A computer vision system for inspecting engine heads during assembly for missing valve spring assembly keys comprises a solid-state camera for taking pictures of the valve spring assemblies and providing picture data upon command to a computer. The computer responds to a position encoder which relates the position of the engine head to the camera. Once the data is stored in the computer, it is analyzed to determine the center of the digitized image of the valve spring assembly and an intensity profile at the expected location of the keys relative to the center of the assembly is utilized to determine whether a key is missing.

Method and apparatus for inspecting engine head valve retainer assemblies for missing keys

Edge detection followed by thinning produces a set of points which lie along edges in the original image. It is important to link together the pixels which lie along the same edge. The resulting associated groups can then be fitted with line segments. This paper presents a new technique for this edge point linking problem. Each edge point is linked to its appropriate neighbor on either side by considering those contours, produced by thresholding, which pass through the given edge point. For each such contour, the edge point nearest the given edge point along the contour (in, say, the clockwise direction) is recorded. The edge point occurring most often as an associate across the set of gray level thresholds, is chosen as the clockwise associate. A figure of merit based on path length and straightness is used to break any ties. The counterclockwise neighbor is chosen similarly. Two points which are mutual associates denote a symmetric link. If all non-symmetric links are deleted, the resulting structure is a set of linear chains of nodes called 'symchains' It is claimed that symchains provide a rich edge structure for further processing.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

David Lee Milgram

Papers

Edge Linking Using Thresholding