Pattern detector for detecting a reference mark or marks formed on a printed circuit board

摘要

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. The central operating portion then compares a row of the angular changes of the reference mark with a row of corresponding angular changes of a reference pattern stored in advance in a reference pattern storage memory. The pattern detector selects those of the row of angular changes of the reference mark that have greatest similarity to the row of angular changes of the reference pattern as being coincident with the reference pattern.