Inline Quality Control of Liquid Crystal Cells

Inline quality control of liquid crystal (LC) cells is usually associated with a real-time noncontact characterization of moved LC cells. Such a characterization enables inspection of the products quality and helps to find in time defects. In the paper, we analyze an approach for fast evaluation of LC cell gap uniformity. The approach is based on detecting interference patterns formed by the quasi-monochromatic light reflected from a tested LC cell. To speed up the data treatment, a simple analytic expression describing the intensity of light interacting with the multilayered structure of an LC cell is derived. The results of the simplified model are compared with rigorous simulations. Two experimental setups are discussed. A CCD camera is used for detecting the interference patterns.