The Development Of Visual Inspection System For LCD’s Value

With the continuous development of digital electronic technology, LCD instrument, as ameasurement of electronic instruments, has been widely used in various fields. Now theproduction of instruments generally have data interface to communicate with computer, but theold tables which are in use does not have such interface, the verification work is currently stillin manual stage. To solve the low efficiency and poor reliability of the manual method, anonline detection system for LCD’s value is developed which is based on machine vision andimage processing technique. The system not only can monitor the instrument in real-time,butalso can recongnize the current value and store the recognition results.In terms of recognition software,an algorithm based on ACSS corner localization isproposed according to the feature of the LCD’s indication area. Firstly,according to theprinciple of ACSS corner detection,designing the method which can be suitable to extractvertices of the indication area to locate it.Secondly,using gradation characteristics of the valueto determine the area of the string and using local threshold to binary the string, then split thestring;Finally,using three-line scanning method to recognize the character. Using this softwareto test200images of three kinds of heat instruments which were collected in the test site, therecognition rate is96.5%which proves robustness and adaptability of the proposed algorithm.In terms of system implementation, the specific model of camera and lens are determinedby the choosing principle. According to the needs of the system, the second time developmentof camera’s drive interface is done with the SDK provided by camera manufacture under theWindows platform to design the instrument monitoring interface and then the recognitionprocedure is embedded in it to achieve the system’s function of real-time monitoring and thesystem can also store recognition results. In the laboratory, the system which uses digitalpressure instrument as the test object is built. The function of the whole system has been testedand the results show that the system can work properly.