Structured Light Projection for Accurate 3D Shape Measurement

Structured light projection systems can be used in a wide range of applications where information about shape or shape deviations is required, from macro- to nano-scale. Systems we have developed, based on projected structured light, combining Gray code and phase shifting fringe projection and using off-the shelf components like B/W CCD cameras and multi-media data projectors, provide robust height measurement images with a high resolution at a low cost. By carefully observing a number of parameters, it is possible to attain this high resolution in a large measurement volume even with low-cost, off-the-shelf components. We are able to achieve a noise floor in phase determination of 30 mrad, which translates to a measurement resolution of 1 part in 10,000 of the object size. The ability to project high contrast structured light patterns in different scales allows the use of this method with this relative resolution from overall shape determination to surface roughness measurements. When we have accurate 3D profiles, subsequent processing and extraction of mechanical parameters such as roughness parameters, wear, faults, sizes, angles and radii is possible. This extraction can be customised to each new application.