| 摘要 |
PURPOSE:To perform a stable tracking, by eliminating the variance of the shape of irradiation of a condensed beam for a tracking sensor. CONSTITUTION:A reflective mirror 10 which reflects the reflected beam passing through an object lens 5 in the tracking direction at right angles is arranged between the object lens 5 and a beam splitter 3. The object lens 5 is displaced for focus control, and the object lens 5 and the reflective mirrror 10 are displaced for the tracking control. That is, in case of the tracking control, the reflective mirror 10 is displaced in the tracking directioj together with the object lens 5 changing the optical axis to make always optical axes of the object and a light condensed pattern on a tracking sensor S1 is alwyas kept constant. |
