减小纯位相型计算全息图量化误差的一种新编码方法

针对纯位相型计算全息图量化误差问题，提出了一种新的编码方法。其主要理论根据基于在复平面上可将一复矢量分解成任意两个复矢量之和。在编码时，将一个编码单元分割成两个子单元，其子单元占该编码单元面积的比值及其刻蚀深度分别由这两个复矢量的模和位相来确定。由于矢量分解是在一椭圆上进行的，所以在相角的选择上有一定的灵活性，便于减小位相量化误差。从模拟结果看，应用这种新的编码方法所得到的再现像有较高的质量，如较高的衍射效率、较大的信噪比以及较好的均匀度。

A New Encoding Method for Reducing Quantization-error of Phase-only Computer-generated Holograms

The phase-only computer-generated hologram (CGH) is a kind of diffractive optical element with high light efficiency, and thus its application is becoming more widespread. Phase encoding plays a key role in the implementation of phase-only CGHs. Conventional phase encoding methods suffer from the fabrication difficulty because of a large amount of encoding cells, and often produce a significantly big error of phase quantization. A new encoding method for reducing quantization-error of phase-only computer-generated holograms is proposed in this paper, which is based on that a complex vector can be arbitrarily decomposed into the sum of two vectors. An encoding cell will be divided into two sub-cells, each area and itching depth allocated to the module and phase of the corresponding vector, respectively. Because of decomposing a complex vector inside an ellipse, it is very flexible to select an appropriate phase angle for the vector. Hence this encoding method is very effective on reducing phase quantization-errors. We have derived the error expression for the phase quantization and the output-plane light distribution resulted from the proposed phase-only CGH, To evaluate the performance of the designed encoding, we have carried out computer experiment for both one-dimensional and two-dimensionalimages. The numeric measures for the reconstructed image produced from phase quantization of eight-and sixteen-level are also presented. The simulation results show that the reconstructed images have higher qualities, such as higher diffractive efficiency, higher signal-to-noise ratio and preferable uniformity. The fact that every encoding cell contains only two sub-cells makes easier the practical implementation of the phase-only CGH.