Image quality enhancement via gradient-limited random phase addition in holographic display

The addition of a random phase is widely utilised to diffuse object information in computer-generated hologram calculations. However, different object regions have nonuniform initial information diffusion abilities. The conventional random phase addition method always causes the excessive diffusion of information, especially for high frequency regions, which influences the reconstructed quality. In this paper, a gradient-limited random phase addition method is developed to avoid excessively diffusing object information. Herein, an image is segmented into two regions according to its frequency characteristics. Correspondingly, wide and narrow optimum ranges of a limited random phase are provided for low and high frequency regions, respectively. The numerical simulation results show that the peak signal-to-noise ratio and structural similarity index of reconstructed images increase by approximately 10% and 13%, respectively. The resolution of the reconstructed test image is improved by approximately 2 line pairs. Additionally, using in time-average method reduces the superposition number. Optical experiments are also performed to verify its feasibility.