A set of first signal light and reference light with a phase difference of almost 0 degree, a set of second signal light and reference light with a phase difference of almost 180 degrees, a set of third signal light and reference light with a phase difference of almost 90 degrees, and a set of fourth signal light and reference light with a phase difference of almost 270 degrees are generated. A first differential signal as a difference between a first light-receiving signal obtained by a first light-receiving element and a second light-receiving signal obtained by a second light-receiving element is calculated, and a second differential signal as a difference between a third light-receiving signal obtained by a third light-receiving element and a fourth light-receiving signal obtained by a fourth light-receiving element is calculated. The first differential signal and the second differential signal are supplied to respective FIR filters. An equalization error is formed from output signals from the FIR filters. Tap coefficients for the FIR filters are controlled to minimize the equalization error.

An optical recording medium includes a plurality of information signal layers. The plurality of information signal layers include a recording layer having a first surface that faces a light irradiation surface and a second surface on the side opposite to the first surface, a first dielectric layer that is provided on the side of the first surface, and a second dielectric layer that is provided on the side of the second surface. The second dielectric layer provided in the information signal layer positioned on the innermost side when viewed from the light irradiation surface contains indium oxide and tin oxide. The recording layer provided in the information signal layer positioned on the innermost side when viewed from the light irradiation surface contains an oxide of a metal MA, an oxide of a metal MB, an oxide of a metal MD, and an oxide of a metal ME, the metal MA is at least one selected from the group consisting of Mn and Ni, the metal MB is at least one selected from the group consisting of W, Mo, Zr and Ta, the metal MD is at least one selected from the group consisting of Cu and Ag, the metal ME is Nb, the contents of the metal MA, the metal MB and the metal ME satisfy the relationship of 0.30≤a.sub.1/(b.sub.1+e.sub.1)≤0.41 (where, a.sub.1: atomic ratio [atomic %] of the metal MA with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME, b.sub.1: atomic ratio [atomic %] of the metal MB with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME, and e.sub.1: atomic ratio [atomic %] of the metal ME with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME), and the atomic ratio e.sub.1 of the metal ME with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME is 5 atomic % or more and 18 atomic % or less.

A configuration for preventing a recording error when a data recording process is performed on both lands and grooves of an optical disc is realized. An information processing device includes a data processing unit configured to control a data recording process on both lands and grooves of an optical disc. The data processing unit performs a process of detecting or matching positions at which data recording states of grooves or lands on both sides adjacent to a data recording target land or groove match when data are recorded on the lands or the grooves. The data processing unit performs, for example, a dummy data recording process or a skipping process as the process of matching the data recording states of the grooves or the lands on both sides adjacent to the data recording target land or groove.

A write-once type information recording medium according to one aspect of the present disclosure includes at least one recording layer. In the information recording medium, the at least one recording layer has a spiral shape in which a land track and a groove track are alternately arranged as a recording track, the recording track is divided into blocks each of which being minimum unit in which recording is performed, and the information recording medium includes a management information area where management information is recorded and a user data area where user data is recorded. Each of the management information areas of both the land track and the groove track on each recording layer of the at least one recording layer is disposed at a same distance from the center of the information recording medium.

A track of an optical disk is formed by wobbling and divided into zones, a clock ratio of a recording clock to a wobble clock is preset for each zone, a wobble signal is detected from the optical disk, the wobble clock is generated from the wobble signal, a present position is identified by reproducing ADIP indicating a position of the track from the wobble signal and the wobble clock, the recording clock is generated with respect to the wobble clock, a data address present position is identified from the present position, a start end position of the ADIP in a recording target zone, a start end position of the data address in the recording target zone, and the clock ratio, a recording start position is identified based on the data address present position; and the data is recorded from the recording start position of the recording target zone.

An apparatus for reading out information from an information carrier includes a reading unit for reading out user information and access information from the information carrier. The user information are stored in a first region of the information carrier and the access information are stored in a second region of the information carrier. The apparatus further includes an access controller for providing access to the user information in dependence on the access information. The access information are stored in a first portion of the second region, and the dummy information are stored in a second portion of the second region according to a similar format as used for storing the access information.

A reproduction apparatus dividing a cross section of superposed light into a plurality of regions in a tangential and/or radial direction includes: an optical system configured to generate each of a first set of signal light and reference light having a phase difference of approximately 0°, a second set of signal light and reference light having a phase difference of approximately 180°, a third set of signal light and reference light having a phase difference of approximately 90°, and a fourth set of signal light and reference light having a phase difference of approximately 270°, using a plurality of superposed light beams corresponding to the divided regions; an optical receiver configured to output signals corresponding to the sets of the signal light and the reference light; and a circuit configured to compute signals as differences between the signals, and obtain a reproduction signal by computation from the computed signals.

A reproduction apparatus dividing a cross section of superposed light into a plurality of regions in a tangential and/or radial direction includes: an optical system configured to generate each of a first set of signal light and reference light having a phase difference of approximately 0°, a second set of signal light and reference light having a phase difference of approximately 180°, a third set of signal light and reference light having a phase difference of approximately 90°, and a fourth set of signal light and reference light having a phase difference of approximately 270°, using a plurality of superposed light beams corresponding to the divided regions; an optical receiver configured to output signals corresponding to the sets of the signal light and the reference light; and a circuit configured to compute signals as differences between the signals, and obtain a reproduction signal by computation from the computed signals.

An optical disk reproducing device includes a division element that divides a reflected light reflected and diffracted by an optical disk into a light flux in a central region and light fluxes in end regions; a photodetector that has a central light receiver that receives the light flux in the central region and at least two end light receivers that receive the light fluxes in the end regions, and outputs a light amount signal corresponding to a light amount of each of the received light fluxes; a non-linear processor that receives each of the light amount signals from the central light receiver and the end light receivers, and outputs linear signals and non-linear signals obtained by processing the light amount signals by linear and non-linear arithmetic operations; an equalization processor that receives the linear signals and the non-linear signals and outputs signals each amplified with a predetermined gain; an adder that adds the amplified signals and outputs an equalization signal; a reproduction signal processor that processes the equalization signal and outputs a reproduction signal and an equalization error signal; and a gain controller that receives the equalization error signal and controls an amplification gain of the non-linear signals.

An optical recording medium includes a plurality of information signal layers. The plurality of information signal layers include a recording layer having a first surface that faces a light irradiation surface and a second surface on the side opposite to the first surface, a first dielectric layer that is provided on the side of the first surface, and a second dielectric layer that is provided on the side of the second surface. The second dielectric layer provided in the information signal layer positioned on the innermost side when viewed from the light irradiation surface contains indium oxide and tin oxide. The recording layer provided in the information signal layer positioned on the innermost side when viewed from the light irradiation surface contains an oxide of a metal MA, an oxide of a metal MB, an oxide of a metal MD, and an oxide of a metal ME, the metal MA is at least one selected from the group consisting of Mn and Ni, the metal MB is at least one selected from the group consisting of W, Mo, Zr and Ta, the metal MD is at least one selected from the group consisting of Cu and Ag, the metal ME is Nb, the contents of the metal MA, the metal MB and the metal ME satisfy the relationship of 0.30≤a.sub.1/(b.sub.1+e.sub.1)≤0.41 (where, a.sub.1: atomic ratio [atomic %] of the metal MA with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME, b.sub.1: atomic ratio [atomic %] of the metal MB with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME, and e.sub.1: atomic ratio [atomic %] of the metal ME with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME), and the atomic ratio e.sub.1 of the metal ME with respect to a total amount of the metal MA, the metal MB, the metal MD and the metal ME is 5 atomic % or more and 18 atomic % or less.