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 t