Research and Development on 3-D Surface Profilometric Technique and System of Free-form Specular Surfaces

Nowadays, the fringe reflection technique is widely used to measure specular objects. However, the exiting specular surface measuring system cannot measure objects with highly curved surface. Because the highly curved surface means that the surface slope distribution range is too large to be measured. In this research, a coordinate system model is used to describe all the parameters in the system and provide a model of optical system design having large slope measurable range from derived model. This research also provides a measuring method which uses Gray Code as structured light and uses two thresholds for encoding structured light information to calculate the initial height value using shadow information next to object’s edge based on three-dimensional vector concept. Then, use the path integration method to reconstruct the whole object surface. It is proved, the maximum error of the proposed system can be controlled under 0.35% of the lateral size of measured samples and the slope measurable range of the proposed system is -0.5 ~ 0.5. At the same time, the proposed system is suitable for measuring spherical and free-form specular objects.