Three-Axis Image Stabilization System

• US 20090160951A1
• Filed: 12/19/2008
• Published: 06/25/2009
• Est. Priority Date: 12/20/2007
• Status: Active Grant

• Current Assignee: Utah State University Research Foundation (Utah State University)
• Original Assignee: Utah State University Research Foundation (Utah State University)
• Inventors: Peterson, James, Anderson, Scott A., Wooden, Jason Lee, Robinson, R. Camden, Davidson, Morgan
• Granted Patent: US 8,212,880 B2
• Time in Patent Office: Days
• US Class Current: 348/208.400
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/45 for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
• CPC Class Codes: H04N 23/51 Housings
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/6811 based on the image signal
• CPC Class Codes: H04N 23/6812 based on additional sensors, e.g. acceleration sensors
• CPC Class Codes: H04N 23/687 by shifting the lens or sensor position

Abstract

An image stabilization system includes an optical assembly configured to receive electromagnetic radiation emitted by a target and produce focused image of the target; a focal plane array, the focal plane array being configured to receive the image and integrate at least a portion of the electromagnetic radiation making up the image to produce an electrical representation of the image; sensors configured to provide kinematic data; a control system receiving the kinematic data and estimating jitter-induced motion of the image on the focal plane and outputting a control signal; and actuators configured to receive the control signal and to translate the focal plane along two orthogonal axes and rotate the focal plane about a third orthogonal axis such that jitter-induced motion of the image on the focal plane is reduced.

Claims

1. A system comprising:

an optical assembly configured to receive electromagnetic radiation emitted by a target and produce an image of said target;

a focal plane array, said focal plane array being configured to receive said image and integrate at least a portion of said electromagnetic radiation making up said image to produce an electrical representation of said image;

sensors configured to provide kinematic data;

a control system receiving said kinematic data and estimating jitter-induced motion of said image on said focal plane and outputting a control signal; and

actuators configured to receive said control signal and to translate said focal plane along two orthogonal axes and rotate said focal plane about a third orthogonal axis such that jitter-induced motion of said image on said focal plane is reduced.

2. The system of claim 1, wherein said third orthogonal axis is substantially parallel to a bore axis of said optical assembly.

3. The system of claim 1, wherein said third orthogonal axis is substantially collinear with a bore axis of said optical assembly.

4. The system of claim 1, wherein said system is configured to reduce jitter-induced motion of said image on said focal plane in a range which includes frequencies above 25 Hz to 500 Hz.

5. The system of claim 1, wherein said actuators are piezo-electric actuators.

6. The system of claim 5, wherein said piezo-electric actuators comprise monolithic flexures and integral non-contact position sensors.

7. The system of claim 5, wherein said piezo-electric actuators comprise an X-Y stage and a rotation stage.

8. The system of claim 7, wherein said focal plane is directly attached to said rotation stage, said rotation stage being attached to said X-Y stage such that actuation of said X-Y stage moves both said rotation stage and said focal plane.

9. The system of claim 1, further comprising a multi-axis gimbal, said multi-axis gimbal providing pointing capabilities to said system.

10. The system of claim 1, wherein said sensors measure angular displacement.

11. The system of claim 1, wherein said sensors are angular rate sensors, said angular rate sensors being configured to provide angular rates of motion about three orthogonal axes.

12. The system of claim 11, wherein said angular rate sensors are magnetohydrodynamic gyroscopes.

13. The system of claim 1, wherein said control system comprises notch filters, said notch filters reducing excitation of resonant frequencies within said system;

the control system further comprising a feed-forward transfer function which provides frequency domain response information of said actuator

14. The system of claim 6, wherein said control system is configured to receive data from said integral non-contact sensors and calculate a measured piezo position;

said control system summing said measured piezo position with said jitter-induced motion of said image on said focal plane to find a positional error of said focal plane.

15. The system of claim 1, wherein said focal plane is an infrared focal plane array, said system being configured for vehicle mounted remote sensing.

16. A system for reducing jitter-induced smear on an infrared focal plane comprising:

an infrared focal plane array configured to receive electromagnetic radiation and integrate at least a portion of said electromagnetic radiation to produce an electrical representation of an image;

a gimbaled optical assembly configured to receive electromagnetic radiation emitted by a target and focus said image of said target on said infrared focal plane array;

gyroscopic sensors configured to provide angular rate data in three orthogonal axes;

a control system receiving said angular rate data and estimating jitter-induced motion of said image on said focal plane and outputting a control signal, said control system comprising notch filters, said notch filters reducing excitation of structural resonant frequencies within said system,

piezo electric actuators configured to receive said control signal and to translate said infrared focal plane along two orthogonal axes and rotate said infrared focal plane about a bore axis such that jitter-induced motion of said image on said infrared focal plane is reduced.

17. A method for reducing jitter-induced smear in an imaging system comprising:

sensing jitter of said imaging system;

calculating jitter-induced motion of electromagnetic energy on a focal plane;

rotating said focal plane about a bore sight axis of said imaging system to reduce said jitter-induced smear within said imaging system.

18. The method of claim 17, further comprising:

measuring angular rates of rotation of said imaging system in three orthogonal axes;

integrating said angular rates of rotation to determine a short term attitude of said imaging system;

mapping said short term attitude of said imaging system to determine said jitter-induced motion; and

calculating a demanded position of said focal plane to reduce said jitter-induced motion of said electromagnetic energy on said focal plane.

19. The method of claim 18, further comprising:

measuring a position of each of three axes of a piezo-electric stabilization system to determine a current position of said focal plane;

differencing said current position of said focal plane and said demanded position of said focal plane to produce a position error.

20. The method of claim 19, further comprising:

outputting a control signal to a three axis piezo-electric actuator;

said actuator moving said focal plane in response to said control signal to reduce said jitter-induced smear.