Abstract: According to one embodiment, a magnetic disk includes a plurality of tracks each having a plurality of servo frames with servo burst data and repeatable runout correction data written thereto. The repeatable runout correction data includes a pattern repeated at a predetermined period and is written so that beginning of write is delayed by a time corresponding to a correction amount with respect to a base point corresponding to a synchronization timing position in the servo frame. A detector detects a phase delay amount corresponding to a time elapsed until the repeated pattern is read from the servo frame by a magnetic head, with respect to the synchronization timing position.

Abstract: A read signal evaluating means for ensuring compatibility in an optical phase multilevel recording and reading system is provided. In addition, a decoding means not large in circuit scale is provided. An optical phase is modulated based on user data, and phase information thus obtained is recorded in a recording medium. Then, the phase information recorded in the recording medium is optically read, and is converted into an electric signal. The signal is subjected to adaptive equalization and to partial response most-likely decoding. A shift in a time axis direction from a target wave of a predetermined pattern is detected from the read phase information and a statistical average is calculated. Meanwhile, a value of the phase read from the predetermined pattern is extracted from the read phase information and a statistical average is calculated.

Abstract: According to one embodiment, a disk storage device includes: a disk on which a servo pattern is recorded; a head; a driver; a signal generator; a demodulator; and a controller. Position signals for detecting an offset position from a center of a track are recorded in a recording area of a servo pattern. The signal generator generates a first timing signal indicating a timing for reading the position signals. When the controller performs a seek operation for moving the head to a target track, the signal generator generates a second timing signal. The period of the second timing signal for reading each of the position signals is made shorter than that of the first timing signal. A center time of the period of the second timing signal is shifted closer to a demodulation center time corresponding to a center of the recording area than that of the first timing signal.

Abstract: A synchronization detecting circuit detects a synchronous signal from a reproduced signal of a recording medium in which a random shift method is employed. A window generator in the synchronization detecting circuit generates a third window having as a central phase one predicted phase in a second predicted coordinate that is obtained by replicating a first predicted coordinate indicating a predicted phase of each synchronous signal that repeatedly appears in the reproduced signal and having a phase width equivalent to twice a random shift width when the synchronous signal is not detected using a first window after the synchronous signal is detected using a second window by a synchronization detector.

Abstract: An optical disc includes a reflective film formed on concave and convex marks after the concave and convex marks are synchronized with the integral multiple of a channel bit length and formed in accordance with modulated main information. Thereafter, continuous or intermittent laser light synchronized with the integral multiple of the channel bit length is irradiated at intervals longer than the longest one of the concave and convex marks in accordance with a spiral track formed in a circumferential direction of the concave and convex marks, whereby an optical characteristic of the reflective film is changed to form a recordable mark and sub-information necessary to reproduce the main information is recorded in a superimposition manner.

Abstract: Servo patterns for patterned media. The servo pattern includes specification of cylinder/track ID with and without a Gray code. The servo pattern space is minimized by the optimum usage of the islands. This is achieved by island allocation rules to take advantage of non-magnetic island. The island allocation also provides for easier lift-off. Logic is used to encode and decode the Gray code. Further, the Gray code is designed to stabilize the magnetic island/non-magnetic island ratio to allow for easier manufacture.