Band-limited double-phase method for enhancing image sharpness in complex modulated computer-generated holograms

Abstract

Herein, we propose a band-limited double-phase method to improve the quality of reconstructed images encoded by double-phase holograms (DPHs) derived from complex-amplitude light waves. Although the quality of images produced by DPHs was improved compared to that of conventional holographic images, it still suffered from degradation because of the spatial shifting noise generated during the conversion from complex-amplitude holograms to phase-only holograms. The proposed method overcomes this shortcoming by defining a band-limiting function according to the spatial distribution of DPHs in the frequency domain to remove the specific spatial frequency components severely affected by the spatial shifting of DPHs. The sharpness of images reconstructed from band-limited DPHs with appropriate optical filtering showed an improvement of 36.84% in simulations and 51.67% in experiments evaluated by 10-90% intensity variation.

Review of computer-generated hologram algorithms for color dynamic holographic three-dimensional display

“…No matter superpixel method or single-pixel method, the spatial shifting noise cannot be eliminated completely by filtering system due to the distribution characteristics of the envelope function. Hence, the weight factor 114 and band-limiting function 115 were proposed successively to suppress the spatial shifting noise. where exp( jθ 1 ) = exp{ j [ φ + cos −1 ( A /2)]} and exp( jθ 2 ) = exp{ j [ φ − cos −1 ( A /2)]} are decomposed two POHs, Aexp(jφ) is the target complex amplitude, M 1 and M 2 are complementary 2D binary gratings (checkerboard patterns), and exp(iφ') is the DPH.…”

48‐1: Invited Paper: Holographic Display Based on Complex‐Amplitude Encoding with Phase‐Only SLMs

“…The dimensions of the rectangular pixel-active window are in line with inter-pixel distances α and β, along the horizontal and vertical axes, respectively. The Fourier transform of the DPH could be expressed by the superposition of a signal term and a noise term [4][5]:…”

“…But the reconstructions of DPHs suffer from the spatial shifting error of non-perfect superposition of the pixelmisplaced phase pairs. We recently proposed a band-limited DPH to suppress the spatial shifting error through redefining the cut-off frequency [4]. The reconstruction combining fewer spatial shifting noises and higher image sharpness could be obtained with numerical band limitation and proper optical filtering.…”

Computing 3D Phase-Type Holograms Based on Deep Learning Method

“…However, for CGH generation, there is an unavoidable problem with the iterative methods because they require a trade-off between computation time and image quality caused by the iterative process [7][8][9]. Non-iterative complex amplitude encoding methods have also been proposed to achieve fast CGH calculation with guaranteed imaging quality, such as the error diffusion method [10] and the double phase encoding method [11,12].…”