JPS62214526A - Optical information recording system - Google Patents

Abstract

PURPOSE:To improve the recording density by dividing time series information into small information blocks, deflecting a laser light onto plural sub-tracks which have been provided in a track guide groove, in accordance with its pattern, and recording the information in the track width direction. CONSTITUTION:Laser light beams of wavelengths alpha1, alpha2 from light sources 7A, 7B become two circular spots 26, 27, respectively, through optical systems 15, 16, a 1/2 wavelength plate 19 (only the light beam of lambda1), polarized prism beam splitters (PBS) 20, 21, a polarizing plate 23, and a lambda/4 plate 24, and irradiate an optical recording medium. On the other hand, the laser light beam which has been reflected by the PSB 21 passes through a polarizing plate 25 and a PBS 22 and made incident on a photodetector 12. By controlling the light sources 7A, 7B the laser spots 26, 27 are deflected to the two sub-tracks in accordance with a pattern of information blocks which have been divided into two, synthesized on the optical recording medium, and recording is executed in the track width direction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording system, and in particular an optical information recording system that can significantly improve recording density. [Prior Art] Optical information recording system Conventionally proposed methods for improving the recording density of recording devices include (1) miniaturization of the laser spot using a short wavelength laser and a highly condensing lens, and (2) various modulation methods and edge reduction of information pits. Improving linear recording density through detection (3) Multiple recording in the depth direction using a multilayer film (4) Wavelength multiplexing recording using photochemical hole burning, etc., but in practical terms, the above (1) and (2) method has been implemented.

Regarding the edge detection (2) above, since edge position deviation occurs due to fluctuations in laser output, etc., peak detection without position deviation is often used. An example of the optical recording procedure in this case is shown in FIG.

In FIG. 9, 1 is time series information, 2 is a coded sequence (here, MFM), 3 is a semiconductor laser output, 5 is a recording pit formed in the center of the track guide groove 4, and 6 is a recording pit 5. It shows the interval between.

Here, time-series information 1 is encoded, a semiconductor laser is emitted at the time when the sign is reversed, and the semiconductor laser output with a wide time width as shown in 3 is used to reach the center of the track guide groove 4 on the optical recording medium. , which form recording pits 5.

[Problem that the invention seeks to solve]

In the recording procedure as described above, the minimum interval between the recording pits 5 (the minimum value of the interval 6) is mainly determined by the spot diameter of the laser beam and the like. In other words, when the pitch of the track guide grooves of an optical information recording device is constant, there is a fundamental problem in that the areal recording density is limited by the minimum interval of the recording pits.

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems in conventional optical information recording systems and to provide an optical information recording system that can significantly improve recording density. Our goal is to provide the following.

[Means for solving problems]

The above-mentioned object of the present invention is to provide an optical information recording system for recording time-series information using a laser beam along a track guide groove of an optical recording medium, in which a plurality of sub-tracks are provided in each of the track guide grooves; Divide the time series information into small information blocks, deflect the laser beam according to the type of pattern of the small information blocks, and divide the small information blocks into one
This is achieved using an optical information recording method that records information in individual pits.

[Effect]

In the present invention, time series information is divided into small information blocks, and a laser beam is directed onto a plurality of sub-tracks provided in track guide grooves on an optical recording medium in accordance with the pattern of the small information blocks. It is deflected to record information in the track width direction.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a configuration diagram showing the main parts of an optical information recording/reproducing apparatus which is an embodiment of the present invention. In the figure, 7A, 7B
are first and second light sources with wavelengths λ□ and λ2, respectively, and semiconductor lasers are used for these, for example, and the light emission is controlled by a drive circuit (not shown).

12 is a photodetector that detects reflected light from an optical recording medium and converts it into an electrical signal, and includes a plurality of light receiving elements (for example, 4
(pieces) arranged in rows. 13 is a coupling lens, and 14 is a prism, which constitute a first optical system 15 that shapes the light from the first light source 7A into a substantially circular laser spot. Further, 16 is a coupling lens, 17 is a prism, and these are the second
A second optical system 18 is configured to shape the light from the light source 7B into a substantially circular laser spot.

Further, 19 is a 1/2 wavelength plate, 20, 21, and 22 are polarizing prism beam splitters, and 23 is 1 wavelength for wavelength λ, and 1/2 wavelength for wavelength λ2.

24 is a 1/4 wavelength plate, and 25 is a polarizing plate that becomes 1/2 wavelength for wavelength λ and 1 wavelength for wavelength λ2. These combine the two laser beams, irradiate the optical recording medium as laser spots 26 and 27, and separate the reflected beams, so that only the second light source with the wavelength λ2, for example, It constitutes an optical system that leads to the detector 12.

In this embodiment, the two independently driven laser spots 26 and 27 configured as described above are positioned within the track guide groove at a very small distance on the optical recording medium. The above-mentioned output difference between the two light sources is used to slightly deflect the combined output peak position of the light spot in the track width direction. Note that during recording and reproduction, focus control and track control are performed by the second light source 7B.

Next, a recording method in the track width direction according to this embodiment will be explained with reference to FIGS. 1 and 3.

FIG. 1 is a diagram for explaining a situation in which recording is performed by deflecting the output of the light source according to the type of small information block described later, which is the main point of this embodiment, and FIG. FIG. 6 is a diagram showing changes in the peak position of the combined output of the light sources. 1st
In the figure, 1 is the time series information, 7a and 7b are
The outputs of the light sources 7A and 7B are respectively shown, 8 is a block obtained by converting the time series information 1 into small blocks, and 9 is a plurality of sub-tracks in the track guide groove 4.

Here, in order to simplify the explanation, the small information block 8 of time series information is assumed to be 2 bits, but n pits (n >
The same applies to case 2).

Here, in the case of 2 bits, the type of small information block is I
I Q Q Igtl Q I IT, It l Q
There are four types: u and "11" (7). Depending on this pattern, the center position of the light beam is adjusted, for example, to the sub-track 9.
, to the 0th sub-track, the 1st sub-track, the 1st 1st sub-track, and the 2nd sub-track. The spacing between the sub-tracks is, for example, 0.1 μm.

Specifically, as shown in FIG. 1(A), the time series information 1 is divided into small information blocks 8 of 2 bits each, and the first light source 7A is The output cuff a and the output cuff b of the second light source 7B are controlled as shown in FIG. 1(B). The changes in the peak position of the combined light output 10 at this time are shown in FIGS. 3(A) to 3(D) in association with the types of the small information blocks 8.

By the above-described control, the information pits 5 corresponding to the small information blocks 8 are recorded on the sub-tracks 9 in the track guide grooves 4 as shown in FIG. 1(C). In this case, the minimum interval between the information pits 5 can be compressed to the same as that shown in FIG. 1, so that 2 bits of the small information block 8 can be expressed with 1 information pit.

Note that the number n of bits in the above-mentioned small information block 8 is determined by the crosstalk margin of the track. For example, the track pitch can be changed to 1.6 μm, which is currently in practical use.
When expanded to 3.2 μm, at least 16 sub-tracks can be provided, and in this case,
As the above-mentioned small information block, n=4, that is, 4
It becomes possible to divide into bits, and one information pit can represent 4 bits.

FIG. 4 is a block diagram showing the main parts of an optical information recording/reproducing apparatus according to another embodiment of the present invention. In the embodiment shown in FIG. 2, the laser beams from two light sources were combined on the optical recording medium, but in this embodiment, the laser beams from one light source were combined using an acousto-optic system. The difference is that it is configured to be deflected by an optical modulator.

In FIG. 4, 7 is a light source, 30 is the acousto-optic modulator, and 12 to 14 and 21.24 are the same components as shown in FIG. 2. FIG. 5 shows that the acousto-optic modulator 3 is a characteristic component of this embodiment.
The light deflection effect due to zero will be explained.

In FIG. 5, 31 is an incident light beam, 32 is a switch, 33 is a driver, 34 is a transducer, and 35 is an acousto-optic element. In order to deflect the light beam 31 on the optical recording medium, the ultrasonic vibration frequency f is determined according to the deflection position. , fl, ... tfl'l, above switch 3
2 and applied to the acousto-optic element 35 by the transducer 34 via the driver 33.

As a result, a periodic refractive index change (indicated by 36) occurs in the acousto-optic element 35 due to the ultrasonic waves, and the laser beam 31
When incident, diffracted light 37 is generated in a direction according to the driving frequency. This is the function of the acousto-optic modulator 30.

According to the apparatus of this embodiment, unlike the apparatus shown in FIG. Since it is deflected by an optical light modulator, it has the advantage of being less susceptible to environmental temperature changes and vibrations.

FIG. 6 is a block diagram showing the main parts of an optical information recording/reproducing apparatus which is still another embodiment of the present invention. In the embodiment shown in FIG. 4, the laser beam from one light source was deflected by an acousto-optic modulator, whereas in this embodiment, one reflecting mirror was provided. The difference is that the laser beam is deflected by the light source itself.

In FIG. 6, reference numeral 38 indicates the above-mentioned reflecting mirror, 39 indicates a semiconductor laser with a beam deflection function, and 12 to 14 and 21, 24 indicate the same components as shown in FIG. 2. The semiconductor laser 39 with a beam deflection function is, for example, a semiconductor laser with a beam deflection function described by Yazu et al. [Semiconductor laser with a beam deflection function]
A semiconductor laser with an asymmetric injection current as disclosed in Vol. 14 No. 4 ρ295 (1985) is used.

In the apparatus of this embodiment, unlike the apparatus shown in FIG. 2, the laser beams from one light source are reflected by a reflecting mirror without combining the laser beams from two different light sources on the optical recording medium. Since the deflection is caused by the deflection, there is an advantage that the structure is simplified.

FIG. 7 is an explanatory diagram of the principle for reproducing the original time-series information from the above-mentioned information pits recorded in the track width direction, and FIG. 8 is a configuration showing an embodiment of a reproducing apparatus for realizing this. It is a diagram.

First, a laser beam is made to follow the information pit 5 in FIG. 7 by the heterodyne method described later. At this time, a track error signal 42 is generated from the track guide groove 4 by the push-pull method.
get. Since this signal represents the amount of deflection of the information pit, the preset reference value and this tracking error signal 42
The principle behind this is to determine which sub-track the information pit is located in by comparing the amplitude value with the amplitude value of the sub-track, and to detect the pattern of the small information block corresponding to that sub-track. .

A specific reproduction method will be described below with reference to FIG.

In FIG. 8, 43 is a 4-split photodetector, and the data signal 4 is calculated by calculating the output of each element a '' d.
4(a+b+c+d) and the diagonal sum difference signal 45((a
+ c) −(b + d)) is obtained. The error signal processing circuit 46 is operated by these two signals, and a track error signal 47 of the information pit string is obtained by the heterodyne method. Regarding the operating principle of the heterodyne method, reference may be made to, for example, Ito's "Optical Pickup" Electronics April 1983 issue ρ383.

The track error signal 47 of the information pit string is sent to a phase compensator 48. A track actuator 50 is driven via a driver 49 to cause the laser beam to accurately follow the information pit 5 and detect pit information.

On the other hand, since the information pits 5 meander within the track guide groove 4 as shown in FIG. 7, when the light beam follows this information pit row. The track error signal 51 from the track guide groove 4 is detected by the photodetector 4.
3 of 4 elements a'' d calculation result ((a+d)-(
b+c)) is detected using the so-called push-pull method.

Furthermore, the gate circuit 53 is opened by a sample pulse from the peak value detection circuit 52 of the data signal 44, and the track error signal 51 of the track guide groove 4 corresponding to the information pit is sampled. This signal and a signal from the reference signal generator 54 representing the position of the sub-track are sent to the track position determination circuit 55, the position of the sub-track is detected, and the decoding processing circuit 56 obtains one-dimensional time series information. .

The optical information recording/reproducing apparatuses shown in the above embodiments are merely examples of the present invention, and the present invention should not be limited to these.

Furthermore, the number n of bits in the small information block 8 mentioned above is determined by the track pitch and the crosstalk margin, and can be freely determined taking this relationship into consideration. That's right.

〔Effect of the invention〕

As described above, according to the present invention, in an optical information recording method that records time-series information using a laser beam along a track guide groove of an optical recording medium, a plurality of sub-tracks are provided in each of the track guide grooves. In addition, the time series information is divided into small information blocks, the laser beam is deflected according to the type of pattern of the small information blocks, and the small information blocks are recorded in one pit. This method records in the track width direction without using a shorter wavelength light source, a highly condensing lens, or a smaller laser spot.
This has the remarkable effect of making it possible to realize an optical information recording system that can significantly improve recording density.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a block diagram showing the main parts of an optical information recording/reproducing apparatus which is an embodiment of the present invention, and FIG. 3 is a track diagram of the present embodiment. FIGS. 4 and 5 are diagrams illustrating the state of multiplex recording in the width direction. FIGS. A configuration diagram showing the main parts of an optical information recording and reproducing apparatus according to another embodiment, and FIG. 7 is an explanation of the principle for reproducing original time-series information from the above-mentioned information pits recorded in the track width direction. 8 is a block diagram showing an embodiment of a reproducing apparatus for realizing this, and FIG. 9 is an explanatory diagram of the recording operation of a conventional optical information recording/reproducing apparatus. time series information, 4: information track, 5: information pit, 6
: Information pit interval, 7A, 7B: 1st ° 2nd light source,
8: Small information block, 9: Sub track, 30: Acousto-optic modulator, 39: Semiconductor laser with beam deflection function, 4
3:4 split photodetector. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure I-3 Audience Figure 9-1

Claims (1)

[Claims] (1) In an optical information recording method in which time-series information is recorded using a laser beam along a track guide groove of an optical recording medium, a plurality of sub-tracks are provided in each of the track guide grooves, and the time-series information is An optical information recording method characterized in that the small information blocks are divided into small information blocks, a laser beam is deflected according to the type of pattern of the small information blocks, and the small information blocks are recorded in one pit.