MEASURING FABRIC MARK IN BOARD USING IMAGE-ANALYSIS

We present an image analysis method for measuring fabric mark that is particularly suited to the analysis of opaque samples such as board. I n the method, an image of the paper surface is obtained with a surface contact optical sensor adapted from the Chapman Smoothness Tester Raw images appear as the combination of random and periodic structures. T he unwanted influence of random structures, a result of formation, on the fabric mark detection is minimized by pressing the sample against a rubber backing. The periodic structures are then analyzed by taking the two-dimensional Fourier transform of the 256 x 256 pixel image. Th e influence of the forming fabric is measured through the identificati on of the unit cell, which is specific to the forming fabric. The degr ee of fabric mark present in the specimen is ranked from the power spe ctrum amplitudes.