Phase Measurement And Surface Reconstruction Using Coloured Structured Light

The most widely used algorithms for 3D surface measurement using structured fringe patterns are phase stepping and Fourier fringe analysis. The techniques currently employed almost always use 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. There are a number of problems and limitations inherent in existing algorithms, these include:

• Inability to process areas, which do not contain any information from a projected fringe pattern due to shadowing etc. These have to be identified, masked and removed from the process of measurement, because the surface cannot be reconstructed there properly.
• Measurements of areas which contains invalid or/and noisy data. In this case the disadvantage is that the accuracy of the measured surface in this area is low.
• Spatially isolated areas, which cannot be measured correctly relatively to each other, because the unwrapping process requires connections between all measurement areas.
• Measurement of discontinuous height steps is difficult because Fourier techniques deal with continuous signals and thus assume that the image extends to infinity in all directions.

My research presents a new method for improving the measurement of three-dimensional 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, see figure 1.