用于投影显示的分色合色膜系的消偏振设计

Design of Nonpolarizing Thin Film Edge Filters Used for Color-separation and Color-recombination in Projection Display Systerm

由于斜入射时,光学薄膜存在一定的偏振效应,将产生S和P偏振光的光谱分离.在Philips棱镜系统中,分色合色膜系通常分色时对S光应用,合色时则对P光应用.从提高光能利用率、减少杂散光和增加系统对比度等因素综合考虑,要求分色合色膜系的S和P偏振光的分离尽可能小.新设计方法采用宽带法布里-珀罗薄膜干涉滤光片中心波长两侧的干涉带作为长波通或短波通截止滤光片,可实现S和P偏振分量的分离几乎为零.

Optical thin films exhibit inevitable polarization effects at oblique incidence, which leads to the spectral splitting of s-and p-polarization components. Generally, s-polarized light initially enters Philips prism, and then the light is modulated to p-polarized light by liquid crystal light valves if they are in 'on state'. Consequently, minimum splitting of s-and p-polarization components is required to gain optimum efficiency and improve contrast of the system. The novel design method is based on a broad-band F-P thin film interference in which both sides of transmittance band can be used for long-wave-pass or short-wave-pass filters, and through suitable refinement it is possible to achieve zero separation between two polarization components.