Patent ID: 6285634
Filing Date: 2001-09-04
Classification: G11B

Abstract:
A bias voltage controlling apparatus for controlling a bias voltage for a focus servo control to control a position of a focal point of a light beam, which is irradiated onto an information record surface of an information record medium, in a direction perpendicular to the information record surface, said bias voltage controlling apparatus comprising:a distinguishing device for distinguishing a type of said information record medium; anda controlling device for optimally controlling the bias voltage on the basis of the type of said information record medium distinguished by said distinguishing device, wherein said controlling device controls the bias voltage so as to reduce a change of a reflection light signal, which is generated in correspondence with a reflection light of the light beam reflected from the information record surface, on a time axis on the basis of the type of said information record medium distinguished by said distinguishing device, andwherein said controlling device comprises:a first controlling device for controlling the bias voltage so as to maximize a level of the reflection light signal; anda second controlling device for controlling the bias voltage so as to reduce the change of the reflection light signal on the time axis, on the basis of the type of said information record medium distinguished by said distinguishing device, after the level of the reflection light signal is maximized by said first controlling device.