| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that it is difficult to suppress the increase of optical system parts to arrange them simply because there is much restriction against a position for installing a detector for a monitor in a front monitoring system. SOLUTION: A cut surface for reflecting a light beam emitted from a laser beam source is formed on a prism which guides the light beam emitted from the laser beam source to an objective lens, and the detector for a front monitor is provided for receiving a light beam reflected by the cut surface. Thereby, an optical path to guide the light beam emitted from the laser beam source is formed by reflection on the cut surface in addition to the optical path to the objective lens, and a position for arranging the detector for a front monitor is shifted from the optical path to the objective lens. |
