| 摘要 |
PURPOSE:To discriminate continuously the contamination of a total reflection mirror, by providing a detector for scattered light in the specific position on the optical path side changed by a total reflection mirror. CONSTITUTION:The laser light 11 emitted from a laser oscillator past the normal optical path is reflected by a total reflection mirror 4 and advances toward the work. If dirt 15 deposits on the mirror 4, the light 11 is scattered by the dirt 15 and scattered light 16 is generated. A detector 18 for scattered light is provided on the inside where the optical path is changed in a protecting cover 17 for the optical path for conducting the light 11, that is, oppositely to the mirror 4 so as to be positioned in a 15-45 deg. range to the axis of the optical path. A pyroelectric element, solar battery, etc. are used for the detector 18 in conformity with the kind of the light 11 to detect the scattered light from the dirt 15. The detected signal is processed with a measuring device and the degree of contamination of the mirror 4 is discriminated. |
