Thermal imaging cameras

• US 7,282,715 B2
• Filed: 01/30/2002
• Issued: 10/16/2007
• Est. Priority Date: 01/31/2001
• Status: Expired due to Fees

• Current Assignee: Thales Optronique SA (Thales SA)
• Original Assignee: Thales Optronique SA (Thales SA)
• Inventors: Barron, Donald Robert
• Primary Examiner(s): Hannaher; Constantine
• Assistant Examiner(s): Taningco; Marcus H
• Application Number:
  US10/470,702
• Publication Number:
  US 20040129889A1
• Time in Patent Office: 2,085 Days
• Field of Search: 250/370.08
• US Class Current: 250/370.08
• CPC Class Codes: C08K 3/01 characterized by their specific function
• CPC Class Codes: C08K 3/38 Boron-containing compounds
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0286 Constructional arrangements for compensating for fluctuations caused by temperature, humidity or pressure, or using cooling or temperature stabilization of parts of the device; Controlling the atmosphere inside a spectrometer, e.g. vacuum
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• 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 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/601 using spectral scanning
• CPC Class Codes: G01N 25/72 Investigating presence of flaws
• 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 13/22 Telecentric objectives or lens systems
• 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 modular hyperspectral thermal camera that combines a wide field-of-view with a low erroneous recognition rate is described. The modular hyperspectral thermal camera provides such low erroneous recognition rates without any requirement for cryogenically cooling the associated optical components. The modular nature of the hyperspectral thermal camera permits easy exchange of the optical components and so provides a device that is easily calibrated and varied in resolution. In addition the modular nature allows the hyperspectral thermal camera to be readily converted to a broad band thermal camera, a full field spectrograph or a thermal bandpass filter camera, as required.

Claims

1. A modular hyperspectral thermal imaging camera comprising a transmissive diffraction grating, a detector and non-cryogenically cooled optical components, comprising an image slit, a telecentric imaging lens, a telecentric collimator and a focusing lens, the image slit comprising a transparent piercing in a highly reflective surround.

2. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the transmissive diffraction grating comprises a linear phase grating and a refractive substrate, characterised in that for a reference radiation of a predetermined reference wavelength an induced diffraction of the linear phase grating compensates an induced refraction of the refractive substrate, such that the reference radiation passes undeviated through the transmissive diffraction grating.

3. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the detector comprises an aperture stop, a cold shield and a photodetector array.

4. A modular hyperspectral thermal imaging camera as claimed in claim 3, wherein the aperture stop comprises an aperture formed within the cold shield.

5. A modular hyperspectral thermal imaging camera as claimed in claim 3 wherein the aperture stop comprises an aperture formed in a convex mirror located externally to the cold shield such that a radius of curvature of the convex mirror matches a distance between the photodetector array and the convex mirror.

6. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the detector comprises a mosaic of photodiodes.

7. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the optical components comprise materials that exhibit very low absorption coefficients.

8. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the transparent piercing leads to air.

9. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the transparent piercing leads to a transmissive material.

10. A modular hyperspectral thermal imaging camera as claimed in claim 9, wherein the entrance slit surround is heated to a temperature just above the atmospheric dew point.

11. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the imaging lens comprises an optical singlet and an air spaced doublet.

12. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the entrance slit is located internally to the imaging lens.

13. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the entrance slit is located externally to the imaging lens.

14. A modular hyperspectral thermal imaging camera as claimed in claim 1, comprising one or more calibration mirrors.

15. A modular hyperspectral thermal imaging camera as claimed in claim 1, comprising a scanning mirror located at the entrance slit, wherein the scanning mirror allows for the field of view of the slit to be scanned through an object field.

16. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the optical components comprise a collimator that is afocal.

17. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the optical components comprise a collimator that comprises a negative aspheric lens, a positive aspheric and a diffractive hybrid lens.

18. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the optical components comprise a focusing lens that provides image rays that are telecentric so forming an image at the detector.

19. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the optical components comprise a focusing lens that comprises a positive lens and a correcting lens.

20. A modular hyperspectral thermal imaging camera as claimed in claim 1, further comprising a cooling jacket for cooling the optical components of the modular hyperspectral thermal imaging camera so enhancing the signal to noise ratio of a detected image.

21. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the components are interchangeable.

22. A modular hyperspectral thermal imaging camera as claimed in claim 1, wherein the a resolution of the hyperspectral thermal imaging camera is altered by changing the transmissive diffraction grating.

23. A modular hyperspectral thermal imaging camera comprising a transmissive diffraction grating, a detector and optical components, wherein the optical components of the modular hyperspectral thermal imaging camera do not require cryogenic cooling, and the transmissive diffraction grating comprises a linear phase grating and a refractive substrate, wherein for a reference radiation of a predetermined reference wavelength an induced diffraction of the linear phase grating compensates an induced refraction of the refractive substrate, such that the reference radiation passes undeviated through the transmissive diffraction grating.

24. A modular hyperspectral thermal imaging camera comprising a transmissive diffraction grating, a detector and optical components, wherein the optical components do not require cryogenic cooling, and wherein the detector comprises an aperture stop, a cold shield and a photodetector array.

25. A modular hyperspectral thermal imaging camera as claimed in claim 24, wherein the aperture stop comprises an aperture formed within the cold shield.

26. A modular hyperspectral thermal imaging camera as claimed in claim 24, wherein the aperture stop comprises an aperture formed in a convex mirror located external to the cold shield such that a radius of curvature of the convex mirror matches a distance between the photodetector array and the convex mirror.

27. A modular hyperspectral thermal imaging camera comprising a transmissive diffraction grating, a detector and optical components, wherein the optical components of the modular hyperspectral thermal imaging camera do not require cryogenic cooling, wherein the detector comprises an aperture stop, a cold shield and a photodetector array, and wherein the aperture stop comprises an aperture formed in a convex mirror located external to the cold shield such that a radius of curvature of the convex mirror matches a distance between the photodetector array and the convex mirror.