3M PBS for High Performance LCOS Optical Engine

摘要

A new 3M Polarizing Beam Splitter (PBS) enables high performance optical engines for Liquid Crystal on Silicon (LCOS) projectors. It overcomes the limitations of previous LCOS optical engines that have insufficient throughput, contrast, and dark state uniformity. These limitations are the direct result of the performance of existing MacNeille PBS's: poor transmission of p-polarized light and reduced contrast at modest beam angles and wavelength sensitivity. 3M has addressed these problems by creating a polarizing film made of alternating layers of different plastics with the refractive indices tailored so that they match in one in-plane direction but not the other. In the unmatched direction, a highly reflective quarter-wave stack is formed, while in the matched direction the film acts as a transparent slab of plastic. This film is laminated between glass prisms to form a PBS with performance far superior to a MacNeille PBS's. For an F/2 beam, across the visible, transmission of p-polarized light exceeds 92% and contrast exceeds 1000:1. High contrast is achievable in an optical engine without the use of a post-polarizer, avoiding this 15% loss that is necessary with a MacNeille PBS. Finally, the input light need not be highly polarized, allowing the engineer additional design freedom.