The purpose of the present invention is to provide a hologram reproducing apparatus and a hologram reproducing method, which are suitable for reproducing hologram. The purpose can be achieved by means of a hologram reproducing apparatus, which reproduces information signals by irradiating an optical information recording medium with reference light, and a hologram reproducing method for the hologram reproducing apparatus. The hologram reproducing apparatus is characterized in being provided with: a polarization conversion section, which converts polarization of diffracted light that is generated when the optical information recording medium is irradiated with the reference light; a light receiving section, which receives the diffracted light having the polarization thereof converted by means of the polarization conversion section; and a servo signal generating circuit section, which generates signals for moving the optical information recording medium or the polarization conversion section using the diffracted light received by means of the light receiving section.

In an optical disc apparatus for reproducing information recorded on a track of an optical disc, an optical head irradiates a light beam onto the track, detects a reflected light reflected by the track, and generates a reproduction signal based on the reflected light. A decoder circuit decodes the reproduction signal, and generates a decoded signal including information recorded on the track. A correlation detector circuit calculates a cross-correlation value between the reproduction signal and the decoded signal. A servo circuit detects a deviation amount of an irradiation position of the light beam onto the track, from the reproduction signal, and controls the irradiation position of the optical head based on the cross-correlation value and the deviation amount.

The first, third, fourth, and seventh photosensors are disposed on one side with respect to the centerline, and the second, fifth, sixth, and eighth photosensors are disposed on another side with respect to the centerline. The first and seventh photosensors are positioned between the third and fourth photosensors in the direction parallel to the centerline. The second and eighth photosensors are positioned between the fifth and sixth photosensors in the direction parallel to the centerline. The first photosensor receives overlapped light of the 0th-order light with the +1st-order diffracted light, the second photosensor receives overlapped light of the 0th-order light with the −1st-order diffracted light, each of the third to sixth photosensors receives the 0th-order light, and does not receive the +1st-order diffracted light and the −1st-order diffracted light, and each of the seventh and eighth photosensors receives at least the 0th-order light.

A method of recovering data from one or more failed data sectors includes estimating a reader offset position from a first or a second read attempt of the one or more failed data sectors at a current set of channel parameters and basing the estimated reader offset position on, at least in part, a position error signal generated during the first or second read attempt. At least one read is performed on the one or more failed data sectors at the estimated reader offset position to obtain one or more samples. The one or more samples are processed to obtain a processed sample. Iterative outer code recovery is performed on the processed sample.

Operations include compensating for a Tracking Error Signal (TES) offset in an optical tape drive. The tracking error offset compensation system detects a control signal for controlling movement of an optical head across a surface of a tape. The tracking error offset compensation system computes an estimated movement of the optical head, based on the initial control signal. The tracking error offset compensation system determines an estimated TES offset, based on the estimated movement of the optical head. The tracking error offset compensation system uses the estimated TES offset to correct a TES. The tracking error offset compensation system transmits the corrected TES, for controlling additional movement of the optical head.

Operations include compensating for a Tracking Error Signal (TES) offset in an optical tape drive. The tracking error offset compensation system detects a control signal for controlling movement of an optical head across a surface of a tape. The tracking error offset compensation system computes an estimated movement of the optical head, based on the initial control signal. The tracking error offset compensation system determines an estimated TES offset, based on the estimated movement of the optical head. The tracking error offset compensation system uses the estimated TES offset to correct a TES. The tracking error offset compensation system transmits the corrected TES, for controlling additional movement of the optical head.

Techniques for performing precise tracking in optical tapes are provided. The techniques include providing and using a servo pattern on an optical tape. The servo pattern includes a first set of parallel physical grooves slanted in a first direction across a width of the optical tape and a second set of parallel physical grooves slanted in a second direction that is different from the first direction across the width of the optical tape. Subsets of the first set of parallel physical grooves alternate with subsets of the second set of parallel physical grooves along a length of the optical tape. Two subsets of the first set of parallel physical grooves separated by one subset of the second set of parallel physical grooves form a servo frame in the optical tape.

Operations include compensating for a Tracking Error Signal (TES) offset in an optical tape drive. The tracking error offset compensation system detects a control signal for controlling movement of an optical head across a surface of a tape. The tracking error offset compensation system computes an estimated movement of the optical head, based on the initial control signal. The tracking error offset compensation system determines an estimated TES offset, based on the estimated movement of the optical head. The tracking error offset compensation system uses the estimated TES offset to correct a TES. The tracking error offset compensation system transmits the corrected TES, for controlling additional movement of the optical head.

The first, third, fourth, and seventh photosensors are disposed on one side with respect to the centerline, and the second, fifth, sixth, and eighth photosensors are disposed on another side with respect to the centerline. The first and seventh photosensors are positioned between the third and fourth photosensors in the direction parallel to the centerline. The second and eighth photosensors are positioned between the fifth and sixth photosensors in the direction parallel to the centerline. The first photosensor receives overlapped light of the 0th-order light with the +1st-order diffracted light, the second photosensor receives overlapped light of the 0th-order light with the 1st-order diffracted light, each of the third to sixth photosensors receives the 0th-order light, and does not receive the +1st-order diffracted light and the 1st-order diffracted light, and each of the seventh and eighth photosensors receives at least the 0th-order light.

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.