Image fusion and subpixel parameter estimation for automated optical inspection of electronic components

The authors present a new approach to automated optical inspection (AOI) of circular features that combines image fusion with subpixel edge detection and parameter estimation. In their method, several digital images are taken of each part as it moves past a camera, creating an image sequence. These images are fused to produce a high-resolution image of the features to be inspected. Subpixel edge detection is performed on the high-resolution image, producing a set of data points that is used for ellipse parameter estimation. The fitted ellipses are then back-projected into 3-space in order to obtain the sizes of the circular features being inspected, assuming that the depth is known. The method is accurate, efficient, and easily implemented. The authors present experimental results for real intensity images of circular features of varying sizes. Their results demonstrate that their algorithm shows greatest improvement over traditional methods in cases where the feature size is small relative to the resolution of the imaging device.