Image quality calibration for multi-degree-of freedom actuator

Patent metadata

Field	Value
Publication number	US-12266137-B2
Application number	US-202318384558-A
Country	US
Kind code	B2
Filing date	Oct 27, 2023
Priority date	Oct 27, 2022
Publication date	Apr 1, 2025
Grant date	Apr 1, 2025

Abstract

A method and a system for optimizing the alignment of an optical system, such as a telescope, using a multi-degree-of freedom (DOF) actuator/hexapod and star field images. The method iteratively adjusts the hexapod in all DOFs using the damped least squares (DLS) optimization algorithm and dynamically changes the size of pixel windows to measure ensquared energy (ES) as a closed loop feedback.

First claim

The invention claimed is:

1. A method for image quality calibration of an optical system using a multi-degree-of freedom (DOF) compensator, the method comprising:
a) receiving a first plurality of images of a scene including a plurality of targets by the optical system with the compensator at an initial position;
b) selecting an initial pixel window of a first size around each of the plurality of targets in the first plurality of captured images, respectively;
c) measuring an initial ensquared energy (ES) in each of the initial pixel windows;
d) moving the compensator in a first DOF to a new position;
e) capturing a second plurality of images of the scene at the new position of the compensator;
f) repeating d to e for all of the multi-DOFs;
g) utilizing the measured ES in each of the pixel windows as a merit function for a damped least squares (DLS) optimization method to move the compensator in all of the multi-DOFs;
h) repeating c-g until a sum of ES in each of the pixel windows from all targets has reached a maximum;
i) moving the compensator to a position where the ES in each of the pixel windows from all targets has reached the maximum;
j) selecting a pixel window of a second size smaller than the first size; and
k) repeating c to j for a predetermined number of times to obtain the image quality calibration of the optical system.

2. The method of claim 1 , wherein the compensator is a hexapod.

3. The method of claim 1 , wherein the targets are stars.

4. The method of claim 1 , wherein the optical system is a telescope or a camera.

5. The method of claim 1 , wherein step g comprises calculating a maximum slope line along which the compensator needs to be moved for each DOF to provide direction of movement decent in multi-DOFs.

6. The method of claim 1 , wherein the first size of the initial pixel window is 10×10.

7. The method of claim 1 , wherein the predetermined number of times is in a range of 5 to 10 times.

8. A calibrated optical system comprising:
a multi-degree-of freedom (DOF) compensator for moving the optical system in multi-DOFs;
an image capturing device for capturing plurality of images of a scene;
a plurality of server motors to move the image capturing device in all of the multi-DOFs; and
a computer for:
a) receiving a first plurality of images of a scene including a plurality of targets by the optical system with the compensator at an initial position;
b) selecting an initial pixel window of a first size around each of the plurality of targets in the first plurality of captured images, respectively;
c) measuring an initial ensquared energy (ES) in each of the initial pixel windows;
d) moving the compensator in a first DOF to a new position;
e) capturing a second plurality of images of the scene at the new position of the compensator;
f) repeating d to e for all of the multi-DOFs;
g) utilizing the measured ES in each of the pixel windows as a merit function for a damped least squares (DLS) optimization method to move the compensator in all of the multi-DOFs;
h) repeating c-g until a sum of ES in each of the pixel windows from all targets has reached a maximum;
i) moving the compensator to a position where the ES in each of the pixel windows from all targets has reached the maximum;
j) selecting a pixel window of a second size smaller than the first size; and
k) repeating c to j for a predetermined number of times to obtain the image quality calibration of the optical system.

9. The calibrated optical system of claim 8 , wherein the compensator is a hexapod.

10. The calibrated optical system of claim 8 , wherein the targets are stars.

11. The calibrated optical system of claim 8 , wherein the image capturing device is a telescope.

12. The calibrated optical system of claim 8 , wherein the image capturing device is a camera.

13. The calibrated optical system of claim 8 , wherein process in g comprises calculating a maximum slope line along which the compensator needs to be moved for each DOF to provide direction of movement decent in multi-DOFs.

14. The calibrated optical system of claim 8 , wherein the first size of the initial pixel window is 10×10.

15. The calibrated optical system of claim 8 , wherein the predetermined number of times is in a range of 5 to 10 times.

16. A calibrated optical system comprising:
Means for moving the optical system in multi-DOFs;
means for capturing a plurality of images of a scene;
means for moving the image capturing device in all of the multi-DOFs; and
means for:
a) receiving a first plurality of images of a scene including a plurality of targets by the optical system with the compensator at an initial position;
b) selecting an initial pixel window of a first size around each of the plurality of targets in the first plurality of captured images, respectively;
c) measuring an initial ensquared energy (ES) in each of the initial pixel windows;
d) moving the compensator in a first DOF to a new position;
e) capturing a second plurality of images of the scene at the new position of the compensator;
f) repeating d to e for all of the multi-DOFs;
g) utilizing the measured ES in each of the pixel windows as a merit function for a damped least squares (DLS) optimization method to move the compensator in all of the multi-DOFs;
h) repeating c-g until a sum of ES in each of the pixel windows from all targets has reached a maximum;
i) moving the compensator to a position where the ES in each of the pixel windows from all targets has reached the maximum;
j) selecting a pixel window of a second size smaller than the first size; and
k) repeating c to j for a predetermined number of times to obtain the image quality calibration of the optical system.

17. The calibrated optical system of claim 16 , wherein the compensator is a hexapod.

18. The calibrated optical system of claim 16 , wherein the targets are stars.

19. The calibrated optical system of claim 16 , wherein the image capturing device is a telescope.

20. The calibrated optical system of claim 16 , wherein the image capturing device is a camera.

Assignees

• Raytheon Co

Inventors

• Johnson Tim P
• Foes Scott R
• Ichkhan Joseph J

Classifications

• H04N23/695

  Control of camera direction for changing a field of view, e.g. pan, tilt or based on tracking of objects · CPC title

• G06T2207/10032

  Satellite or aerial image; Remote sensing · CPC title

• H04N23/81

  for suppressing or minimising disturbance in the image signal generation · CPC title

• G02B23/00

  Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices · CPC title

• H04N17/002

  for television cameras · CPC title