Uniaxial 3D Shape Measurement

Authored by: Otani Yukitoshi

Handbook of 3D Machine Vision

Print publication date:  March  2013
Online publication date:  April  2016

Print ISBN: 9781439872192
eBook ISBN: 9781439872208
Adobe ISBN:

10.1201/b13856-12

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Abstract

Recently, noncontact three-dimensional (3D) profilometry has been required in the field of manufacturing inspection for industry, biometrics, and robot vision. Table 11.1 shows typical 3D methods that have already been proposed for this purpose. We can classify the type of optical axis based on measuring depth data by a stereoscopic or uniaxis method. The stereoscopic method is the most popular for measuring 3D shapes. It uses a parallax where two or more optical axes are imaging, or one is for illuminating specified patterns and the other is imaging. The stereo method has two axes of an optical system with projection and observation and originated as aerophotography. A 3D measurement by the stereo machine is proposed multi-eye which is employed multioptical axes and differential illumination. A moiré topography is an elegant method and an easy-to-understand way to produce a contour map by superimposing gratings [1,2]. Optical sectioning in the pattern projection is the oldest method for noncontact 3D measurement [3]. It has been expanded for different methods and production, such as spot scanning, Gray code, random-dots color pattern, and grating projection [4]. However, it has a drawback in measuring deep holes, steep height, and shadow portions (shown in Figure 11.1). Figure 11.1(a) shows a conventional method. It cannot capture the projected pattern because of different axes.

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