"Uniaxial 3D phase-shifting profilometry using a dual-telecentric structured light system in micro-scale devices," (2020)

M. Zhong, J. Cui, J.-S., Hyun, L. Pan, P. Duan, and S. Zhang, "Uniaxial 3D phase-shifting profilometry using a dual-telecentric structured light system in micro-scale devices," Measurement Science and Technology, 31(8), 085003 (2020); doi: 10.1088/1361-6501/ab63b2

Abstract

This paper presents a novel uniaxial microscopic 3D profilometry method using a structured light system with dual-telecentric lenses in micro-scale devices. Specifically, a telecentric lens can produce an orthographic view of an object and provide the exact size of objects in \textit and \textit-direction. An electronically focus-tunable lens attached to the projector rapidly and precisely changes the focal plane of the projected structured patterns, a camera captures the structured patterns from the same perspective, and a computational framework analyzes the relationship between captured structure images and the drive current of the electronically focus-tunable lens to obtain depth information for each pixel. By replacing the normal lens with telecentric lenses, the proposed method dodges perspective error and is easier for precision measurement. We developed a shadow-free coaxial 3D shape measurement system with dual telecentric lenses that achieved approximately 5.86 $\mu$m spatial resolution and 4.18 $\mu$m root-mean-square (RMS) error with a depth range of 1200 $\mu$m.