High-speed three-dimensional shape measurements using multiwavelength spatiotemporal phase shifting

Toshitaka Wakayama,Toru Yoshizawa

doi:10.1117/1.oe.53.11.112207

Abstract

Phase shifting using digital light processing (DLP) projectors enables high-speed three-dimensional (3-D) shape measurements based on a pattern projection method. However, faster phase shifting is required in industry to reduce the measurement time. For this purpose, it is necessary to precisely control the fringe pattern, but conventional DLP projectors afford limited control of the pattern due to their low-refresh rate (typically 120 Hz). Here, a multiwavelength spatiotemporal phase-shifting technique is proposed for faster 3-D shape measurements using a 3CCD camera. The projector consists of a single micro-electro-mechanical system mirror and three laser diodes of different wavelengths. The intensity modulation is transformed from the time to the spatial domain. The phases of the fringe patterns are independently controlled at each wavelength. Images are simultaneously captured of the projected patterns deformed in accord with the surface profile of the objective. The method is validated using a gray code technique for the height measurement of a sample in large steps.©The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part

Highlights

High-speed three-dimensional (3-D) shape measurements based on a pattern projection technique are employed in mechanical, automobile, aircraft, medical, and heavy industries.[1]
A few papers have been published on 3-D shape measurements using a liquid crystal grating, a digital mirror device (DMD), a single micro-electro-mechanical system (MEMS) mirror, a linear LED array, and a polygonal mirror.[2,3,4,5,6]
We have developed a 3-D shape measurement system using a multiwavelength spatiotemporal phase-shifting technique and demonstrated its performance and applications

Summary

Introduction

High-speed three-dimensional (3-D) shape measurements based on a pattern projection technique are employed in mechanical, automobile, aircraft, medical, and heavy industries.[1]. We demonstrate to independently shift the phase of fringe patterns and measure 3-D shape of samples with large steps To overcome this limitation and achieve high-speed 3-D measurements, a multiwavelength spatiotemporal phaseshifting technique is proposed in the present work.[20] This makes it possible to project three color fringe patterns with different periods using only one MEMS mirror and three laser diodes. This technique can control the initial phase of the periodic patterns.

Multiwavelength Spatiotemporal Phase-Shifting Technique

High Speed 3-D Shape Measurements

Experimental Setup and Performance Check

Conclusions