Research On Measurement System Of Smart Watch Shell’s Geometric Size Based On Machine Vision

Since geometric size measurement is an indispensable part of the smart watch shell manufacturing process,while the traditional measurement method is to have manual sampling inspection with precise instruments,in which there are shortcomings of slow speed and low precision,thus creating a fact that it can not meet enterprise’s large-scale automated production needs.However,machine vision technology is an advanced detection technology with untouched measurement,high precision detection,fast speed and so on.It is common that machine vision technology has been applied to size measurement,Using it can not only do on-line detection of product size parameters,but also evaluate production quality in time and sort out high-quality production.This paper developed a detection system of smart watch shell’s geometric size based on machine vision to measure the shell’s size parameters quickly and accurately.The main research work includes:1.Aiming at the complicated shell structure and the concrete requirements of shell size measurement,a set of visual measurement scheme with four stations working together has been designed.The hardware platform is constructed by using a variety of light source combinations and low distortion telecentric lens.The system meets the demands in many aspects such as precision,speed and reliability.2.According to the geometric feature classification extracted from the shell image,the measured dimension is divided into two types: length dimension and height dimension,which would be studied on by the detection principle and image processing algorithm.For the length dimension,we extract straight line and circle with the Canny operator to detect the edge and least square method to match curve.For the height dimension,we present an improved laser triangulation method which simplifed the height measurement principle,and we extract laser stripe center with the threshold method,then we realize the accurate calculation of the geometric position of the image.3.According to the imaging characteristics of the telecentric lens,the telecentric lens imaging model is analyzed and simplified.The camera calibration of the measuring system is completed by the traditional camera calibration method,which improves the measurement accuracy of the detection system.4.According to the actual demand of the measurement system,the shell size measurement software system is designed in the VS2012 integrated development environment.It has the functions of image acquisition,camera calibration,image processing and motion control.The software system is combined with the hardware platform to form a complete shell size measurement system.Then,through the precision and repetitive experiment,the accuracy and repeatability of the system are verified,which satisfies the testing requirement of the size measurement system.