| 摘要 |
1,265,241. Lasers. TURLABOR A.G., and PIERRES HOLDING S.A. 25 Feb., 1970 [27 Feb., 1969], No. 9030/70. Heading H1C. A laser comprises an optically pumped YAG rod 4 placed adjacent one of two planar resonator mirrors 5 and 6, the separation L of the mirrors exceeding the length l of the rod by a factor of at least ten and preferably by a factor of fifty to one hundred. The rod 4 is pumped by light from a flash tube 7 in an elliptical reflector 9, and the incident light is stated to cause the centre of the rod to become hotter than the outside so that in use the rod becomes distorted and acts as a lens. The length of the resonator and the use of planar mirrors minimizes the effect of this on the efficiency of the laser, and at operational temperatures the efficiency is stated to be an order of magnitude greater than that obtained with a conventional resonator using spherical mirrors. The output beam is well collimated, and the efficiency allows a relatively weak pumping source to be used, thus prolonging active life. The separation of the resonator mirrors, which is a few metres, is preferably one half of the focal distance of the lens formed by the rod at its operating temperature. The laser is intended for drilling holes of close tolerance, for example in watch jewels, and for this purpose a focusing lens system 2 with a removable telescope portion 17 is provided. The telescope controls the beam diameter, and is followed by divergent and convergent lenses 18 and 19. The distance of focus F from lens 19 is greater than the focal length f of this lens because of the divergent lens, and hence spluttering of the drilled material on to lens 19 is reduced. The power supply 11 for the flashlamp is controlled by a radiation detector 12 which receives a portion of the laser output, and also by the device which feeds the watch jewel or other workpiece to the drilling zone. The rod 4 may be placed adjacent mirror 6, in which case the flashlamp would be side by side with the rod. This is stated to give a more uniform energy distribution in the focal region F. |
