Minimax spectrum shaping with a bandwidth constraint

Optical phase step method for absolute ranging interferometry using computer-generated holograms

One main problem of an interferometric measurement is to evaluate the object distance from the interference function. One of the known methods that delivers the object phase is the phase step method. Here we introduce computer-generated holograms to realize parallel phase steps without phase modulation of the reference path.

Synthesis of diffractive optical bar codes

A new type of diffractive optical bar code (DOBC) is proposed. Rather than scanning directly, the DOBC is coherently illuminated, and the first diffraction order is sensed. The spacing between the bars is chosen so that the thresholded diffraction pattern yields a specified binary code. Two approaches are investigated for synthesis of the DOBC: phase shaping and a gradient-based, nonlinear, constrained optimization technique. The two design methods are compared based on numerical results, and the validity of the overall design approach is verified by optically sensing the diffraction patterns for a number of fabricated DOBC's.

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.

Synthesis of digital holograms by direct binary search

A new approach to the design of computer-generated holograms makes optimal use of the available device resolution. An iterative search algorithm minimizes an error criterion by directly manipulating the binary hologram and observing the effect on the desired reconstruction. Several measures of error and efficiency useful in assessing the optimality of digital holograms are defined. Methods for designing digital holograms that are based on projections and error diffusion are presented as established techniques for comparison to direct binary search.

Binary phase digital reflection holograms: fabrication and potential applications

A novel technique for the fabrication of binary-phase computer-generated reflection holograms is described. By use of integrated circuit technology, the holographic pattern is etched into a silicon wafer and then aluminum coated to make a reflection hologram. Because these holograms reflect virtually all the incident radiation, they may find application in machining with high-power lasers. A number of possible modifications of the hologram fabrication procedure are discussed.