Abstract:
A surface defect detection method according to the present invention is a method of optically detecting a surface defect of a steel product, and includes an irradiating step of irradiating illumination lights from different directions to an identical inspection target portion by using at least two distinguishable light sources; and a detecting step of acquiring images by reflection lights of the respective illumination lights and detecting a surface defect in the inspection target portion by performing difference processing between the acquired images. An incident angle of the illumination lights of the respective light sources are within a range of 60° to 82.5° relative to the inspection target portion.
Abstract:
PROBLEM TO BE SOLVED: To provide a shape evaluation method and a steel plate shape correction method, capable of properly correcting a steel plate shape, by properly evaluating the shape by specifying a frequency of shape evaluation.SOLUTION: When evaluating a shape of a shape measurement surface of a shape evaluation object body by using a computer having the arithmetic processing function, a difference in the preset length is applied to the shape measurement surface of the shape evaluation object body, and a clearance is determined by making a band-pass filter act on point group data of a measurement point position on the shape measurement surface of the shape evaluation object body by using the band-pass filter having a frequency response characteristic when measuring the clearance between the difference and the shape measurement surface. Thus, the clearance between the difference and the shape measurement surface can be accurately determined by setting the band-pass filter as a band-pass filter for determining curvature of the shape measurement surface, or by setting the band-pass filter as a band-pass filter for determining a difference between output of a low-pass filter being high in frequency and output of a low-pass filter being low in the frequency.