Patent ID: 9138790
Filing Date: 2015-09-22
Classification: B21B,B21C,G01B,G01N

Abstract:
1. A method for measuring a flatness of a sheet material, comprising: projecting a staggered pattern of a light and dark pattern composed of light portions and dark portions onto a surface of the sheet material travelling in a longitudinal direction thereof such that a first direction of the staggered pattern corresponds to the longitudinal direction of the sheet material and a second direction of the staggered pattern corresponds to a width direction of the sheet material, the light portions of the staggered pattern being arranged in a staggered form at a first pitch in the first direction and at a second pitch in the second direction; arranging an image pickup device at a position at which specularly reflected light of the staggered pattern from the surface of the sheet material can be received, and acquiring a pattern image by picking up the staggered pattern on the surface of the sheet material with the image pickup device; setting a shape measurement line extending along the first direction of the staggered pattern at a predetermined position in the acquired pattern image; averaging picture element concentrations on a straight line which passes a picture element on the shape measurement line and extends in the second direction of the staggered pattern, and has a length two times or more the second pitch of the light portions to calculate an average picture element concentration; calculating a distribution of the average picture element concentrations along the shape measurement line; and calculating a surface shape of the sheet material along the shape measurement line based on the calculated average picture element concentration distribution, and calculating the flatness of the sheet material based on the calculated surface shape.