A reversible recording medium according to an embodiment of the present disclosure is a reversible recording medium that includes recording layers and heat-insulating layers that are alternately stacked, in which the recording layers each include a reversible heat-sensitive color developing composition and a first light-heat converting agent. In this reversible recording medium, the recording layers are different from each other in a developing color of their respective reversible heat-sensitive color developing compositions and are different from each other in an absorption wavelength of their respective first light-heat converting agents. This reversible recording medium further includes a heat-generating layer that includes a second light-heat converting agent having an absorption wavelength that is different from the absorption wavelength of the first light-heat converting agent included in each of the recording layers.

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.

System on chips (SoCs) based on a microprocessor or a neural processor (e.g., brain-inspired processor) electrically coupled with electronic memory devices and/or optically coupled with an optical memory device, along with embodiment(s) of a building block (an element) of the microprocessor/neural processor, the electronic memory device and the optical memory device are disclosed. It should be noted that a microprocessor can be replaced by a graphical processor.

The present disclosure is to provide a photopolymer composition including a polymer matrix or a precursor thereof having a specific chemical structure; a photoreactive monomer; and a photoinitiator. The present disclosure is also to provide a hologram recording medium, an optical element, and a holographic recording method using the photopolymer composition.

The present disclosure is to provide a photopolymer composition including a polymer matrix or a precursor thereof having a specific chemical structure; a photoreactive monomer; and a photoinitiator. The present disclosure is also to provide a hologram recording medium, an optical element, and a holographic recording method using the photopolymer composition.

An optical disc device capable of detecting a reference position of an optical disc in a rotating direction includes an optical disc rotation drive unit, an optical sensor, and a control circuit. The optical disc rotation drive unit rotates the optical disc provided with a rotation reference mark. The rotation reference mark is formed into a shape having a width changing in the radial direction of the optical disc. The optical sensor detects the rotation reference mark. The control circuit controls the optical disc rotation drive unit and the optical sensor, extracts a detection signal of the rotation reference mark as a pulse waveform from an output signal of the optical sensor with the optical disc being rotated, and specifies a rotation reference position of the optical disc in accordance with the pulse waveform.

An optical disc device capable of detecting a reference position of an optical disc in a rotating direction includes an optical disc rotation drive unit, an optical sensor, and a control circuit. The optical disc rotation drive unit rotates the optical disc provided with a rotation reference mark. The rotation reference mark is formed into a shape having a width changing in the radial direction of the optical disc. The optical sensor detects the rotation reference mark. The control circuit controls the optical disc rotation drive unit and the optical sensor, extracts a detection signal of the rotation reference mark as a pulse waveform from an output signal of the optical sensor with the optical disc being rotated, and specifies a rotation reference position of the optical disc in accordance with the pulse waveform.

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.

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.