General methodology for LCoS panel compensation

Abstract

A general three-step methodology is presented to optimize contrast when compensating LCoS panels. The first step acts to compensate the in-plane residual retardation, while the second one improves the field of view (FOV) using either MacNeille-type or wire-grid polarizing beamsplitters (PBS). The orientation of the LCoS panel and compensator, relative to the MacNeille PBS, are very critical to achieve good system contrast. The final step is to account for reflections from anisotropic material, which appear as on-state light, limiting contrast.

P-155: High Performance Contrast Enhancing Films for VAN-Mode LCoS Panels

“…The back reflection contrast of the TR is limited by reflections from the various interfaces in the structure. A main source of contrast degradation is anisotropic reflection [4] at the retarder materialglass substrate interface. The birefringence ∆n of the retarder material should be ∆n <0.02 in order to have a negligible effect on the overall system contrast.…”

“…The out-ofplane retardance can vary from 150nm to 350nm depending on pretilt angle, LC material and cell gap. In order to achieve high contrast and fully utilize the potential of a wire grid polarizer based light engine architecture the in-and out-of-plane retardance of the VAN mode panel has to be compensated [4,5]. This can be achieved by using a birefringent film commonly referred to as trim retarder (TR) which preconditions the polarization state of the illuminating light and further corrects the reflected light from the micro display, so that the combination of LCoS panel and TR acts close to the ideal reflection of a mirror in the off-state of the display as indicated in Figure 2, i.e.…”

System Contrast

“…Based on the previous compensation schemes, a two-film approach should perform well, whereby a small uniaxial a-plate compensator corrects for head-on contrast and a uniaxial QWP corrects for both PBS geometry and the LC out-of-plane retardance [Chen J., 2004a]. Although in general both retarders can be oriented independently, aligning the QWP to the PBS's s-polarization axis yields more achromatic solutions.…”

Optimization of contrast for MTN45 LCOS panel

“…1 However, LCOS is catching up. [2][3][4] The contrast improvement in the contrast of LCOS panels has attracted a lot of attention recently. Especially the mixed TN45 (MTN45) mode of LCOS is of great interest because it has a response time of about 0.1 msec.…”