| 摘要 |
PROBLEM TO BE SOLVED: To stably perform image pick-up over a long period by preventing the damage of an optical system caused by spatters and fumes during welding by a simple constitution, and to reduce the production cost. SOLUTION: A shutter 16 composed of a pair of shutter blades 15a, 15b is arranged in front of a transparent protective board 10 provided at a photographing window in a photographing means 2, and the pair of shutter blades 15a, 15b are rocked right and left via link mechanisms 14a, 14b by the stroke of a plunger 17 when a solenoid 13 is driven, so that the shutter 16 is opened and shut. In this way, there is no need of narrowing light made incident on the photographing means 2 by a pinhole, and there is no need of using a special lens as a lens 6 in an optical system of the photographing means 2, thus the production cost of the photographing means 2 is reduced. COPYRIGHT: (C)2006,JPO&NCIPI
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