| 摘要 |
PURPOSE:To prevent a false signal and a false information siganl from being generated by forming a light reflecting surfaces which is a half-reflecting surface and reflects light in a direction different from that of the fitting surface of a beam splitter on the fitting surface and reduce extremely the quantity of part of a beam which is reflected by the fitting surface and strikes on a photodetecting element. CONSTITUTION:Part of a laser beam which is incident on the beam splitter 4 from a laser diode 1 and reflected by the half-reflecting surface 4a toward the fitting surface 21a is reflected by the light reflecting surfaces 22a of a concave part 22 to enter the beam splitter 4 again from a surface A and exit from a surface C as stray light. At this time, the beam is reflected by the tapered reflecting surface 22a in a different direction from the incidence direction and the beam is refracted when striking on the surface A of the splitter 4 and exiting from the surface C, so the light exits from the splitter as stray light in a direction different from the optical path of a siganl detection part 10. Consequently, the quantity of the stray light incident on the photodetecting element 9 of a detection part 10 is made small enough not to exert influence upon the servo system. |
