JPH06301979A - Method and device for reproducing information - Google Patents

Abstract

PURPOSE:To obtain an information reproducing method by which the packing density of a recording medium can be increased by driving an ultrasonic deflector by means of amplitude-modulated signals and reproducing information by using moving interference fringes generated by the interference between a plurality of simultaneously generated diffracted light rays. CONSTITUTION:An amplitude modulator 6 outputs carrier signals inputted from a carrier generator 8 to an ultrasonic deflector 2 after modulating the carrier signals in amplitude by using sine wave signals inputted from a sine wave signal generator 7. The deflector 2 generates two diffracted light rays 9 by simultaneously diffracting a laser beam from a semiconductor laser 100 in two directions. The diffracted light rays 9 are made incident to a recording medium 108 through a lens 101, beam splitter 103, and lens 102 so as to generate reflected light rays 107. The reflected light rays 107 are made incident to a detector 105 and the information recorded on the medium 108 is reproduced by using interference fringes formed by interference between the diffracted light rays 9. When such a constitution is used, the track pitch of the medium can be reduced and an information reproducing method by which the packing density of the medium can be increased is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reproducing method and device for realizing a high density optical disk device.

[0002]

2. Description of the Related Art A conventional recording / reproducing method of this kind of apparatus is shown in FIG.
This will be described with reference to (a) and (b). 4A shows a recording / reproducing device, and FIG. 4B shows a disk medium. Figure 4
In (a) and (b), 100 is a semiconductor laser, 10
1, 102 and 104 are lenses, 103 is a beam splitter, 105 is a detector, 106 is a recording / reproducing laser beam,
Reference numeral 107 is the reflected light from the disk medium, 108 is the disk medium, 109 is the track, and 110 is the recorded area. Laser light 106 from the semiconductor laser 100 enters the disk medium 108 via the lens 101, the beam splitter 103, and the lens 102, and recording is performed.
On the other hand, when reproducing, light 1 from the semiconductor laser 100
06 enters the disk medium 108 through the lens 101, the beam splitter 103, and the lens 102, and the reflected light 107 from the disk medium 108 passes through the lens 102, the beam splitter 103, and the lens 104, and the detector 10
Upon incidence on 5, reproduction is performed.

Conventionally, in this type of apparatus, the intensity distribution of the laser light 106 for recording and reproduction has a Gaussian distribution, and is condensed in a substantially circular shape on the disk medium 108. As the form of recording, the energy of the laser beam 106 causes
When the information is written by changing the reflectance of the recording medium by making a hole or by utilizing the phase change between the crystalline state and the amorphous state, a magnetic bias is added to the recording medium and the laser beam 106 is turned on. In some cases, the information is written by reversing the magnetization when turned off.

[0004]

In any of the above recording modes, the laser beam 106 on the disk medium 108 has a full width at half maximum of at most 0.8 when the wavelength is near 0.8 μm.
The limit is about 8 μm, and the recording density is limited by this focused beam diameter. For example, on a disk medium having a diameter of 130 mm, the shortest distance between recorded pits is about 1.
It is about 5 μm, and when reproducing such a pit interval, the signal output during reproduction is reduced to about 1/2 due to waveform interference. The limit is about 1/2 reduction from the S / N condition, and the conventional device of this type limits the capacity of one side to 325 MB with a medium of 5.25 inches.

It is an object of the present invention to provide an information reproducing method and an apparatus capable of achieving higher density than a conventional optical disk apparatus.

[0006]

In order to solve the above-mentioned problems, the information reproducing method of the present invention is such that the information recorded by the interference fringes formed by the interference of a plurality of diffracted lights simultaneously generated from the ultrasonic deflector. Is performed.

Further, the information reproducing apparatus of the present invention includes a reproducing light source, a carrier signal generating means for generating a carrier signal of a predetermined wavelength, and an input signal for generating an amplitude modulating input signal of a wavelength different from the carrier signal. Generating means, amplitude modulating means for amplitude-modulating the carrier signal with the input signal, and an ultrasonic deflector for diffracting the light beam from the reproduction light source in a plurality of directions by the amplitude-modulating signal by the amplitude modulating means,
It is characterized by comprising means for causing a plurality of diffracted lights from the ultrasonic polarizer to enter a recording medium, and means for causing a reflected light of the plurality of diffracted lights from the recording medium to enter a detector.

Further, the information reproducing apparatus of the present invention is characterized in that a space shielding plate is arranged on the detector to detect a part of the moving interference fringes.

[0009]

According to the above-mentioned means, the present invention is characterized in that the ultrasonic deflector composed of traveling ultrasonic waves is driven by the amplitude modulation signal, and the information is reproduced by the moving interference fringes generated by the interference of a plurality of diffracted lights which are simultaneously generated. And

[0010]

Embodiments of the present invention will be described with reference to FIGS. 1, 2 and 3. 1 to 3, those parts which are the same as those corresponding parts in FIG. 4 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 1, 2 is an ultrasonic deflector, and 6 is an amplitude modulator. 7
Is a sine wave signal generator, and the frequency is, for example, 1 to 10M.
It is about Hz. Reference numeral 8 denotes a carrier wave generator for an amplitude modulation signal which drives ultrasonic waves, and has a frequency of about 100 MHz. Reference numeral 9 denotes two diffracted lights simultaneously generated from the ultrasonic deflector 2, 10 denotes an interference fringe formed by the interference of the two diffracted lights, 1001 denotes an interference fringe on the detector 105, and 11 denotes the interference fringe 10. Direction, 12 is the rotation direction of the disk medium 108, 13 is the beam pattern on the disk medium 108,
1301 is a beam pattern on the detector 105.

That is, the sine wave signal generator 7 generates a sine wave signal for amplitude modulation having a frequency of, for example, about 1 to 10 MHz and outputs it to the amplitude modulator 6. The carrier wave generator 8 also generates a carrier wave signal having a frequency of about 100 MHz and outputs it to the amplitude modulator 6. This amplitude modulator 6 is a carrier wave generator 8
The carrier wave signal input from the ultrasonic wave deflector 2 is amplitude-modulated by the sine wave signal input from the sine wave signal generator 7.
Output to. The ultrasonic deflector 2 simultaneously diffracts the laser light beam generated from the semiconductor laser 100 in two directions by the amplitude modulation signal input from the amplitude modulator 6 to generate two diffracted lights 9. Two diffracted lights 9 generated simultaneously from the ultrasonic deflector 2 are incident on the disk medium 108 via the lens 101, the beam splitter 103, and the lens 102. The disk medium 108 generates reflected light 107 based on the two diffracted lights 9 incident from the ultrasonic deflector 2, and the reflected light 107 is incident on the detector 105 via the lens 102, the beam splitter 103, and the lens 104. It Therefore, the information recorded on the disk medium 108 can be reproduced by the interference fringes 10 formed by the interference of the two diffracted lights 9 simultaneously generated from the ultrasonic deflector 2.

The ultrasonic deflector 2 has the frequency band 14 shown in FIG. 2, and since the carrier wave signal is amplitude-modulated by the sine wave signal, the spectrum of the signal for driving the ultrasonic deflector 2 is as shown in FIG. consisting of the carrier frequency f ₀ and an upper sideband signal f ₀ + f _i and a lower sideband signal f ₀ -f _i to. If the upper sideband signal f ₀ + f _i is set outside the frequency band 14 of the ultrasonic deflector 2, the signals that substantially drive the ultrasonic deflector 2 are the carrier wave signal f ₀ and the lower sideband. It will signal f ₀ -f _i. There are two ultrasonic diffracted lights corresponding to these two signals. When these two diffracted lights interfere, an interference fringe 10 having a pitch proportional to the frequency of the sine wave signal is formed. Further, in the interference of light diffracted by a traveling wave ultrasonic wave instead of a standing wave, the interference fringe 10 has a constant velocity MVa.
To move. Here, M = fc / fo.

A method of reproducing information using such moving interference fringes 10 will be described with reference to FIGS. 3 (a), 3 (b) and 3 (c). In the figure, 20 is a space shielding plate. Figure 3 (a)
In the recorded information pattern 110, the black pattern 1101 is the recording information of the track 109, and the white pattern 1102 is the recording information of the adjacent track as shown in FIG. In this method, the moving speed MVa of the interference fringes and the rotating speed Vd of the disk medium 108 are made equal to each other, and the moving speed MVa shown in FIGS.
As shown in, the information is reproduced by synchronizing the position of the interference fringe 10 and the position of the pattern 1101 of the recorded information. As a method of synchronizing the two, for example, the information pattern 110 previously formed on the disk medium 108 is reproduced, and the frequency of the sine wave signal for driving the ultrasonic deflector is adjusted so that the signal output thereof becomes maximum. Then, a method of synchronizing the position of the interference fringe 10 and the position of the recording information pattern 1101 can be considered. Interference fringe 1 on the detector 105 for reproduction
Although 001 moves, as shown in FIG. 3C, if only the interference fringe having the maximum peak is always selected using the space shield plate 20, the recorded information can be detected in 1-bit units.
Here, the interval of the interference fringes is a value from submicron to several microns on the disk medium 108, but on the detector 105, by increasing the magnification of the reflected light condensing optical system, it is expanded from 10 μm to several hundred μm. It is possible to set the length of the transmission region of the space shield plate 20 to such a level, and it is possible to easily reproduce high density recording.
In the experiment, a slit portion of about 20 μm was formed on the glass plate by vapor deposition of chromium, and signal reproduction for high density recording was performed.

According to this method, only the information of the track 109 is detected, the information of the adjacent track is not reproduced even if it is extremely close, and the track pitch of the optical disk medium can be narrowed. According to this method, it is easy to reproduce an optical disc medium that is already on the market, and it is possible to secure backward compatibility in the memory. As the recording medium, an existing magneto-optical medium, phase change medium or the like can be applied.

[0015]

As described above, according to the present invention,
Since the track pitch of the optical disk medium can be narrowed, a high density optical disk device can be realized.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of a spectrum of a frequency band and an amplitude modulation signal of the ultrasonic deflector according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a signal reproducing method according to the present invention.

FIG. 4 is a structural explanatory view showing a recording / reproducing method of a conventional optical disc device.

[Explanation of symbols]

100 ... Semiconductor laser, 101, 102, 104 ... Lens, 103 ... Beam splitter, 105 ... Detector, 10
6 ... Laser light, 107 ... Reflected light from the disk medium, 1
08 ... Disk medium, 109 ... Track, 110 ... Recorded area, 2 ... Ultrasonic deflector, 6 ... Amplitude modulator, 7 ...
Sine wave signal generator, 8 ... Carrier wave generator, 9 ... Diffracted light, 1
0 ... Interference fringes, 1001 ... Interference fringes on the detector, 11 ... Direction of movement of interference fringes, 12 ... Rotation direction of disk medium, 1
3 ... Beam pattern on disk medium, 1301 ... Beam pattern on detector, 14 ... Frequency band of ultrasonic deflector, 20 ... Space shield plate.

Claims (3)

[Claims] 1. An information reproducing method characterized in that recorded information is reproduced by interference fringes formed by interference of a plurality of diffracted lights simultaneously generated from an ultrasonic deflector. 2. A reproducing light source, a carrier signal generating means for generating a carrier signal of a predetermined wavelength, an input signal generating means for generating an amplitude modulating input signal of a wavelength different from the carrier signal, and the carrier signal. Amplitude modulation means for amplitude-modulating by the input signal, an ultrasonic deflector for diffracting the light beam by the reproduction light source in a plurality of directions by the amplitude-modulation signal by the amplitude modulation means, and a plurality of diffracted light by the ultrasonic polarizer. An information reproducing apparatus comprising: a unit for causing a recording medium to enter; and a unit for causing reflected light of the plurality of diffracted lights from the recording medium to enter a detector. 3. The information reproducing apparatus according to claim 2, wherein a space shield plate is arranged on the detector to detect a part of the moving interference fringes.