METHOD AND APPARATUS FOR USING TEMPERATURE CONTROLLED VARIABLE DIAPHRAGMS OR SWAPPABLE FIXED APERTURES WITH INFRARED CAMERAS

• US 20040238741A1
• Filed: 05/28/2003
• Published: 12/02/2004
• Est. Priority Date: 05/28/2003
• Status: Active Grant

• Current Assignee: OPTO-Knowledge Systems, Inc.
• Original Assignee: OPTO-Knowledge Systems, Inc.
• Inventors: Garman, John Dwight, Gat, Nahum
• Granted Patent: US 7,157,706 B2
• Time in Patent Office: Days
• US Class Current: 250/338.1
• 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 5/0831 Masks; Aperture plates; Spatial light modulators
• CPC Class Codes: G01J 5/084 Adjustable or slidable
• CPC Class Codes: G01J 5/0865 having means for replacing an element of the arrangement by another of the same type, e.g. an optical filter
• CPC Class Codes: G03B 9/04 Single movable plate with two or more apertures of graded size, e.g. sliding plate or pivoting plate
• CPC Class Codes: G03B 9/06 Two or more co-operating pivoted blades, e.g. iris type shutters functioning as diaphragms by limiting extent of opening movement G03B9/08
• CPC Class Codes: H04N 23/75 by influencing optical camera components
• 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 continuously variable diaphragm or swappable fixed aperture for use in thermal infrared cameras, which aperture or diaphragm can be cooled to cryogenic temperatures. The invention contemplates mounting aperture control means, if necessary, in a vacuum or extending the control mechanism through a vacuum in a thermally isolated manner to avoid radiation load on the photocell. The inventive method implements such a diaphragm and control system. The invention makes possible the object of using a single thermal infrared camera under a wide variety of target-scene radiation conditions that may be rapidly changing, with interchangeable or zoom camera lenses requiring matching or different size cold stops, and under other such dynamic situations.

Claims

1. In a thermal infrared camera, the improvement comprising an aperture mechanism so that the aperture size can be adjusted by an aperture control means.

2. An improvement to a thermal infrared camera as in claim 1 wherein said aperture mechanism is selected from one of a variable diaphragm, an iris, an aperture wheel, a partial aperture wheel, and an aperture stick.

3. An improvement to a thermal infrared camera as in claim 1 wherein said aperture mechanism is thermally coupled to a temperature control means.

4. An improvement to a thermal infrared camera as in claim 1 wherein said aperture mechanism is mounted to the radiation shield.

5. An improvement to a thermal infrared camera as in claim 1 wherein said aperture control means is selected from at least one of mechanical, piezoelectric, and electromagnetic means.

6. An improvement to a thermal infrared camera as in claim 1 wherein said temperature control means is selected from at least one of a cryogenic fluid, a mechanical cryo-refrigerator, a pulsed tube, and a Peltier cooler.

7. An improvement to a thermal infrared camera as in claim 1 wherein said aperture mechanism is controlled by a logic control means, said logic control means reading the signal level of said at least one photocell and causing said aperture control means to adjust said aperture mechanism to increase or decrease the level of said radiation reaching said at least one photocell so as to maintain optimal radiation levels.

8. An improvement to a thermal infrared camera as in claim 7 wherein said logic circuit reads the exposure level of at least one of said photocell and at least one secondary sensor.

9. An improvement to a thermal infrared camera as in claim 7 wherein the user may affect said logic circuit through external control means.

10. An improvement to a thermal infrared camera as in claim 1 wherein said aperture mechanism is controlled by a logic control means, said logic control means receiving the f-number of the lens and causing said aperture control means to adjust said aperture mechanism to maintain the desired cold stop.

11. An improvement to a thermal infrared camera as in claim 10 wherein said logic control means receives the zoom position of said lens and causes said aperture control means to adjust said aperture mechanism to maintain said desired cold stop.

12. An improvement to a thermal infrared camera as in claim 1 wherein the optics of said camera comprises at least one lens with at least one aperture requirement wherein said aperture control means adjusts said aperture size to match the aperture requirements of said optics.

13. An improvement to a thermal infrared camera as in claim 12 wherein said at least one lens is comprised of a wide field of view configuration and a narrow field of view configuration and said aperture control means provides at least two aperture sizes.

14. An improvement to a thermal infrared camera as in claim 12 wherein said at least one lens is comprised of a continuously variable zoom compound lens and said aperture mechanism provides at least two aperture sizes.

15. An alterable aperture for use in thermal infrared cameras that can be controlled by an aperture control means to change the aperture size.

16. An alterable aperture as in claim 15 wherein said aperture mechanism is selected from one of a variable diaphragm, an iris, an aperture wheel, a partial aperture wheel, and an aperture stick.

17. An alterable aperture as in claim 15 wherein said aperture mechanism is thermally coupled to a temperature control means.

18. An alterable aperture as in claim 15 wherein said aperture mechanism is mounted to the radiation shield.

19. An alterable aperture as in claim 15 wherein said aperture control means is selected from one of mechanical, piezoelectric, and electromagnetic means.

20. An alterable aperture as in claim 15 wherein said temperature control means is selected from at least one of a cryogenic fluid, a mechanical cryo-refrigerator, a pulsed tube, and a Peltier cooler.

21. In a thermal infrared camera, the improvement comprising implementing a thermally coupled aperture mechanism disposed spaced preceding the radiation shield within the optical path of the focusing lens, said aperture mechanism controlled by separate control means.

22. An improvement to a thermal infrared camera as in claim 21 wherein the variable aperture arrangement replaces the optical entrance of said radiation shield, thereby forming one side of said radiation shield.

23. An improvement to a thermal infrared camera as in claim 21 wherein said variable aperture arrangement is selected from one of a variable diaphragm, an iris, an aperture wheel, a partial aperture wheel, and an aperture stick.

24. An improvement to a thermal infrared camera as in claim 21 wherein said separate control means is selected from one of a stepper motor, DC motor, a piezoelectric motor, a rotary dial, and an electromagnetic means.

25. An improvement to a thermal infrared camera as in claim 21 wherein said aperture mechanism is controlled by a logic control means, said logic control means reading the signal level of a sensor and causing said aperture control means to adjust said aperture mechanism to provide the appropriate aperture size.

26. An improvement to a thermal infrared camera as in claim 21 wherein said aperture mechanism is controlled by a logic control means, said logic means responding to the f-number of said focusing lens and causing said aperture control means to adjust said aperture mechanism to maintain the desired cold stop.

27. Method of making adjustable the level of radiation received at a photoelectric cell in a thermal infrared camera, comprising the steps of:

replacing the fixed aperture with an alterable aperture mechanism;

connecting aperture control means to said alterable aperture mechanism to allow altering the aperture size;

creating mounting means for said aperture control means within said thermal infrared camera;

thereby allowing control over said aperture size permitting said thermal infrared camera to match the input f-numbers.

28. Method as in claim 27 that includes the added step of thermally coupling said aperture control means to a temperature control means.

29. Method as in claim 27 that includes the added step of mounting said aperture mechanism to the radiation shield.

30. Method as in claim 27 wherein said variable aperture is selected from a variable diaphragm, an iris, an aperture wheel, a partial aperture wheel, and aperture stick.

31. Method as in claim 27 wherein said aperture control means is selected from mechanical, piezoelectric, and electromagnetic control means.

32. Method as in claim 27 that includes the added step of providing logic control means to allow automatic aperture size selection.

33. Method as in claim 32 that includes the added step of providing manual input means to said logic control means to allow user selected aperture sizes.

34. Method of making aperture-matched optics changes in a thermal infrared camera, comprising the steps of:

replacing the fixed aperture with an alterable aperture mechanism;

connecting aperture control means to said alterable aperture mechanism to allow altering the aperture size;

creating mounting means for said aperture control means within said thermal infrared camera;

thereby allowing control over said aperture size permitting said thermal infrared camera to be used with optics of varying prescription, f-number, or focal length.

35. Method as in claim 34 that includes the added step of thermally coupling said aperture control means to the temperature control means.

36. Method as in claim 34 that includes the added step of providing logic control means to allow automatic aperture size selection.

37. Method as in claim 34 wherein said variable aperture is selected from a variable diaphragm, an iris, an aperture wheel, a partial aperture wheel, and aperture stick.

38. Method as in claim 34 wherein said aperture control means is selected from mechanical, piezoelectric, and electromagnetic control means.