An information recording and playback device includes a recording and playback unit, and a controller. The controller divides a recording area of an optical disk into a first recording area which is at an inner circumference side, and a second recording area which is at an outer circumference side. The controller controls the recording and playback unit such that the unit records or plays back data in the first recording area at a first speed, and records or plays back data in the second recording area at a second speed slower than the first speed. The predetermined radius is set to a boundary between an area in which a control residual exceeds a predetermined reference value when servo control related to focusing and tracking is performed on the recording area of the optical disk, and an area in which the control residual does not exceed the predetermined reference value.

A method for providing tracking error signals in an optical data storage system includes a step of receiving a wobble signal having a first frequency from the wobble detection system. The wobble detection system includes an optical pick up unit that detects positions of the head relative to lands and grooves. Characteristically, the wobble signal is amplitude modulated for positions intermediate between the land and the groove. The method further includes a step of receiving a primary tracking error signal from the wobble detection system. The wobble signal is multiplied with a synchronous signal to about a product signal. The product signal is positive for a first direction of motion and negative for a second direction of motion that is opposite that of the first direction. The product signal is integrated to obtain a quadrature track error signal.

[Object] To prevent the occurrence of stuck without increasing the number of components and also to restore thread engagement of a rack with a lead screw to a normal condition. [Solution] Provided is an optical pickup including: a light source; an objective lens; an optical element; and an optical element driving device. The optical element driving device includes a lead screw having a threaded engagement portion with a thread groove formed in the threaded engagement portion, a drive unit configured to allow the lead screw to rotate, a thrust bearing configured to support an end portion of the lead screw on a side opposite to the drive unit in an axial direction of the lead screw, and a rack having a plurality of first tooth portions provided spaced apart in the axial direction to be threadably engaged with the threaded engagement portion and a second tooth portion provided closer to the thrust bearing in the axial direction than the first tooth portion to be threadably engaged with the threaded engagement portion, the first tooth portion and the second tooth portion being positioned on opposite sides across the lead screw, the rack being moved in the axial direction with a rotation of the lead screw. The lead screw includes a non-threaded engagement portion formed at the end portion of the lead screw on the thrust bearing side, the non-threaded engagement portion having no thread groove.

A hologram recording and playback device is provided with: a medium rotation unit which rotates a hologram recording medium around a predetermined rotational axis; a movement unit which is capable of moving the position of the medium rotation unit within a plane that is perpendicular to the rotational axis; an orthogonal incident angle modification unit which is capable of modifying an orthogonal incident angle; a medium rotation control unit which controls the medium rotation unit so as to rotate the hologram recording medium; an eccentricity compensation unit which performs positioning control of the movement unit; an orthogonal incident angle control unit which controls the orthogonal incident angle modification unit; and an orthogonal incident angle calculation unit which calculates the orthogonal incident angle.