Abstract: An apparatus for automatically mounting chip componenhts on a printed circuit board or the like generally require a pattern detector for detecting a reference mark formed on the circuit board so that the chip components may be properly placed on the circuit board. The pattern detector includes a camera for producing image data from the reference mark and an image processing unit for processing an analog image singal outputted from the camera. The image processing unit includes an A/D converter for converting the image data into digital data in binary form and a central operating portion for detecting contour lines of the reference mark in binary form. The central operating portion calculates angles of tangent lines with respect to the horizontal line at a plurality of locations on the contour lines and further calculates angular changes between two adjoining locations.

Abstract: A width measuring device for measuring a width between first and second parallel edges of a track of a disk includes a video scanner for cross scanning the track within a predetermined area, and a sampling point detector for detecting crossing points between the edges of the track and a plurality of scanning lines. The number of occurrence of the sampled points are counted to provide distribution curves for the both side edges. Each distribution curve is divided into groups such that one group extends from one zero occurrence point to a next zero occurrence point with at least one peak point occurring between the two zero occurrence points. One dominant group is selected from each side, and an average point of the dominant group is defined as hypothetical centers. A valid region which expands a predetermined range from the hypothetical center is set for each side, and an average value of the valid region is calculated for each side.