| 摘要 |
PURPOSE:To make a decision on whether there is a video disc installed or not by detecting reflected light flux of large diameter from the video disc. CONSTITUTION:When focus lens 7 servo-controlled to focus irradiation laser light flux on video disc 8 is set at an initial position, disc 8 is irradiated with light flux of large diameter. The light flux of large diameter reflected by disc 8 through this irradiation passed through the opposite light passage to the irradiation light passage and is detected by photo detector 14. In this constitution, a decision on whether the video disc is set or not is made depending upon the generation of a detection signal generated when detector 14 detects the light after the irradiation starts. The output signal of this element is used to prevent the video disc and focus lens from coming in contact. |
