Range image measurement and shaded image measurement: Two non-contact coordinate measurement approaches designed for special application tasks

Abstract

Reproduction of sculptured surfaces is a common and difficult process in the manufacturing industry, such as mould and die cavity making for plastic toys. In this paper, two surface measurement techniques, namely range image measurement (RIM) and shaded image measurement (SIM), were investigated. The principle of the two approaches is based on the techniques of non-contact surface coordinate measurement. In RIM the range data of a surface are measured by laser scanning, while in SIM the coordinates of the surface are obtained by a shape from shading model and the photometric stereo technique. The acquired information from these two different surface feature measuring techniques can be used to reconstruct the surface profile by surface models such as the Bezier and B-spline models. The features of the modelled surface can subsequently be used to produce the surface on a numerically controlled (NC) machine. The validity of the approaches was examined by two machining tests, one being a medical trial and the other an industrial case. The results of the tests showed that the principle of the two approaches is workable, but some technical problems of the SIM technique need to be overcome.

Keywords

laser scanning shape from shading photometric stereo

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