Methods and apparatus for compensating a radiation sensor for temperature variations of the sensor

• US 6,730,909 B2
• Filed: 04/27/2001
• Issued: 05/04/2004
• Est. Priority Date: 05/01/2000
• Status: Expired due to Term

• Current Assignee: BAE Systems Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Incorporated (BAE Systems Plc)
• Inventors: Butler, Neal R.
• Primary Examiner(s): GAGLIARDI, ALBERT J
• Application Number:
  US09/844,714
• Publication Number:
  US 20020074499A1
• Time in Patent Office: 1,103 Days
• Field of Search: 250/338.1, 250/339.04, 250/339.03, 250/339.09, 250/341.5, 250/352, 250/332, 250/252.1
• US Class Current: 250/338.1
• CPC Class Codes: G01J 5/10 using electric radiation detectors
• CPC Class Codes: G01J 5/16 Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: G01J 5/22 Electrical features thereof
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/671 for non-uniformity detection or correction
• CPC Class Codes: H04N 25/673 by using reference sources
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• 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

Methods and apparatus for compensating a radiation sensor for temperature variations of the sensor. In one example, the radiation sensor is a thermal sensor having at least one property that varies as a function of temperature. The thermal sensor outputs signals based on thermal radiation of interest from a particular radiating body in its view. These signals may contain significant undesirable components due in part to changes in temperature of the sensor itself. Methods and apparatus of the invention compensate the sensor for temperature variations of the sensor that are not due to the radiation of interest, so as to significantly reduce undesirable components in the instantaneous signals output by the sensor. In one example, this is accomplished without thermally stabilizing the sensor itself (i.e., dynamic temperature compensation). In another example, the sensor is thermally stabilized selectively at various predetermined temperatures as a function of the ambient temperature in the proximity of the sensor.

Claims

1. A method of compensating a radiation sensor for changes in at least one operational characteristic of the sensor due to a temperature variation of the sensor, wherein the sensor includes a plurality of radiation detectors and the at least one operational characteristic of the sensor that changes due to the temperature variation of the sensor includes at least one of an offset error variation and a gain variation associated with the plurality of radiation detectors, the method comprising acts of:

a) dynamically adjusting at least one calibration parameter associated with the radiation sensor based on the temperature variation of the sensor, wherein the at least one calibration parameter associated with the sensor includes at least one of an offset error value for each radiation detector and a gain value for each radiation detector, and wherein the act a) includes an act of dynamically adjusting at least one of at least one offset error value and at least one gain value based on the temperature variation of the sensor to compensate for a respective at least one of the offset error variation and the gain variation; and

b) applying the dynamically adjusted at least one calibration parameter to at least one output signal of the radiation sensor.

2. The method of claim 1, further comprising an act of:

c) allowing a temperature of the radiation sensor to freely vary over a significant range.

3. The method of claim 2, wherein the act c) comprises an act of:

applying essentially no thermal stabilization to the radiation sensor.

4. The method of claim 2, further comprising an act of:

d) thermally stabilizing the radiation sensor at a plurality of different temperatures based at least in part on an ambient temperature in proximity of the radiation sensor.

5. The method of claim 4, wherein the act d) further comprises an act of:

selecting the plurality of different temperatures from within a temperature range spanning approximately 100 degrees Celsius.

6. The method of claim 5, wherein the act d) further comprises an act of:

selecting the plurality of different temperatures from within a temperature range of approximately −

40 degrees Celsius to approximately +60 degrees Celsius.

7. The method of claim 4, wherein the plurality of different temperatures are selected from within a temperature range, and wherein the act d) further comprises acts of:

dividing the temperature range into a plurality of sub-ranges; and

selecting temperature from within each sub-range as a predetermined stabilization temperature so as to approximately minimize a power consumption over each sub-range of a thermal stabilization device used for the step d).

8. The method of claim 7, wherein the act of selecting one temperature from within each sub-range includes act of:

determining a center temperature within each sub-range; and

adding a predetermined number of degrees Celsius to the center temperature within each sub-range to determine the predetermined stabilization temperature within each sub-range.

9. The method of claim 8, wherein the act of adding a predetermined number of degrees Celsius includes an act of adding approximately 10 degrees Celsius to the center temperature within each sub-range to determine the predetermined stabilization temperature within each sub-range.

10. The method of claim 4, wherein the plurality of different temperatures includes at least three different temperatures, and wherein the act d) comprises an act of:

thermally stabilizing the radiation sensor at at least three different temperatures based at least in part on the ambient temperature in proximity of the radiation sensor.

11. The method of claim 4, wherein the act d) comprises acts of:

measuring the ambient temperature in proximity of the radiation sensor;

dynamically selecting one of a plurality of different predetermined stabilization temperatures in a vicinity of the measured ambient temperature; and

thermally stabilizing the radiation sensor at the selected one of the plurality of different predetermined stabilization temperatures.

12. The method of claim 4, wherein the act a) comprises an act of dynamically adjusting the at least one calibration parameter based on the respective different temperatures at which the radiation sensor is thermally stabilized.

13. The method of claim 12, wherein the radiation sensor includes a plurality of radiation detectors, wherein the at least one calibration parameter includes a plurality of offset maps and a plurality of gain maps, each offset map including an offset error value for each radiation detector at a different one temperature of the respective different temperatures and each gain map including a gain value for each radiation detector at a different one temperature of the respective different temperatures, and wherein the act a) comprises an act of:

selecting one offset map of the plurality of offset maps and one gain map of the plurality of gain maps based on a corresponding one of the respective different temperatures at which the radiation sensor is thermally stabilized.

14. The method of claim 2, further comprising an act of:

d) dynamically adjusting at least one operating parameter associated with the radiation sensor based on the temperature variation of the sensor.

15. The method of claim 14, wherein the at least one operating parameter associated with the sensor includes at least one of a DC bias voltage applied to the sensor, a DC bias current applied to the sensor, and an AC bias waveform applied to the sensor, and wherein the act d) comprises an act of:

dynamically adjusting at least one of the DC bias voltage applied to the sensor, the DC bias current applied to the sensor, and the AC bias waveform applied to the sensor based on the temperature variation of the sensor.

16. The method of claim 15, wherein the act d) comprises an act of:

dynamically adjusting the DC bias voltage and the DC bias current applied to the sensor so as to maintain an essentially constant bias power.

17. The method of claim 15, wherein the act d) comprises an act of:

dynamically adjusting an amplitude of the AC bias waveform applied to the sensor based on the temperature variation of the sensor.

18. A method of compensating a radiation sensor for changes in at least one operational characteristic of the sensor due to a temperature variation of the sensor, comprising an act of:

a) dynamically adjusting at least one calibration parameter associated with the radiation sensor based on the temperature variation of the sensor, wherein the act a) comprises an act of applying at least one compensation function to the at least one calibration parameter to compensate for the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

19. The method of claim 18, wherein the at least one compensation function includes a linear approximation of the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

20. The method of claim 18, wherein the at least one compensation function includes an interpolated piece-wise linear approximation of the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

21. The method of claim 18, wherein the at least one compensation function includes a nonlinear function representing the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

22. The method of any of claim 19 to 21, further comprising an act of:

b) allowing a temperature of the radiation sensor to freely vary over a significant range.

23. The method of claim 22, wherein the act b) comprises an act of:

applying essentially no thermal stabilization to the radiation sensor.

24. An apparatus, comprising:

a controller to compensate a radiation sensor for changes in at least one operational characteristic of the sensor due to a temperature variation of the sensor, the controller configured to dynamically adjust at least one calibration parameter associated with the radiation sensor based on the temperature variation of the sensor;

wherein the sensor includes a plurality of radiation detectors and the at least one operational characteristic of the sensor that changes due to the temperature variation of the sensor includes at least one of an offset error variation and a gain variation associated with the plurality of radiation detectors;

wherein the at least one calibration parameter associated with the sensor includes at least one of an offset error value for each radiation detector and a gain value for each radiation detector;

wherein the controller is configured to dynamically adjust at least one of at least one offset error value and at least one gain value based on the temperature variation of the sensor to compensate for a respective at least one of the offset error variation and the gain variation; and

wherein the controller is further configured to apply the dynamically adjusted at least one calibration parameter to at least one output signal of the radiation sensor.

25. The apparatus of claim 24, wherein the apparatus is configured to allow a temperature of the radiation sensor to freely vary over a significant range.

26. The apparatus of claim 25, wherein the apparatus does not include a thermal stabilization device to thermally stabilize the radiation sensor.

27. The apparatus of claim 25, further comprising at least one thermal stabilization device to thermally stabilize the radiation sensor, wherein the controller is configured to control the at least one thermal stabilization device to thermally stabilize the radiation sensor at a plurality of different temperatures based at least in part on an ambient temperature in proximity of the radiation sensor.

28. The apparatus of claim 27, wherein the controller is configured to select the plurality of different temperatures from within a temperature range spanning approximately 100 degrees Celsius.

29. The apparatus of claim 28, wherein the controller is configured to select the plurality of different temperatures from within a temperature range of approximately −

40 degrees Celsius to approximately +60 degrees Celsius.

30. The apparatus of claim 27, wherein the controller is configured to select the plurality of different temperatures from within a temperature range, and wherein the controller is further configured to:

divide the temperature range into a plurality of sub-ranges; and

select one temperature from within each sub-range as a predetermined stabilization temperature so as to approximately minimize a power consumption over each sub-range of the at least one thermal stabilization device.

31. The apparatus of claim 30, wherein the controller is further configured to:

determine a center temperature within each sub-range; and

add a predetermined number of degrees Celsius to the center temperature within each sub-range to determine the predetermined stabilization temperature within each sub-range.

32. The apparatus of claim 31, wherein the controller is configured to add approximately 10 degrees Celsius to the center temperature within each sub-range to determine the predetermined stabilization temperature within each sub-range.

33. The apparatus of claim 27, wherein the plurality of different temperatures includes at least three different temperatures, and wherein the controller is configured to control the at least one thermal stabilization device to thermally stabilize the radiation sensor at least three different temperatures based at least in part on the ambient temperature in proximity of the radiation sensor.

34. The apparatus of claim 27, wherein the controller is further configured to:

measure the ambient temperature in proximity of the radiation sensor;

dynamically select one of a plurality of different predetermined stabilization temperatures in a vicinity of the measured ambient temperature; and

control the at least one thermal stabilization device to thermally stabilize the radiation sensor at the selected one of the plurality of different predetermined stabilization temperatures.

35. The apparatus of claim 27, wherein the controller is configured to dynamically adjust the at least one calibration parameter based on the respective different temperatures at which the radiation sensor is thermally stabilized.

36. The apparatus of claim 35, wherein the radiation sensor includes a plurality of radiation detectors, wherein the at least one calibration parameter includes a plurality of offset maps and a plurality of gain maps, each offset map including an offset error value for each radiation detector at a different one temperature of the respective different temperatures and each gain map including a gain value for each radiation detector at a different one temperature of the respective different temperatures, and wherein the controller is configured to select one offset map of the plurality of offset maps and one gain map of the plurality of gain maps based on a corresponding one of the respective different temperatures at which the radiation sensor is thermally stabilized.

37. The apparatus of claim 25, wherein the controller is further configured to dynamically adjust at least one operating parameter associated with the radiation sensor bused on the temperature variation of the sensor.

38. The apparatus of claim 37, wherein the at least one operating parameter associated with the sensor includes at least one of a DC bias voltage applied to the sensor, a DC bias current applied to the sensor, and an AC bias waveform applied to the sensor, and wherein the controller is configured to dynamically adjust at least one of the DC bias voltage applied to the sensor, the DC bias current applied to the sensor, and the AC bias waveform applied to the sensor based on the temperature variation of the sensor.

39. The apparatus of claim 38, wherein the controller is further configured to dynamically adjust the DC bias voltage and the DC bias current applied to the sensor so as to maintain an essentially constant bias power.

40. The apparatus of claim 38, wherein the controller is further configured to dynamically adjust an amplitude of the AC bias waveform applied to the sensor based on the temperature variation of the sensor.

41. An apparatus, comprising:

a controller to compensate a radiation sensor for changes in at least one operational characteristic of the sensor due to temperature variation of the sensor, the controller configured to dynamically adjust at least one calibration parameter associated with the radiation sensor based on the temperature variation of the sensor;

wherein the controller is configured to apply at least one compensation function to the at least one calibration parameter to compensate for the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

42. The apparatus of claim 41, wherein the at least one compensation function includes a linear approximation of the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

43. The apparatus of claim 41, wherein the at least one compensation function includes an interpolated piece-wise linear approximation of the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

44. The apparatus of claim 41, wherein the at least one compensation function includes a nonlinear function representing the changes in the at least one operational characteristic of the sensor due to the temperature variation of the sensor.

45. The apparatus of any of claims 42 to 44, wherein the apparatus is configured to allow a temperature of the radiation sensor to freely vary over a significant range.

46. The apparatus of claim 45, wherein the apparatus does not include a thermal stabilization device to thermally stabilize the radiation sensor.