| 摘要 |
PURPOSE:To reduce a laser noise by using the superposition of a high frequency effectively by specifying the modulation frequency of a high frequency superposition circuit and the optical path length of a laser beam in an optical disk device having a separable optical system. CONSTITUTION:A movable optical system 16 is is moved in the radius direction of an optical disk 1, and a fixed optical system 17 is fixed on the extension of a moving line. Assuming the speed of light as C and the width of the effective recording range of the disk 1 as (l), the modulation frequency (f) of the high frequency superposition circuit is set less than C/4l, and the optical path length L of the laser beam from a laser beam element 5 which changes when the optical system 16 is moved is set so as to satisfy equation I. By constituting a device in such way, it is possible to include the variable range of the optical path length L within the range of an optical path where the superposition of the high frequency can function effectively. In such a way, the laser noise can be reduced by the superposition of the high frequency even in the optical disk device having the separable optical system. |
