相位分布及编码尺度对计算全息再现像的影响

Influence of phase distribution and coding scale on the reconstruction of computer generated hologram

研究了傅里叶变换计算全息编码中相位分布和编码尺度对再现像的影响.基于罗曼Ⅲ型编码原理,用Mat-lab计算得到傅里叶变换计算全息图,通过液晶光阀输出全息图实现再现,研究再现像的特征在物图加随机相位和增大编码尺度前后的变化.结果表明:物图不加随机相位的全息图,其再现像具有高通效果,实现了边缘提取;物图加随机相位,再现相当于低通滤波,再现像被平滑,当物频谱结构丰富时,平滑作用更明显,甚至无法辨识再现像;增大编码单元尺寸,即提高编码精度可使再现像清晰.

The influence of phase distribution and coding scale on the reconstruction of computer generated hologram was researched.Based on the Lohmann Ⅲ coding method and Matlab computing tool,computer generated hologram（CGH） was designed and optically reconstruction using liquid crystal light valve.Changes of the reconstructed image caused by the random phase intendedly added to the original image and the increase of the coded cell size were investigated.The results showed that high-pass effect or edge extraction could be achieved for the original image with no phase-randomization.When the phase was randomized,low-pass filtering and smoothing effects were observed,especially when the spectrum of the object went rich,the image became hard to be recognized.However,increasing the coded cell size could improve the coding accuracy and yield clear images.