Efficient Encoding Method for Computer-Generated Hologram

A computer-generated hologram (CGH) can be used to detect an aspheric surface with high accuracy. To enhance the encoding efficiency of the CGH, this paper proposes an encoding method for the segmented description of engraved stripes with a circular arc as the primitive, dividing the encoding process into two steps: binary encoding and curve description. The binary encoding employs the Newtonian iteration method to discretize the phase contour dividing line. The curve description combines the dichotomy and the minimum root-mean- square criterion of the residual error. Furthermore, by leveraging the circular arc to encode the discrete points of the engraved stripes, the engraved stripes are obtained. In this paper, the CGH is designed, encoded, and generated for an off-axis aspheric surface. To obtain an encoding accuracy higher than lambda/1000, the operation time is only 3 h, the encoded file is only 39 MB, and the etching time is only 40 min. This demonstrates that the proposed method can considerably enhance the encoding efficiency compared with the traditional encoding method. Error analysis suggests that the wavefront root-sum square (RSS) error of the CGH is only 0. 00255 lambda, demonstrating that the proposed encoding method is efficient and feasible.