| 摘要 |
PURPOSE:To obtain an optical head whose focusing servo and tracking servo do not disalign from each other by continuously varying the astigmatism of luminous flux made incident on an objective lens in switching between recording- reproduction mode and deletion mode. CONSTITUTION:To record a signal on a disc vapor-deposited a recording thin film, a laser beam modulated according to the recording signal is condensed to a small beam spot having about 1mum diameter and irradiated on a information recording plane 10a to satisfy the quick heating and cooling condition, and the signal is recorded. To reproduce the recorded signal, a continuous laser beam of about 1/10 of the output for recording is condensed to the beam spot likewise as in recording and irradiated on the plane 10a, and the quantity of reflected light beam is detected by adding the output signals of detectors 13 and 14. To delete the recorded signal, a continuous laser beam is condensed to a small elliptical beam spot having about 1mumX10mum diameter long in the advancing direction of the disc, and irradiated on the plane 10a to satisfy gradual heating and cooling condition, and the recorded signal is deleted. |
