Method for detecting misformed clips in packaging*
K I Jolic, Romesh Nagarajah, Pio Iovenitti · Measurement Science and Technology · 2001
A technique is described for detecting misformed clips in hermetically sealed packages. The technique involves use of a machine vision system incorporating an image processing algorithm, that calculates the directions of contours of intensity in grey-scale images of clips. The algorithm approximately locates the clip by scanning a box over the contour direction transformed image, and finding the position of the box such that the standard deviation of the directions in the box is a minimum. The clip is accurately located by scanning a rectangular template over the contour direction transformed image in the vicinity of the approximate location of the clip, and determining the best-fit position of the template. Accurate location of the clip enables the critical clip dimensions to be calculated and used for assessment of clip integrity. The clip integrity is considered acceptable if all of the critical dimensions lie within an acceptable range, as defined by predetermined upper and lower thresholds.