Research On Probe Calibration Technology Of Light-pen Three-coordinate Measurement System Based On Monocular Vision

With the development of the national economy,the modern manufacturing industry as an important pillar has become an important cornerstone.In the development process of modern manufacturing,industrial measurement has become an indispensable part of the industrial development process.And with the development of the automotive industry and aerospace industry that require high-precision real-time measurement,real-time and on-the-spot rapid measurement is often required to solve problems in industrial sites.Therefore,the stage of visual measurement system has gradually attracted everyone’s attention.The light-pen type three-coordinate vision measurement system based on monocular vision is more unique as a typical visual measurement system.The system combines visual measurement technology with image recognition technology to form a new measurement system based on the principle of target imaging,The system greatly improves the portability of measurement,and at the same time has the advantages of simple operation,convenient use and high measurement accuracy.Aiming at the problems of late start of domestic light pen type visual measurement system,poor measurement accuracy and measurement stability,this thesis participated in the construction of a new light pen type three-coordinate measurement system,and completed the selection and processing of corresponding equipment.The test determines the pose domain of the system,standardizes the measurement operation of the light pen in the system,and improves the measurement stability of the measurement system.A new self-calibration method is proposed,which is simple to operate and does not require any instruments,which greatly improves the portability of the system while ensuring the stability of the system measurement.The main work is as follows:(1)Participated in the selection of a set of light-pen type three-coordinate vision measurement system,and completed the selection of cameras,the design and processing of light-pen,and the selection of light-pen probe.During the design and processing of the light pen,the material of the light pen is analyzed and selected in detail,and the distribution of the feature points and the material of the feature points are also analyzed accordingly.(2)A self-calibration method for the center of the optical pen probe based on spherical fitting is proposed for the calibration of the center of the optical pen probe in the measurement system.Fit the feature points of the light pen on the corresponding sphere,and the obtained sphere center coordinates are the actual position of the center of the light pen probe.The new self-calibration method ensures the measurement accuracy of the light pen and greatly improves the portability of the system.(3)The pose domain of the system is established and the image processing of the measurement system is completed.The pose of the light pen also affects the measurement accuracy of the light pen to a certain extent.An auxiliary measurement device is designed to determine the pose field of the light pen,which ensures the measurement stability of the light pen to a certain extent.In the aspect of image processing,the calibration principle of CCD camera is introduced,and then the extraction method of the feature point region is analyzed and given.Finally,the Gaussian surface fitting method is selected to locate the center of the feature point,and the related work of image processing is completed.(4)The corresponding experiments and analysis have been completed.Firstly,a single-point repeatability experiment was carried out on the system to verify the measurement stability of the system.Then,the proposed probe center self-calibration method is verified by experiments,and the experimental results are satisfactory,indicating that the probe center self-calibration method can ensure the measurement accuracy and measurement stability of the system,and greatly improve the portability of the system.Finally,in order to determine the pose domain of the system,a threshold measurement experiment was carried out on the three rotation axes of the system X,Y,and Z.In the experiment,the measurement data in three directions were analyzed in detail,and the measurement thresholds in the three coordinate directions were obtained,which standardized the measurement pose of the light pen and ensured the measurement stability of the system.