SURFACE INSPECTION APPARATUS

WIPO Patent Application WO/2011/111528

A1

Disclosed is a surface inspection apparatus which comprises an annular illumination device (3) that includes a ring-shaped light emitting unit (3A) and a light shielding plate (3B), the light shielding plate (3B) having an optical opening of which diameter is smaller than the inside diameter of the light emitting unit (3A) and being disposed between the light emitting unit (3A) and a steel plate (2) so as to be concentric with the light emitting unit (3A), and an imaging unit (4) that is disposed on the center line (C) of the opening of the light shielding plate (3B) and that captures images of the surface of the steel plate (2) through the opening. Only light beams diffracted by the edge portion of the opening of the light shielding plate (3B) among light beams emitted from the light emitting unit (3A) are incident on an imaging area (A) on the surface of the steel plate (2) to be imaged by the imaging unit (4). The distance H between the light emitting unit (3A) and the surface of the steel plate (2) is set such that the average brightness level in the imaging area (A) is more than or equal to a predetermined level and a difference in the brightness level in the imaging area (A) is in a predetermined range. With this, minute point-like flaws can be accurately detected.

OKUNO MAKOTO (JP)
TAKADA HIDEKI (JP)
MURATA SAIICHI (JP)

PCT/JP2011/054013

September 15, 2011

February 23, 2011

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JFE STEEL CORP (JP)
OKUNO MAKOTO (JP)
TAKADA HIDEKI (JP)
MURATA SAIICHI (JP)

G01N21/892

WO2005119227A1

2005-12-15

JP2007155455A	2007-06-21
JPH09113466A	1997-05-02

SAKAI, HIROAKI (JP)
Hiroaki Sakai (JP)

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