用于液晶投影显示的薄膜偏振分束器

为提高液晶投影机的光能利用率和图像对比度,设计了一种宽角度宽波长的光学薄膜偏振分束器（PBS）.采用多种薄膜材料产生多个Brewster角,通过优化膜层数目和膜层厚度,获得了宽角度宽波长的PBS.以SF57和SF2玻璃作为棱镜材料,采用TiO2、Ta2O5、Al2O3、SiO2作为薄膜材料,基于上述原理采用全自动的Needle设计方法,设计了4种典型膜系,优化后的膜层数目为50～60层,空气中的光束孔径角达到±10.5°,达到的技术指标为：对于P偏振光,在420～460nm和460～680 nm波长范围内,积分透射率分别达到88.0%和93.4%；而对于S偏振光,在420～680nm波长范围内,积分透射率为0.095%.该PBS应用于F/2.8的光学系统中,能够显著提高整个系统的性能.

Thin-film polarizing beam splitters used in liquid crystal projection display

In order to improve the energy efficiency and  image contrast of liquid crystal display (LCD) projector, a wide-angle and broadband optical thin-film polarizing beam splitter (PBS) was designed. Several thin-film materials was adopted to achieve multi-kinds of Brewster’s angles. The number and thickness of the films were optimized to obtain the wide-angle and broadband PBS. Using SF57 and SF2 glasses as prism materials, and TiO2, Ta2O5, Al2O3, SiO2 as film materials, four typical PBS multi-layer designs were given based on the above principle and the automatic Needle design method. The layer number of the optimized thin-film is 50～60, and the incident angle in air for the PBS reaches ±10.5°. The measured results showed that the integrated transmittance of P-polarization was 88.0% and 93.4% respectively at wavelength of 420—460 nm and 460—680 nm as well as that of S-polarization was 0.095% at wavelength of 420—680 nm. The PBS can be applied to F/2.8 optical systems to improve their performance obviously.