彩色全息显示中液晶空间光调制器位相调制偏差的矫正方法

Correction method for phase-modulation deviation of liquid crystal spatial light modulator in full-color holographic display

采用三基色激光照明并结合时分复用或空间复用技术,可实现基于液晶空间光调制器(LC-SLM)的彩色全息显示.但由于在不同激光波长入射条件下LC-SLM的位相调制特性曲线不同,难以同时满足多波长入射条件下2π线性位相调制的要求,致使彩色全息再现结果受到共轭像和零级斑的干扰.针对该问题,本文通过实验测试获得LC-SLM在不同波长入射时的位相调制特性曲线,并分析了RGB激光器各分量的位相调制特性曲线非线性偏差和调制幅度偏差对多阶位相型傅里叶变换相息图再现效果的影响.根据"查表法"建立了各波长入射条件下满足2π线性位相调制的灰度映射关系,并对RGB分量相息图进行修正.通过对修正前后RGB分量相息图的数值模拟再现和光电再现实验与分析,结果表明:该方法有效地克服了LC-SLM位相调制特性曲线偏差的不利影响,从而改善了彩色全息显示中各分量相息图的再现质量.

It is feasible to realize full-color holographic display based on liquid crystal spatial light modulator by use of multiwavelength illumination combined with time division multiplexing （TDM） or space division multiplexing （SDM）. However,the modulation characteristics of liquid crystal spatial light modulator （LC-SLM） vary with the wavelength of incident laser beam. Especially,the non-linearity and the modulation-depth mismatch of phase modulation curve are the important factors influencing the reconstruction quality of phase hologram in full-color holographic display. In order to solve this problem,a novel method is proposed to correct the gray-scale of phase holograms in the RGB channels with the established gray-mapping model according to the phase modulation curves measured under different wavelengths,and compensate the effects of non-linearity and the modulation-depth mismatch of phase modulation curves. Analysis of numerical and optical reconstruction results are carried out. It is verified that the method is effective to improve the qualities of reconstructed images in the RGB channels.