In this paper, a non-contact 3D profile measurement technique was presented which is based on the projection of parallel beams. An arc light which was assumed to be point light source was positioned in the focal point of an parabolic mirror. After it was reflected by the parabolic mirror, uniform parallel beams were projected. These parallel beams, passing through LCD, produce 27 coded patterns. The purpose of these coded patterns is to ensure their relative positions. CCD images where then taken on these coded patterns in order to perform space coding on each of the measurement points. It was followed by the calibration process with special designed model to obtain the internal and external parameters of the CCD such as focal length and ratio of pixel size. Using the triangulation theory, coordinate transformation between the measured object and the CCD will transform the 2D image plan into 3D coordinate profile. The parallelism of these projection beams eliminates the disadvantages of diffused projection light patterns, simplifies the mathematical algorithms, and reduces image processing error of the projected patterns. This can be more efficient and accurate technique for 3D profile measurement as compared with other non-contact structured light techniques.
Parallel Projection Beams for Non-Contact 3D Profile Measurement
