Patent ID: 9482520
Filing Date: 2016-11-01
CPC Classification: B21B,B21C,G01B

Claim Text:
1. A method for measuring flatness of a plate material, comprising: acquiring a pattern image by measuring the flatness of the plate material by analyzing the acquired pattern image, wherein if L α represents an angle formed between a vertical direction and a straight line formed by projecting the optical axis of the image capture unit onto a plane that contains a direction parallel to a rolling direction and the vertical direction, a value of a being positive if the optical axis of the image capture unit is inclined from the vertical direction toward the looper side, β represents an angle formed between the vertical direction and a straight line formed by projecting the optical axis of the projection unit onto the plane, a value of β being positive if the optical axis of the projection unit is inclined from the vertical direction toward the rolling stand side, hc represents a distance in the vertical direction between a pass line, which is a straight line passing through crest points of respective lower side work rolls of pairs of upper and lower work rolls that are respectively disposed at the adjacent rolling stands, and an image principal point of a lens of the image capture unit, and hp represents a distance in the vertical direction between the pass line and an image principal point of a lens of the projection unit, then L 0 , α, β, hc and hp satisfy the following mathematical expression (1)