Effects of pinhole diameters on beam characteristics for silicon thin film optical inspection

Peak power density stability and beam-wander precision of probe laser are important factors affecting the inspection results in the precision thin film optical measurements. Pinhole is frequently used as a spatial filter in the optical inspection system. In this work, four different diameters of pinhole are investigated experimentally. It is found that pinhole diameter of 0.3 mm is considered to be a promising candidate for mounting in front of probe laser for silicon thin film optical inspection due to better peak power density stability and better beam-wander precision.