Optics of LCOS projection system based on wire-grid polarizers

The efficiency and the contrast ratio of the projection system based on wire-grid polarizers (WGP) are investigated as a function of the incident angle. We shall show that of the four possible combinations of configurations, only one offers the best contrast and efficiency. We also shall show that WGP offers some distinct advantages over conventional polarizers, in terms of large extinction ratios and large numerical apertures. Also it is found that the optimal incident angle onto the WGP is dependent on the physical design of the polarizer, and is seldom 45°. At the optimal angle, both the transmission and reflection contrast can be quite good. However, WGP suffer from the drawback of large absorption due to free carrier absorption by the metal grid.