Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
1999-08-04
2003-12-02
Neyzari, Ali (Department: 2655)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
C369S013320, C369S300000
Reexamination Certificate
active
06657927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a floating optical head which is preferably used for high density recording. In particular, the present invention relates to a microminiature floating optical head and a microminiature floating magneto-optical head which are monolithically provided with a light source, a detector, and an optical system on a substrate. The present invention also relates to an apparatus which is provided with such an optical head or such a magneto-optical head for recording or reproducing information.
2. Description of the Related Art
The recording density of the optical disk is restricted by the spot diameter of the light source. The spot diameter of the light source is represented, for example, by &lgr;/NA provided that the numerical aperture of the objective lens to be used is NA (usually about 0.5) and the wavelength is &lgr;. The spot diameter is about 1.2 &mgr;m when the wavelength is 680 nm and NA is 0.55. Therefore, it is necessary to reduce the spot diameter in order to improve the recording density. According to the expression described above, when it is intended to reduce the light spot diameter, it is convenient that the NA of the objective lens is increased, or the wavelength is shortened. For this purpose, a variety of approaches have been tried. When an objective lens having high NA is used, the focal distance is relatively short. Therefore, it is necessary to use the objective lens in a state in which it is fairly close to the optical recording medium. For this purpose, it has been suggested that a floating head as used for the magnetic disk is used for the magneto-optical recording medium.
However, in the case of the optical head for the magneto-optical recording medium, it is necessary that a large lens and a large mirror are provided on the floating head to introduce the light up to the disk. Therefore, a problem arises in that the floating head has a considerably heavy weight, and a long time is required for the floating head to make access to a predetermined recording or reproducing area. Further, when it is intended to arrange the floating heads for several sheets of disks as in the magnetic disks to perform recording and reproduction independently thereon, a drawback appears in that the volume of the apparatus is increased because the floating head is large.
For example, Japanese Patent Application Laid-Open No. 6-251410 discloses an optical head comprising a semiconductor laser and a photodetector formed on a substrate via a buffer layer, an opening formed under a laser beam-radiating surface and a receiving surface, a first glass layer charged in the opening, a grating formed on a lower surface of the first glass layer, a second glass layer formed under the first glass layer, and a grating lens having an aperture of not more than 1 mm formed on a lower surface of the second glass layer. The optical head can be produced in a monolithic manner by using the semiconductor process such as a photomask exposure process. The optical head is characterized in that the surface light emission laser and the photodiode can be simultaneously produced. Further, the optical head uses the grating. Therefore, the reflected light beam from the recording medium can be branched while allowing the incident light into the recording medium to be perpendicular to the surface thereof. Further, the optical head reduces the influence of the returning light beam of the reflected light beam directed to the laser light source.
However, the optical head disclosed in Japanese Patent Application Laid-Open No. 6-251410 uses the grating. Therefore, in order to make it possible to reliably detect the diffracted light beam from the grating by using the photodetector, it is necessary to ensure the thickness of the first glass layer, i.e., the predetermined distance from the photodetector to the grating. For this reason, the optical head involves a problem in that the volume of the apparatus is large.
Further, the conventional floating optical head, in which the head floats over the magneto-optical recording medium to perform recording and reproduction, is insufficient concerning the fact that a large magnetic field should be applied with good following performance to the information-recording medium which is irradiated with the recording or reproducing light beam. In order to respond to the further advancing progress of the magneto-optical recording medium to realize the high density in future, it is demanded to obtain a magneto-optical or magnetic head which makes it possible to apply a large magnetic field at a sufficiently high speed.
The present invention has been made in order to solve the problems involved in the conventional technique, an object of which is to provide a floating optical head which has a further miniaturized size, which has a light weight, and which makes it possible to accelerate the access speed to an information-recording medium thereby, and an apparatus provided with such an optical head which makes it possible to record or reproduce information on an information-recording medium.
Another object of the present invention is to provide a floating optical head which includes a laser light source and a detector and which is easily produced, and an apparatus including such a floating optical head.
Still another object of the present invention is to provide an optical head provided with a magnetic field-applying device which makes it possible to apply a large magnetic field at a high speed to a magneto-optical recording medium, and an apparatus including such an optical head.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an optical head for being used for an optical apparatus for recording or reproducing information by radiating light onto an information-recording medium, the optical head comprising:
a laser light source for radiating a laser beam onto the information-recording medium;
a detector for detecting the laser beam reflected from the information-recording medium; and
an optical guide unit for introducing, into the detector, the laser beam reflected from the information-recording medium, wherein:
the laser light source, the detector, and the optical guide unit are formed on a common substrate in a monolithic manner.
According to the optical head of the present invention, the laser light source, the detector, and the optical guide unit are formed on the common substrate in the monolithic manner. Therefore, it is possible to realize the head having a miniaturized size and a light weight. All of the elements of the head as described above can be formed on the substrate by means of the semiconductor process. Therefore, the head can be produced easily and correctly although it has an elaborate structure. The head includes the optical guide unit which is formed on the common substrate together with the detector. Accordingly, an optical path for the laser beam from the optical guide unit to the detector is formed on the substrate. Therefore, it is possible to ensure, within the substrate surface, the optical path length necessary to perform the tracking and the focusing servo. Thus, the thickness of the optical head can be made extremely thin. Therefore, when the optical head is accommodated in a slider, the slider itself can be made thin.
The optical head of the present invention may further comprise an objective lens for collecting the laser beam from the laser light source onto the information-recording medium, and a magnetic coil coated on the objective lens. The optical head may further comprise a yoke for the magnetic coil. Accordingly, the optical head functions as a magneto-optical head, and it is preferably used to perform recording and reproduction on a magneto-optical recording medium. Especially, the magneto-optical head can make access from one surface of the magneto-optical recording medium. Therefore, the recording can be performed on both surfaces of the magneto-optical recording medium. Accordingly, a recording or reproducing apparatu
Awano Hiroyuki
Watanabe Hitoshi
Hitachi Maxell Ltd.
Neyzari Ali
Oliff & Berridg,e PLC
LandOfFree
Optical head and apparatus provided therewith does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical head and apparatus provided therewith, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical head and apparatus provided therewith will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3122614