Shutterless infrared imager algorithm with drift correction

• US 8,067,735 B2
• Filed: 02/24/2010
• Issued: 11/29/2011
• Est. Priority Date: 12/19/2008
• Status: Active Grant

• Current Assignee: Fluke Corporation (Fortive Corp.)
• Original Assignee: Fluke Corporation (Fortive Corp.)
• Inventors: Rekow, Mathew N., King, Stephen R, Brest, Betsy, Carlson, Paul S., Heinke, Thomas, Warnke, Stefan H.
• Primary Examiner(s): Gaworecki; Mark R
• Application Number:
  US12/711,649
• Publication Number:
  US 20100237245A1
• Time in Patent Office: 643 Days
• Field of Search: 250/330, 250/332, 250/338.1
• US Class Current: 250/332
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 5/064 Ambient temperature sensor; Housing temperature sensor; Constructional details thereof
• CPC Class Codes: G01J 5/80 Calibration using comparison with reference sources G01J5/52
• CPC Class Codes: H04N 23/20 for generating image signals from infrared radiation only
• 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

An infrared imaging system having functionality for maintaining image quality in the presence of temperature drift of the system. Such functionality is applied repetitively to maintain image quality of a target scene, yet without continuous actuation of a shutter of the system. The functionality of the imaging system results from implementing an imager algorithm. In use, the imager algorithm functions with a calibration curve created for the imaging system, with the curve comprising a plot of system output versus target scene temperature.

Claims

1. An infrared (IR) imaging apparatus comprising:

a lens for focusing IR energy from a target scene;

a focal plane array (FPA) comprising a plurality of IR detector elements; and

an enclosure disposed between the lens and the FPA, the enclosure defining an inner aperture and an outer aperture, the inner aperture located near the FPA and the outer aperture located away from the FPA, the enclosure adapted to selectively allow passage of focused IR energy from the lens to the FPA via the outer aperture and then the inner aperture, the inner aperture being larger than the outer aperture.

2. The apparatus of claim 1 wherein the inner aperture comprises a planar opening, wherein the enclosure comprises one or more sides extending outward from the apparatus, and wherein space between the one or more sides of the enclosure defines the planar opening.

3. The apparatus of claim 2 wherein the one or more sides comprise one or more side walls of the enclosure.

4. The apparatus of claim 3 wherein the one or more enclosure side walls each comprises an integral body.

5. The apparatus of claim 3 wherein the one or more enclosure side walls each comprise portions extending between the FPA and the lens, the portions having inner edges near the FPA, wherein the inner edges define the inner aperture.

6. The apparatus of claim 5 wherein the inner edges are separated from the FPA.

7. The apparatus of claim 5 further comprising a window for the FPA, wherein the enclosure side walls extend between apparatus structure surrounding the FPA window and the lens, wherein the apparatus structure forms a narrowing of the inner aperture, the narrowing of the inner aperture at its narrowest being larger than the outer aperture.

8. The apparatus of claim 7, wherein the apparatus structure is located between the FPA and the enclosure side walls.

9. The apparatus of claim 1 wherein the inner aperture is larger than the FPA.

10. The apparatus of claim 1 wherein the enclosure comprises selectively movable means to prevent the passage of IR energy there through.

11. The apparatus of claim 10 wherein the selectively moveable means comprises a shutter.

12. The apparatus of claim 11 wherein the shutter is positioned proximate to the outer aperture and selectively adjustable to cover the outer aperture.

13. The apparatus of claim 1 wherein the enclosure is formed of one isothermal material.

14. The apparatus of claim 1 wherein the outer aperture is proximate to the lens.

15. The apparatus of claim 1, further comprising a processor in communication with the FPA and configured for making initial measurements of the IR imaging apparatus during a single blocking of the FPA detector elements and for making continued measurements of the IR imaging apparatus during continued use of the IR imaging apparatus when the FPA detector elements are exposed to the IR energy from the target scene, the processor configured for storing the initial measurements and configured for using a calibration curve for the IR imaging apparatus with which the initial and continued measurements are used in maintaining image quality in presence of temperature drift during the continued use of the IR imaging apparatus.

16. An infrared (IR) imaging apparatus comprising:

a lens for focusing IR energy from a target scene;

a focal plane array (FPA) comprising a plurality of IR detector elements; and

an enclosure disposed between the lens and the FPA, the enclosure defining an inner aperture and an outer aperture, the inner aperture located near the FPA and the outer aperture located away from the FPA, the enclosure formed such that its temperature is uniformly provided across its surfaces, the enclosure formed of one isothermal material.

17. The apparatus of claim 16 wherein the inner aperture comprises a planar opening, wherein the enclosure comprises one or more sides extending outward from the apparatus, and wherein space between the one or more sides of the enclosure defines the planar opening.

18. The apparatus of claim 17 wherein the planar opening is larger than the outer aperture.

19. The apparatus of claim 17 wherein the planar opening is larger than the FPA.

20. The apparatus of claim 17 wherein the planar opening is larger than the outer aperture and the FPA.

21. The apparatus of claim 16 wherein the enclosure comprises a shutter to prevent the passage of IR energy there through.

22. The apparatus of claim 21 wherein the shutter is positioned proximate to the outer aperture and selectively adjustable to cover the outer aperture.

23. The apparatus of claim 16, wherein the enclosure is integrally formed of the one isothermal material.

24. The apparatus of claim 16 wherein the outer aperture is proximate to the lens.

25. An infrared (IR) imaging apparatus comprising:

a lens for focusing IR energy from a target scene;

a focal plane array (FPA) comprising a plurality of IR detector elements; and

an enclosure disposed between the lens and the FPA, the enclosure defining an inner aperture and an outer aperture, the inner aperture located near the FPA and the outer aperture located away from the FPA, the enclosure adapted to selectively allow passage of focused IR energy from the lens to the FPA via the outer aperture and then the inner aperture, the inner aperture being larger than the outer aperture, wherein temperature drift of the IR detector elements can be based in part on temperature of the enclosure, and

a single temperature sensor operatively coupled to the enclosure for monitoring temperature drift of the enclosure.

26. The apparatus of claim 25 wherein the inner aperture comprises a planar opening, wherein the enclosure comprises one or more sides extending outward from the apparatus, and wherein space between the one or more sides of the enclosure defines the planar opening.

27. The apparatus of claim 25, wherein the enclosure is formed such that its temperature is uniformly provided across its surfaces.

28. An infrared (IR) imaging apparatus comprising:

a lens for focusing IR energy from a target scene;

a focal plane array (FPA) comprising a plurality of IR detector elements; and

an enclosure disposed between the lens and the FPA, the enclosure defining an inner aperture and an outer aperture, the inner aperture located near the FPA and the outer aperture located away from the FPA, the enclosure being an integrally formed structure wherein the inner aperture at its narrowest being larger than the outer aperture.

29. The apparatus of claim 28 wherein the enclosure comprises one or more side walls with portions extending between the FPA and the lens, the portions having inner edges near the FPA, wherein the inner edges define the inner aperture.

30. The apparatus of claim 29 wherein the inner edges are separated from the FPA.

31. The apparatus of claim 29 further comprising a window for the FPA, wherein the enclosure side walls extend between apparatus structure surrounding the FPA window and the lens, wherein the apparatus structure forms a narrowing of the inner aperture, the narrowing of the inner aperture at its narrowest being larger than the outer aperture.

32. The apparatus of claim 31, wherein the apparatus structure is located between the FPA and the enclosure side walls.