Profile Measuring Techniques Study In The Entire Imaging Measuring Method

With the development of computer techniques, image measuring techniques is more and more widely used in the inspection of industrial parts. However, currently the imaging measuring devices, confined by the precision requirement, mostly aimed at small area imaging. For this reason, the object of measuring is single geometrical element, such as circle, line etc. The image measuring devices cannot give the estimate to the complicated profile, so that its application is restrained.To solve the problem above, in this thesis, the entire imaging measuring method which based on template is adopted, and high precision image feature extraction is studied. In addition, a new method of linear profile measurement based on image is proposed and proved to be doable by the experiments. This method makes the measurement of micro-parts more accurate, more efficient and more intelligent. The main research work in this thesis includes:1. Variety kinds of edge detection methods are analyzed. The subpixel edge location algorithm is mainly investigated. The image feature extraction of line is studied, moreover, experiments are performed to validate the measurement of angle and the distance of parallel.2. Many current methods of profile measurement and estimative arithmetic of profile error are studied. A new method of linear profile measurement called the method of minimum distance between discrete points of actual profile and theoretic profile, whose object is micro-parts which are located based upon enough benchmarks is proposed. The experiments indicate that this method is accurate. In addition, an improved algorithm which can simply judge whether the profile is qualified is proposed.3. The profile measurement, which found on only one benchmark(micro gear) or mutual benchmarks (end gap of piston ring), is demonstrated by instance. Furthermore, a method of measuring profile without benchmark is brought up and analyzed.