| 摘要 |
PURPOSE:To surely prevent the thermal failure of optical parts by irradiating the observation light of prescribed wavelength to the arbitrary position of the optical parts in a laser beam take-out part, and counting the number of the rings of the interference fringes passing this position thereby detecting the change in the temp. of said position. CONSTITUTION:Prior to outputting of laser beam 12, the laser output 14 from a laser beam generator 13 for observation is irradiated to the position slightly spaced from the center of an optical part 11, and said position is fixed. If the laser beam 12 is outputted by driving a laser oscillating part 10 after this, interference fringes are generated by the convex lens effect of the optical part 11. The interference fringes are received by a photodetector 15, and are photoelectrically converted. When the count values of a counter circuit 16 exceeds prescribed number, an alarm signal is emitted from an alarm generator 17, and consequently, a laser power source part 18 stops operating and the laser oscillating part 10 stops outputting the laser beam 12. Thereby, the temp. rise of the optical part 11 is averted and its thermal failure is prevented. |
