| 摘要 |
PURPOSE:To prevent stray light, which is caused by reflection on a facing surface and reflection from a monitor optical detector, from being incident to a signal optical detector by inclining the surface, which faces to the monitor optical detector of a beam splitter, to the optical axis of an optical beam which advances from a light source to an optical disk surface. CONSTITUTION:A beam splitter 20 is formed with inclining the angle of an upper surface, at least, by theta to the optical axis of a beam 3. By forming the beam splitter in such a way, a reflected light (stray light 11a) on such an upper surface 12a is reflected in a direction which is inclined by 2theta to the optical axis of the stray light in the case of not-inclination. A reflected light 4 is refracted on the upper surface 12a, goes to be a beam 4a and incident to a monitor optical detector 13. Then, one part of the reflected light is reflected on the surface of the monitor optical detector, goes to be a stray light 14a and advances. This stray light 14a and the stray light 11a are separated from an original signal light 9 in position. Then, a signal detector 10 to be arranged on a signal optical axis can photo-detect only an original effective signal wholly without receiving the influence of the stray lights 11a and 14a. |
