Infrared video camera system with uncooled focal plane array and radiation shield

• US 6,144,031 A
• Filed: 04/21/1997
• Issued: 11/07/2000
• Est. Priority Date: 04/21/1997
• Status: Expired due to Term

• Current Assignee: Teledyne FLIR LLC (Teledyne Technologies Incorporated)
• Original Assignee: Inframetrics, Incorporated (Teledyne Technologies Incorporated)
• Inventors: Confer, Charles L., Neilson, Andrew C., Herring, Robert J., Manitakos, Daniel L., Bin-Nun, Uri, Haded, Kevin J.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US08/845,124
• Time in Patent Office: 1,296 Days
• Field of Search: 250/352, 250/353, 250/330, 250/370.15, 250/252.1, 250/338.4
• US Class Current: 250/352
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/045 Sealings; Vacuum enclosures; Encapsulated packages; Wafer bonding structures; Getter arrangements getter arrangements per se H01L23/26 and H01L21/3221
• CPC Class Codes: G01J 5/06 Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801
• CPC Class Codes: G01J 5/061 by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 27/0018 with means for preventing ghost images anti-reflection coatings G02B1/11
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• 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

An infrared video camera system comprises an uncooled infrared sensor mounted and a thermally conductive thin walled radiation shield for shielding radiation from reaching an active surface of the uncooled infrared sensor. A TEC maintains the sensor active surface and the radiation shield at a substantially constant temperature. The uncooled infrared sensor and radiation shield are further housed in a hollow thermally conductive vacuum cover which is vacuum sealed with a base assembly and includes a vacuum sealed infrared transparent window in an aperture at a top end of the vacuum cover for allowing infrared radiation to reach the active surface and for forming a vacuum chamber enclosing the infrared sensor and radiation shield. A relay optical cell mounted to a camera body comprises at least one optical element for relaying an image formed at its entrance onto the active surface. An imaging optical assembly is interchangeably mounted to the relay optical cell and comprises at least one optical element for imaging an infrared scene to be imaged onto the entrance aperture of the relay cell. A plurality of different field of view imaging optical assemblies are interchangeably mounted without substantially changing the field of view of the sensor active surface.

Claims

1. An uncooled infrared sensor assembly comprising:

(a) an uncooled infrared sensor having an active surface for providing an analog video signal in response to infrared radiation falling thereon;

(b) a radiation shielding chamber formed to surround the uncooled infrared sensor for shielding radiation from said active surface, the chamber providing continuous walls for shielding the sensor and a shield aperture for defining a field of view of said active surface thereby limiting the radiation entering the chamber to a prescribed solid cone angle defined by the shield aperture; and

,

(c) wherein the chamber walls provide a substantially uniform non-varying infrared radiation scene to the active surface for all angles not included in the prescribed solid cone angle.

2. An uncooled infrared sensor assembly according to claim 1 further comprising, a device for maintaining the infrared sensor, the active surface and the radiation shielding chamber walls at a substantially constant uniform temperature.

3. An uncooled infrared sensor assembly according to claim 2 wherein the continuous chamber walls are assembled to provide a substantially uninterrupted thermally conductive path between the device and the continuous chamber walls.

4. An uncooled infrared sensor assembly according to claim 1, wherein the continuous chamber walls comprise:

(a) a header base having a top surface for supporting the uncooled infrared sensor with the active surface facing away from the top surface, the header base further including pins passing therethrough for electrically connecting the infrared sensor to an electronics module outside the chamber walls;

(b) a header cover flange mounted onto the header base, the header cover flange including, a first rectangular flange for surrounding the uncooled infrared sensor while providing a gap between the first rectangular flange and the sensor, and wherein a thermoelectric cooling device is mounted into the gap in thermal contact with the infrared sensor and the first rectangular flange, the thermoelectric device being controlled to maintaining the sensor and the continuous chamber walls at a substantially constant uniform temperature;

(c) a thermally conductive radiation shield base, having a second rectangular flange on a bottom side thereof, and circular flange on a top side thereof, the radiation shield base being attached by the second rectangular flange to a carrier board mounted between the second rectangular flange and the first rectangular flange;

(d) a thermally conductive thin walled cylindrical radiation shield, which is open at a bottom end thereof for attaching to the radiation shield base, at the circular flange thereof, and, open at a top end thereof, to provide a shield aperture for defining the solid cone angle of radiation entering the chamber; and

,

(e) wherein each of the header base, the infrared sensor, the header cover flange, the carrier board, the radiation shield base and the radiation shield are thermally conductively assembly together such the entire chamber is maintained at a substantially constant uniform temperature by the thermoelectric cooler.

5. An infrared sensor assembly according to claim 2 further comprising:

(a) a temperature sensor for sensing a temperature proximate to said active surface; and

,

(b) an electrical driver, in communication with said device and said temperature sensor, for driving said device to maintain the infrared sensor, the active surface. and the chamber walls at the substantially constant uniform temperature.

6. An uncooled infrared sensor assembly according to claim 1 wherein said substantially constant uniform temperature is in the range of 0°

C. to 40°

C.

7. An infrared sensor assembly according to claim 1 wherein said uncooled infrared sensor is an array of microbolometric detector elements.

8. The apparatus of claim 7 wherein the substantially uniform non-varying temperature is in the range of 0°

C. to 40°

C.

9. An infrared sensor assembly according to claim 1 wherein said uncooled infrared sensor is a pyroelectric sensor.

10. An infrared sensor assembly according to claim 2 wherein said device is thermally conductively connected at a first side to said uncooled infrared sensor and at a second opposite side to a first heat sink, said infrared sensor assembly further comprising:

(a) a heat pipe connected at a first end to said first heat sink; and

,

(b) a second heat sink connected to said heat pipe at a second opposite end to said first end.

11. An infrared sensor assembly according to claim 1 wherein said chamberwalls include an inner surface and wherein the inner surface is treated to provide high emmissivity for absorbing infrared radiation falling thereon.

12. An infrared sensor assembly according to claim 1 wherein said chamber walls include an outer surface and wherein the outer surface is treated to provide low emmissivity for reflecting infrared radiation falling thereon.

13. An infrared sensor assembly according to claim 1 wherein the chamber walls include an inner surface, further comprising;

a sensor baffle having a sensor aperture substantially matching the size and shape of said active area, said sensor baffle being mounted inside the chamber and proximate to the active area for locking radiation reflected from the inner surface of the chamber walls from reaching said active surface.

14. An uncooled infrared sensor assembly according to claim 1 wherein said uncooled infrared sensor and said radiation shielding chamber are housed in a vacuum chamber maintained below atmospheric pressure and further wherein the infrared sensor, the active surface and the radiation shielding chamber walls and the vacuum chamber are maintained at a substantially constant uniform temperature.

15. An infrared video camera system, comprising

(a) a camera body for housing an electronics module;

(b) an uncooled infrared sensor having an active surface for providing an analog video signal in response to infrared radiation falling thereon, the analog video signal being communicated to the electronics module for signal processing thereby;

(c) a radiation shielding chamber formed to surround the uncooled infrared sensor for shielding radiation from said active surface, the shielding chamber providing continuous walls for shielding the sensor and a shield aperture for defining a field of view of said active surface thereby limiting the radiation entering the chamber to a prescribed solid cone angle defined by the shield aperture; and

,

(d) wherein the chamber walls provide a substantially uniform non-varving infrared radiation scene to the active surface for all angles not included in the prescribed solid cone angle.

16. An infrared video camera system according to claim 15, wherein the continuous chamber walls comprise:

(a) a header base having a top surface for supporting the uncooled infrared sensor with the active surface facing away from the top surface, the header base further including pins passing therethrough for electrically connecting the infrared sensor to an electronics module outside the chamber walls;

(b) a header cover flange mounted onto the header base, the header cover flange including, a first rectangular flange for surrounding the uncooled infrared sensor while providing a gap between the first rectangular flange and the sensor, and wherein a thermo-electric cooling device is mounted into the gap in thermal contact with the infrared sensor and the first rectangular flange, the thermoelectric device being controlled to maintaining the sensor and the continuous chamber walls at a substantially constant uniform temperature;

(c) a thermally conductive radiation shield base, having a second rectangular flange on a bottom side thereof, and circular flange on a top side thereof, the radiation shield base being attached by the second rectangular flange to a carrier board mounted between the second rectangular flange and the first rectangular flange;

(d) a thermally conductive thin walled cylindrical radiation shield, which is open at a bottom end thereof for attaching to the radiation shield base, at the circular flange thereof, and, open at a top end thereof, to provide a shield aperture for defining the solid cone angle of radiation entering the chamber; and

,

(e) wherein each of the header base, the infrared sensor, the header cover flange, the carrier board, the radiation shield base and the radiation shield are thermally conductively assembly together such the entire chamber is maintained at a substantially constant uniform temperature by the thermoelectric cooler.

17. An uncooled camera system according to claim 15 further comprising a device for maintaining the uncooled infrared sensor, the active surface and the radiation shielding chamber walls at a substantially constant uniform temperature.

18. An infrared sensor assembly according to claim 17 further comprising:

(a) a temperature sensor for sensing a temperature proximate to said active surface; and

,

(b) an electrical driver, in communication with said device and said temperature sensor, for driving said device to maintain the infrared sensor, the active surface, and the chamber walls at the substantially constant uniform temperature.

19. An infrared video camera system according to claim 17 further comprising:

(a) a first heat sink thermally conductively mounted to said device;

(b) a second heat sink mounted external to said camera body; and

,

(c) a heat pipe thermally connected between said first and second heat sinks for drawing thermal energy from said first heat sink to said second heat sink mounted externally to said camera body.

20. An infrared video camera system according to claim 19 wherein said second heat sink has a larger heat sink capacity than said first heat sink.

21. An infrared video camera system according to claim 15, further comprising:

(a) a relay optics cell mounted to said camera body, said relay optics cell including a relay optics cell exit aperture at a camera end and a relay optics cell entrance aperture at an opposite end to said camera end, said relay optics cell further comprising at least one optical element for relaying an image of said entrance aperture onto the active surface, said image of said entrance aperture substantially filling the active surface; and

,

(b) an imaging optics assembly mounted to said relay optics cell at said opposite end, said imaging optics assembly comprising at least one optical element for forming an IR scene image onto said entrance aperture said IR scene image substantially filling said entrance aperture.

22. An infrared video camera system according to claim 21 wherein said relay optics cell further comprises a mounting interface for mounting an optical filter element substantially coincident with said entrance aperture.

23. An infrared video camera system according to claim 22 wherein said mounting interface provides a device for interchangeably mounting of a plurality of optical filter elements.

24. An infrared video camera system according to claim 21 wherein a plurality of imaging optics assemblies, each having a different field of view, are interchangeably mountable with said relay optics cell and wherein each of said plurality of imaging optics assemblies forms an IR scene image which is substantially coincident with and substantially fills said entrance aperture.

25. An infrared video camera system according to claim 21 wherein, said active surface comprises a plurality of image pixels, said infrared video camera further comprising:

(a) a shutter for blocking radiation from reaching said active surface;

(b) a processing module included in said electronics module for receiving and processing an analog video dark signal value from each of said plurality of image pixels while said active area is blocked by said shutter said processor further receiving and processing an analog video scene signal value from each of said plurality of image pixels while said active area is illuminated by an infrared scene;

(c) a memory module for storing each of said analog video dark signal values; and

,

(d) wherein said processor module processes each of said analog video scene signal values received from each of said plurality of image pixels while said camera is viewing an infrared scene by adjusting each of said analog video scene signal values according to a corresponding dark signal value.

26. An infrared video camera system according to claim 25 wherein said shutter is mounted within a hollow cavity inside said relay optics cell.

27. An infrared video camera system according to claim 21 wherein said active surface includes a plurality of image pixels and wherein said infrared video camera is used to determine the temperature of a black body radiator, said infrared video camera further comprising:

(a) a processing module included in said electronics module for receiving and processing an analog video known black body signal value from each of said plurality of image pixels while said active area is illuminated by a black body of known black body temperature said processor further receiving and processing an analog video scene signal value from each of said plurality of image pixels while said active area is illuminated by an infrared scene which includes a black body of unknown black body temperature;

(b) a memory module for storing said analog video known black body signal value for each of said plurality of pixels; and

,

(c) wherein said processor module processes each of said analog video scene signal values received from each of said plurality of image pixels while said camera is illuminated by an infrared scene which includes a black body of unknown black body temperature by adjusting each of said analog video scene signal values according to a corresponding analog video known black body signal value.

28. In an infrared imaging system which includes an uncooled infrared sensor for providing an analog signal in response to infrared radiation falling onto an active surface thereof, a method for artificially creating a reference background image comprising the steps of:

(a) sufrounding the uncooled infrared sensor with a radiation shielding chamber comprising a continues surrounding wall and a shield aperture formed in the surrounding wall;

(b) defining a field of view of the active surface by sizing and positioning the shield aperture to limit the radiation entering the chamber to a prescribed solid cone angle defined by the shield aperture; and

,

(c) wherein the continuous surrounding chamber wall provides said reference background image to the active surface for all angles not included in the prescribed solid cone angle.

29. The method according to claim 28 further comprising the step of maintaining the continuous surrounding chamber wall and the infrared sensor at a substantially constant uniform temperature such that said reference background image comprises a substantially uniform non-varying radiation scene.

30. The method according to claim 29 wherein the substantially constant uniform temperature is in the range of 0°

C. to 40°

C.

31. The method according to claim 29, further comprising the step of, providing a substantially thermally conductive path between the infrared sensor and the continuous surrounding chamber wall.

32. The method according to claim 31 further comprising steps of:

(a) enclosing the infrared sensor and the radiation shielding chamber within a vacuum chamber, said vacuum chamber including a vacuum chamber surrounding wall and a vacuum chamber aperture for allowing infrared radiation to enter the vacuum chamber, and wherein the vacuum chamber aperture is sealed by a transparent window; and

,

(b) maintaining the interior of the vacuum chamber at a pressure below atmospheric pressure to facilitate maintaining the infrared sensor, the active surface and the radiation shielding chamber surrounding wall at a substantially constant uniform temperature.

33. The method according to claim 32, further comprising the step of;

providing a substantially thermally conductive path between the infrared sensor, the radiation shielding chamber walls and the vacuum chamber surrounding wall.

34. The method according to claim 28, wherein the infrared imaging system includes a camera body for housing the uncooled infrared sensor, the method further comprising the steps of:

(a) providing a relay optics cell mounted to the camera body, said relay optics cell including a relay optics cell exit aperture, at a camera end thereof, and a relay optics cell entrance aperture, at an opposite end to the camera end, said relay optics cell further comprising at least one optical element for relaying an image of said relay optics cell entrance aperture onto the active surface such that the image of said relay optical cell entrance aperture substantially fills the active surface; and

,

(b) providing an imaging optics assembly mounted to said relay optics cell at said opposite end, said imaging optics assembly comprising at least one optical element for forming an image of an infrared scene onto said relay optics cell entrance aperture, such that the image of the infrared scene substantially filling the relay optics cell entrance aperture.

35. The method of claim 34 wherein a plurality of interchangably mountable imaging optical assemblies are provided for mounting, one at a time, to the relay optics cell and wherein each of the imaging optical assemblies includes at least one optical element further comprising the steps of:

(a) providing each of the interchangably mountable imaging optical assemblies with one of a different field of view or a different magnification; and

,

(b) forming an image of an infrared scene onto said relay optics cell entrance aperture with one of the plurality of interchangably mountable imaging optical assemblies such that the image of the infrared scene formed by the one imaging optical assembly substantially fills the relay optics cell entrance aperture.