Machine-vision plays an important role in an automatic inspection for printed circuit boards (PCBs). The conventional image comparison methods, such as direct comparison of two images and image expansion-contraction for design-rule inspection, have some difficulties in finding large defects, missing paterns, and a short. To cope with these problems, topological information on PCBs is introduced in this proposed method.
This paper is concerned with an optical inspection system, in which topological information on conductors and insulators of PCBs are used for the detection on defects.
The principle is mainly based on the topological comparison method which compares the standard graph obtained from the skeltons of the conductor and insulator images of the standard PCB with those of inspection boards. Topological information incoorporates weighted graphs composed of several types of nodes and edges, connections, and their locations.
By this method all of the flaws mentioned above are detected together with their positions and the types of defects are allmost discriminated. Experimental results as well as some pertinent problems are also presented.
抄録全体を表示