Lensless polarization camera for single-shot full-Stokes imaging

Nakkyu Baek, Yujin Lee, Taeyoung Kim, Jaewoo Jung, Seung Ah Lee* 

Abstract

Lensless cameras have recently emerged as a compact imaging system based on a computational imaging system with various multiplexing capabilities. In this paper, we propose a compact and low-cost lensless camera that enables snapshot full-Stokes polarization imaging. While polarization imaging provides additional contrast based on birefringence and surface properties of the object, most commercial devices employ image sensors with linear polarizers (LPs) patterned on each pixel and are insensitive to circular polarization (CP). We show that our polarization-sensitive lensless camera enables snapshot full-Stokes imaging with a regular CMOS image sensor.

For full-Stokes lensless polarization camera, we designed our device to multiplex three linear polarizations and one circular polarization at the aperture plane. By placing a polarization-encoded aperture in front of the phase mask,  a point source illumination generates a polarization encoded 2D PSF on the image sensor. If we image a scene through this camera, the captured raw measurement would be an integration of convolution of each division of the PSF and the polarization-responsive intensity of the scene. We can computationally reconstruct the four polarization intensities which can be converted into Stokes parameters and other parameters including degree of polarization (DoP), angle of polarization  (AoP) and ellipticity.

Reference