| 摘要 |
PURPOSE:To improve light condensing characteristics by a method wherein a magnifying mirror is composed of a concave or convex mirror whose surface facing a collimating mirror is coated with a non-reflective coating film and a partially reflective film provided on the non-reflective coating film at the center part of the concave or convex mirror. CONSTITUTION:Non-reflective coating films 5 are applied to both the inside and outside surfaces of a convex mirror 4 which also serves as a window mirror. Further, a partially reflective film 20 is provided on the non-reflective coating film 5 on the inside surface facing a collimating mirror 1 at the center part of the surface. A laser beam 7 reflected and magnified by the partially reflective film 20 is amplified by a laser medium 3 and, at the same time, collimated into a parallel beam by the collimating mirror 1 and taken outside through the convex mirror 4 as a laser beam 8. The laser beam 8 is composed of a part transmitted through the partially reflective film 20 and a part transmitted through the non-reflective coating film 5. As the part transmitted through the partially reflective film 20 has a partially transmitting property, the inside of the laser beam 8 is filled and the ratio, M value, of the outer diameter to the inner diameter of an annular beam corresponds to infinity. With this constitution, a high quality laser beam can be taken out without degrading an oscillation efficiency. |
