| 摘要 |
PROBLEM TO BE SOLVED: To easily change a beam diameter or focal spot size without changing beam collimation or a focal surface by interposing a third lens element between two lens elements spaced apart and relatively moving two lens elements and the third lens element. SOLUTION: An optical compensating zoom unit is provided with a pair of the same type moving lenses (a). The pair of lenses (a) are integrally combined so as to move by the same distance through a zooming range while keeping a mutual distance constant. One lens (b) of a second type is interposed between these moving lenses (a). Three positions where an image surface coincides with a reference surface relative to these three lens units (a correctly focused position) exist within the range of zooming. An output beam from a laser means is converted into a focused beam by the optical system. The optical system is positioned within an optical path locating in front of an optical fiber means. The laser system is further provided with a focusing optical element. |
