| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and device capable of detecting a foreign matter with high sensitivity.SOLUTION: A long belt-like sheet 1 is wound on a roll 7 installed in the midway of a conveyance path of the sheet 1. Incident light having a laser beam as a light source is projected parallel to an axial direction of the roll 7 and from one side edge 11 of the sheet 1 toward another side edge 12 onto an inspected portion 20 constituted of a portion wound on the roll 7 or a peripheral portion thereof in the sheet 1. The incident light is reflected by a reflection mirror 26 installed on the other side edge 12 side so that reflection light passes along an optical path the same as an optical path of the incident light. The returned reflection light is received by a light receiver installed on the one side edge 11 side, and a light receiving amount of the reflection light is measured. On the basis of the degree of the light receiving amount, whether or not a foreign matter is present on a surface of the sheet 1 is inspected. |
