Iterative encoding of high-efficiency holograms for generation of spot arrays

An iterative discrete on-axis encoding method for computer-generated holograms (termed IDO encoding) has been developed. The binary IDO method employs simulated annealing to optimize the hologram phase delay and reduce sensitivity to fabrication tolerances. Computer-simulation results indicate that binary phase IDO encoding is capable of generating two-dimensional spot arrays with diffraction efficiencies larger than 70%. An experimentally fabricated hologram, designed to account for a 6% manufacturing hologram thickness tolerance, produced a 3 x 3 array of spots with 59% diffraction efficiency. The binary IDO algorithm can be employed to encode arbitrary images with twofold rotation symmetry.