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.