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.