PURPOSE: To evaluate the diaphragm on the surface of a material accurately and to prevent the yield of products from decreasing by irradiating light slantingly for the waving of the surface of the material which is caused in the heat treatment line of continuous annealing, etc., detecting its reflected light by an image sensor, and processing its detection signal.
CONSTITUTION: The material 2 such as a steel plate which is carried out of a continuous annealing furnace is irradiated with light from light sources 5 and 6 through slit observation windows 9 and 10 slantingly in the width direction of the plate. The reflected light is detected by the image sensor 7. Its analog video signal is inputted to a primary processing means 203 through an A/D converter 202 to calculate data on the brightness on the surface of the material 2 and the data is stored in a memory. A width arithmetic means 204 reads out the data to calculate the width of the material and a meandering arithmetic means 205 calculates the extent of the meandering. A detection range arithmetic means 206 determines a diaphragm detection range R on the basis of the width of the material, a variation rate arithmetic means 207 finds the rate of variation in the brightness in the R, and a diaphragm width and area arithmetic means 208 calculates the mean value of the brightness to perform the evaluation 209 of the diaphragm.
KIHARA SEIJI
SATO TOSHIHARU
KAWAGUCHI HARUO
