Full-field measurement method for optical parameters of transparent elements based on rotating analyzer and RGB imaging

To address the need for full-field measurement of the principal-axis orientation, phase retardance, and optical path difference of transparent birefringent samples, a multi-parameter imaging method based on a rotating analyzer and a conventional RGB camera was proposed. The system recorded the intensity response of each spatial pixel at 36 analyzer orientations and combined a Stokes-vector model with least-squares fitting to achieve joint pixel-wise retrieval of the three optical parameters. To mitigate the effects of the broad spectral responses and spectral overlap of the RGB channels, narrowband filtering and sample-free calibration for each spectral band were introduced to correct the angular zero offset and background term. Experiments with a standard quarter-wave plate yielded a mean absolute error of 2.065° for the principal-axis orientation, while the maximum relative error in phase retardance, compared with measurements from a commercial instrument at different wavelengths, was 3.18%. Experiments on a stressed acrylic plate further revealed continuous, spatially nonuniform birefringence distributions. By integrating same-pixel multi-angle polarization modulation, band-specific narrowband calibration, and joint pixel-wise retrieval of three optical parameters into a conventional RGB imaging system, the proposed approach extends traditional single-point rotating-analyzer measurement to multi-wavelength, multi-parameter full-field characterization. It also enabled quantitative extraction of the principal-axis orientation, phase retardance, and optical path difference at selected pixel locations within the effective measurement region, thereby unifying full-field distribution characterization and local feature analysis on a single measurement platform.