Selection of ambient light for laser digitizing of quasi-lambertian surfaces

Abstract

Present work deals with the influence of ambient light on the quality of surfaces digitized with a laser triangulation probe. Laser triangulation systems project a laser beam onto the surface of the workpiece, so that an image of this projection is captured in a photo-sensor. The system is then able to establish vertical position for each point on the projection, processing the information contained in the mentioned image. As the sensor does not only capture the light projected by the laser, but also captures the ambient light emitted in the same wavelength of the laser beam, ambient light becomes a potential error source. A methodology for testing different light sources under the same digitizing conditions has been developed and applied to the digitizing of a 99% quasi-lambertian reflectance standard. Tests have been carried out for six different types of ambient light sources and the resulting point clouds have been set for comparison. Three different criteria have been used to analyze the quality of the point cloud: the number of captured points, the average dispersion of the test point cloud with respect to a reference point cloud, and the distribution of such geometric dispersion across the whole surface. Results show that best quality is obtained for low pressure sodium lamps and mercury vapor lamps. © 2009 Springer Netherlands.