57.2: Error Analysis in LCoS Phase Uniformity Measurement with Classical Polarimetric Method for Holographic Display Applications

Abstract

The classical polarimetric method has been widely used in Liquid Crystal on Silicon (LCoS) phase depth measurement with a simple optical setup. However, the current method does not provide sufficient accuracy to measure the phase uniformity due to interference caused by LCoS cover glass reflections. This paper is aimed at mathematically analyzing the errors caused by non‐ideal glass reflections, and proposing procedures to reduce or eliminate such errors. The measurement is discussed in three conditions, including an ideal condition with no reflections off the LCoS cover glass, a second condition with only forward reflection off the cover glass and a third condition with only backward reflection off the cover glass. It is discovered that the backward reflection has the largest contribution to the overall measurement error, and is the main obstacle to high‐quality measurements. Several procedures including optical alignment, gap thickness measurement and phase estimation based on gap thickness are proposed, making the uniformity measurement more qualitative and consistent.