| 摘要 |
PURPOSE:To relatively accurately execute focusing of laser beam by changing distance between a condenser lens and a high reflection metal plate while scanning along a slit having the same width as width of laser beam waist arranged to the high reflection metal plate and deciding the position where the intensity of reflecting returned beam is minimum to the focus. CONSTITUTION:The laser beam is made to scan onto the high reflection metal plate 11 in the arrow mark direction shown as the figure (a) to measure 3 the reflecting beam. Then, the laser beam comes to the above slit position and at the time when the intensity of the reflecting returned beam is rapidly reduced shown as the figure (b), the scanning direction is changed 90 deg. angle and the beam is made to scan along the slit shown as the figure (c). Together with this, the distance L between the condenser lens 7 and the metal plate 11 is continuously changed, and at the time of becoming L = focus length L of the lens 7, i.e., the position where the intensity of the reflecting returned beam is minimum is decided to the focus. Therefore, the focusing having much more accuracy than that of the ordinary method without any consumption of material for testing can be executed. |
