Sub-percent Characterization and Polarimetric Performance Analysis of Commercial Micro-polarizer Array Detectors

TL;DR

This study calibrates and analyzes the polarimetric performance of Sony's low-cost CMOS micro-polarizer array detectors, achieving sub-percent accuracy suitable for remote sensing applications.

Contribution

It provides a comprehensive calibration methodology and performance analysis for commercial micro-polarizer array detectors, enabling their use in precise polarization measurements.

Findings

Achieved sub-percent polarimetric accuracy with calibrated detectors

Identified key detector characteristics affecting polarimetric performance

Demonstrated benefits of using a rotating half-wave plate for improved sensitivity

Abstract

Polarization imaging can yield crucial information in multiple applications of remote sensing, such as characterization of clouds, aerosols, and the Aurora Borealis. Some applications require sub-percent polarimetric sensitivity and accuracy in determining the Stokes parameters, which can be a challenge to attain. In 2018, Sony released a low-cost CMOS-based imaging chip with integrated micro-polarizer array for general polarization measurements. We implement the calibration steps required for these Sony chips to reach sub-percent polarimetric accuracies. To analyze their performances, we have compared the characteristics of four different detector packages by three manufacturers housing either the monochromatic version or the RGB color variant. We present a comprehensive overview of the effects that these characteristics have on the polarimetric performance of the camera. They include dark noise, behavior over different gain settings, detector/pixel artifacts, and polarimetric effects determined by polarizer extinction ratios, polarizer orientations, and accuracy of polarimetric zero points due to differential pixel gains. In addition to calibrations using unpolarized light and fully linearly polarized light, we assess the polarimetric sensitivity within a tilting and rotating glass-plate set-up. We discuss the benefits of adding a rotating half-wave plate as an additional temporal modulator to generically mitigate some of the detector effects, and achieve better polarimetric sensitivity/accuracy albeit at the expense of lower temporal resolution. We conclude by presenting and discussing the polarimetric limits to which we were able to calibrate the detector effects for practical purposes. By reaching a compound absolute polarimetric uncertainty of less than a percent, these very compact, low-cost detectors are enabled for a multitude of scientific goals.