Using coloured structured light in 3-D surface measurement

The widest used algorithms for 3-D surface measurement using structured fringe patterns are phase stepping and Fourier fringe analysis. The techniques currently employed use mostly monochrome fringe patterns as a tool for phase information measurement and further surface reconstruction. However, the information contained in colour images is much more than that of monochrome, in this case, a new colour technique can be employed to analyse a measured scene with colour fringe patterns. This paper presents a new method for improving the measurement of 3-D shapes by using colour information of the measured scene as an additional parameter. The new method is based on primary colours (red, green and blue) to increase the number of the illuminated fringe patterns, which will remove or significantly reduce the common drawbacks of existing methods. The proposed technique produces a number of coloured structured lighting patterns, which are projected from different angles onto the scene. These patterns are analysed using masking algorithms, a specially adapted multi-colour version of the standard Fourier fringe analysis method and calibration routines. In this way a number of the standard difficulties are overcome. (c) 2004 Elsevier Ltd. All rights reserved.