Jaemyung Ryu

Abstract Optical inspection systems use large numerical apertures (NAs) to achieve high resolution. However, as the NA increases, the depth of field decreases significantly, causing images to blur easily with slight object shifts. Conventional methods maintain focus by mechanically moving the entire lens or specific lens groups. However, these methods increase the system volume, require high-performance motors, and necessitate precise inertial control when the lens group mass is substantial.