General line of sight stabilization system

• US 7,466,343 B2
• Filed: 07/20/2004
• Issued: 12/16/2008
• Est. Priority Date: 07/20/2004
• Status: Expired due to Fees

• Current Assignee: OPTO-Knowledge Systems, Inc.
• Original Assignee: OPTO-Knowledge Systems, Inc.
• Inventors: Gat, Nahum
• Primary Examiner(s): Vu; Ngoc-Yen T
• Assistant Examiner(s): Saunders; Paul
• Application Number:
  US10/710,538
• Publication Number:
  US 20060017816A1
• Time in Patent Office: 1,610 Days
• Field of Search: 348/146, 348/208.99
• US Class Current: 348/208.11
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G02B 27/644 compensating for large deviations, e.g. maintaining a fixed line of sight while a vehicle on which the system is mounted changes course
• CPC Class Codes: H04N 23/60 Control of cameras or camera modules

Abstract

A line of sight stabilization system using two mirrors pivotally mounted to a fixed platform that can be used with existing imaging systems to provide pitch, roll, and yaw compensation while maintaining image orientation. By deflecting only the photons, the inventive system avoids the need to stabilize the entire imaging sensor and optics system. The only mass to move is that of the two imaging system mirrors. By monitoring attitude changes via an inertial measurement system, proceeding platform positions can be estimated for subsequent image acquisitions, and efficient mirror positioning can provide optimal image orientation and stabilization. This approach requires small motors with low torque, providing a less expensive, lightweight, and small image orientation and stabilization system.

Claims

1. A compact line of sight stabilization system for use with an imaging system located about an unstable carrier platform, said stabilization system comprising:

at least two mirrors, each of said mirrors being mounted to a fixed platform by aiming means and in a plane substantially parallel to a target to provide substantially orthogonal observation of a ground position;

said aiming means allowing independent rotation of said mirrors about at least one of the axes in the plane of said mirrors;

at least one of said mirrors being mounted by aiming means allowing rotation about at least two of said axes;

a hardware control means for directing said aiming means in response to measurements taken from three orthogonally positioned gyrometers that measure a rotation rate of the unstable carrier platform about the at least two of said axes;

wherein the aiming means occurs without reorientation of the fixed platform relative to the unstable carrier platform; and

wherein movement of the at least one of said mirrors occurs in a substantially continuous pattern that predicatively mirrors motion of and approximately angular velocities and accelerations of the unstable carrier platform;

said stabilization system being mounted in a line of sight of said imaging system; and

said stabilization system providing at least one of pitch, row, yaw, and forward motion compensation corrections while maintaining consistent image orientation, for said imaging system.

2. The stabilization system as in claim 1 wherein said imaging system comprises at least one of a pushbroom, whiskbroom, Fourier transform, and electronically tunable filter type sensor systems.

3. The stabilization system as in claim 1 wherein said imaging system comprises one of a multispectral, hyperspectral, or ultraspectral sensor system.

4. The stabilization system as in claim 1 wherein said carrier platform is selected from an airplane, a helicopter, a satellite, an automobile, or a boat.

5. The stabilization system as in claim 1 wherein said aiming means is selected from at least one of a mechanical, piezoelectric, and electromagnetic means.

6. The stabilization system as in claim 1 wherein said hardware control means receives movement data from at least one of pitch rate, roll rate, yaw rate, and forward motion rate sensors.

7. The stabilization system as in claim 6 wherein said sensors exist independently of said stabilization system.

8. The stabilization system as in claim 6 where said sensors comprise at least one of an inertial measurement system and an attitude and heading reference system.

9. The stabilization system as in claim 6 wherein said hardware control means comprises a computer system receiving said movement data from said at least one sensor, said computer system additionally comprising algorithm means for determining the current angle of said carrier platform from said sensor data and the integration over time of said movement rates.

10. The stabilization system as in claim 9 wherein said mirrors are aimed responsively to said current angle of said carrier platform.

11. The stabilization system as in claim 10 wherein said computer system comprises additional algorithms to predict subsequent angles for said carrier platform from said movement data and said current angle.

12. The stabilization system as in claim 11 wherein said predictive algorithm additionally accounts for at least one of system noise, drift, and temperature-induced errors.

13. The stabilization system as in claim 11 wherein said hardware control means aims said mirrors to compensate for said predicted new angle, before said carrier platform reaches said new angle.

14. The stabilization system as in claim 11 further comprising a feedback algorithm wherein said feedback algorithm determines whether said line of sight matches the line of sight obtained from said predictive angle algorithm.

15. The stabilization system as in claim 14 wherein said hardware control means applies an optimization algorithm to compensate for mismatches found by said feedback algorithm.

16. The stabilization system as in claim 1 wherein said aiming means causes at least one of said mirrors to rotate such that said mirrors adjust said line of sight of said imaging system providing compensation for at least one of pitch, roll, yaw, and forward motion.

17. The stabilization system as in claim 1 wherein said imaging system requires a stable and non-changing image during exposure time and wherein said stabilization system provides said forward motion compensation to provide said imaging system with said nonchanging image.

18. The stabilization system as in claim 1 wherein said imaging system is an ultraspectral imaging system.