A Novel Approach for 3D Discontinuity Measurement by Combining Relative and Absolute Methods

With increasing demand for surface acquisition, 3D ranging techniques have been developing rapidly in the past decades. This paper introduces a ranging method using structured light designed for 3D measurement. A two-dimensional, binary fringe pattern is proposed in this method, and a feature, i.e., a white cross, is placed at the center of the fringe grating. White square grids are alternated by black stripes vertically or horizontally elsewhere. The relative position of a given point on the fringe with respect to the center is identified. A pair of emitting and receiving angles for each point in the fringe and CCD frames, respectively, is acquired by image processing and pattern recognition algorithms. Also, the coordinate of each 3D point can be calculated. Compared with traditional digital moire methods, this method achieves an absolute measurement of 3D surfaces and discontinuity measurement can be solved more easily.