JPH02172020A - High-density recording and reproducing method for optical disks, optical memory devices, and optical record carriers - Google Patents

Abstract

PURPOSE:To execute high-density recording without being affected by the fluctuation in pit shape by irradiating the optical disk with the 1st laser beam and the 2nd laser beam while these laser beams are shifted zigzag in a track direction with half the size of the spacing between the guide tracks as a limit. CONSTITUTION:The 1st laser beam 5a from a laser diode 1a and the 2nd laser beam 5b from a 2nd laser diode 1b are guided to the recording medium surface of the optical disk 7. The irradiation points of the beams 5a, 5b are relatively parted in the radial direction and the radial directions are shifted with half the size of the spacing between the tracks as the limit. The reflected light beams of the beams 5a, 5b from the optical disk 7 are made incident to detectors 8a, 8b. A switch 11 is closed and the laser beams 5a, 5b are subjected to servo control so as to be brought to the positions symmetrical with the track center at the time of data recording. The switch 11 is opened and only the laser beam 5a is so servo-controlled as to coincide with the track center at the time of data reproducing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-density recording and reproducing method for an optical disc in a write-once optical disc memory and an optical memory device l! Section concerning optical record carriers.

[Conventional technology]

The conventional recording/reproducing method of write-once optical disk memory is the seventh
As shown in the figure, the reproduction laser beam spot tracks on the recording pit added at the location indicating "1" of the modulation code (Figure 7-a), and the reflected light intensity signal (R
The method is to obtain the reproduced data (Fig. 7-d) from the pit position signal (restored modulation code: Fig. 7-d) extracted by the differential method of the peak position of the F-fold signal (Fig. 7-b).
A film is used as a highly reliable method (pit position detection method). However, with the demand for higher density even in write-once optical disc memory, read-only
The pit edge detection method used in D (compact discs) and the like is being applied to write-once optical disk memories, and a recording/reproducing method that improves the recording density is being put into practical use. By the way, the recording and playback principle of the above-mentioned CD is 1.For example, ``Fundamentals of Digital Audio'' by Hiromi Toso (Ohmsha)
The concept of this method when applied to a write-once type will be explained with reference to FIG. 6. Every time the modulation code 14111 appears (for example, the interval is 2 to 7 in the case of a 2-7 modulation code), the recording pits are added so as to alternately turn on and off.
The reproduction laser beam spot is tracked in Fig. 6-a),
The RF multiplied signal indicating the reflected intensity by the spot is compared with the binarization level of a predetermined level (Fig. 6-b), a binarized output is obtained (Fig. 6-○), and the binarized output is re-edited. By differentiating the signal, the edge signal, that is, the modulated data, is restored (FIG. 6-d) and the reproduced data (FIG. 6-0) is obtained.

Here, the main problem with the above-mentioned high-density method is that the leading and trailing edge positions of the additionally written recording pits shift uncertainly due to the characteristics of the recording medium and the influence of jitter. As described in Japanese Patent Application Laid-Open No. 62-008370, a reference mark is recorded at the beginning of an execution unit area (sector) for recording and reproduction, and the mark is recognized during reproduction, and any additional information is recorded thereafter. Measures were taken to correct the recorded pit length.

[Problem to be solved by the invention]

The conventional technology disclosed in Japanese Patent Application Laid-open No. 62-008370 takes into consideration such factors as fluctuations in recording power between the leading and trailing parts of a sector, lack of homogeneity of recording medium characteristics, and fluctuations in DC level during reproduction. Not there,
Particularly when the sector length is relatively long (for example, IK bytes or more), there is a problem in that the error rate in the latter half of the sector becomes significantly worse.

An object of the present invention is to provide a high-density recording and reproducing method that is not affected by pit shape fluctuations during recording, DC level fluctuations during reproduction, and sector length. The object of the present invention is to provide a recording/reproducing method that further increases the density of the data.

Another object of the present invention is to provide an optical disk memory device having a high-density recording and reproducing function capable of reproducing even a recorded record carrier using a pit position detection method or the like.

[Means to solve the problem]

In order to achieve the above purpose, for example,
The two laser beam spots generated by a multi-laser head as shown in Publication No. 287433 are distributed symmetrically up and down from the center of the track (pattern spot shape*), and the recording modulation code is output as “ 1
This is a recording method in which the two laser beams are alternately driven every time ``'' appears.

In addition, in order to reproduce the data recorded by the above method, a method is adopted in which one of the two laser beams is caused to track the center of the track, that is, the center portion between the pits that are distributed vertically and recorded. This is what I did.

In addition, in order to increase the transfer rate and further increase the density of the pit edge detection method, the two laser beam spots should each track the center of adjacent tracks or the center of recording pits added in a staggered pattern. This is how it was done.

Furthermore, in order to improve the separation characteristics during reproduction of recorded pits added in a staggered manner, diffracted light generated by the recorded pits is utilized.

In addition, in order to improve reliability and transfer rate when performing high-density recording, a reproduction-only laser is added to perform reproduction at the same time as recording and compare data.

Furthermore, in order to perform zigzag recording evenly distributed above and below from the center of the track, independent track error detection circuits are provided in each of the two laser beam systems, and tracking operation is performed using the summed information of the two track error signals. This is what I was supposed to do.

In addition, in order to keep the track direction deviation dimension (fluid dimension) of the two laser beam spots always constant, and to arbitrarily set the chiral dimension, it is necessary to
The difference information of the two track error signals is compared with the target dimension, and the actuator is driven through a low-pass filter.
The entire optical system is rotated.

Furthermore, in order to achieve upward compatibility with conventional recording methods,
At the time of high-density recording, a flag indicating this fact is added at a predetermined location, and the reproduction clock frequency is controlled in the reproduction operation depending on the presence or absence of the high-density flag.

[Effect]

To effectively utilize recording pits distributed vertically and additionally written on the center of a track in blank areas of a recording medium.

As a result, by distributing the track center vertically for recording and reproducing, it is possible to perform high-density recording and reproducing while keeping the laser beam spot shape constant.

Furthermore, a tracking loop is formed by the addition signal of the track error signals of the two beam systems, aiming at the midpoint between the two track error signals.

Further, the optical system rotation servo loop based on the differential signal operates to control the amplitude of the two laser spots. As a result, tracking control is always performed with the track center as a reference while the two laser beam spots maintain a constant amplitude (staggering dimension), and stable high-density recording and reproduction can be performed.

〔Example〕 Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) A first example will be described below using FIGS. 1, 2, 3, 4, and 5.

FIG. 1 is a block diagram. The first laser beam 5a emitted by the first laser diode 1a passes through a wavelength separation filter 2, changes its course by a polarizing beam splitter 4, and is driven by a two-dimensional actuator that moves the objective lens in two-dimensional directions (track direction and focal direction). 6, the light becomes a minute spot and is focused on the recording medium surface of the optical disk 7. On the other hand, a second laser diode lb (835 nm in the example) having a different multiple oscillation wavelength serves as the first laser diode la.
and 773 nm).
is 0 reflection mirror 3. The wavelength division filter 2 and the polarization beam splitter 4 respectively change the directions and focus the light onto the recording medium surface of the optical disk 7 as a minute spot via the two-dimensional actuator 6, but the spot position is the same as the first one.
It is approximately 25 μmall in the radial direction relative to the irradiation point of the laser beam 5a, and the radial direction is approximately on a horizontal line (strictly speaking, it is 0.8 μm, which is about half the value of the track spacing of 1.6 μm).
The reflected light from the optical disk 7 of the above-mentioned two beams 5a and 5b passes through the polarizing beam splitter 4, and the first laser beam reflected wave passes through the first detector 8a. , the second beam reflected waves are respectively incident on second detectors 8b, which convert light intensity changes into current changes, and current-voltage conversion amplifiers 9a and 9b.
The output signal of the first conversion amplifier 9a (6) is amplified to a signal of the required level by the RF signal (RF multiplied signal 49a). Focusing is performed by moving the dimensional actuator 6 in the vertical direction, and the first tracking (TR) circuit 10a uses the track deviation information included in the output signal 9a.
performs a tracking operation. At this time, the tracking signal of the second tracking circuit tab using the output signal 49b of the second conversion amplifier 9b is transferred to the first tracking circuit 10a by closing the switch 11 only during recording.
The tracking signal is added by the adder 12, and the tracking coil of the two-dimensional actuator 6 is driven through the tracking amplifier 13 to perform a tracking operation.

That is, since the switch 11 is closed during data recording, the first tracking signal indicating the track deviation of the first laser beam and the second tracking signal indicating the track deviation of the second laser beam are separated. The synthesized signal becomes a tracking signal, and the two laser beams are servo-controlled so that they are at symmetrical positions across the track center. When reproducing data, the switch 11 is opened, so that the first laser beam will be servo-controlled to coincide with the track center. For data recording, as described above, the mode is first set so that the two laser beams are at symmetrical positions across the track center, and then the recorded data 56 is code-converted by the modulation circuit 18 (in the embodiment, it is code-converted into 2 to 7 modulation codes). ), the odd-numbered "1" output from the modulation circuit 18 is the odd-numbered output 37, the even-numbered "1" output is the even-numbered output 3, and the even-numbered output 39 is the programmable pulse delay circuit. The delay code data 40 is delayed by a predetermined time by 19, and the recording signal 38.41 is generated by the laser driver circuits 20a and 20b to the first laser diode 1a and the second laser diode 1b. During operation, the switch 11 is opened as described above, so that the first laser beam 5a is
Since only the RF signal 49a of the first laser beam is held at the center of the track, only the RF signal 49a of the first laser beam is effective (at this time, it is preferable to turn off the second laser beam).

A pit position signal 50 is obtained from the RF multiplied signal 9a by a pit position detection circuit 15, and a reproduced clock 53 generated by a reproduced clock generation circuit 16 is used to generate reproduced data 55 in a demodulation circuit 17.

FIG. 2 is a detailed block diagram of the recording system, and FIG. 4 is a time chart at the time of recording in the block diagrams of FIGS. 1 and 2. A specific example of the recording operation will be described below using FIG. 2 while referring to FIG. 4. The recorded data 56 (Fig. 4-1) edited by a microprocessor etc. is latched in the register 25 for each modulation unit, becomes a modulation code 35 (Fig. 4-b) according to the program of the modulation ROM circuit 26, and is output to the inverter. The odd-numbered (1st, 3rd, 5th...) 41177 that appears in the modulation code 35 is inverted at 27 and triggers the flip-flop 28 to create the frequency-divided modulation code 36 (Fig. Separated by gate circuit 30 #
1 modulation code 37 (FIG. 4-d), which triggers the monostable multi-circuit 31 that determines the recording pulse width, passes through the amplifier 33, and becomes the #1 recording signal 38 ((FIG. 4-e).
The even-numbered (second, fourth, etc.) “1” is separated and extracted by the gate circuit 29 and becomes the #2 modulation code 39 (Fig. 4-f).
), and the delay time until the first laser beam and the second laser beam irradiate the same point (in the example, the beam spot gap is 25 μm, but since the disk rotates at a constant speed, the delay time between the inner and outer peripheries is The programmable pulse delay circuit 19 delays the beam delay time (t) by a calculated or measured value.
o) Delayed output 40 (fourth
Figure-g) is similar to the odd-numbered processing of the monostable multi-circuit 3
#2 recording signal 41 (Fig. 4-h
), and FIG. 4(a) shows the relationship between the optical spot and the recording spot, and the distance G (in the example, 2
5 μm) apart from the first laser beam spot 22a.
and the second laser beam spot 22b are located symmetrically with the track center 23 in between, and the first laser beam spot 22a is located at the recording pit 21a-1e21a-
2+21a-3 and 21a-4, and the second laser beam spot 22b generates 21b-1, 21b-2 and indicates that the second laser beam spot 22b is about to record 2+21a-3 and 21b-3, respectively. Note that register 25. Modulation RO
M circuit 26. The inverter 27, flip-flop 28, and gate circuits 29 and 30 constitute the modulation circuit 18, and the monostable multicircuit 31 (or 32) and amplifier 33 (
or 34) respectively constitute the laser driver circuit 20a (or 20b).

Next, the reproducing operation will be explained using the detailed block diagram of the reproducing system shown in FIG. 3 and referring to the time chart during reproducing shown in FIG. 5. Inverter 42. Flip-flop43. Gate episode @44. Phase comparison circuit 45 and voltage controlled oscillator (
The reproduced clock generation circuit 16 shown in FIG. 1 is configured by the VCO) 46, and the demodulation circuit 17 shown in FIG. 1 is configured by the register 47 and the demodulation ROM circuit 48.

A first laser beam 22a having reflection brightness information of the first laser beam 22a.
The RF signal 49a (FIG. 5-b) is converted into a pit position signal 50 (FIG. 5-0) by the pit position checking circuit 15, and is transmitted through the inverter 42 at every falling edge of the pit position signal 50. The inverting flip-flop 43 is triggered to obtain the pit position frequency division signal 51 (FIG. 5-d), and the inversion side signal of the frequency division signal 51 (the output of the flip-flop 43) and the pit position signal 50 are combined. The gate circuit 44
By performing the AND operation, the phase comparator input signal 52 (Fig. 5-8) is obtained using only the odd-numbered pit position signals.
The phase comparison circuit 45 compares the phase of the output signal of the voltage controlled oscillation circuit 46, that is, the phase of the reproduced clock signal 53 (FIG. 5-f).

The pit position signal is latched in the register 47 at the timing of the clock signal 53, and the reproduced modulation code signal 54 (fifth
The demodulating ROM circuit 48 generates reproduced data 55N (FIG. 5-h) and sends it to a microprocessor or the like that manages the system. FIG. 5(a) illustrates the relationship between the laser beam spot and the recording pit, and corresponds to the waveforms in FIG. 5(b) to (h). 22
a is the first laser beam spot, 22b is the second laser beam spot (in the example, the light was turned off during reproduction), and 21a-1 to 21a-4 are recording pits recorded by the first laser beam. (odd-numbered pits to be reproduced) and 21b-1 to 21b-3 are recording pits (even-numbered pits to be reproduced) recorded by the second laser beam.

It shows that the first laser beam spot 22a used during reproduction passes over the track center 23. In addition,
Pre-pit 24 placed in advance at the center of the track
Although there will be a difference in the reproduced RF signal level between the recorded pits 21 (address information and synchronization pits, etc.) and the additionally recorded recording pits 21, a conventional pit position detection circuit using a differential method that is commonly used can also be detected as location information.

(Example 2) The second embodiment will be explained using FIG. 8 and FIG. 9.

FIG. 8 is a spot correlation diagram showing the relationship between two laser beam spots and the track center. First laser beam spot 22a and second laser beam spot 22b
The longitudinal distance between the two spots is approximately 25 μm due to adjustment of the optical system, and the intersection angle θ (parallelism) between the straight line connecting the two spots 22a and 22b and the track center 23, and the track direction deviation between the spots. The relationship with the dimension W is as shown in the following equation.

W= 25 ・sin θ (um) For example, if θ=O, W=O, and if θ=1”, W~
It becomes 0.44 μm. This is described in detail in 2008, when W is desired to be 0.8 μm, which is half the track spacing (1.6 μm), the rotation should be made approximately 2.36 times.

FIG. 9 shows a second embodiment in which the high-density recording and reproducing described in the first embodiment is performed while automatically controlling the track direction deviation amount (fluid dimension) W of the two laser beams based on the above principle. It is a block configuration diagram showing an embodiment, and includes a piezo actuator 58 that slightly rotates a base 57 of an optical system that generates two laser beam spots. Actuator driver 62. A low-pass filter 61 and two subtraction circuits 59 and 60 are added to the first embodiment shown in FIG. 1, and the additional functions will be mainly described below. The output signal of the first tracking circuit 10a extracts the track deviation signal from the reflected signal 49a of the first laser beam spot, and the second tracking circuit 10b extracts the track deviation signal from the reflected signal 49b of the second laser beam spot. Difference information between the output signal and the output signal of , a voltage equivalent to 0.8 μm in the embodiment) is subtracted by the second subtraction circuit 60, and from the rotation angle error Δθ, the low-pass filter 6
1 to remove alternating current components such as eccentric components, and expand and contract the piezo actuator 58 via the actuator driver 62, a one-cycle system that operates so that the above-mentioned Δθ becomes zero is constructed. Note that the track deviation signal output from the second tracking circuit 10b is added by the first tracking circuit 10a and the addition circuit 12 by closing the switch 11 only during recording, and then sent to the two-dimensional actuator 6 via the tracking amplifier 13. Since a tracking control system is configured to drive the laser beam, the two laser beam spots mentioned above are distributed symmetrically above and below the track center 23 during recording, and only the first laser beam spot is guided to the track center 23 during playback. will be done. Also, during playback, the target plover dimension is set to zero and two spots are guided on the same track.
Function to perform heavy check, target plover size is 1.6μm
Good results were also obtained with the function of reproducing data from two tracks at the same time and the function of reproducing data with the same spot position relationship as when recording.

(Embodiment 3) A third embodiment will be described below using the block diagram of FIG. 10. A mode flag detection circuit 63 is added to FIG. 1 showing the first embodiment, and the oscillation frequency of the reproduced clock generation circuit 16 can be switched using the detection circuit output signal. That is.

High-density recording flag information indicating high-density recording is recorded at a predetermined location on a disc that has undergone high-density recording as described in the first embodiment. During playback, a reflected signal from the disc is recorded. 49 is converted into a pit position signal by the pit position detection circuit 15, and the pit position signal is input to the reproduced clock generation circuit 16 and the demodulation circuit 17 at the same time.

It is also input to the mode flag detection circuit 63 to extract the high-density recording flag information described above, and if the flag is extracted, the oscillation frequency of the reproduced clock generation circuit is doubled (in the embodiment, it is normally 10.51M). ) lz and 21.02 MHz when the high-density flag was detected) was also configured to obtain fairer reproduction data.

(Example 4) A fourth example will be described below using FIG. 11 and with reference to FIG. 12. FIG. 11 is a block diagram showing a method for improving the resolution during reproduction of recorded pits distributed above and below from the tracking center in the first embodiment, and the detector 8 in FIG. 1 showing the first embodiment. ．． The current-voltage conversion amplifier 9 and the tracking circuit 10 are disassembled in detail, and the full-wave rectifier circuit 73. A window comparator 74, an adder circuit 76, and a waveform separation circuit 77 are added, and FIG. 12 is a time chart showing the pit state and waveform thereof. The laser beam reflected from the surface of the optical disk recording medium passes through a Knifezi prism 64 and a condensing lens 65.

It is converted into voltage by the voltage conversion amplifier 68a, 68%.

On the other hand, the focus information component is detected by the focus detector 67.
The light is condensed into a current and voltage converted by a conversion amplifier 69, and is input to an autofocus circuit N14 to drive an AF coil. The pair of diffracted light components converted into voltages are differentially outputted by an error amplifier 7o to produce a diffracted light difference signal, that is, a tracking error signal 7.
8 (FIG. 12-C), and constitutes a dragging control system by passing through a low-pass filter 711, a phase compensation circuit 72, and a coil driver 13 to a tracking coil (not shown). Here, the component of the diffracted light difference signal 78 before passing through the low-pass filter 71 also includes a deviation signal of the additional recording pit from the track center (when the deviation signal is a negative signal, the deviation signal of the additional recording pit from the track center is included). This indicates that there is a pit on the upper side, and a positive signal also indicates that a pit is formed on the lower side).

The total reflection scene from the disk surface is obtained by adding the signal 79 (FIG. 12-d) obtained by rectifying the diffracted light difference signal 78 by a full-wave rectifier circuit 73, and the above-mentioned diffracted light component and focus information component by an adding circuit 75. Reflecting RF signal 49 (Fig. 12-b
) are added in an adder circuit 76 to obtain a composite RF multiplied signal 0 (first
Make Figure 2-8) and compare. In comparison with the RF signal 49 before synthesis, the synthesized RF multiplied signal 0 is detected between adjacent pits (for example, the recording pit 21a shown in FIG. 12-a).
-1 and 21b-1) are larger, indicating that the resolution of pit position detection by the pit position detection circuit 15 has improved, indicating a positive G density that is not easily affected by the recording pit shape. It becomes a rebirth. Also, Figure 12-d
However, as is clear, it is possible to recognize the recording pit position even if the diffracted light difference signal 78 and its full-wave rectified outflow cuff 9 are used as they are, and by using the diffracted light difference signal 78 with the window comparator 74, Pit identification signal 81
(Fig. 12-f) and upper pit identification signal 82 (first
2-g) is outputted and input to the waveform separation circuit 77, where the lower pit RF signal 83 (FIG. 12-h) and the upper pit RF signal 84 (FIG. 12-1) are extracted and separated. Here, the above-mentioned extraction and separation were carried out. Two RF' signals 83.84
By using these as input signals to independent pit edge detection circuits or pit position detection circuits, it is possible to equivalently increase the density in the track direction.1 Pit edge detection, which is originally a method for high density recording in the radial direction In this type of case, high-density recording and playback is also possible in the track direction. Note that FIG. 12-a shows the recording pit 21. Laser beam 22. The state of the track center 23 and pre-pits 24 is shown in an arrangement corresponding to the waveform diagram in b-1 of the figure.

(Example 5) FIG. 13 is a time chart showing the relationship between the laser beam spot and the recording pit when three laser beam heads are used, and the recording/reproducing waveform at that time. An example will be explained. The basic recording and reproducing operation has the same configuration and method as the first embodiment, but two laser beam spots 2 are arranged staggered in the track direction.
2a.

22b in the track direction, that is, the track center 2
A third laser beam spot 22 is located on the same line as 3, and is separated by G2 from the second laser beam spot 22b.
c is added, and the recording operation explained in the first embodiment (the same figure ((
Using the third laser beam spot 22c added at the same time (see the waveform diagrams in b) to (i)), the reproduced signal waveform 49c is
By decoding the reproduced data from the reproduced signal 49c and performing a real-time check with the data currently being recorded, the reliability and time efficiency of data recording are improved.

According to the first embodiment, double-density recording and reproduction using the pit position detection type can be easily realized, and according to the second embodiment, the amount of deviation in the track direction between the two beam spots can be arbitrarily set. According to this, it is now possible to play back conventional pit position detection type discs recorded using a single beam. Furthermore, according to the fourth embodiment, even if it is a pit edge detection type, it is possible to further increase the density, and in addition, by using three laser sources as in the fifth embodiment, time efficiency is improved, etc. There is an effect.

【Effect of the invention〕

According to the present invention, even if pit position detection type recording/reproduction is performed, the recording/reproduction method can easily become as high-density (double density) as the pit edge detection type; (double density) recording and playback can be realized.

Since upward compatibility with conventional methods can be maintained regardless of the detection method, it is possible to provide a highly versatile, high-density, high-transfer-rate optical memory system.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the first embodiment, Figure 2 is a detailed block diagram of the recording system, Figure 3 is a detailed block diagram of the reproduction system, Figure 4 is a time chart during recording, and Figure 5 is reproduction. FIG. 6 is a time chart diagram explaining the conventional method of pit edge detection type, FIG. 7 is a time chart diagram explaining the conventional method of pit position detection type,
FIG. 8 is a spot correlation diagram, FIG. 9 is a block diagram showing the second embodiment, FIG. 10 is a block diagram showing the third embodiment, and FIG. 11 is a fourth embodiment. Block configuration diagram, Figure 12 is the time chart diagram of Figure 11, Figure 13
The figure is a time chart diagram showing the fifth embodiment. DESCRIPTION OF SYMBOLS 1... Laser diode, 2... Wavelength separation filter, 6... Two-dimensional actuator, 7... Optical disk, 8... Detector, 10... Tracking circuit, 1
5... Pit position detection circuit, 17... Demodulation circuit, 1
8... Modulation circuit, 19... Pulse delay circuit, 20.
... Laser driver circuit, 21 ... Recording pit, 22
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Claims (1)

[Claims] 1. Irradiating different points on an optical recording medium with a first laser beam using a first laser diode as a light source and a second laser beam using a second laser diode as a light source. In an optical memory device for recording, reproducing, and erasing data, the first laser beam and the second laser beam are guided onto the optical recording medium in a zigzag direction in the track direction with a limit of one half of the track spacing dimension. A high-density recording and reproducing method for optical discs, which records or erases data by irradiating the disc in a staggered manner. 2. Recording and reproducing data by irradiating different points on the optical recording medium with a first laser beam using a first laser diode as a light source and a second laser beam using a second laser diode as a light source. and a high-density recording and reproducing method for an optical disk, characterized in that, in an optical memory device that performs erasing, data is reproduced by controlling one of the two laser beams to travel. 3. In the high-density recording and reproducing method for an optical disk according to claim 2, the first laser beam and the second laser beam are directed approximately at the center of each of the data recording pits or at the approximately center between the recording pits of the same track and different tracks. A high-density recording and reproducing method for optical discs that is characterized by reproducing data by making each laser beam run. 4. In the high-density recording and reproducing method for optical disks according to claims 2 and 3, both or one of the first laser beam and the second laser beam is a reproduction laser beam, and the reproduction laser beam is a reproduction laser beam. A diffracted light intensity difference signal and a reflected light intensity signal are detected from the optical disk, and data is reproduced by using the diffracted light intensity difference signal or by the diffracted light intensity difference signal and the reflected light intensity signal. High-density recording and playback method. 5. Using a multi-laser head having at least three or more laser light sources, the first laser beam, second laser beam, and third laser beam output from the laser light sources are directed to different points on the optical recording medium. 1. A high-density recording and reproducing method for an optical disk, in which at least one of the three laser beams is used exclusively for reproducing, in an optical memory device for recording, reproducing, and erasing data by irradiating the laser beam with the laser beam. 6. Recording and reproducing data by irradiating different points on the optical recording medium with a first laser beam using a first laser diode as a light source and a second laser beam using a second laser diode as a light source. and an optical memory device that performs erasing, detects a first tracking signal indicating a track deviation of the first laser beam and a second tracking signal indicating a track deviation of the second laser beam, A high-density recording and reproducing method for an optical disc, characterized in that a tracking signal and the second tracking signal are added to generate an added tracking signal, and the generated added tracking signal is used as a tracking control signal. 7. The high-density recording and reproducing method for an optical disk according to claim 6, wherein the first tracking signal indicating the track deviation of the first laser beam or the second tracking signal indicating the track deviation of the second laser beam is A high-density recording and reproducing method for optical discs, which is characterized in that data is reproduced by switching to a tracking control signal. 8. Recording and reproducing data by irradiating different points on an optical recording medium with a first laser beam using a first laser diode as a light source and a second laser beam using a second laser diode as a light source. In an optical memory device that performs erasing, a first tracking signal indicating a track deviation of the first laser beam and a second tracking signal indicating a track deviation of the second laser beam are detected, and the first tracking signal is detected. An optical head equipped with an optical system that generates a subtraction tracking signal by subtracting the signal and the second tracking signal, and uses a signal of the difference between the low frequency component of the generated subtraction tracking signal and the target plover dimension value. A high-density recording and reproducing method for an optical disc, characterized in that the control signal controls the base rotation angle of the optical disc. 9. Using the high-density recording/reproducing method according to claims 2 to 7, adding an information flag specifying the high-density recording/reproducing/erasing mode, and controlling the reproduction clock frequency by detecting the mode flag to perform reproduction. An optical memory device characterized by: 10. Recording and reproducing data by irradiating different points on an optical recording medium with a first laser beam using a first laser diode as a light source and a second laser beam using a second laser diode as a light source. and an optical memory device for erasing, in which the first laser beam and the second laser beam are irradiated onto the optical recording medium in a staggered manner in the track direction with a limit of one half of the guide track interval dimension. An optical record carrier characterized by having data recorded thereon.