Study On Rapid 3D Surface Measurement System Based On Laser Visual Inspection

A 3D vision measuring system based on stereovision theory and laser scanning isstudied in this thesis. Reviewed the different current methods of 3D surfacemeasurement, a binocular stereo vision method based on laser beam scanning technologyis proposed in this paper. It overcomes the disadvantages of the most existing methodssuch as perplexing framework, complicated coding and hard data processing. To completethe design of scanning configuration, five semiconductor laser generators are regulararranged in space and a precision stepper motor combining with a harmonic speed changeris used. The theory of binocular stereo vision and system precision is analysed in order tooptimize the sensor. Many technologies are adopted for completing the measurement of3D free surface, such as camera calibrating, laser beam scanning, image pretreatment andepipolar constraint matching. The system is simple, portable and can achieve rich data. Itcan get three-dimensional coordinates of the free form in field. The measurement isnon-contact and quick with high precision. So the system can fully satisfy modernmeasurement.The main works of this thesis are summarized as follows:1. The theory of binocular stereo visual measurement and its mathematical model areintroduced. The precision of the sensor is analyzed.2. A new binocular vision sensor based on laser beam scanning technique is developed.It include scanning mechanism mostly based on a precision stepper motor combiningwith a harmonic speed changer and the sensor control module which realizes thecommunication between sensor and computer. The sensor can easily change thescanning resolving power and frequency by only modifying the software.3. A special image processing software is programmed according to the characteristic oflaser beam scanning image. Median filter, auto-threshold and morphologicaltechnology are used for rough-precise characteristic point getting. And epipolarconstraint matching method is used for characteristic point match.4. The installation and hardware test of sample system is completed. Completing aexperiment of 3D measurement and the different parts of the object'sthree-dimensional coordinates are achieved by image collecting and processing.