Patent ID: 6335982
Filing Date: 2002-01-01
Classification: G01N

Abstract:
A streak inspection method of inspecting an existence of a linear streak on a sheet object to be inspected in a transportation direction, by taking a picture of the sheet object to be inspected during transportation to obtain a video signal, and converting the video signal to obtain a plurality of brightness data for every pixel, said streak inspection method comprising:a first change calculation step of emphasizing density changes in vertical and horizontal directions by applying a first emphasizing filter on the plurality of brightness data for every pixel; an average calculation step of dividing the density changes emphasized in said change calculation step into a plurality of first lattices composed of a plurality of data, and calculating an average value of the divided data to obtain average changes for every first lattice; an change addition step of dividing the average changes calculated in said average calculation step into a plurality of second lattices composed of a plurality of rows and columns in a lengthwise and breadthwise direction, and adding the average changes in each second lattice to obtain average change sums for each second lattice; a second change calculation step of emphasizing the density changes in vertical and horizontal directions by applying a second emphasizing filter on the average change sums obtained in said change addition step; and a defect judgement step of judging a streak by comparing the density changes emphasized in said second change calculation step with a predetermined threshold value.