Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
2002-03-14
2003-05-13
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044230, C369S044240, C369S112010
Reexamination Certificate
active
06563781
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an optical information storage device for accessing information by irradiating a light on a surface of a recording medium, and an optical head used for such an information storage device.
BACKGROUND ART
Conventionally, as a medium for storing a voice, image information, a character, a computer program or the like, an optical disk such as a CD, a CD-ROM, a CD-R, a DVD, a PD or an MO, has been known. An optical information storage device has also been known, which forms a condensing spot by using the optical head to condense a laser beam or the like on such an optical disk, and accesses the optical disk by using the condensing spot. Such an optical information storage device is now a focus of attention because of portability of a recording medium, a large capacity and a light weight. With achievement of higher performance of a computer in recent years, there is a demand for a great increase in an information recording density by such an optical information storage device.
The information recording density by the above-described optical information storage device is higher as a size of the condensing spot on the optical disk is smaller. Thus, developments of a shorter wavelength laser beam source, and studies of a higher NA of an objective lens have been actively conducted. Regarding achievement of the higher NA of the objective lens, there has been known a method for realizing an objective lens, which has a numerical aperture set to exceed 1 and reach about 1.4 by condensing a light in a medium of a high refractive index, as in the case of an oil immersion lens of an optical microscope. However, the size of the condensing spot cannot be greatly reduced by the shorter wavelength of the laser beam source or the higher NA of the objective lens, and thus it is difficult to greatly increase the recording density. In addition, a technology has been presented, which physically forms a condensing spot of a smaller size by using a pinhole. However, in the technology using the pinhole, a quantity of light is small, efficiency of light utilization is 0.1% or lower, and positioning of the condensing spot with respect to the pinhole is difficult. Thus, there are difficulties of stable information accessing, high-speed information transferring and reproducing. Moreover, during tracking, the condensing spot and the pinhole must be translated at a high speed. However, it is difficult to realize a low-priced actuator or the like for moving the pinhole at a high speed.
With respect to the foregoing technologies, a magneto-optical recording technology based on a laser pulse magnetic field modulation system has been presented, which records information by a mark length smaller than the size of the condensing spot. To greatly increase the recording density, narrowing of a track pitch is essential. In the above-described magneto-optical recording technology, however, it is impossible to narrow such a track pitch.
DISCLOSURE OF THE INVENTION
The present invention has been developed to solve the foregoing problems, and an object of the present invention is to provide an optical information storage device capable of performing stable information accessing at a high recording density, and an optical head.
In order to achieve the foregoing object, in accordance with a fist aspect of the present invention, there is provided an optical information storage device for performing information access by irradiating a light on a surface of a recording medium, the recording medium having a track irradiated with the light to at least reproduce information, comprising:
a medium holding section for holding the recording medium in a predetermined position; and
an optical head for irradiating the light on the surface of the recording medium held by the medium holding section,
wherein the optical head includes
a light source for emitting a light,
a light shielding body provided with a slit,
a light shielding body holding section for holding the light shielding body in a position close to/in contact with the surface of the recording medium such that the slit of the light shielding body intersects the track by an angle of 45° or lower,
condensing means for condensing the light emitted from the light source on the slit of the light shielding body, and
moving means for moving the light condensed on the slit by the condensing means along the slit.
According to the optical information storage device of the first aspect in the present invention, preferably, the holding section holds the light shielding body such that the slit of the light shielding body intersects the track by an angle of 5° or lower.
In order to achieve the foregoing object, in accordance with a second aspect of the present invention, there is provided an optical information storage device for performing information access by irradiating a light on a surface of a recording medium, the recording medium having a plurality of linear tracks provided at predetermined intervals on the surface and irradiated with the light to access information, comprising:
a medium holding section for holding the recording medium in a predetermined position; and
an optical head for irradiating the light on the surface of the recording medium held by the medium holding section,
wherein the optical head includes
a light source for emitting a light,
a light shielding body provided with a slit,
a light shielding body holding section for holding the light shielding body in a position close to/in contact with the surface of the recording medium such that the slit of the light shielding body intersects the tracks by an angle of 45° or lower,
condensing means for condensing the light emitted from the light source on the slit of the light shielding body, and
moving means for moving the light condensed on the slit by the condensing means along the slit by changing an incident angle of the light made incident on the condensing means, and
a following relationship is established among an interval Tp between the tracks, a focal distance f of the condensing means, a minimum changing amount &Dgr;&thgr; of angle changed by the moving means, and an angle &agr; of intersection of the slit with respect to the tracks:
Tp
/(sin &agr;·
f·
&Dgr;&thgr;)≧10
In this case, any tracks can be used as long as they allow information to be linearly recorded. The tracks are not limited to those physically formed as grooves, and tracks formed only magnetically or optically on a plane may also be used.
The “slit” means an optical slit. Any slits can be used as long as they diaphragm luminous fluxes only in a predetermined direction, and a slit having a light transmitting portion filled with a transparent material such as glass may also be used.
In addition, the light shielding body holding section may be a carriage moving on a rail, or a swing arm rotating around a predetermined point of view. The carriage or the swing arm may hold a slider having the light shielding body loaded.
According to the optical information storage device of each of the first and second aspects of the present invention, since the slit intersecting the track by the foregoing angle physically reduces a size of the condensing spot in a slit width direction, a track pitch can be narrowed. As a result, it is possible to perform information accessing at a high recording density. Especially, by using the device in combination with a magneto-optical recording technology based on a laser pulse magnetic field modulation system, a very high recording density can be realized. Because of no eclipsing of the condensing spot and no losses of efficiency of light utilization in a longitudinal direction of the slit, the efficiency of light utilization is high, and the recording medium can be irradiated with a sufficient quantity of light. As a result, it is possible to perform stable information accessing and high-speed data transferring. Moreover, since the light condensed on the slit is moved along the slit by the moving means, tracking accuracy is high in a direction orthogonal to the track, and thus it
Aoyama Nobuhide
Hasegawa Shin-ya
Odajima Wataru
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