Abstract
AbstarctWith the advent of intelligent manufacturing, phase measuring deflectometry (PMD) has been widely studied for the measurement of the three-dimensional (3D) shape of specular objects. However, existing PMDs cannot measure objects having discontinuous specular surfaces. This paper presents a new direct PMD (DPMD) method that measures the full-field 3D shape of complicated specular objects. A mathematical model is derived to directly relate an absolute phase map to depth data, instead of the gradient. Two relevant parameters are calibrated using a machine vision-based method. On the basis of the derived model, a full-field 3D measuring system was developed. The accuracy of the system was evaluated using a mirror with known positions along an accurate translating stage. The 3D shape of a monolithic multi-mirror array having multiple specular surfaces was measured. Experimental results show that the proposed DPMD method can obtain the full-field 3D shape of specular objects having isolated and/or discontinuous surfaces accurately and effectively.
Highlights
With the development of the three-dimensional (3D) optical shape measurement technique, it has been widely applied in the fields of reverse engineering, biological recognition and digitalization of cultural relics, etc
This paper presented a new full-field 3D shape measurement method for specular surfaces that uses the direct relationship between absolute phase and depth
The same fringe pattern sets were displayed on the two screens and reflected by the specular surfaces of the measured objects
Summary
With the development of the three-dimensional (3D) optical shape measurement technique, it has been widely applied in the fields of reverse engineering, biological recognition and digitalization of cultural relics, etc. PMD has been applied to measure an aspheric mirror and dynamic specular surface and to detect subsurface cracking[8], from a micro-size to a large specular surface[9,10,11,12,13,14] Such a technique needs to display straight sinusoidal fringe patterns on a screen or to project a structured pattern onto ground glass. This paper presents a new direct PMD (DPMD) method that measures the full-field 3D shape of specular objects having isolated and/or discontinuous surfaces by directly building the relationship between the absolute phase map and depth data[24]. Experimental results for a monolithic multi-mirror array having multiple specular surfaces show that the proposed measurement method can obtain the full-field 3D shape of specular objects with isolated and/or discontinuous surfaces accurately and effectively
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