Patent ID: 6906986

Claim:
A vibration quantity measuring apparatus for a disc recording and reproducing system having a focus and tracking loop including a controller which controls focus and tracking of a disc received in the disc recording and reproducing system and an actuator, wherein a vibration occurs in the focus and tracking loop in response to rotating of the disc, the apparatus comprising: an error gain adjusting unit which adjusts an amplitude of a focus and tracking error, which occurs in response to the rotating of the disc, and maintains the amplitude constant; a loop gain adjusting unit which compensates for a gain difference the actuator, wherein the loop gain adjusting unit compares a closed loop phase of the focus and tracking loop and a reference closed loop phase, and maintains a gain of the focus and tracking loop constant; and a measuring unit which calculates and outputs a vibration quantity, using the focus and tracking error adjusted by the error gain adjusting unit and the focus and tracking loop adjusted by the loop gain adjusting unit, and an output of the controller which controls the focus and tracking of the disc.