| Optical measurement technology is a crucial branch in the field of measurement and is widely used in modern industry.Traditional contact measurement methods have problems such as easy damage to the contact surface,slow speed,and are hard to satisfy the needs of large-scale and high-precision measurement,and even dynamic field measurement.In this context,as a non-contact measurement technology,structured light three-dimensional measurement technology not only has advantages in cost and speed,but also has good accuracy and resolution.Therefore,it is widely used in many fields,including reverse engineering and detection.In practical measurement work,parameter calibration of structured light systems is a critical process to ensure measurement accuracy.The technology of conventional camera calibration has become increasingly perfect,however,projectors are difficult to accurately calibrate due to their inability to establish accurate associations between pixel coordinate systems and world coordinate systems like cameras,so they still have high research value.Therefore,this paper proposed a sinusoidal structured light projection three-dimensional measurement system,and studied its related technologies,including phase contour measurement,fringe image processing,camera calibration,projector calibration,and system calibration and measurement accuracy.The main work and innovations are as follows:1.A sinusoidal structured light three-dimensional measurement system is designed and built based on phase contour measurement.According to the measurement theory and equipment,the overall measurement scheme of the system is designed.The related techniques of sinusoidal structured light fringes are analyzed and studied,including fringe generation,phase extraction,phase unwrapping,and the selection of phase unwrapping starting points.At the same time,the advantages and disadvantages of several commonly used filtering noise reduction and edge extraction algorithms are compared and analyzed,and the traditional gamma correction is used to the optical nonlinear error of the projector itself.2.The calibration objects include the internal and external parameters of cameras and projectors,as well as the external parameters of the system.The coordinate systems and mathematical models of cameras and projectors are analyzed,and the shortcomings of the checkerboard calibration board in terms of calibration accuracy are analyzed.Several calibration methods of system are compared with each other,and the advantages and disadvantages of whether to calibrate the projector in terms of calibration complexity and accuracy are studied.Finally,two calibration schemes are compared and analyzed through experiments.The experimental results prove that the calibration project mentioned in this paper has better calibration accuracy.3.The experimental platform was designed and built,and the equipment and application software were introduced at length.Experiments have verified that the circular calibration board has a higher calibration accuracy than the checkerboard calibration board during camera calibration.In the process of projector calibration,the pseudo camera method based on coordinate mapping has higher calibration accuracy than the inverse camera method based on coordinate transformation.Then several standard parts were measured,and the experimental results showed that the threedimensional measurement system had good accuracy.4.The main innovation of this article lies in: firstly,in the process of obtaining phase information of feature points using phase shifting method,circular light spots are used to determine the starting point of phase,which has better performance compared to traditional bright lines;Secondly,a circular calibration board was used in the process of calibrating the projector,which has better calibration accuracy compared to checkerboard calibration board and color calibration board. |
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