Sanyo Electric Co., Ltd.

Hitoshi Terasaki

Shuichi Ichiura

Yoichi Tsuchiya

Osamu Ota

Seizo Kato

Yasuyuki Kano

Yoshimoto Yamaguchi

Toshio Ito

Yoshiaki Maeno

Yoshihisa Suzuki

Masato Yamada

Masahiro Higuchi

Youichiro Goto

Mikio Ichihashi

Yasuhiro Kodama

Two mirrors are placed in such a manner as to line in a Z-axis direction in a beam irradiation head. These mirrors are located at a position beyond a normal scan range of the laser light in the Z-axis direction and within a limit range of scanning of the laser light, and the angles of inclination of mirrors are adjusted so as to reflect incident laser light toward a PD. In the case where a lens is driven in a Z-axis direction (a lateral scanning direction), driving current values Ia, Ib of an actuator at the times when reflected light from these two mirrors enters the PD at the maximum light quantity are detected. A driving current Imz required to position a lens for irradiation at a neutral position and a drive amount &#x394;zd of the lens for irradiation per a unit driving current are then determined based on the detected driving current Ia and Ib.

Beam irradiation apparatus

In a beam irradiation device of the present invention, laser beams emitted from a semiconductor laser impinge on an irradiation lens supported by a lens actuator. The laser beams that have passed through the irradiation lens change in outgoing angle in the direction of a y-z plane as the lens actuator is driven. A laser beam scan in the target region is thus performed. A part of the laser beams that have passed through the irradiation lens is reflected and separated by a beam splitter. The separated beams are converged on a PSD through a converging lens. A DSP control circuit monitors a scan position of the laser beams that have passed through the irradiation lens based on a signal from the PSD. When an irradiation position has deviated from a scan trajectory, the DSP control circuit controls an actuator driving circuit to draw the irradiation position back onto the scan trajectory. This beam irradiation device can realize a smooth and stable beam scan operation with a simple construction.

Beam irradiation device

An optical disk includes a track having a track pitch that is k times (0<k<1) the track pitch of a compact disk format. The track is formed by a pit having a pit length shorter than k times the pit length of the compact disk format. The track pitch P&mgr;m and shortest pit length L&mgr;m are set to satisfy the relationship of L<(A/1.6)&times;P where A&equals;(V/4.3218)&times;3 when a standard compact disk having linear velocity of V m/second is compressed. When the recording density is to be increased to two times that of the compact disk, the track pitch is set to approximately 0.9-1.4 &mgr;m, more preferably approximately 1.1-1.3 &mgr;m, and further preferably to approximately 1.2 &mgr;m. Since the track pitch is not compressed as much as the pit length in this optical disk, generation of crosstalk can be suppressed. Also, jitter in a reproduced signal can be suppressed since the track pitch is set to 1.2 &mgr;m or in the vicinity thereof.

Optical disk having high recording density

An optical disc player for reproducing an optical disc having a pit width of 0.2-0.35 .mu.m, a pit depth of 100-120 nm, and a track pitch of 0.7-0.85 .mu.m. The optical disc player includes a semiconductor laser having a wavelength of 590-670 .mu.m and a laser beam projector which projects the laser beam from the laser onto the optical disc with a spot of a predetermined diameter.

High density optical disc player

Two or three different signal recording regions are formed in one optical disk. One signal recording region is positioned at a depth of 0.6 mm from a disk surface and is formatted in accordance with a single layer or two layer DVD standard, for example. Remaining signal recording region is positioned at a depth of 1.2 mm from the disk surface and is formatted in accordance with the CD, CD-R or MO disk standard, for example. By using such an optical disk, whether a manufactured optical pickup device is capable of reproducing two or three different types of optical disks can be checked quickly.

Optical recording medium for checking compatibility of an optical pickup

A high density optical disc having a track pitch of 0.85 .mu.m, a shortest pit length of 0.49 .mu.m, a pit depth of 100 nm, and a pit width of 0.35 .mu.m is rotated at a linear velocity of 2.4-2.8 m/s such that the same is optically reproduced by a laser beam having a wavelength of 635 nm which is converged to a spot size of 0.9 .mu.m by an objective lens having a numerical aperture of 0.6. Accordingly, data is read from the optical disc at a transfer rate of 5.6 Mbps.

High density optical disc and optical disc player

An optical disc having a track pitch of 0.85 .mu.m, a shortest pit length of 0.49 .mu.m, a pit depth of 100 nm, and a pit width of 0.35 .mu.m is rotate at a linear velocity of 2.4-2.8 m/s such that the same is optically reproduced by a laser beam having a wavelength of 635 nm which is converged to a spot size of 0.9 .mu.m by an objective lens having a numerical aperture of 0.6. Accordingly, data is read from the optical disc at a transfer rate of 5.6 Mbps.

An optical disc having a track pitch of 0.85 .mu.m, a shortest pit length of 0.49 .mu.m, a pit depth of 100 nm, and a pit width of 0.35 .mu.m is rotated at a linear velocity of 2.4-2.8 m/s such that the same is optically reproduced by a laser beam having a wavelength of 635 nm which is converged to a spot size of 0.9 .mu.m by an objective lens having a numerical aperture of 0.6, Accordingly, data is read from the optical disc at a transfer rate of 5.6 Mbps.

An apparatus is disclosed that reproduces data recorded on a recording medium having a plurality of pits formed in the medium that stores the data. The medium is designed to be compatible with an information reproducing apparatus having a lens with a first numerical aperture NA1 for focusing a laser beam of a first wavelength .lambda.1 on the recording medium. The apparatus of the present invention comprises a laser generator for generating a laser beam of a second wavelength .lambda.2 and a lens having a second numerical aperture NA2 for focusing the laser beam from the laser generator. The second wavelength .lambda.2 of the laser beam and the second numerical aperture NA2 of the lens are set to satisfy the relationship: (.lambda.2/NA2)&lt;(.lambda.1/NA1).

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Gifu, Japan

Hitoshi Terasaki