The Research of On-line Inspection Method of Printed Matter Based on Optical Information Processing

摘要

Two on-line inspection methods of printed matter based on optical image subtraction are proposed, using two kinds of spatial light modulation (SLM) respectively, which are TFT-LCD and CRT-LCLV. The test image of printed matter is obtained by CCD, while the standard image of printed matter is saved in computer. The test image and standard image are jointly displayed on SLM by computer as the input image of an optical image subtraction system, which is an optical 4f system with a sine-grating between two lenses. The subtraction image will occur at the output plane, which contain all defects of the test image. Comparing to machine vision method, this inspection method of printed matter based on optical image subtraction is advantaged because the inspection process is accomplished by the optical system, avoiding any complicated arithmetic. The precision of printed matter inspection is defined by the frequency of SLM and the sine-grating. The relationship between parameters of the subtraction image and parameters of optical system is analyzed.