| 摘要 |
PROBLEM TO BE SOLVED: To enable one pair of carriages to share one fixed optical unit by selectively guiding a luminous flux from the fixed optical unit to either of two carriages. SOLUTION: A selecting mechanism selectively guiding a laser luminous flux from a fixed optical unit 4 to either of two carriages 3a, 3b has a movable prism 50 movable in up and down and this prism 50 is a right-angled isosceles triangle when it is seen from the side face and two planes orthogonally crossing with each other respectively become deflection planes 51, 52. Both planes 51, 52 are respectively inclined by 45 deg. with respect to an incident luminous flux from a galvanomirror 26. When this movable prism 50 is placed at the lower side, the incident luminous flux from the galvanomirror 26 is made incident on the deflection plane 51 of the upper side to be deflected to a vertically upper direction. On the other hand, when it is placed at the side of an upper side, the incident luminous flux is made incident on the deflection plane 52 of the lower side to be deflected to a vertically down direction. |
