Maximizing Diffraction Efficiency of Bleached, Time-Integration-Exposure, Silver Halide Holograms

Time-Integration holograms, where the exposure pattern is recorded as a sequentially applied sum of individual fringe patterns (either sinusoidal "Young’s" fringes or Gabor zone plates), suffer from poor diffraction efficiency and, consequently, low signal-to-noise ratio on reconstruction [1,2]. The reason is straightforward: The total exposure pattern, as in the case of incoherent holography [3], has a low signal-to-bias ratio when many contributing exposures--each bringing its own bias with it--are applied. Since the recorded signal exposure is low compared to the bias exposure, the signal variations in the wave amplitude transmittance function of the processed hologram are small, and diffraction efficiency is therefore low. At the same time, noise in the reconstruction, determined by such sources as dust- and film-grain-scattered light, remains at an essentially constant level.