利用改进的Gerchberg-Saxton(GS)算法和广义相衬(GPC)结构，用纯相位空间光调制器(SLM)实现彩色图像的重现。提取出彩色图像的红、绿、蓝三色信息，利用改进的GS算法和相应波长的GPC结构，计算出输入面的纯相位分布。将所得相位分别编码加载到三个SLM上，用相应波长的激光分别照射三个SLM，在GPC输出面上进行合成，可以得到目标图像。与常规计算全息(CGH) 相比，该方法不需要移除零级衍射光，除具有较好的像质外，还提高了光能利用率；另外，根据不同波长设计固定的相衬滤波器(PCF)参量，不会因目标图像的不同而改变，放宽了GPC应用的限制条件。

A method of two-dimensional (2D) color image projection is described, which uses three phase-only spatial light modulators (SLMs), an improved Gerchberg-Saxton (GS) algorithm and the generalized phase contrast (GPC) method. Intensity information of the three primary colors (i.e., red, green and blue) is respectively extracted from a 2D color image, and the computed phase is encoded and loaded to the corresponding SLM. The target color image can be synthesized as a result of color mixing at the output planes of the GPC devices by simultaneously projecting the red, green and blue laser beams to the corresponding phase-only SLMs. Compared with the conventional computer-generated holography (CGH), this method does not need to block the zero-order diffraction beam and has higher light efficiency as well as better image quality. In addition, parameters of the phase contrast filters (PCFs) are designed as fixed values according to different wavelengths, which need not be changed for different target images and expand the application fields of GPC.