Miniature infrared camera

• US 6,023,061 A
• Filed: 12/03/1996
• Issued: 02/08/2000
• Est. Priority Date: 12/04/1995
• Status: Expired due to Term

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: Microcam Corporation
• Inventors: Bodkin, William Andrew
• Primary Examiner(s): ISRAEL, ANDREW
• Application Number:
  US08/758,339
• Time in Patent Office: 1,162 Days
• Field of Search: 250/338.3, 250/338.4, 250/349, 250/352, 250/370.08, 250/370.15, 250/252.1 A, 250/33.2, 250/338.1
• US Class Current: 250/332
• CPC Class Codes: B64U 20/87 Mounting of imaging devices, e.g. mounting of gimbals
• CPC Class Codes: B64U 2101/30 for imaging, photography or videography
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 5/0215 Compact construction
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/0808 Convex mirrors
• CPC Class Codes: G01J 5/0813 Planar mirrors; Parallel phase plates
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence
• CPC Class Codes: G02B 9/02 having one + component only simple lenses G02B3/00
• CPC Class Codes: G02B 9/12 having three components only
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• CPC Class Codes: H04N 23/52 Elements optimising image sensor operation, e.g. for electromagnetic interference [EMI] protection or temperature control by heat transfer or cooling elements
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/695 Control of camera direction for changing a field of view, e.g. pan, tilt or based on tracking of objects
• CPC Class Codes: H04N 25/63 applied to dark current
• 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

A miniaturized IR camera mounts within a vehicle such as an airborne reconnaissance airplane. The camera includes a two dimensional uncooled FPA, a compound lens for imaging IR radiation onto the FPA, means for adjusting the distance between the lens and the FPA to adjust focus, an electronic module that controls camera read out, calibration, and signal processing, and means for flexibly coupling the FPA to the module. In accord with the invention, the module and the FPA are reconfigurable within the vehicle so that the FPA head can be fit into a tight place, or into a location that is separate from the rest of the camera, such as on top of a vehicle. The invention further provides for calibration techniques whereby the scene, sky or shutter are used to thermally calibrate the several uncooled detectors. Focus, tilt and tip adjustments permit simple adjustment of the FPA to achieve proper focus and alignment. The electronics module can be controlled through manual interface, remote signals, or internal clocking. Heat sinks dissipate heat from the FPA as well as from a TE Cooler, if present.

Claims

1. A miniaturized IR camera for mounting within a vehicle, comprising a two dimensional uncooled FPA, a compound lens for imaging IR radiation onto the FPA, means for adjusting a distance between the lens and the FPA to adjust focus, an electronic module that controls camera read out, calibration, and signal processing, and means for flexibly coupling the FPA to the module wherein the module and the FPA are separately reconfigurable within the vehicle.

2. A camera according to claim 1, wherein the uncooled FPA comprises a two-dimensional array of microbolometers.

3. A camera according to claim 1, wherein the uncooled FPA comprises a two-dimensional array of ferroelectric devices.

4. A camera according to claim 1, further comprising one or more batteries to power the camera.

5. A camera according to claim 1, wherein the FPA is constructed and arranged so as to respond to radiation in the 8-12 micron region.

6. A camera according to claim 1, wherein the FPA is constructed and arranged so as to respond to radiation in the 3-5 micron region.

7. A camera according to claim 1, wherein the FPA is constructed and arranged so as to respond to radiation in the 2-14 micron region, and further comprising filter means for selecting a waveband of operation within the region.

8. A camera according to claim 7, wherein the filter means comprises means for filtering the region to one of (a) 8-12 microns, (b) 3-5 microns, and (c) 1-2 microns.

9. A camera according to claim 7, further comprising means for cooling the filter means so as to reduce background flux from the filter means.

10. A camera according to claim 1, further comprising means for cooling the lens to reduce background flux from the lens.

11. A camera according to claim 1, further comprising memory means for storing selective information including at least one of (a) IR image data, (b) calibration data, (c) command and control sequences, (d) scaling information, and (e) user-selected options.

12. A camera according to claim 1, further comprising (a) memory means for storing digital calibration information and (b) means for calibrating the FPA selectively for thermal sensitivity relative to the digital calibration information.

13. A camera according to claim 1, further comprising (a) memory means for storing digital calibration information, (b) means for capturing image data of the sky as the digital calibration information, and (c) means for compensating the FPA for thermal sensitivity so as to more accurately identify thermal temperature differences in a thermal scene.

14. A camera according to claim 13, wherein the means for capturing image data of the sky comprises a gravity switch for generating a calibration cycle signal when the camera inverts.

15. A camera according to claim 1, further comprising (a) an image averaging subsystem that captures a blurred image of a scene viewed by the camera, (b) means for integrating multiple frames of image data during motion of the camera relative to the scene, (c) means for dividing the multiple frames of image data by a total number of frames used in the image data to determine an integrated scene average, and (d) means for compensating the FPA for thermal sensitivity so as to more accurately identify thermal temperature differences in a thermal scene.

16. A camera according to claim 1, further comprising a gravity shutter, the gravity shutter having a shutter surface viewable as an image by the FPA and closing when the camera is tilted backwards or to a specified angle, and a switch for detecting closing of the shutter so as to generate a signal which initiates a calibration cycle, the gravity shutter and the switch providing for acquisition of a calibrated image on the shutter surface, the calibration image being stored in memory and used as a calibration offset for the FPA.

17. A camera according to claim 1, further comprising a manual lens cover to cover the lens, and a software module having a calibration routine that is started by one of (a) a tilt of the camera and/or (b) a manual button.

18. A camera according to claim 1, further comprising a reflective optical element which reflects IR energy from the lens and onto the FPA.

19. A camera according to claim 1, wherein the lens comprises at least one refractive optical element constructed from Germanium.

20. A camera according to claim 1, wherein the lens comprises one aspheric surface.

21. A camera according to claim 1, wherein the lens has one fold mirror to reduce the overall volumetric dimensions of the camera.

22. A camera according to claim 1, further comprising an IR transparent plastic sacrificial cover to protect the lens from physical damage.

23. A camera according to claim 1, further comprising means for controlling the temperature of the FPA.

24. A camera according to claim 23, wherein the means for controlling the temperature is a TE Cooler.

25. A camera according to claim 23, wherein the means for controlling the temperature comprises a passive heat sink which dissipates heat through thermal convection.

26. A camera according to claim 23, wherein the means for controlling the temperature comprises a vented airflow which dissipates heat by venting external air through openings in a housing surrounding the camera and over a heat sink.

27. A camera according to claim 23, wherein the means for controlling the temperature comprises a heat pipe which dissipates heat to an external radiator in an air stream.

28. A camera according to claim 1, wherein the camera has a primary field of view, and further comprising at least one additional IR camera, the additional IR camera having a supplemental field of view formed by (a) a second two dimensional uncooled FPA, (b) a second compound lens for imaging IR radiation onto the second FPA, (c) means for adjusting a distance between the second lens and the second FPA to adjust focus, (d) a second electronic module that controls the additional camera read out, calibration, and signal processing, and (e) means for flexibly coupling the second FPA to the second module wherein the second module and the second FPA are reconfigurable within the vehicle, the camera and the additional IR camera having overlapping fields of view which, in combination, provide a composite field of view that is larger than either of the primary and supplemental fields of view.

29. A camera according to claim 1, further comprising means for sensing solar energy and converting solar energy to power to supply power to the module.

30. A camera according to claim 1, further comprising means for translating, tipping and tilting the FPA relative to an optical axis.

31. A camera according to claim 30, wherein the means for translating, tipping and tilting comprises a three-screw configuration.

32. A camera according to claim 31, wherein the three-screw configuration comprises a differential screw mechanism which has two nested threaded components to selectively obtain displacements equal to a pitch difference between the nested threaded components.

33. A camera according to claim 1, further comprising means for selecting the operational spectral band of the FPA.

34. A camera according to claim 33, wherein the means for selecting the operational spectral band comprises one or more of the following:

a single fixed filter in the optical path to the FPA;

a filter wheel;

a single, continuously-varying filter disc;

an electro-optic tunable filter; and

a dispersive element.

35. A camera according to claim 1, further comprising means for remotely communicating data to and from the module.

36. An IR reconnaissance airplane, comprising:

an airplane;

a miniaturized IR camera for mounting within the airplane and for capturing a scene of the ground from the airplane, the camera comprising a two dimensional uncooled FPA, a compound lens for imaging IR radiation onto the FPA, means for adjusting a distance between the lens and the FPA to adjust focus, an electronic module that controls camera read out, calibration, and signal processing, and means for flexibly coupling the FPA to the module wherein the module and the FPA are reconfigurable within the airplane.

37. An airplane according to claim 36, further comprising (a) memory means for storing digital calibration information, (b) means for capturing image data of the sky as the digital calibration information, and (c) means for compensating the FPA for thermal sensitivity so as to more accurately identify thermal temperature differences in the scene.

38. An airplane according to claim 37, wherein the means for capturing image data of the sky comprises means for rotating the airplane so that the camera views the sky.

39. An airplane according to claim 36, further comprising means for remotely piloting the airplane.

40. A method for calibrating an IR camera within an airplane, the camera of the type having an uncooled focal plane array, comprising the steps of contolling the airplane so that the camera views the sky, acquiring and storing one or more frames of data representative of a uniform sky scene, and compensating the uncooled focal plane array so as to achieve greater signal uniformity for a uniform temperature scene.

41. A method according to claim 40, further comprising the step of utilizing one of (a) a gravity switch to initiate a calibration cycle when the airplane tilts, and (b) a gravity-controlled shutter which closes when the airplane tilts so that the camera views a substantially uniform scene.

42. A method according to claim 40, further comprising the step of controlling a calibration cycle of the camera by telemetric data remotely communicated to the camera.