Lensless light field imaging with angular resolution improvement

Abstract

Lensless light-field imaging is the process to encode the light field information of object through an optical encoder, and then recover the light field information of object through a reconstruction algorithm. In traditional lens-based light field imaging, each microlens in microlens-array corresponds to an angular sampling, and it needs to adjust the microlens-array to alter the angular resolution. In this paper, a commercial holographic diffuser is used as an optical encoder, and a flexible overlapping segmentation method of angular sampling is proposed for the Point Spread Function (PSF). The surface microstructures of holographic diffuser allow any region of it to encode and recover light information of object independently, corresponding to an angular sampling. Calibration of PSF for the lensless imaging system is done firstly, and encoded image of object is captured; then the PSF is divided into different regions as sub-PSFs, corresponding to different angular samplings; after that, light field images of object is reconstructed with corresponding sub-PSFs through reconstruction algorithm; with these light field images, digital refocusing can be achieved finally. Different from evenly segmentation of angular sampling in microlens-array, the overlapping segmentation method divides PSF into sub-PSFs while adjacent sub-PSFs overlap each other. This improves angular resolution of imaging system and ensures low error in reconstruction of light field images. Experiments show that, the overlapping segmentation method can guarantee the reconstruction accuracy of lensless light-field imaging system while flexibly adjusting and improving the angular resolution.