METHOD AND DEVICE FOR MEASURING THE POSITION OF A PATTERN

Pixels A, B, C, D and E of a reference image X, which are suitable for use in a pattern matching operation, are automatically determined on a pattern of the reference image. The automatic determination of the pixels is done based on a change of brightness at areas around the selected pixels. Coordinates of all of the selected pixels, such as (x.sub.1, y.sub.1), (x.sub.2, y.sub.2), (x.sub.3, y.sub.3), (x.sub.4, y.sub.4) and (x.sub.5, y.sub.5) are stored in memory. A scan of the image to be detected is done at a fixed offset area for each of the selected pixels. The values of the difference in brightness between the selected pixels and the scanned points are accumulated. The minimum value of the accumulated difference is detected, and the coordinate of the scanned point which provides the minimum accumulated difference is determined as a deviation of the detected image from the reference image.