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 technique that reduces the possibility that data will not be recorded due to a shortage of test areas. A test area, in which test writing for laser power control is performed, is set in each recording layer of an optical recording medium having a plurality of recording layers, and information indicating a position of the set test area is recorded on the optical recording medium. Furthermore, recorded information of an optical recording medium is reproduced, the optical recording medium including a plurality of recording layers and in which a test area, in which test writing for laser power control is performed, is set in each of the recording layers and information indicating a position of the set test area is recorded; and the information indicating the position of the test area is acquired.

Provided are a read head and methods for reading a multi-layered optical data storage medium comprising a transparent substrate having layers of voxels embedded therein. The read head comprises an imaging system for capturing images of groups of voxels, wherein the read head is configured to bring the imaging system into focus on variable depths in a multi-layered optical data storage medium; and an autofocus system for identifying depth positions of voxels in the multi-layered optical data storage medium by sampling an area in the optical data storage medium. The autofocus system comprises a light source for illuminating the area; and a detector for detecting light from the light source transmitted through the multi-layered optical data storage medium. A method of reading data from a multi-layered optical storage medium comprises capturing, using an imaging system, images of sectors in a first track. The multi-layered optical data storage medium and imaging system are held at fixed lateral positions during the capture of the images.

An optical disc including at least three layers of recording layers that each record information in an information track. The recording layer includes: an inner circumferential side region positioned on the inner circumferential side; a data region which is positioned to the outer circumferential side of the inner circumferential side region and records content information; and an outer circumferential side region positioned to the outer circumferential side of the data region. The content information is recorded in the data region of the three or more layers, and a point on an upper layer and a point on a lower layer one layer below the upper layer at which playback switches from content information of the upper layer being played back in an inner circumferential direction to content information of the lower layer, are set to be more to the outside than an innermost circumferential position of the data region.

A method of writing data to a transparent substrate comprises forming a first voxel by focusing a first laser pulse on a first location in a transparent substrate; and forming a second voxel by focusing a second laser pulse on a second location in the transparent substrate. The first laser pulse and the second laser pulse have different amplitudes, resulting in the first and second voxels having different strengths. Also provided are a system useful for implementing the method; an optical data storage medium obtainable by the method; and a method of reading data from the optical data storage medium.

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.

According to an optical disc, a track, where data is recorded in predetermined block units, is formed by wobbling at a spatial period in accordance with a radial position, and the track is divided into zones in a radial direction. Data is recorded in each of the zones at a predetermined line density based on a ratio n/m of the number of bits of a bit pattern of recording data to one wavelength of wobbling. The optical disc includes a first area having one of the zones, a second area having one of the zones different from the one of the zones in the first area, and a line density of data different from a line density of data in the first area, and a BCA where a zone format identifier specifying a zone table defining a boundary position of each of the zones and the ratio n/m is recorded.

A data readout device (114) for reading out data from at least one data carrier (112) having data modules (116) located at least two different depths within the at least one data carrier (112) is disclosed. The data readout device (114) comprises: at least one illumination source (122) for directing at least one light beam (124) onto the data carrier (112); -at least one detector (130) adapted for detecting at least one modified light beam modified by at least one of the data modules (116), the detector (130) having at least one optical sensor (132), wherein the optical sensor (132)has at least one sensor region (134), wherein the optical sensor (132)is designed to generate at least one sensor signal in a manner dependent on an illumination of the sensor region (134)by the modified light beam, wherein the sensor signal, given the same total power of the illumination,is dependent on a beam cross-section of the modified light beam in the sensor region (134); and -at least one evaluation device (136) adapted for evaluating the at least one sensor signal and for deriving data stored in the at least one data carrier (112) from the sensor signal. Further, a data storage system (110), a method for reading out data from at least one data carrier (112) and a use of an optical sensor (132) for reading out data are disclosed.

When recording is performed by focusing a short pulse laser on an inside of a transparent medium such as quartz glass, and forming a minute deformed region in which the refractive index is different from that of surroundings thereof, it is difficult to ensure a recording quality. Therefore, a recorded dot length in a depth direction is monitored 111 and a power of the laser light is adjusted based on the monitored recorded dot length, or a difference between a focus position where a region of the recorded dots appears brighter than the surroundings and a focus position where the region of the recorded dots appears darker than the surroundings is measured and the power of the laser light is adjusted based on the difference.

A method of writing data to a transparent substrate comprises forming a first voxel by focusing a first laser pulse on a first location in a transparent substrate; and forming a second voxel by focusing a second laser pulse on a second location in the transparent substrate. The first laser pulse and the second laser pulse have different amplitudes, resulting in the first and second voxels having different strengths. Also provided are a system useful for implementing the method; an optical data storage medium obtainable by the method; and a method of reading data from the optical data storage medium.