| 摘要 |
<p>A signal processor (6) receives the pick-up (5) signal and reproduces an RF signal output (7). An objective lens (3) is moved along the optical axis, controlled by a focus servo (8) and drive (9). In order to discriminate different types of optical disks and to vary the gain of the servo control accordingly, a discriminating circuit is provided, which compares the signal level of the reflected light with two predetermined reference levels (Vref1,Vref2). In case of a reproduction-only disk, which has high reflectivity (90 per cent), the signal level is higher than both reference levels, whilst in case of a recording disk with lower reflectivity (10-20 per cent), the signal level becomes between the two reference levels.</p> |
