Speckle reduction in holography: a using time-multiplexing technique

Abstract

This study proposes a time-multiplexing technique to eliminate speckles from hologram reconstruction. The object points constituting a reconstructed image were divided into several groups that consisted of sparse object points. These object point groups were then sequentially displayed. The sparseness and temporal summation suppressed speckle generation. The object point group decomposed into multiple bit planes to represent the gray levels of the object points, and binary holograms were generated from the bit plane patterns by using the half zone plate technique. The binary holograms were displayed using a high-speed spatial light modulator (SLM), which is illuminated by a light whose intensity is appropriately modulated. We used a digital micromirror device with a resolution of 1,024 × 768 as a highspeed SLM. The reconstructed image consisted of 8 × 4 object point groups. Each object point group consisted of 16 × 24 object points, and each object point was generated by a half zone plate displayed by 64 × 32 pixels. Each object point group decomposed into eight bit planes; thus the reconstructed image was displayed with 256 gray levels. The reconstructed images consisting of 128 × 96 object points were displayed at a frame rate of 52 Hz.