoke index coding of scene pixels to provide polar pixel coding of spatial information of the scene.
9. The method of claim 1 , wherein the imaging system is configured to be mounted on spinning munition.
10. The method of claim 1 , wherein the image of the scene is received at the rotating imaging system via an objective lens of the rotating imaging system.
11. The method of claim 1 , wherein the polar coded aperture comprises a polar shaped coded aperture with a code geometry configured as a polar pattern with R rings and S spokes, with S/R=4.
12. The method of claim 11 , wherein the outer radius of ring r is Δ√{square root over (r)}, with Δ denoting the outer radius of the first ring.
13. The method of claim 1 , wherein the polar coded aperture comprises a polar shaped coded aperture with a code geometry configured as an Inner/Outer polar geometry with S in and S out inner and outer spokes, and R in and R out inner and outer rings.
14. The method of claim 1 , further comprising rotating one or both of the polar coded aperture and the CVF to compensate for a target image that is off-center with respect to the array of sensors.