Patent ID: 7295312

Claim:
A system for determining polarization profiles of points in a scene from video frames using Stokes parameters, the system comprising: a scene having a region that emits scene light rays that correspond to the points in the scene; a motorized rotating Stokes filter wheel having three linear polarizers, a circular polarizer, and a reference screen consecutively located in apertures on the wheel in a first radial band, and five trigger holes located adjacent to respective ones of the polarizers and the screen in a second radial band that is outward on the wheel from the apertures; a sensor that generates a trigger signal when any one of the trigger holes passes by the sensor; a narrowband color filter; a video camera having a video frame; an optical chopper controller; and a computer system containing programming, and having a frame grabber apparatus, wherein the optical chopper controller transmits a speed control signal to control rotational speed of the motor, and the programming sends a mode control signal to the video camera to establish mode of operation and exposure time; the programming internally transmits to the frame grabber apparatus a frame grab control signal that determines a selected number of video frames for capture by the frame grabber apparatus, and a starting time for the capture of the video frames; when the frame grabber initiates capture, the chopper controller receives the trigger signal from the sensor, and generates a capture control signal in response to the trigger signal, and transmits the capture control signal to the frame grabber apparatus, and the frame grabber apparatus transmits the capture control signal to the video camera activating exposure, and the video camera transmits the captured video image to the frame grabber to be processed by the programming; the scene light rays are transmitted consecutively through the polarizers in the Stokes filter wheel and the color filter to the video camera; images corresponding to the scene light rays are projected onto respective pixels in the video frame and recorded as respective two-dimensional (2-D) arrays in response to the trigger signal; and the images corresponding to the scene light rays from four unique images obtained from light transmitted consecutively through the three linear polarizers and the circular polarizer of the rotating Stokes filter wheel are formatted by the frame grabber apparatus and are used by the programming to calculate respective Stokes parameters of the points in the scene, and the image corresponding to the reference screen indicates a completed revolution of the rotating Stokes filter wheel.