Front lens shutter mount for uniformity correction

• US 20050231627A1
• Filed: 08/28/2003
• Published: 10/20/2005
• Est. Priority Date: 09/20/2002
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Miller, Christopher R., Murphy, Robert H
• Granted Patent: US 8,436,905 B2
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: G01J 3/0232 using shutters
• CPC Class Codes: G01J 5/0805 Means for chopping radiation
• CPC Class Codes: H04N 25/671 for non-uniformity detection or correction
• CPC Class Codes: H04N 25/672 between adjacent sensors or output registers for reading a single image
• 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 imaging system comprising a lens, a detector array (e.g., focal plane array), a signal processing module and a shutter, wherein the shutter is positioned in front of the lens (between the lens and the scene being imaged). This front lens shutter mount configuration allows offset correction to compensate for internal radiant flux and other deficiencies associated with conventional systems.

Claims

1. An imaging system comprising:

a focal plane array (FPA) having a plurality of pixels;

a lens adapted to focus radiation from a scene in front of the lens onto the FPA behind the lens;

a shutter located in front of the lens, the shutter having a closed state that produces a spatially uniform reference image signal and allows internal radiant flux of the system to reach detectors of the FPA, and an open state that allows an open state image signal that includes external scene radiation and internal radiant flux from the system to reach detectors of the FPA; and

a signal processing module operatively coupled to the FPA, and adapted to correct the open state image signal based on the spatially uniform reference image signal.

2. The system of claim 1 further comprising:

a shutter controller operatively coupled to the shutter, and adapted to command the shutter to its opened and closed states.

3. The system of claim 2 further comprising:

a system controller communicatively coupled to the shutter controller and the signal processing module, and adapted to control operation of the imaging system.

4. The system of claim 3 where the system controller is communicatively coupled to a network thereby enabling the imaging system to communicate with other systems also communicatively coupled to the network.

5. The system of claim 1 further comprising:

a temperature controller adapted for illuminating the scene with radiation, thereby allowing reflected radiation to be received by the system.

6. The system of claim 5 further wherein the temperature controller includes a laser for illuminating the scene.

7. The system of claim 1 further wherein the shutter has a lens side surface that is located within five millimeters of the front of the lens.

8. The system of claim 1 wherein for any one session of imaging system operation, each of a plurality of open state image signals are corrected based on the closed state image signal.

9. The system of claim 1 wherein the closed state image signal is periodically generated to account for changes in the imaging system.

10. A method for imaging a scene, where method is carried out by an imaging system configured with a front lens mounted shutter, the method comprising:

closing the front lens mounted shutter so that external scenes are blocked from being imaged;

generating a closed state image signal that includes internal radiant flux of the system;

opening the front lens mounted shutter thereby allowing the imaging system to receive external scene radiation;

generating an open state image signal based on the received scene radiation; and

correcting the open state image signal based on the closed state image signal.

11. The method of claims 10 wherein correcting the open state image signal includes compensating for pixel-to-pixel non-uniformities of a detector array included in the imaging system.

12. The method of claims 10 wherein correcting the open state image signal includes compensating for offsets between the opened and closed states of the lens.

13. The method of claims 10 wherein correcting the open state image signal includes compensating for pixel-to-pixel non-uniformities and offsets between the opened and closed states of the lens.

14. The method of claims 10 wherein the external scene radiation includes IR radiation and the imaging system includes an IR sensitive FPA for generating the closed and open state image signals.

15. A method for manufacturing an imaging system, the method comprising:

providing a lens adapted to focus radiation from a scene in front of the lens onto a detector array behind the lens; and

providing a shutter located in front of the lens, the shutter having a closed state that allows a closed state image signal that includes internal radiant flux of the system to be generated by the detector array, and an open state that allows an open state image signal that includes external scene radiation to be generated by the detector array.

16. The method of claim 15 further comprising:

providing a detector array having a plurality of pixels for detecting scene radiation; and

operatively coupling a signal processing module to the detector array, the signal processing module adapted to correct open state image signals based on closed state image signals.

17. The method of claim 16 further comprising:

operatively coupling a shutter controller to the shutter, the shutter controller adapted to command the shutter to its opened and closed states.

18. The method of claim 17 further comprising:

operatively coupling a system controller to the shutter controller and processing module, the system controller adapted to control operation of the imaging system.

19. The method of claim 15 further comprising:

providing a laser adapted to illuminate a scene with radiation, thereby allowing reflected radiation to be received by the system.

20. The method of claim 15 further wherein the shutter has a lens side surface that is located within five millimeters of the front of the lens.