Multispectral imaging chip using photonic crystals

• US 20060054780A1
• Filed: 09/15/2004
• Published: 03/16/2006
• Est. Priority Date: 09/15/2004
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Barker, Delmar L., Shah, Nitesh N., Schmitt, Harry A., Garrood, Dennis J.
• Granted Patent: US 7,145,124 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02F 1/03 based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect G02F1/061 takes precedence
• CPC Class Codes: G02F 2202/32 Photonic crystals
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 25/44 by partially reading an SSIS array
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

On-chip multispectral imaging and data management is provided in the form of an Adaptive Focal Plane Array (AFPA) that is capable of spectral tunability at the pixel level. Layers of photonic crystals are registered with pixels of a broadband focal plane array. Spectral tuning is accomplished by switching the photonic crystal layers on/off and/or by changing their material structure to tune their photonic band gaps and provide a passband for incident photons. The photonic crystal layers are preferably segmented to independently address different regions or “cells” of pixels down to a pixel-by-pixel resolution. The AFPA may simultaneously sense different regions of a scene at different spectral wavelengths, spatial resolutions and sensitivities.

Claims

1. A multispectral imaging (MSI) chip, comprising:

a focal plane array (FPA) that detects incident photons over a broad spectral band;

at least one photonic crystal layer having one or more photonic band gaps that block transmission of photons over one or more portions of the broad spectral band; and

a tuning mechanism that tunes said photonic band gaps to filter photons through said at least one layer within a passband to said FPA.

2. The MSI chip of claim 1, wherein the FPA is pixelated to detect M×

N images of incident photons originating from a scene.

3. The MSI chip of claim 2, wherein said layers are segmented to independently filter cells comprising P×

Q pixels.

4. The MSI chip of claim 3, wherein P equals Q equals 1.

5. The MSI chip of claim 3, wherein said FPA simultaneously detects photons in a first passband in a first cell and photons in a different second passband in a second cell.

6. The MSI chip of claim 3, further comprising:

a read out integrated circuit (ROIC) that reads out the detected photons for each pixel in the FPA; and

a processor that controls the ROIC to read out the detected photons at a specified spatial resolution and integration period and controls the tuning mechanism to set the passband to a specified wavelength and resolution in the different cells independently.

7. The MSI chip of claim 6, wherein the processor processes the read out photons to detect any anomalies in an image.

8. The MSI chip of claim 7, wherein the processor controls the ROIC and tuning mechanism to reconfigure the spatial resolutions, integration periods and passbands of the different cells based on the detection of said anomalies to better resolve said anomalies.

9. The MSI chip of claim 7, wherein the processor controls the ROIC to store and average sequential temporal images of a scene, detect and correct spatial registration mismatches across one or more temporal images, measure and compress the range of intensities for an image, cell-by-cell.

10. The MSI chip of claim 7, wherein the processor sets an initial configuration based on a priori knowledge of the scene and/or possible anomalies.

11. The MSI chip of claim 1, wherein at any given wavelength in the broad spectral band there are two overlapping photonic band gaps, said tuning mechanism moving the overlapping band gaps that cover the passband away from the passband allowing transmission.

12. The MSI chip of claim 11, wherein the tuning mechanism controls the width of the passband by the relative placement of edges of the previously overlapping band gaps.

13. The MSI chip of claim 1, wherein the photonic band gaps are non-overlapping and switchable between reflective and transmissive states, said tuning mechanism switching all of the band gaps to the reflective state except one and switching the one layer whose band gap encompasses the passband to the transmissive state.

14. The MSI chip of claim 1, wherein at least one of said photonic crystal layers exhibits a plurality of said photonic band gaps.

15. The MSI chip of claim 14, wherein the tuning mechanisms tunes one of said plurality of photonic band gaps while leaving the others unchanged.

16. The MSI chip of claim 1, wherein the number of photonic crystal layers is between 1 and 12.

17. The MSI chip of claim 1, wherein the photonic band gaps select either the transverse magnetic (TM) or transverse electric (TE) polarization of the incident light.

18. The MSI chip of claim 1, wherein said broad spectral band spans 1-12 microns.

19. The MSI chip of claim 1, wherein said broad spectral band is selected from one of 0.4-0.7 microns in a visible band, 0.9-1.8 microns in a short wave infrared (IR) band, 3-6 microns in a medium wave IR band, 8-14 microns in a long wave IR band, 14-22 microns in a very long IR band and 0.1 mm-1 mm in a microwave band.

20. A multispectral imaging chip, comprising:

an M×

N pixelated focal plane array (FPA) that detects incident photons over a broad spectral band;

a plurality of photonic crystal layers each having a photonic band gap structure with a different photonic band gap that blocks transmission of photons over a portion of the broad spectral band, said layers being segmented to independently address cells comprising P×

Q pixels in the FPA;

a read out integrated circuit (ROIC) that reads out the detected photons for each pixel in the FPA;

a tuning mechanism that tunes said photonic band gaps to filter photons through a passband in each cell to said FPA; and

a processor that controls the ROIC to read out the detected photons at a specified spatial resolution and integration period and controls the tuning mechanism to set the passband to a specified wavelength and resolution in the different cells independently.

21. The MSI chip of claim 20, wherein P equals Q equals 1.

22. The MSI chip of claim 20, wherein the processor (a) based on a priori knowledge of the scene and/or possible anomalies sets an initial configuration for the ROIC to read out the detected photons at a specified spatial resolution and integration period and for the tuning mechanism to set the passband to a specified wavelength and resolution in the different cells, (b) processes the read out photons to detect any anomalies in a scene, (c) controls the ROIC and tuning mechanism to reconfigure the spatial resolutions, integration periods, and passbands of the different cells based on the detection of said anomalies to better resolve said anomalies.

23. The MSI chip of claim 20, wherein at any given wavelength in the broad spectral band there are two overlapping photonic band gaps, said tuning mechanism moving the overlapping band gaps that cover the passband away from the passband allowing transmission and controlling the width of the passband by the relative placement of edges of the previously overlapping band gaps.

24. The MSI chip of claim 20, wherein the photonic band gaps are non-overlapping and switchable between reflective and transmissive states, said tuning mechanism switching all of the band gaps to the reflective state except one and switching the one layer whose band gap encompasses the passband to the transmissive state.

25. The MSI chip of claim 20, wherein at least one of said photonic crystal layers exhibits a plurality of said photonic band gaps, said tuning mechanisms tuning one of said plurality of photonic band gaps while leaving the others unchanged.

26. A multispectral imaging chip for detecting anomalies in a scene, comprising:

an M×

N pixelated focal plane array (FPA) that detects incident photons over a broad spectral band;

a plurality of photonic crystal layers each having a photonic band gap structure with a different photonic band gap that blocks transmission of photons over a portion of the broad spectral band, said layers being segmented to independently address cells comprising P×

Q pixels in the FPA;

a read out integrated circuit (ROIC) that reads out the detected photons for each pixel in the FPA;

a tuning mechanism that tunes said photonic band gaps to filter photons through a passband in each cell to said FPA; and

a processor that (a) based on a priori knowledge of the scene and/or possible anomalies sets an initial configuration for the ROIC to read out the detected photons at a specified spatial resolution and integration period and for the tuning mechanism to set the passband to a specified wavelength and resolution in the different cells, (b) processes the read out photons to detect any anomalies in a scene, (c) controls the ROIC and tuning mechanism to reconfigure the spatial resolutions, integration periods, and passbands of the different cells based on the detection of said anomalies to better resolve said anomalies.

27. The MSI chip of claim 26, wherein P equals Q equals 1.

28. The MSI chip of claim 26, wherein at any given wavelength in the broad spectral band there are two overlapping photonic band gaps, said tuning mechanism moving the overlapping band gaps that cover the passband away from the passband allowing transmission and controlling the width of the passband by the relative placement of edges of the previously overlapping band gaps.

29. The MSI chip of claim 26, wherein the photonic band gaps are non-overlapping and switchable between reflective and transmissive states, said tuning mechanism switching all of the band gaps to the reflective state except one and switching the one layer whose band gap encompasses the passband to the transmissive state.

30. The MSI chip of claim 26, wherein at least one of said photonic crystal layers exhibits a plurality of said photonic band gaps, said tuning mechanisms tuning one of said plurality of photonic band gaps while leaving the others unchanged.