Image quality calibration for multi-degree-of freedom actuator
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.
1 . A method for image quality calibration of an optical system using a multi-degree-of freedom (DOF) compensator, the method comprising:
receiving a plurality of images of a scene including a plurality of targets by the optical system with the compensator at a position;
selecting a pixel window around each of the plurality of targets in the plurality of captured images, respectively;
measuring an ensquared energy(ES) in each of the pixel windows;
responsive to determining the ES is a maximum among ES values of a variety of pixel windows, retaining the compensator at the position where the ES in each of the variety of pixel windows from all targets has reached the maximum; and
calibrating the optical system at the position using a variety of window sizes.
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:
receiving a plurality of images of a scene including a plurality of targets by the optical system with the compensator at a position;
selecting a pixel window around each of the plurality of targets in the plurality of captured images, respectively;
measuring an ensquared energy(ES) in each of the pixel windows;
responsive to determining the ES is a maximum among ES values of a variety of pixel windows, retaining the compensator at the position where the ES in each of the variety of pixel windows from all targets has reached the maximum; and
calibrating the optical system at the position using a variety of window sizes.
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:
receiving a plurality of images of a scene including a plurality of targets by the optical system with the compensator at a position;
selecting a pixel window around each of the plurality of targets in the plurality of captured images, respectively;
measuring an ensquared energy(ES) in each of the pixel windows;
responsive to determining the ES is a maximum among ES values of a variety of pixel windows, retaining the compensator at the position where the ES in each of the variety of pixel windows from all targets has reached the maximum; and
calibrating the optical system at the position using a variety of window sizes.
17 . The calibrated optical system of claim 16 , wherein the means for moving the optical system include 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 means for capturing the plurality of images include a telescope.
20 . The calibrated optical system of claim 16 , wherein the means for capturing the plurality of images include a camera.