Calibration algorithms for polarization filter array camera: survey and evaluation

Abstract

A polarization filter array (PFA) camera is an imaging device capable of analyzing the polarization state of light in a snapshot manner. These cameras exhibit spatial variations, i.e., nonuniformity, in their response due to optical imperfections introduced during the nanofabrication process. Calibration is done by computational imaging algorithms to correct the data for radiometric and polarimetric errors. We reviewed existing calibration methods and applied them using a practical optical acquisition setup and a commercially available PFA camera. The goal of the evaluation is first to compare which algorithm performs better with regard to polarization error and then to investigate both the influence of the dynamic range and number of polarization angle stimuli of the training data. To our knowledge, this has not been done in previous work.

A Practical Calibration Method for RGB Micro-Grid Polarimetric Cameras

“…2. It is grounded on the super-pixel calibration method detailed in [11], [23], which is a well-established method in the literature. The originality of our calibration algorithm is that no information about the input light polarization state is required.…”

“…( 10) constitutes the super-pixel calibration equation, and it can be solved for A if the polarization states of the N input calibration light samples are known . These states corresponds to the N columns of the matrix: (11) where S 0n is the intensity of the n th calibration light sample, ρ n is its degree of linear polarization (DoLP), and α n is its angle of linear polarization (AoLP), for n = 1, ..., N . These parameters can be obtained with high accuracy but at the expense of a complex laboratory set-up and time consuming experiments.…”

“…In this section, we describe how to estimate the angles of linear polarization of the N calibration light samples represented by α n with n = 1, ..., N in Eq. (11). For the visible light wavelengths, the polarization angle measured by a single super-pixel can be considered independent of the color.…”

Snapshot spectropolarimetric imaging using a pair of filter array cameras

“…(Using the polarimetric characterization in Ref. 42, we found that the polarization measurement is near to ideal for these sensors (very high extinction ratios of the micropolarizers), so there is no need to calibrate polarimetrically. )…”

Review of spectral and polarization imaging systems

“…Number of acquisitions needed, along with the selection of the angle of analysis have been previously discussed by Tyo et al 14 Angles could differ from the ones used to calculate the Stokes vector in Eq. 2, and polarization elements do not need to be ideal, thus the polarimeter has to be polarimetrically calibrated [15][16][17] by estimating W. Afterward, S can be deduced by an inversion procedure, and polarization properties of light beams like Angle Of Linear Polarization (AOLP), Degree Of Polarization (DOP), or ellipticity, can be derived from the Stokes vector.…”