Coded aperture imaging system having adjustable imaging performance with a reconfigurable coded aperture mask

• US 7,888,626 B2
• Filed: 05/23/2006
• Issued: 02/15/2011
• Est. Priority Date: 05/23/2005
• Status: Expired due to Fees

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Slinger, Christopher W, Lewis, Keith L
• Primary Examiner(s): Le, Que T
• Application Number:
  US11/920,345
• Publication Number:
  US 20090095912A1
• Time in Patent Office: 1,729 Days
• Field of Search: 250/226, 250/216, 250/208.1, 250/234, 250/237.R, 25036304-3631
• US Class Current: 250/226
• CPC Class Codes: G01T 1/295 using coded aperture devices, e.g. Fresnel zone plates handling of radiation of particles, e.g. using diaphragms, collimators, diffraction G21K1/00
• CPC Class Codes: G02B 2207/129 Coded aperture imaging
• CPC Class Codes: G02B 27/00 Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
• CPC Class Codes: G06T 1/0007 Image acquisition
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/58 Means for changing the camera field of view without moving the camera body, e.g. nutating or panning of optics or image sensors
• CPC Class Codes: H04N 23/951 by using two or more images to influence resolution, frame rate or aspect ratio
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• 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

This invention relates to coded aperture imaging apparatus and methods. In one aspect a coded aperture imager has at least one detector array and a reconfigurable coded aperture mask means. A reconfigurable coded aperture mask means can display various coded aperture masks to provide imaging across different fields of view and/or with different resolution without requiring any moving parts or bulky optical components. More than one detector array can be used to provide large area imaging without requiring seamless tiling and this represents another aspect of the invention. The present invention also relates to the use of coded aperture imaging in the visible, ultraviolet or infrared wavebands. The use of coded aperture imaging for imaging through a curved optical element is taught as the image decoding can automatically remove any aberrations introduced by the curved element.

Claims

1. A coded aperture imaging system configured to operate in the ultra violet, visible or infrared wavelength interval and comprising a detector array and a coded aperture mask, the coded aperture mask is electrically reconfigurable to produce coded aperture arrays providing one of:

different fields of view,

different resolutions, and

different image encryption properties.

2. An imaging system as claimed in claim 1 wherein the coded aperture arrays provide different fields of view, each coded aperture array occupies part of the coded aperture mask and the position of each coded aperture array in the mask defines the respective field of view.

5. An imaging system as claimed in claim 1 wherein the coded aperture mask is non-planar.

6. An imaging system as claimed in claim 1 wherein the coded aperture mask is reconfigurable in less than 10 ms.

7. An imaging system as claimed in claim 1 wherein the coded aperture mask comprises a bistable spatial light modulator.

8. An imaging system as claimed in claim 1 wherein the coded aperture mask comprises a liquid crystal spatial light modulator.

9. An imaging system as claimed in claim 1 wherein said detector array has an output and including a processor adapted to decode the detector array output to provide an image.

10. An imaging system as claimed in claim 9 wherein the processor is adapted to apply a variety of decoding algorithms to decode the detector array output.

11. An imaging system as claimed in claim 9 wherein the processor is arranged to combine multiple frames of data from the detector array output, the frames having been acquired with different coded aperture arrays.

12. An imaging system as claimed in claim 1, wherein the detector array output is undecoded and the system comprises at least one of a transmitter and a recorder for at least one of transmitting and recording the undecoded detector array output.

13. An imaging system as claimed in claim 12 wherein the reconfigurable coded aperture mask is adapted to vary the coded aperture array displayed in order to vary image encryption.

23. A coded aperture imaging system as claimed in claim 1 wherein the coded aperture imaging system has a plurality of detector arrays each arranged to receive radiation from a scene through the coded aperture mask.

24. A coded aperture imaging system as claimed in claim 23 wherein each detector array has an active detector area for receiving radiation and a non-active peripheral area.

25. A coded aperture imaging system as claimed in claim 24 wherein the active area of at least one detector array is not coterminous with the active area of a neighbouring detector array.

27. An imaging system as claimed in claim 1 wherein the coded aperture mask has pixels which are electrically switchable between transparent and opaque states to provide different coded aperture arrays.

28. An imaging system as claimed in claim 5 wherein the non-planar coded aperture mask forms part of an external surface of a platform.

29. An imaging system as claimed in claim 28 wherein the non-planar coded aperture mask has an aerodynamic shape.

3. A coded aperture imaging system comprising a detector array and a coded aperture mask which is reconfigurable, and the reconfigurable coded aperture mask incorporates a controller adapted to cause at least one coded aperture mask to provide a coded aperture array.

4. An imaging system as claimed in claim 3 wherein the controller is pre-programmed with a plurality of different coded aperture arrays for displaying on the coded aperture mask.

14. A method of imaging comprising the steps of:

arranging a detector array to view a scene through a reconfigurable coded aperture array; and

causing a coded aperture array to be displayed on the coded aperture mask.

15. A method of imaging as claimed in claim 14, further comprising the step of displaying a first coded aperture array on the coded aperture mask and subsequently displaying a second coded aperture array to the coded aperture mask.

16. A method of imaging as claimed in claim 15 wherein the first and second coded aperture arrays have different fields of view and/or resolution.

17. A method of imaging as claimed in claim 14 wherein the method comprises the step of decoding the output of the detector array to provide an image.

18. A method as claimed in claim 17 wherein the step of decoding comprises applying one or more of a deconvolution algorithm, a cross-correlation algorithm and an iterative solution search.

19. A method as claimed in claim 15 wherein the method involves combining data acquired using a plurality of different coded aperture arrays in decoding the image.

20. A method of imaging as claimed in claim 14 including imaging through a non-planar element.

21. A method of imaging as claimed in claim 20 wherein the non-planar element forms part of an external surface of a platform.

22. A method of imaging as claimed in claim 20 wherein the non-planar element has an aerodynamic shape.

26. A method of coded aperture imaging in the ultra violet, visible or infrared wavelength interval and comprising the steps of:

arranging a detector array to view a scene through a display; and

displaying a selected coded aperture array on a coded aperture mask to provide for the display to form the selected coded aperture array, wherein the display is reconfigurable to produce coded aperture arrays arranged to provide one of;

different fields of view,

different resolutions, and

different image encryption properties.