HDR Reconstruction Based on the Polarization Camera

Abstract

The recent development of the on-chip micro-polarizer technology has made it possible to acquire – with the same ease of operation as a conventional camera – spatially aligned and temporally synchronized polarization images simultaneously in four orientations. This development has created new opportunities for interesting applications including those in robotics. In this letter, we investigate the use of this sensor technology in high-dynamic-range (HDR) imaging. Specifically, observing that natural light can be attenuated differently by varying the direction of the polarization filter, we treat the multiple images captured by the polarization camera as a set captured at different exposure times, useful to the reconstruction of an HDR image. In our approach, we first study the radiometric model of the polarization camera, and relate the polarizer direction, degree and angle of polarization of light to the exposure time of a pixel in the polarization images. Subsequently, by applying the standard radiometric calibration procedure of a camera, we recover the camera response function. With multiple polarization images at known pixel-specific exposure times, we can then proceed to estimate the irradiance maps from the images and generate an HDR image. Two datasets are created to evaluate our approach, and experimental results show the dynamic range by our approach can be increased by an amount dependent on light polarization. We also use two robotics experiments on feature matching and visual odometry to demonstrate the potential benefit of this increased dynamic range.