Patent ID: 6731574
Filing Date: 2004-05-04
Classification: G11B

Abstract:
A focus servo controlling apparatus for performing a focus servo control by changing a condition of a focus servo loop from an open condition to a close condition in correspondence with a level of a reflection light signal, which is obtained as a reflection light of a light beam reflected from an information record medium is detected by a light receiving element, said apparatus comprising:a disturbance level detecting device for detecting a level of a disturbance light signal, which is obtained as a disturbance light other than the reflection light is received by said light receiving element; and a controlling device for setting a level, which is larger than the level of the disturbance light signal detected by said disturbance level detecting device, as a threshold level and for changing the condition of the focus servo loop from the open condition to the close condition on the basis of a timing when the level of the reflection light signal becomes equal to or larger than the set threshold level.