Study On The Key Technology Of High Accuracy Image Measurement System For Subminiature Accessory

With the development of computer techniques, image measuring techniques are widely used in the industry, by right of the advantages such as non-contact, high accuracy and so on. The number of high-precision subminiature accessory applied in the industry is exponential increasing year by year, due to the constant progress of industrial level. However, the existing image measuring instrument is difficult to meet the measurement demand of high accuracy and efficiency, for the measurement efficiency is low which is restricted by the contradiction between precision and field range. This thesis is studied on the key technology of high accuracy image measurement system, including the building and accurate adjustment of the hardware system, edge location technology of high accurate, system calibration, image super-resolution reconstruction and so on. The Vision Inspection Instrument for Escape Wheel(VIIEW) was built for the measurement of escape wheel which was one of the highest precision parts in the horological industry, and has realized the measurement of different specifications of escape wheel with more precise and efficient. Besides,The VIIEW, of wich the relative accuracy is better than 1/2000, also finished the debugging and acceptance in the industrial field. The main contributions and innovative points of the thesis include:1. A high accuracy image measurement system for the precise measurement of the escape wheel is designed and built. It mainly includes: determined the measurement mode based on entire imaging; adopted the self-designed object telecentric lens, which make the distortion of annular area containing the key parameters of the escape wheel(area close to the field margin) minimum; finished the designing of lighting system.2. The highly accurate adjustment of the verticality between optical axis and object plane and the focusing of object plane are studied. One kind of image definition criterion algorithm which is based on the image interpolation and the algorithm of detecting verticality based on regional image definition are proposed respectively. According to experiments, both of the methods are effective, and realized the highly accurate adjustment in the VIIEW.3. The highly accurate location technology of image edge is studied, including edge detection of pixel level, contour tracking technique and edge location of sub-pixel level. A sub-pixel location algorithm based on matching template is proposed. By building relevant matching template considering the edge of different type, carrying correlation operation between matching template and the image edge, and finding the position of most correlation, high accurate edge location of sub-pixel is achieved.4. System calibration with high precision, calculation of escape wheel's parameters and software designing are completed. Realizing the high precision and greater efficiency measurement of escape wheel's 11 parameters of many types, the VIIEW can work in the industrial field reliably and stablely after finishing field debugging and obtaining acceptance test.5. The reconstruction technique of super-resolution based on image sequence is studied to improve the resolution of the original image, which helps to improve the measuring precision. In order to solve the problem that the micro-displacement of high accuracy is difficult to realize in the reconstruction of super-resolution based on precise micro-displacement, the reconstruction technique of super-resolution based on random micro-displacement is proposed. This method can promote the measuring precision when using in the image measurement which proves to be effective by designed experiment.