SYSTEM AND METHOD FOR CHANGING SPECTRAL RANGE OF A CRYOGENICALLY COOLED DETECTOR

• US 20110199605A1
• Filed: 02/17/2011
• Published: 08/18/2011
• Est. Priority Date: 02/18/2010
• Status: Active Grant

• Current Assignee: Rafael Advanced Defense Systems Limited (Government of Israel)
• Original Assignee: Rafael Advanced Defense Systems Limited (Government of Israel)
• Inventors: YAACOBI, Ami
• Granted Patent: US 9,157,806 B2
• Time in Patent Office: Days
• US Class Current: 356/51
• 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 5/0808 Convex mirrors
• CPC Class Codes: G01J 5/084 Adjustable or slidable
• CPC Class Codes: G01J 5/602 using selective, monochromatic or bandpass filtering

Abstract

It is provided an optical system for changing a spectral range of a cryogenically cooled detector. The optical system allows selective spectral transfer of radiation, and provides a reflecting field of view at an undesired range directed towards cold surfaces. A removable spectral filter having a high transmittance at a first spectral range and a low transmittance at a second spectral range is disposed outside a cold shield. A reflective surface faces the detecting device and provides the detector a reflecting field of view at the second spectral range directed towards the cold shield, and a blackened cold skirt thereof. Alternatively, a dichroic mirror is disposed inside the cold shield and has a high reflectance at a first spectral range and a high transmittance at a second range. The detecting device includes a first arm and a second arm of the cold shield to accommodate respective optical channels. A removable selective mirror having a high reflectance at the first spectral range is disposed outside the cold shield. A reflecting field of view at the undesired spectral range directed towards a blackened surface of the cold shield or a thermo-electric cooler is provided.

Claims

1. An optical system for changing an operational spectral range of a cryogenically cooled infra-red detecting device, the device having an infra-red detector disposed within a cold shield and adapted for receiving incoming radiation, the optical system being adapted for:

(a) allowing transfer to the detector of incoming radiation at a desired spectral range while preventing transfer thereof at an undesired spectral range;

(b) providing a reflecting field of view at said undesired spectral range directed towards at least one cold surface.

2. The optical system of claim 1, wherein the system includes a removable spectral filter disposed outside the cold shield, the spectral filter has a high transmittance at a first spectral range and a substantially lower transmittance for a second spectral range.

3. The optical system of claim 2 wherein said high transmittance is higher than 70% and said low transmittance is lower than 20%.

4. The optical system of claim 1 wherein the optical system includes a reflective surface facing the detecting device for providing the detector a reflecting field of view at said second spectral range directed towards the cold shield.

5. The optical system of claim 4 wherein the detecting device includes a blackened cold skirt surrounding a coupling window of the cold shield and said reflective surface providing the detector a reflecting field of view directed towards the cold shield and said blackened cold skirt.

6. The optical system of claim 4 wherein said reflective surface is a concave reflecting surface facing the detecting device.

7. The optical system of claim 1 wherein a dichroic mirror is disposed inside the cold shield in front of an infra-red detector, said dichroic mirror has a high reflectance at a first spectral range and a high transmittance at a second spectral range, and the detecting device includes a first arm and a second arm of the cold shield to accommodate respective optical channels for said first spectral range and for said second spectral range.

8. The optical system of claim 7 wherein the system further includes a removable selective mirror disposed outside the cold shield and having a high reflectance at said first spectral range.

9. The optical system of claim 8 wherein said removable selective mirror prevents reception by the detecting device of incoming radiation at said second spectral range.

10. The optical system of claim 6 wherein the system includes an optical train for providing a reflecting field of view at said undesired spectral range directed towards at least one cold surface.

11. The optical system of claim 10 wherein said at least one cold surface is a blackened surface of the cold shield.

12. The optical system of claim 10 wherein said at least one cold surface is a thermo-electric cooler.

13. A method for changing an operational spectral range of a cryogenically cooled infra-red detecting device, the device having an infra-red detector disposed within a cold shield, and being adapted for receiving incoming radiation, the method comprising:

(a) allowing transfer to the detector of incoming radiation at a desired spectral range;

(b) preventing transfer thereof at an undesired spectral range; and

(c) providing a reflecting field of view at said undesired spectral range directed towards at least one cold surface.

14. The method of claim 13, wherein the method includes placing and removing spectral filter outside the cold shield, the spectral filter has a high transmittance at a first spectral range and a substantially lower transmittance for a second spectral range.

15. The method of claim 13 wherein the method includes placing and removing a reflective surface facing the detecting device for providing the detector a reflecting field of view at said second spectral range directed towards the cold shield.

16. The method of claim 13 wherein the method includes disposing a dichroic mirror inside the cold shield in front of an infra-red detector, said dichroic mirror has a high reflectance at a first spectral range and a high transmittance at a second spectral range, and the detecting device includes a first arm and a second arm of the cold shield to accommodate respective optical channels for said first spectral range and for said second spectral range.

17. The method of claim 16 wherein the method further includes placing and removing a selective mirror outside the cold shield, and said removable selective mirror has a high reflectance at said first spectral range.

18. The method of claim 16 wherein the method includes providing an optical train for providing a reflecting field of view at said undesired spectral range directed towards at least one cold surface.

19. An optical system for controlling radiation provided to a cryogenically cooled detecting device equipped with a cold shield, the detecting device being adapted to detect the incoming radiation from a certain field of view, the optical system being adapted for:

(a) blocking portion of the field of view of the incoming radiation from arriving the detecting device; and

(b) providing a reflecting field of view compatible with the blocked portion directed towards at least one cold surface.

20. The optical system of claim 19, wherein said system includes:

(i) a substantially circular aperture for blocking portion of the incoming radiation; and

(ii) a reflecting surface for reflecting field of view compatible with the blocked portion directed towards at least one cold surface.

21. The optical system of claim 20 wherein the detecting device includes a blackened cold skirt surrounding a coupling window of the cold shield and said reflective surface providing the detector a reflecting field of view directed towards the cold shield and said blackened cold skirt.