Coordinate Measurement System Based On Coded Target

With the increasing demand of on-site measurement in modern industrial,traditional coordinate measuring machines can not fulfill the requirement of measuring.The light pen coordinate measuring system got wide research and application due to its flexibilility,simple structure and easy operation.Most of the existing light pen measurement systems in China have small measurement range and low accuracy,so a coordinate measurement system based on coded targets in this thesis was designed,which is mainly composed of a handheld coded target(light pen),image acquisition equipment,and computer with measurement software.A coded target with adjustable brightness is used in this system for measurement,which not only expands the measurement range but also improves the measurement accuracy.A system prototype that can be automatically measured and its key technology were researched in this thesis.When obtaining the three-dimensional space information of a measured point,you only need to press the trigger button to start the measurement to get the measured point space coordinates.The main tasks completed in this thesis are as follows:1.The current research status of the light pen coordinate measurement system was analyzed.A coordinate measurement system based on the coded target was designed.The measurement model of the system was analyzed.That the measurement accuracy of the coded target is higher than that of the ordinary target was verified through simulation.2.The overall design of the coded target including the drive circuit,the housing structure and the wireless communication between the coded target and the host computer were completed.The computer control of the brightness of the target light spot which can change automatically on this basis was realized.The designed target has the characteristics of simple communication,high stability,light weight,strong practicability and low cost.3.The system automatic measurement software was designed.The computer can control the CCD camera to collect the target image after receiving the signal sent by the target.After judging the brightness of the light spot in the image,it automatically sends the data for controlling the brightness adjustment of the target light spot according to the result.After image processing,a normalized correlation algorithm is used to correlate the target image.After image processing,the computer performs correlation matching between the target image and the standard template image through a normalized correlation algorithm,and finally calculates the spatial coordinates of the measured point.4.A large number of experiments were designed and conducted.The system can achieve measurement within the measurement range of 3m,the stability accuracy of x,y,and z can reach 0.010mm,0.014mm and 0.228mm.The necessity of the coded target to be able to measure different postures and to automatically adjust the light spot of the target has been proved in the experiment.And that the measurement accuracy of the coded target is higher than that of the ordinary target,which was verified the correctness of the simulation.