Polarization Measurements Using a COTS Digital Camera
Technical rept. 20 Feb-14 Jun 204
BATTELLE SCIENTIFIC SERVICES PROGRAM PAYSON AZ
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This paper presents a methodology to obtain polarization profiles using a COTS commercialoff- the-shelf digital camera. It contains calibration techniques to insure robust and accurate determination of the Stokes parameters and the system polarization state. It calculates the Stokes parameters for each scene pixel along with the degree of polarization, azimuth and ellipticity angles for each of the RGB channels. A detailed calculation shows that the quasimonochromatic approximation for the wavelength dependence of the quarter wave plate can be extended to include the broad band RGB channels. A simple and inexpensive camera calibration converts RGB values to optical density and then to relative intensity values. An analysis is presented for the wavelength dependent response of the tuned zero-order quartz quarter-wave retarder, the broad band RGB channels and the fourth Stokes parameter. The noise characteristics of the digital camera are analyzed along with a detailed calibration of the imagery for target characterization applications. An extensive validation process using white light compares known polarization states with the empirical results from the COTS camera. A RGB pseudo-coloring scheme, related to the Poincare sphere, is introduced for the visualization of polarization parameters of daylight scenes.