Polarization Error Analysis and Polarization Calibration Method for Division of Focal-plane Polarimeter Camera
The Division of Focal-plane Polarimeter camera(DoFP)has unique advantages such as small size,high integration,and strong real-time performance,and is widely used in the field of defect detection.The core components of a division of focal-plane polarimeter camera consist of a Complementary Metal Oxide Semiconductor Photodetector(CMOS),a micro-polarizer array,and a micro lens array device.The division of focal-plane polarimeter camera integrates photodetectors and micro polarizer devices on the same focal plane.By placing a photolithography metal grating linear polarizer array at the front end of a pixel,information acquisition corresponding to one linear polarization direction is achieved for each pixel.Therefore,one frame of imaging can complete the detection of energy in multiple polarization directions.To meet the application requirements of defect detection,it is necessary to ensure the imaging quality of division of focal-plane polarimeter cameras.According to the previous theoretical analysis,the key factors affecting imaging quality are mainly the polarization azimuth deviation of each imaging unit and the non-uniformity of the response of each imaging unit,among which the non-uniformity of response is mainly manifested as the non-uniformity of transmittance.This paper introduces the Stokes model,and establishes a polarization response model for division of focal-plane polarimeter camera cameras.We focused on analyzing the impact of angle errors in relative transmittance and polarization azimuth angle on the measurement polarization error of division of focal-plane polarimeter camera cameras by using the method of calculating partial derivatives.We also analyzed the trend of the measurement polarization error changing with the polarization degree and polarization angle of the incident light.A polarization azimuth measurement system was established to measure the four polarization azimuth angles of a micro polarization array.The system uses an integrating sphere and a rotating polarizer as the standard radiation source,with the rotating polarizer as the reference polarizer installed on a one-dimensional precision rotating table,so that linearly polarized light in different polarization directions can be obtained by rotating the polarizer.Polarization cameras collect incident light at different polarization angles,and obtain the polarization azimuth angle of the polarization camera micro polarization array through Malus's model fitting model,thereby achieving calibration of the polarization azimuth angle.The relative transmittance was measured using an integrating sphere reference light source.The response values of different polarization azimuth angles were measured at different integration times,which are the mean of the polarization directions corresponding to all super-pixels.The complete polarization response value was calculated based on the equivalent extinction ratio,and the ratio of complete polarization response values for P1～P3 and P4 was calculated.After eliminating the influence of extinction ratio,calculate the relative transmittance of P1～P4,with relative transmittance values of 0.965,1.000,1.010,and 1.000,respectively.Finally,the measurement polarization degree was calculated based on the polarization response model,as well as the relative transmittance and polarization azimuth test results.In order to verify the calibration effect,the polarization measurement results of incident light with different polarization angles were calculated.The response value used for calculation here is the mean of the polarization direction corresponding to all super-pixels.The light generated by the combination of an integrating sphere light source and a standard polarizer is used as the incident light for verifying the polarization accuracy of a polarization camera,and the outgoing light can be approximated as perfectly linearly polarized light.Verify the measurement accuracy of division of focal-plane polarimeter camera by rotating the standard polarizer at an interval of 10° and 180°.The measurement results show that the average measurement result of polarization degree before calibration is 0.964 4,with a relative standard deviation of 1.02％.After calibration,the average measurement result of polarization degree is 0.998 9,with a relative standard deviation of 0.44％.The experimental results show that the detection scheme can calibrate the performance of the division of focal-plane polarimeter camera with high calibration accuracy,laying the foundation for the high-precision application of division of focal-plane polarimeter camera.
Remote sensingDivision of focal-plane cameraMeasurementRelative transmissionPolarization azimuthPolarization calibrationError analysis
万方数据
维普
