Liquid Coating's Surface Topology Measurement via Structured Illumination and Stereoscopic Vision

This mechanical engineering research thesis describes the theory, research & development, prototyping, and testing of two laboratory methods of surface topology measurement. These methods are intended to be generally applicable in a commercial context at the Spraying Systems Company. The first method is structured illumination, which measures the refraction of a known lighting structure through a transparent or translucent liquid coating. The second method provides a means of perceiving depth of an opaque liquid coating using stereoscopic vision for configurations or conditions where structured illumination does not work. Structured illumination uses a high-definition LCD display to project a grid pattern of light from beneath horizontally oriented optical glass coated on top with the sample fluid. This provides a determination of surface topology with ± 63 microns of error. Stereoscopic vision uses a pair of Intel RealSense cameras spaced a fixed distance apart and Intel RealSense software to calculate depth from the difference in parallax between the cameras, just as human binocular vision achieves depth perception. Stereoscopic vision provides determination of surface topology with ± 1 mm of error. Precision and accuracy can be improved by using higher resolution stereoscopic cameras. Both laboratory methods will prove practical and useful for a broad range of both research and commercial applications measuring surface topology at the Spraying Systems Company.