In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

Provided is a reproducing apparatus including: a reproduction signal generating circuit that calculates a first difference signal which is a difference between a first light receiving signal obtained by the first light receiving element and a second light receiving signal obtained by the second light receiving element, and a second difference signal which is a difference between a third light receiving signal obtained by the third light receiving element and a fourth light receiving signal obtained by the fourth light receiving element, and uses the first difference signal, the second difference signal, a phase difference between a crosstalk component and an average phase of the signal light beam, and an optical path length difference between the signal light beam and the reference light beam to obtain a reproduction signal; and a phase extraction circuit that obtains a successive change amount and updates with a successive variation.

Provided is a reproducing apparatus including: a reproduction signal generating circuit that calculates a first difference signal which is a difference between a first light receiving signal obtained by the first light receiving element and a second light receiving signal obtained by the second light receiving element, and a second difference signal which is a difference between a third light receiving signal obtained by the third light receiving element and a fourth light receiving signal obtained by the fourth light receiving element, and uses the first difference signal, the second difference signal, a phase difference between a crosstalk component and an average phase of the signal light beam, and an optical path length difference between the signal light beam and the reference light beam to obtain a reproduction signal; and a phase extraction circuit that obtains a successive change amount and updates with a successive variation.

An optical path correction subassembly, an optical detection assembly, and an optical detection system are provided. The optical path correction subassembly can be optionally configured to be applied to a light detector. The optical path correction subassembly includes a holder structure and an optical path correction structure carried by the holder structure, and the optical path correction structure has a light beam guiding surface arranged as a reverse inclination inclined relative to a vertical line. The light beam guiding surface of the optical path correction structure can be configured to effectively or accurately guide a predetermined light beam to a light receiving surface of the light detector so as to facilitate collection of the predetermined light beam. The light beam guiding surface of the optical path correction structure can be arranged at an acute angle relative to the light receiving surface of the light detector.

An optical path correction subassembly, an optical detection assembly, and an optical detection system are provided. The optical path correction subassembly can be optionally configured to be applied to a light detector. The optical path correction subassembly includes a holder structure and an optical path correction structure carried by the holder structure, and the optical path correction structure has a light beam guiding surface arranged as a reverse inclination inclined relative to a vertical line. The light beam guiding surface of the optical path correction structure can be configured to effectively or accurately guide a predetermined light beam to a light receiving surface of the light detector so as to facilitate collection of the predetermined light beam. The light beam guiding surface of the optical path correction structure can be arranged at an acute angle relative to the light receiving surface of the light detector.

The invention makes it possible to perform highly integrated recording of information and read out the information in a universal method while maintaining long-term durability. Digital data (D) to be stored is divided by a prescribed bit length u to create a plurality of unit data (U1 to U4). The bits constituting the unit data (U1) are arranged in a two-dimensional matrix to create a unit bit matrix (B(U1)), which is converted to a geometrical pattern to thereby create a unit bit graphic pattern (P(U1)). Further, alignment marks (Q) are arranged at four corners to create a unit recording graphic pattern (R(U1)). A drawing pattern (P(E)) is created as an assembly of the unit recording graphic patterns (R(U1) to R(U4)), and is provided to an electron beam lithography system as drawing data (E) whereby a pattern is drawn in a resist layer on a glass substrate. The resist layer is developed and the glass substrate is etched, and thus the digital data (D) is recorded on the substrate as a physically structured pattern.

A method of performing a write operation in a holographic data storage system, in which schedule schedules at least one write operation across multiple non-contiguous write intervals, the write operation pertaining to a set of data to be stored in a region of a holographic recording medium. In each of the non-contiguous write intervals, the region of the holographic recording medium is exposed to an interference pattern caused by interference between a reference beam and an input beam carrying the set of data. The multiple non-contiguous write intervals have a total aggregate duration of sufficient length to cause a persistent state change in the exposed region, such that the set of data is recoverable from that region by the end of a final write interval of the multiple non-contiguous write intervals.

A method of performing a write operation in a holographic data storage system, in which schedule schedules at least one write operation across multiple non-contiguous write intervals, the write operation pertaining to a set of data to be stored in a region of a holographic recording medium. In each of the non-contiguous write intervals, the region of the holographic recording medium is exposed to an interference pattern caused by interference between a reference beam and an input beam carrying the set of data. The multiple non-contiguous write intervals have a total aggregate duration of sufficient length to cause a persistent state change in the exposed region, such that the set of data is recoverable from that region by the end of a final write interval of the multiple non-contiguous write intervals.

Provided is a reproducing apparatus including: a reproduction signal generating circuit that calculates a first difference signal which is a difference between a first light receiving signal obtained by the first light receiving element and a second light receiving signal obtained by the second light receiving element, and a second difference signal which is a difference between a third light receiving signal obtained by the third light receiving element and a fourth light receiving signal obtained by the fourth light receiving element, and uses the first difference signal, the second difference signal, a phase difference between a crosstalk component and an average phase of the signal light beam, and an optical path length difference between the signal light beam and the reference light beam to obtain a reproduction signal; and a phase extraction circuit that obtains a successive change amount and updates with a successive variation.