| 摘要 |
PURPOSE:To provide a sharper image and the reduction in the size of a device by providing a shielded light transmission hole for observation and observation window to said device and forming a gas flow passage for cooling between the grating disposed before the observation window and the observation window. CONSTITUTION:The observation window 11 consists of heat-resistant glass, etc. and is disposed behind the light transmission hole 10. The window 11 is disposed to incline by a prescribed angle with the optical axis of a detector 14 and the cooling gas flowing toward an arc point 4 is passed through the gas flow passage 17. The intrusion of the fume generated by the arc into the hole 10 is prevented by the flow of the cooling gas. The spatter entering the hole 10 is quickly cooled by the cooling gas and the intrusion thereof into the window 11 side is prevented by the grating 12. The sticking of partly intruded and small-granulated spatter to the window 11 is prevented as well. The sharp arc image is obtd. by the above-mentioned method and since the device is disposed near the arc light, the size thereof is reduced. |
