Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
2001-08-14
2004-08-24
Young, W. R. (Department: 2652)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044120, C369S120000, C369S112080
Reexamination Certificate
active
06781944
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical information processor capable of processing signals at high speed and at high recording density.
Hitherto, in applications of an optical information processor, in order to read/record high-density information (optical memory) from/to a recording medium such as an optical disk, it is indispensable to shorten the wavelength of a semiconductor laser as a light source. As an example of conventional techniques, a blue-violet laser having the shortest wavelength out of semiconductor laser devices is described in Japanese Journal Applied Physics Letters, Vol. 35, 1996, pp. L74 to L76.
The conventional technique, however, can utilize the features of only the light source and does not contribute to reduction in size and weight of an optical head including optical devices such as a light-emitting device and a light-receiving device and an optical system in an optical pickup mechanism. The conventional technique does not have a system configuration for processing an optical signal by near-field recording which converges a laser beam emitted from a light-emitting device to a near field pattern by an integrated focusing lens and forms a very small spot on a recording medium (optical recording medium). In the near-field recording, information can be recorded/read to/from a memory smaller than that determined by the wavelength of a laser beam and the numerical aperture of an optical system lens, so that recording of higher density can be achieved.
SUMMARY OF THE INVENTION
The conventional technique uses the configuration of an existing optical head and cannot achieve reduction in size and weight of an optical head and address to a demand of higher processing speed. Consequently, the features of only the light source do not contribute to a higher-speed access of an optical information processor.
FIG. 26
is a schematic diagram showing a conventional optical pickup mechanism. A transmission beam (laser beam)
13
emitted from a light-emitting device (semiconductor laser device)
7
sequentially passes through a polarized light separating diffraction grating
6
and a &lgr;/4 wave plate
5
. An optical path
10
is changed by a beam splitter
4
and also by a reflecting mirror
3
. The beam passes through an objective lens
2
and is focused on a recording surface of a recording medium (optical recording medium, disk)
1
to form an image. A reflected beam
24
reflected by the recording medium
1
passes through the objective lens
2
and is reflected by the reflecting mirror
3
and passes through the beam splitter
4
. After that, the beam is condensed by a condenser lens
8
onto a light-receiving face of a light-receiving device
9
.
As described above, the conventional optical pickup mechanism is constructed by discrete optical devices and the optical devices are optically connected via a space, so that the volume is large and weight is heavy. The dimensions of the mechanism are, for example, about 60×40×10 mm.
The inventor herein has found that a small, light optical head can be formed by integrating a light-emitting device (semiconductor laser) and a light-receiving device on the same substrate in a flat shape, allowing a laser beam (transmission beam) emitted from the light-emitting device to travel perpendicular to a substrate face, and integrating a diffraction light separating device and a condensing device (lens) hierarchically in the direction perpendicular to the substrate.
It was also confirmed that, with the configuration, by designing each of the devices in consideration of the outgoing direction of the transmission beam and reception of a condensed beam and a diffracted beam, an optical information processor capable of recording/reproducing information to/from a recording mark in a recording medium by near-field recording which converges a beam to a near-field pattern and diffraction beam splitting control, and performing high-density recording and reproduction at high speed which cannot be achieved by the conventional techniques can be achieved.
An object of the invention is to provide an optical information processor capable of recording information at high recording density and reproducing the information at high speed.
The above and other objects and novel features of the invention will become apparent from the description of the specification and the appended drawings.
The outline of representative ones of inventions disclosed in the application will be briefly described as follows.
(1) An optical information processor having a light-emitting device, a light-receiving device, and a plurality of optical devices positioned in an optical path and for controlling light, constructing an optical system for forming an image on a recording face of a recording medium by a transmission beam emitted from a front light-outgoing end of the light-emitting device and for forming an image on a light-receiving face of the light-receiving device by a reflected beam reflected by the recording face, and reproducing information recorded on the recording medium and/or recording information to the recording medium, including: a substrate having, on one face thereof, a light-emitting device (semiconductor laser device) for emitting a transmission beam in an in-plane direction and a plurality of light-receiving devices for receiving reflected beams of the transmission beam from the inside of the plane, which is made of a base material capable of forming the light-emitting device and the light-receiving devices by crystal growth and an insulating material through which the transmission beam and the reflected beam pass; a diffraction light separating device stacked on the other face of the substrate, for correcting and changing an optical path so that the reflected beams from the recording medium are received by the light-receiving device; a &lgr;/4 wave plate stacked on the diffraction light separating device; and a dielectric plate stacked on the &lgr;/4 wave plate, constructing a lens for converging the transmission beam onto a recording face of the recording medium and converging the reflected beam from the recording medium onto the substrate side.
The substrate, the diffraction light separating device, the &lgr;/4 wave plate, and the dielectric plate are integrated mechanically and physically, and construct an optical head attached to a suspension arm of an optical pickup mechanism of an optical information processor. The optical head is light to an extent that it can bear a high-speed swing. The substrate, the diffraction light separating device, the &lgr;/4 wave plate, and the dielectric plate are bonded by an intermolecular force of thermo compression bonding under high vacuum of about 10
−9
to 10
−10
Torr.
The lens is constructed so as to form an image as a near field image on a recording face of a recording medium by the transmission beam and to reproduce/record information of near-field recording from/to the recording medium. The near field image is formed in a range from a few nm to a few hundreds nm from the surface of the dielectric plate.
Each of the lens and the diffraction light separating device is formed by a diffraction grating, when a diffraction grating lens is used as the lens, the reflected beam is diffracted to generate a primary diffracted beam, the diffracted primary beam is separated via the diffraction light separating device, and separated beams are received by the light-receiving devices. The diffraction grating is constructed by at least two kinds of areas having different refractive indices and is, desirably formed in a crystal having high anisotropy. At least two kinds of areas having different refractive indices in the diffraction grating are formed by diffusion of an impurity or ion implantation.
The light-emitting device is a semiconductor laser formed from a semiconductor crystal as a base formed by selective growth using an insulating mask on one face of the substrate, an active layer for emitting a laser beam from its end face is disposed along a direction perp
A. Marquez, Esq. Juan Carlos
Fisher Esq. Stanley P.
Hitachi , Ltd.
Reed Smith LLP
Young W. R.
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