| 摘要 |
METHOD AND APPARATUS FOR DETECTING CHARACTERISTIC FEATURES OF SURFACES A novel system is provided for detecting the presence of a characteristic feature on an illuminated surface of an object when used in conjunction with known electro-optical systems for determining the position of the centroid of the outline of the object with relation to the supporting surface and the rotation of the object relative to the rotational orientation of a test part. The surface is illuminated at an angle that enhances the contrast of the characteristic feature while using a vidicon-type image converter tube which scans the field which includes the object. The location, with respect to the centroid, of a circular window area encompassing the characteristic feature and the radius of the circular window are determined utilizing a television monitor connected to the vidicon. Next the operator determines and stores a pair of separated threshold levels which control a level detector which compares the vidicon output to the threshold level to derive a binary output so that one of the threshold levels separates the white area in the window area from the gray-black area while the other threshold level separates the black area in the window area from the white-gray areas. The system then analyzes and stores the relative amounts of white, gray and black areas in the window as a signature signal representative of the characteristic feature of the surface. Following this "teach" phase, the system may be used to determine whether a subsequent object contains a feature which correlates well with the characteristic of the test part by analyzing the output of the vidicon at the window for both threshold levels and determining the correlation between these levels and the values obtained during the teach phase. In an alternative embodiment the window location, size, and threshold levels are determined by the system without operator intervention by analyzing the vidicon outputs derived by the scan of two objects which are identical except that one contains a characteristic feature while the other does not. The system then determines the differences between the two pictures to select an appropriate window area, size, and threshold values which best highlight the differences between the two pictures. |
