Apparatus and method for edge detection

摘要

A method for detecting an abrupt rising edge from a first smooth surface to a second smooth surface includes the steps of a) illuminating one of the first surface and the second surface with a light beam having a focal point generally at the second surface; b) measuring the intensity of the light reflected from the illuminated surface, the measured intensity being greater for light reflected from the first surface than for light reflected from the second surface; c) altering the relative position of the edge and the light beam; and repeating steps a) - c) until the measured intensity is above or below a predefined threshold. An apparatus for detecting the edge of a plate mounted on a support, the plate and the support forming a plate system, includes the following: an optical print head for illuminating the plate system with a light beam having a focal point generally at the plate, a detector for measuring the intensity of the light reflected from the plate system, and means for altering the relative position of the edge and the light beam. The optical print head includes a laser diode and a writing optical fiber connected to the laser diode. The optical print head includes a focus optical fiber and the detector includes a photodiode connected to said focus optical fiber. <IMAGE>