A set of first signal light and reference light with a phase difference of almost 0 degree, a set of second signal light and reference light with a phase difference of almost 180 degrees, a set of third signal light and reference light with a phase difference of almost 90 degrees, and a set of fourth signal light and reference light with a phase difference of almost 270 degrees are generated. A first differential signal as a difference between a first light-receiving signal obtained by a first light-receiving element and a second light-receiving signal obtained by a second light-receiving element is calculated, and a second differential signal as a difference between a third light-receiving signal obtained by a third light-receiving element and a fourth light-receiving signal obtained by a fourth light-receiving element is calculated. The first differential signal and the second differential signal are supplied to respective FIR filters. An equalization error is formed from output signals from the FIR filters. Tap coefficients for the FIR filters are controlled to minimize the equalization error.

There is provided an optical medium reproduction device that optically reproduces an optical medium in which a plurality of tracks are provided, the optical medium reproduction device including: a detection unit configured to divide a cross-section of a beam returning from the optical medium into at least one channel corresponding to an outer region in a radial direction, at least one channel corresponding to a region that is different in position in a tangential direction, and a channel corresponding to the other region, and form detection signals of the channels; a multi-input equalizer unit including a plurality of equalizer units to which the detection signals of the plurality of channels are supplied, respectively, the multi-input equalizer unit being configured to calculate outputs of the plurality of equalizer units and output the outputs as an equalized signal in a manner that a phase difference between two of the regions is set to be a predetermined phase difference; and a binarization unit configured to perform a binarization process on the equalized signal to obtain binary data.

There is provided an optical medium reproduction device that optically reproduces an optical medium in which a plurality of tracks are provided, the optical medium reproduction device including: a detection unit configured to divide a cross-section of a beam returning from the optical medium into at least one channel corresponding to an outer region in a radial direction, at least one channel corresponding to a region that is different in position in a tangential direction, and a channel corresponding to the other region, and form detection signals of the channels; a multi-input equalizer unit including a plurality of equalizer units to which the detection signals of the plurality of channels are supplied, respectively, the multi-input equalizer unit being configured to calculate outputs of the plurality of equalizer units and output the outputs as an equalized signal in a manner that a phase difference between two of the regions is set to be a predetermined phase difference; and a binarization unit configured to perform a binarization process on the equalized signal to obtain binary data.

The first, third, fourth, and seventh photosensors are disposed on one side with respect to the centerline, and the second, fifth, sixth, and eighth photosensors are disposed on another side with respect to the centerline. The first and seventh photosensors are positioned between the third and fourth photosensors in the direction parallel to the centerline. The second and eighth photosensors are positioned between the fifth and sixth photosensors in the direction parallel to the centerline. The first photosensor receives overlapped light of the 0th-order light with the +1st-order diffracted light, the second photosensor receives overlapped light of the 0th-order light with the −1st-order diffracted light, each of the third to sixth photosensors receives the 0th-order light, and does not receive the +1st-order diffracted light and the −1st-order diffracted light, and each of the seventh and eighth photosensors receives at least the 0th-order light.

A system includes a polarization selective optical element configured to diffract a light reflected by an object into a plurality of signal lights. The system also includes at least one optical sensor configured to receive the signal lights and generate a plurality of tracking signals for tracking the object.

A system includes a polarization selective optical element configured to diffract a light reflected by an object into a plurality of signal lights. The system also includes at least one optical sensor configured to receive the signal lights and generate a plurality of tracking signals for tracking the object.

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 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.

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.

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.