Shape measurement of objects with large discontinuities and surface isolations using complementary grating projection

Yudong Hao; Yang Zhao; Dacheng Li

doi:10.1117/12.368499

4 November 1999 Shape measurement of objects with large discontinuities and surface isolations using complementary grating projection

Yudong Hao, Yang Zhao, Dacheng Li

Author Affiliations +

Proceedings Volume 3898, Photonic Systems and Applications in Defense and Manufacturing; (1999) https://doi.org/10.1117/12.368499
Event: International Symposium on Photonics and Applications, 1999, Singapore, Singapore

Abstract

Grating projection 3D profilometry has three major problems that have to be handled with great care. They are local shadows, phase discontinuities and surface isolations. Carrying no information, shadow areas give us no clue about the profile there. Phase discontinuities often baffle phase unwrappers because they may be generated for several reasons difficult to distinguish. Spatial phase unwrapping will inevitably fail if the object under teste have surface isolations. In this paper, a complementary grating projection profilometry is reported, which attempts to tackle the three aforementioned problems simultaneously. This technique involves projecting two grating patterns form both sides of the CCD camera. Phase unwrapping is carried out pixel by pixel using the two phase maps based on the excess fraction method, which is immune to phase discontinuities or surface isolations. Complementary projection makes sure that no area in the visible volume of CCD is devoid of fringe information, although in some cases a small area of the reconstructed profile is of low accuracy compared with others. The system calibration procedures and measurement results are presented in detail, and possible improvement is discussed.

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Yudong Hao, Yang Zhao, and Dacheng Li "Shape measurement of objects with large discontinuities and surface isolations using complementary grating projection", Proc. SPIE 3898, Photonic Systems and Applications in Defense and Manufacturing, (4 November 1999); https://doi.org/10.1117/12.368499

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