A configuration for reducing a possibility of data recording or reproduction being unperformable due to a reading error of disc management information is realized. A data processing unit records management information corresponding to a first surface as main management information on the first surface which is a data recording surface on which data recording is performed and further records mirror management information having the same content as the main management information on a second surface different from the first surface. The management information is, for example, a temporary disc management structure (TDMS) including defect region information of one surface of a disc. When one piece of management information between the main management information and the mirror management information is successfully read, data recording or reproduction can be correctly performed.

Provided are media, systems and methods for optical data storage. A nanocomposite material for use as an optical data recording medium comprises nanoparticles embedded in a host matrix, wherein the host matrix comprises a material having a high structural stability, and the nanoparticles comprise optical functional components having a first physical or chemical state and a property of permanent transition to a second physical or chemical state upon exposure to corresponding optical radiation, whereby information may be recorded in the first and second physical or chemical states of the optical functional components over an extended time period.

The invention relates to a method for selecting compounds which can be used as additives in photopolymer formulations for producing light holographic media, and to photopolymer formulations which contain at least one softener which are selected according to the claimed method. The invention also relates to the use of photopolymer formulations for producing holographic media.

The present invention relates to an information storage medium and a method for long-term storage of information.

The present invention relates to an information storage medium and a method for long-term storage of information.

A nonlinear light absorption material includes a compound having a nonlinear light absorption property at a wavelength of 390 nm or more and 420 nm or less and represented by the formula (1) as a main component:

##STR00001##

in the formula (1), X is an oxygen atom.

A nonlinear light absorption material includes a compound having a nonlinear light absorption property at a wavelength of 390 nm or more and 420 nm or less and represented by the formula (1) as a main component:

##STR00001##

in the formula (1), X is an oxygen atom.

An optical information processing device writes and reads information on an information recording medium having recording layers. The optical information processing device includes: first and second light sources; a light condensing element that condenses light from the first and second light sources on the medium; a first photodetector that receives light reflected by the medium after being emitted from the first light source and generates a first focusing error signal; a second photodetector that receives light reflected by the medium after being emitted from the second light source and generates a second focusing error signal; and a focusing control circuit that controls the light condensing element by using the first focusing error signal in such a manner that the light from the second light source is condensed on each of the recording layers. The second focusing error signal is used to add a correction to the focusing control circuit.

An optical information processing device writes and reads information on an information recording medium having recording layers. The optical information processing device includes: first and second light sources; a light condensing element that condenses light from the first and second light sources on the medium; a first photodetector that receives light reflected by the medium after being emitted from the first light source and generates a first focusing error signal; a second photodetector that receives light reflected by the medium after being emitted from the second light source and generates a second focusing error signal; and a focusing control circuit that controls the light condensing element by using the first focusing error signal in such a manner that the light from the second light source is condensed on each of the recording layers. The second focusing error signal is used to add a correction to the focusing control circuit.

An information recording medium according to the present disclosure is an information recording medium of a write-once-read-many type and records or reproduces information when irradiated with laser light. The information recording medium includes: a substrate; a plurality of information layers at least one information layer of which includes a recording film that is a WO-based recording film comprising at least tungsten (W) and oxygen (O); and a dielectric film A in contact with the WO-based recording film, the dielectric film A comprising at least 30 mol % tin oxide.