According to a positioning method for a hologram in a disk-type holographic storage medium, a guide groove is formed in advance in the disk-type storage medium and is scribed with a positioning marker that includes index information, position information and crossing angle information. The positions of a positioning laser beam and a recording/reproducing laser beam are applied to the same medium position. When an optical head accesses a recording/reading position at a high speed, the shift multiplex recording/reading is performed starting from a marker position. A servo system controls the laser beams to move along the guide groove and ensures that a focused beam is focused on the medium. According to the method, the position and angular information can be quickly positioned in process of performing cross-shift multiplex recording/reading, the recording/reading speed of the system is improved, and random access is achieved.

The present invention relates to a holographic storage device and method for simultaneously recording and reading on two sides, and pertains to the technical field of optical holographic storage. The device and method disclosed in the present invention use a characteristic that orthogonal light would not interfere with each other and a Bragg selectivity characteristic for holographic storage, and use two optical heads to constitute two interference fields orthogonal in polarization directions on two sides of a same position of a holographic storage medium, so as to perform two-path simultaneous recording and reading on a hologram. The device and method provided in the present invention implement two-path parallel recording and reading of holographic storage, and combine shift multiplexing and circumferential rotation multiplexing, thereby improving the speed of an information data recording and reading process while increasing a capacity of the holographic storage.

The present invention discloses a reflective holographic storage method and device, in which a reflection layer is plated on a back side of a holographic storage medium, and a new reference light is formed by utilizing the reflection layer, so that a phase conjugate reproduction light of a hologram is obtained. According to the invention, a recording device and a reading device can be provided on the same side of a medium, thereby obtaining a more compact system, reducing design difficulty, improving system stability, and improving the SNR (signal-noise ratio) of reproduction light by the interference between reproduction light and a conjugate reproduction light.

A method for reading and writing with holographic system includes the following operations: (a) providing a reference light and a signal light; (b) transferring the reference light and the signal light to an optical recording medium, for recording an interference grating; (c) changing the reference light and the signal light and repeating the operations (a) to (b) until M interference gratings are recorded on the optical recording medium; (d) providing a reading light to the optical recording medium, for reading the M interference gratings at the same time to generate an interference result, wherein the interference result is a result that diffraction signals of the M interference gratings interfere to each other; and (e) changing the reading light and repeating the operation (d), for obtaining N interference results. A holographic storage system is also disclosed herein.

A holographic multiplexed recording method for increasing storage capacity is disclosed. In a holographic recording and reproducing device, the moving direction of a storage medium is not coplanar with the plane where the optical axes of signal light and reference light are located, or the relative moving direction of the storage medium and the signal light or the reference light is not coplanar with the plane where the optical axes of the signal light and the reference light are located. Through the method, a certain angle exists between the grating vector direction and the moving direction or the relative moving direction, so that the phenomenon that the grating vector directions are the same does not occur when the medium is subjected to multiplexed recording after being rotated or flipped. Not only is multiplexing number increased, but also crosstalk caused by the same grating vector direction is prevented.

The present invention relates to a holographic data storage device with a single-arm structure, and belongs to the technical field of optical holographic storage. According to the device disclosed in the present invention, a part of a reference arm and a part of a signal arm are integrated together to form a single-arm structure, which can not only reduce the number of optical and mechanical elements, but also reduce the system volume and cost without degrading performance. In addition, a signal beam and a reference beam share the same relay lens, so that the impact of environmental interference on the two beams is equal, and the stability of the entire system is improved.

The present invention relates to the technical field of holographic multiplexing storage, and in particular, to a multiplexing method for increasing storage capacity in a disc-type holographic storage medium. According to the method disclosed by the present invention, holograms with different grating vector directions can be overwritten and recorded in the same storage medium according to Bragg selection characteristics of volume holographic records, and the obtained holograms do not affect each other. According to the method disclosed by the present invention, on the premise of ensuring low crosstalk between data pages, the multiplexing number of shift multiplexing storage is increased by using a cross-shift multiplexing method, and the storage density is improved.

An optical encoder is provided. The encoder includes an optical disc mounted on a shaft, the optical disc containing pit and land markings; an optical pickup unit for an optical disc that receives light from the optical disc and supplies as an output an electrical signal representative of the received light, comprising: a reading head objective lens, and dynamic steering actuators that control the focus and tracking of the reading head objective lens; a processor that receives as an input the electrical signal from the optical pickup unit and reports motion of the substrate based on the received at least one electrical signal.

The present disclosure is to provide a photopolymer composition including a polymer matrix or a precursor thereof including a reaction product of a reactive isocyanate compound having a hydrogen bonding functional group capable of forming multiple hydrogen bonds and at least one isocyanate group, and a polyol having at least two hydroxyl groups; a photoreactive monomer; and a photoinitiator, a hologram recording medium produced from the photopolymer composition, an optical element including the photopolymer composition and a holographic recording method using the photopolymer composition.

An improved optical encoder uses an optical pick-up unit that provides for degrees of freedom in the tracking and focus axes that are unavailable in conventional optical encoders thereby improving the encoders' performance. In an embodiment the encoder employs an optical disc marked with pits and lands which may be arranged in a spiral pattern. The optical disc is mounted on the shaft whose motion is to be monitored by the optical encoder. The encoder may be arranged to read the markings on the optical disc using the three-beam pickup method.