JP3225668B2 - Optical recording medium, recording method and reproducing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, a method for recording and reproducing the same, and a method for generating a tracking error signal, and more particularly to an exclusive logical operation (EX-ROM) type optical recording capable of high-density recording. The present invention relates to a medium, a recording method and a reproducing method of the optical recording medium.

[0002]

2. Description of the Related Art An optical recording medium, for example, a constant angular velocity (C
As shown in FIG. 19, the pit format of an optical disc rotated and driven by AV (Constant Angular Velocity) has a pit width and a pit length of 0.5 μm and 0.
The pit 71 formed at 86 μm has a radius of 1.6 μm.
formed at a track pitch of .mu.m
In a track direction. These dimensions are based on manufacturing restrictions and the diameter of the spot 72 on the recording surface of the optical disc irradiated with the laser beam emitted from the reproducing laser diode.

In order to increase the recording density of an optical recording medium,
It is conceivable to reduce the track pitch, the pit length, and the spot size of the laser beam. For example, in a magneto-optical disk, pits recorded based on data in an access unit and pits in other access units are independent, and there is a restriction that all data in an access unit must be rewritten. The spot scanning speed is reduced while maintaining the spot size of, and the pit length is substantially shortened by overwriting, in which the next pit is overlapped with a part of the previously formed pit, and the density is increased. Is being planned. That is, a magneto-optical disk having a higher recording density in the track direction and having a higher recording density than a compact disk (CD) as a read-only optical disk having the same diameter is realized.

[0004]

In order to increase the recording density in the radial direction of the optical disk, for example, it is conceivable to narrow the track pitch. However, if the spot size of the laser beam remains unchanged, Irradiation is also made on pits on adjacent tracks, causing crosstalk, lowering the S / N (Signal to Noise ratio),
In the worst case, a problem is encountered that data cannot be reproduced.

Therefore, it is conceivable to reduce the track pitch and also reduce the spot size of the laser beam. However, the spot size of the laser beam is proportional to the wavelength of the laser beam, and the aperture ratio NA (Nu
Since this is inversely proportional to merical aperture, there arises a problem that a new development of a short-wavelength laser light source and an expensive and large lens are required to increase the numerical aperture NA.

Therefore, it is conceivable to increase the recording density by maintaining the spot size of the laser beam, narrowing the track pitch, and narrowing the pit width so as to prevent the occurrence of crosstalk. In the manufacture of, there arises a problem that the yield is lowered and a cutting device conventionally used cannot be used.

The first embodiment of the present invention has been made in view of such circumstances, and an optical recording medium capable of high-density recording without changing the pit width, pit length, and spot size of a laser beam. It is another object of the present invention to provide a recording method for an optical recording medium capable of increasing the recording density as compared with the related art, and a reproducing method for the optical recording medium.

When information is recorded and reproduced along an optical recording medium such as an optical disk along a track, a tracking servo control is performed so that a spot of a laser beam always scans the center of the track (hereinafter referred to as a tracking center). There is a need.

As the tracking servo control, a sample servo control method is known in addition to the continuous servo control method. As shown in FIG. 20, tracking servo control in the sample servo control method is performed using a pair of wobble pits 51a and 51b which are formed in advance in a different direction from the tracking center by 1/4 track. Specifically, the laser beam spot 5
After sampling the amount of reflected light when the laser beam 3 passes through the wobble pits 51a and 51b, a tracking error signal is obtained from the difference between these signals. The spot 53 is disc-shaped so that the tracking error signal becomes "0". And the tracking servo control is applied.

[0010] Further, a laser beam spot is moved to an adjacent track or another distant track, and a track jump for recording information on this track or reproducing the recorded information is performed by a tracking servo control loop. Is opened once, the spot is moved to the vicinity of the target track, and then the tracking servo control is performed in a closed loop so that the spot is drawn into the target track.

When the above-described track jump, that is, when the spot of the laser beam scans obliquely across the track, the tracking error signal in the sample servo control method is a sine wave as shown in FIG. It is not uniquely determined for the displacement x from the center. What is uniquely determined for the displacement x is
Only the range (shown by hatching) 61 is included. That is, the spot can be stably drawn into the tracking center when the spot is located in the range 61. On the other hand, when the displacement x is large and the spot is located outside the range 61, the tracking servo control becomes unstable or oscillates. Such a state is particularly likely to occur when the relative moving speed of the spot of the laser beam in the radial direction of the disk is high, such as in a track jump.

For example, at the time of a track jump, there is an error in the distance by which the spot is moved while the tracking servo control loop is turned off. Spots may be drawn into the track. In such a case, the track jump must be performed again, but the next track jump cannot be performed until the tracking servo control loop is stabilized.
As described above, the conventional tracking servo has a problem that the track jump cannot be stably performed.

In order to increase the recording density of the optical disk, it is conceivable to reduce the pit shape, the track pitch, and the spot size of the laser beam. For example, in a magneto-optical disk, pits recorded based on data in an access unit and pits in other access units are independent, and there is a restriction that all data in an access unit must be rewritten. The scanning speed of the spot is reduced while maintaining the above, and the pit length for recording information is substantially shortened by overwriting by overlapping the next pit with a part of the previously formed pit. We are trying to increase the density. That is, a magneto-optical disk having a higher recording density in the track direction and having a higher recording density than a compact disk (CD), which is a read-only optical disk having the same diameter, has been realized.

On the other hand, in order to increase the recording density in the radial direction of the disk, for example, it is conceivable to narrow the track pitch. However, if the spot size of the laser beam remains unchanged, the laser beam will Irradiation is also applied to the pits, causing crosstalk, lowering the S / N or, in the worst case, making it impossible to reproduce data. In particular, in the sample servo control method, as shown in FIG. 20, the wobble pits 51a and 51b shifted by 1/4 track in the radial direction of the disk are required, so that the track pitch cannot be reduced.

Therefore, it is conceivable to reduce the track pitch and also reduce the spot size of the laser beam. However, the spot size is proportional to the wavelength of the laser beam and inversely proportional to the numerical aperture NA of the objective lens.
There has been a problem that new development of a short-wavelength laser light source and a need for an expensive and large lens to increase the aperture ratio NA are required.

Further, a second embodiment of the present invention aims to further improve the stability of the above-mentioned reproduced signal.

[0017]

According to a first aspect of the present invention, in order to solve the above-mentioned problems, a track pitch of 1 / n of a spot size of a laser beam on a recording surface is used, and a preceding continuous ( (n-1) Data obtained by a predetermined logical operation of data recorded on one track and input data is recorded on the next track. Further, in the first embodiment of the present invention, at a track pitch of 1 / n of a spot size of a laser beam on a recording surface, a predetermined value of the data recorded on the preceding (n-1) consecutive tracks and the input data is determined. Is recorded on the next track.

According to a first aspect of the present invention, there is provided a reproducing method for reproducing the above-mentioned optical recording medium, wherein the track pitch is n.
A reproducing laser beam having twice the spot size is irradiated on the recording surface of the optical recording medium, and the amount of reflected light is multi-valued to reproduce data.

Further, a first aspect of the present invention is a reproducing method for reproducing the optical recording medium, wherein a reproducing laser beam having a spot size of n times the track pitch is irradiated on a recording surface of the optical recording medium. Data is reproduced based on the intensity distribution of the reflected light.

In order to improve the above-mentioned first embodiment ,
According to the second embodiment of the present invention, the data and the input data have a track pitch of 1 / n of the spot size of the laser beam on the recording surface, and are recorded on the preceding (n-1) consecutive tracks. Is recorded on the next track, and the pit depth is λ /
A reproducing method is provided, wherein n signals are detected from an optical recording medium characterized by being formed at 4 to λ / 8, and these detected signals are equalized.

Further, according to the second embodiment of the present invention, the differential operation of the equivalent signal is performed to generate a push-pull signal.

More preferably, the push-pull signal is provided as a main RF signal.

Further, the sum of the above equivalent signals is calculated and provided as a sub main signal.

[0024]

In the optical recording medium according to the first embodiment of the present invention, data is recorded at a track pitch of 1 / n of the spot size of the laser beam. Further, in the recording method for an optical recording medium according to the first embodiment of the present invention, data is recorded at a track pitch of 1 / n of a spot size of a laser beam.

Further, in the reproducing method of the optical recording medium according to the first embodiment of the present invention, a reproducing laser beam having a spot size of n times the track pitch is irradiated on the recording surface of the optical recording medium, and the reflected light of the laser beam is reflected. The data is reproduced by detecting a multi-valued light amount. In the method for reproducing an optical recording medium according to the first embodiment of the present invention, a recording surface of the optical recording medium is irradiated with a reproducing laser beam having a spot size of n times the track pitch,
Data is reproduced based on the intensity distribution of the reflected light.

In the reproducing method according to the second embodiment of the present invention, the data has a track pitch of 1 / n of the spot size of the laser beam on the recording surface, and is recorded on the preceding (n-1) consecutive tracks. Data obtained by a predetermined logical operation of the data and the input data is recorded on the next track,
A reproducing method is provided, wherein n signals are detected from an optical recording medium having a pit depth of λ / 4 to λ / 8, and these detected signals are equalized. Is done. In other words, time equalization is performed before performing differential operation,
A push-pull signal is generated, and this push-pull signal is used as a main signal. Further, the sum of the time equivalent signals is calculated and used as a sub signal of the main signal.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an optical recording medium, an optical recording arrangement recording method and an optical recording medium reproducing method according to a first embodiment of the present invention will be described with reference to FIGS. In this embodiment, the present invention is applied to an optical recording medium, for example, a constant angular velocity (CAV).
The present invention is applied to a read-only optical disk which is driven to rotate by Angular Velocity, and FIG. 1 is a diagram showing a format of pits formed on a recording surface of the optical disk.

The format of the pits formed on the recording surface of the optical disk has a track pitch of 1 / n of the spot size of the reproduction laser beam on the recording surface, and was recorded on the previous consecutive n-1 tracks. A pit is formed based on data obtained by a predetermined logical operation of data and input data. Specifically, as shown in FIG. 1, the diameter (spot size) of the spot 11 of the reproduction laser beam on the recording surface is set to 1.5 to 1.5, for example, the same as that used in a compact disk reproducing apparatus or the like. Assuming that the diameter is 1.6 μm, the pit width and the pit length of this optical disk are each set to 0.
The pits 12 of 5 μm and 0.86 μm are formed with a track pitch of 1 / n of the spot size, for example, 0.8 μm which is 1/2. The pit 12 is shown in FIG.
As shown in FIG. 7, for example, when "1" continues as recording data, it is combined with an adjacent pit on the same track, and its length is formed to be a value proportional to the number of consecutive "1". Have been.

Track # (number) i (i = 1, 2, 3,.
..) is recorded on the previous track #
It is formed based on a predetermined logical operation between the data recorded in (i-1) and the input data, for example, data obtained by logical agreement (or equality) which is negative logic of exclusive OR.

As shown in Table 1,

[Table 1]

The input data for track #i is 1, 0, 1, 0, 1, 0, 1, 0, 1, 0 for track # 0, and 0, 1,. 1, 1, 0, 0, 0, 1, 1, 0 for track # 2, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1 for track # 3 and 0, 0, 1, 1, 1, 1, 0, 0, 0, 1 and track # 0 is the innermost track.

Since the pits 12 are not formed inside (before) the innermost track of the recording data for the track # 0, the initial value of the recording data is set to, for example,
It is set to “0”, and as shown in Table 2, the input data is directly used as the recording data.

[0033]

[Table 2]

Next, as shown in Table 2, the recording data for track # 1 is data (0, 0, 1) obtained by logically matching the recording data for track # 0 with the input data for track # 1. , 0, 0, 1, 0, 0, 1, 1).

As shown in Table 2, the record data for track # 2 is data (0, 0, 1, 1) obtained by logically matching the record data for track # 1 with the input data for track # 2. , 1, 0, 0, 0, 1, 1). Hereinafter, similarly, the recording data for each track #i is obtained, and based on the recording data, for example, when the recording data is “1”, the pit 12 is formed.

The recording capacity of this optical disk is, for example,
The pit width and pit length are the same as those of the conventional compact disc, and are n times, for example, twice as large as the compact disc having the same radius. Note that the above-described predetermined logical operation is not limited to logical coincidence, and may be, for example, an exclusive OR, an OR, or the like.

A method for reproducing data from an optical disk having the above-described pit format will be described. As shown in FIG. 2, an optical disk reproducing apparatus used for reproducing the optical disk irradiates the optical disk 1 with a laser beam and detects the amount of reflected light reflected on the recording surface 1a. A signal processing unit 30 for reproducing data from a reproduction signal from the optical pickup 20.

The optical pickup 20 includes a laser light source 21
A collimator lens 22 for collimating the light emitted from the laser light source 21; an objective lens 23 for converging the collimated light from the collimator lens 22 to irradiate the recording surface 1a of the optical disc 1; A beam splitter 24 disposed between the optical disc 1 and the objective lens 23 for separating the reflected light reflected on the recording surface 1a of the optical disc 1 is connected to a photoelectric conversion element (hereinafter, referred to as a photoelectric conversion element) for detecting the amount of the reflected light separated by the beam splitter 24. , Detector) 25,
A condensing lens 26 disposed between the beam splitter 24 and the detector 25 for condensing the reflected light separated by the beam splitter 25, and for reproducing a high frequency (RF) signal based on a signal from the detector 25, And a preamplifier 27 for reproducing a servo error signal such as a tracking error signal.

The optical pickup 20 has substantially the same configuration as that of a conventional optical pickup used in a compact disk reproducing apparatus and the like. / 2, and as shown in FIG. 1, two adjacent tracks #i and #
Tracking servo control is performed so that scanning is performed simultaneously with (i-1) (hereinafter, the width scanned by the spot is referred to as a scanning track width). The signal processing unit 30 includes a signal discriminating circuit 31 for reproducing data from the RF signal from the preamplifier 27, a phase synchronization circuit (phase locked loop, PLL) 32 for reproducing a clock from the RF signal from the preamplifier 27, A contra roller 33 for performing control such as tracking servo control and focus servo control based on the servo error signal from
Based on the clock from the PLL 32, the controller 3
3 and a spindle motor 35 for driving the optical disc 1 to rotate.

In this optical disk reproducing apparatus, the optical disk 1 is driven to rotate at a constant angular velocity by the spindle motor 35. The laser light source 21 is composed of, for example, a semiconductor laser and emits a laser beam having the same wavelength as that of a conventional optical pickup. The collimator lens 22 converts the light emitted from the laser light source 21 into parallel light,
4 is incident. The beam splitter 24 is formed of, for example, a half mirror, and allows light emitted from the laser light source 21 to pass through the objective lens 23. The objective lens 23 has an aperture ratio NA equivalent to that of a conventional optical pickup. Therefore, the spot size of the laser beam on the recording surface 1a is twice the track pitch.

As shown in FIG. 1, pits 12 are formed on the storage surface 1a of the optical disk 1 based on the recording data, and as shown in FIG. 3A, two adjacent tracks # (i -1) When there is no pit 12 in #i, the intensity distribution of the reflected light is bilaterally symmetric on the paper. FIG.
As shown in (b), pit 1 is added to track # (i-1).
2 and the pit 12 exists in the track #i, the diffraction at the pit 12 causes the intensity distribution of the reflected light to be:
The right side becomes stronger on paper. As shown in FIG. 3C, a pit 12 exists on track # (i-1),
When there is no pit 12 at i, the intensity distribution of the reflected light becomes stronger on the left side on the paper. As shown in FIG. 3D, when the pits 12 are present on two adjacent tracks # (i-1) and #i, the intensity distribution of the reflected light is symmetrical and the pits 12 are not present. Weaker than. As described above, the reflected light having the intensity distribution based on the presence or absence of the pits 12 is converted into parallel light by the objective lens 23, then re-enters the beam splitter 24, and a part of the reflected light is separated (reflected). .

The condenser lens 26 is composed of, for example, a cylindrical lens for obtaining a focus error signal by the astigmatic method, and condenses the reflected light on the light receiving surface of the detector 25. The detector 25, as shown in FIG.
The light receiving area has four areas 25a, 25b, 25c, 2
5d. The far field pattern on the light receiving surface of the detector 25 is, as shown in FIG.
There is no pit 12 in track # (i-1) and track #
When the pit 12 exists in i, the areas 25a and 25d
Are bright, and the regions 25b and 25c become dark (shown by oblique lines) due to diffraction at the pits 12. On the other hand, as shown in FIG. 5B, when the pit 12 exists in the track # (i-1) and the pit 12 does not exist in the track #i, the area 25
a and 25d are dark, and the regions 25b and 25c are bright.
Also, as shown in FIG. 5C, when pits 12 exist in two adjacent tracks # (i-1) and #i,
All the regions 25a, 25b, 25c, 25d become dark. As shown in FIG. 5D, when there are no pits 12 in two adjacent tracks # (i-1) and #i,
All the areas 25a, 25b, 25c, 25d become bright.

The preamplifier 27 includes, for example, a plurality of differential amplifiers, and
Based on the levels detected at 5b, 25c, 25d,
For example, if the levels detected in the regions 25a, 25b, 25c, and 25d are A, B, C, and D, respectively, the focus error signal, the tracking error signal, and the RF
The signals are obtained by equations 1, 2, and 3, respectively.

[0044]

(Equation 1)

[0045]

(Equation 2)

[0046]

(Equation 3)

The signal discriminating circuit 31 detects the level of the RF signal from the preamplifier 27, and sets the value to “0” when the level is within a predetermined range, and sets the value to “1” otherwise.
Thus, data having the same value as the input data is reproduced. More specifically, when tracking is performed so that the spot scans track # (i-1) and track #i simultaneously, when there is no pit 12 in both tracks # (i-1) and #i, FIG. 6 shows three cases where the pits 12 are present on one track and the pits 12 are present on both tracks # (i-1) and #i.
As shown in (a), the RF signal has three levels, a high (H) level, an intermediate (M) level, and a low (L) level. Therefore, the level of the RF signal is determined based on the two threshold values, and the value is set to “0” when the signal is at the M level, and is set to “1” when the signal is at the H and L levels. Data can be reproduced.

For example, when reproducing the track # 1 shown in FIG.
When the tracking servo control is performed so that # 1 is scanned simultaneously, the level of the reproduction signal from the preamplifier 27 becomes M, L, H, L, M, M, M, L, H, M levels. By setting “0” and L level and H level to “1”, data (0, 1, 1, 1, 0, 0, 1, 1, 0) having the same value as the input data shown in Table 1 is obtained. Obtainable. As described above, by multi-value detection of the RF signal, data can be reproduced for each track using a reproduction laser beam having a spot size of, for example, twice the track pitch. That is, data can be reproduced without shortening the wavelength of the laser light source or increasing the numerical aperture NA of the objective lens as compared with a conventional compact disk reproducing apparatus. FIG. 6 (a)
The beam position on the horizontal axis of the graph shown in FIG.
, The position of the spot 11 in the track direction is shown.

The PLL 32 receives the RF signal from the preamplifier 27.
A clock is reproduced from the signal, and this clock is supplied to the system controller 34. System controller 34
Controls the signal discriminating circuit 31, the controller 33, and the like based on the clock from the PLL 32. Under the control of the system controller 34, the controller 33 uses the focus error signal and the tracking error signal obtained by the above equations 1 and 2 to set these signals to “0”.
The “two-axis device” that drives the objective lens 23 in the optical axis direction and the radial direction of the disk is controlled so that That is, focus servo control and tracking servo control are performed. Further, the controller 33 performs spindle servo control, and controls the rotation speed of the spindle motor 35 to be constant at the angular velocity. Also, the controller 33
Also controls the entire biaxial device to slide in the radial direction of the disk.

As described above, in this embodiment, data is reproduced from the optical disc 1 in which the pits 12 having the same shape as, for example, a compact disc are recorded at a high density at a track pitch of 1 / n of the spot size of the reproduction laser beam. At this time, data can be reproduced for each track by detecting the level of the RF signal proportional to the amount of reflected light by multi-level detection, for example, by ternary detection.

A description will be given of a reproducing method different from the above-described embodiment. The optical disk reproducing apparatus used in this reproducing method has the same circuit configuration as that of the above-described embodiment (see FIG. 2), and thus the duplicated description will be omitted. The optical disk reproducing apparatus reproduces data based on the level (A + D) and the level (B + C) obtained by the preamplifier 27. Specifically, the reproduction signal RFa obtained by the region 25a and the region 25d of the detector 25 and the reproduction signal RFb obtained by the region 25b and the region 25c are compared with a predetermined threshold value. If "1" is set, the same value as the recorded data shown in Table 2 is reproduced simultaneously for two tracks. When playing track #i, the spot is track #
(I-1) Tracking is performed so that track #i is scanned simultaneously, and track # (i-1) (reproduction signal RF
By performing a logical operation corresponding to the logical operation used at the time of recording the reproduced data reproduced from a) and the reproduced data reproduced from the track #i (reproduced signal RFb), for example, by obtaining a logical match, the data for the track #i is obtained. Can be played.

As shown in FIG. 1, when the spot 11 scans the track # 0 and the track # 1 at the same time, the reproduction data obtained from the track # 0 is 1, 0, 1, 0, 1,. 0, 1, 0, 1, 0, and the reproduced data from the track # 1 becomes 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, and these reproduced data are reproduced simultaneously. Therefore, by determining the logical coincidence of these reproduced data, data of 0, 1, 1, 1, 0, 0, 0, 1, 1, 0 can be obtained.
Data having the same value as the input data for 1 can be reproduced.

That is, when data is reproduced from the optical disk 1 in which the pits 12 having the same shape as that of the compact disk are recorded at a high density at a track pitch of 1 / n of the spot size of the reproduction laser beam, the intensity of the reflected light is By detecting the distribution by the detector 25 that divides the light receiving area into a plurality of parts, data can be reproduced for each track.

Next, a recording method for an optical disk having a pit format as shown in FIG. 1 will be described. A method for producing a read-only optical disk will be briefly described. The manufacturing process of a read-only optical disk is roughly divided into a mastering process (mastering process) and a disc-forming process (replication process). The mastering process is a metal mastering (stamper) used in the disc making process
The disc making step is a process for mass-producing an optical desk as a replica of the disc using a stamper. Specifically, in the mastering process, a photoresist is applied to a polished glass substrate,
Data (information) is recorded on the photosensitive film by exposure with a laser beam. That is, cutting is performed. The data to be recorded must be prepared in advance, and this preparation step is also called pre-mastering. Then, when the cutting is completed, after performing a predetermined process such as development, information is transferred onto the metal surface by, for example, electroforming, and a stamper necessary for duplicating the optical disk is created.

Next, by using this stamper, information is transferred onto a resin substrate by, for example, an injection method or the like, a reflective film is formed thereon, and processing such as processing into a required disk shape is performed. To complete the final product. Therefore, the recording method for an optical recording medium according to the first embodiment of the present invention is applied to the above-described pre-mastering and cutting.

More specifically, as shown in FIG. 7, the cutting device irradiates a laser beam to the glass substrate 41 coated with a photoresist to perform the cutting.
0, a drive unit 50 for driving the glass substrate 41 to rotate, and a signal processing unit 60 for converting the input data into print data and controlling the optical unit 40 and the drive unit 50. The optical unit 40 includes a laser light source 42, an optical modulator 43 that modulates light emitted from the laser light source 42 based on recording data, a prism 44 that bends an optical axis of a modulated beam from the optical modulator 43, An objective lens 45 that condenses the modulated beam reflected by the prism 44 and irradiates the photoresist surface of the glass substrate 41 with the light is formed. The driving unit 50 includes a motor 51 that rotationally drives the glass substrate 41, and a pulse (hereinafter, referred to as a pulse) for detecting a rotation speed of the motor 51.
An FG generation circuit 52 for generating an FG pulse), a slide motor 53 for moving (sliding) the glass substrate 41 in the radial direction, a motor 51, and a slide motor 5
3 and a servo controller 54 for controlling the rotation speed of the objective lens 45 and the tracking control of the objective lens 45.

The signal processing unit 60 forms, for example, input data by adding an error correction code or the like to the source data from the computer, and performs a predetermined logical operation on the input data from the formatting circuit 61. Operation circuit 62 for forming recording data by using the logic operation circuit 62, a driving circuit 63 for driving the optical modulator 43 based on the recording data from the logic operation circuit 62, and a clock generator for supplying a clock to the logic operation circuit 62 and the like. 64
And a system controller 65 that controls the servo controller 54 and the like based on a clock from the clock generator 64 and the like.

In this cutting device, the glass substrate 41 is driven to rotate by the motor 51 and is slid while the glass substrate 41 is being rotated by the slide motor 53. Specifically, the servo controller 54 controls the motor 51 so that the glass substrate 41 rotates at a constant angular velocity, and the feed pitch in the radial direction is 1 / n of the spot size of the reproduction laser beam, for example, as described above. As described above, when the spot size of the reproduction laser beam is 1.6 μm and n is 2, the slide motor 53 is controlled so as to be 0.8 μm per rotation.

The laser light source 42 is, for example, He-Cd
The output light is made of a laser and is incident on the optical modulator 43. The light modulator 43 is, for example, of the acousto-optic effect type, modulates the light emitted from the laser light source 42 based on the recording data, and modulates the modulated beam via the prism 44 and the objective lens 45 onto the photo-resist of the glass substrate 41. Irradiate the resist surface. As a result, the photoresist is exposed based on the recording data. Specifically, the wavelength of the emitted light from the laser light source 42 and the aperture ratio NA of the objective lens 45 are such that the spot size of the converged modulated beam is 1 / n of the spot size of the reproduction laser beam on the photoresist surface. If the spot size of the reproduction laser beam is set to 1.6 μm and n is set to 2, as described above, the photoresist is exposed with a width of 0.8 μm or less.

The formatting circuit 61 divides source data from a computer into selectors and segments, adds addresses of selectors and segments, error correction codes, and the like, forms input data, and performs a logical operation on the input data. The signal is supplied to a circuit 62. In addition, the formatting circuit 61 includes focusing,
Servo byte for tracking is calculated by logical operation circuit 62
To supply. The logical operation branch 62 is, for example, (n-
1) A memory having a capacity for storing the recording data for the track is built in, and the recording data recorded on the previous (n-1) consecutive tracks are sequentially stored and, as described above, this storage is performed. The recording data to be recorded on the next track is formed by a predetermined logical operation of the existing recording data and the input data, and this recording data is supplied to the drive circuit 63. The drive circuit 63 drives the optical modulator 43 based on the recording data from the logical operation circuit 62.

As a result, a modulated beam modulated on the basis of the recording data is applied to the photoresist surface of the glass substrate 41, and for example, an exposed portion corresponding to the pit 12 as shown in FIG. And then development,
The stamper is completed by electroforming. Then, a large number of optical disks are duplicated and produced using this stamper.

In the optical disk produced as described above, the track pitch can be set to 1 / n, for example, 1/2 of the spot size of the reproduction laser beam, and the recording density can be made the same as that of a conventional optical disk having the same radius. It can be twice as large as a compact disc. Further, by reducing the feed pitch (track pitch) of the conventional cutting device, the conventional device can be used, and no new capital investment is required.

The first embodiment of the present invention can be applied not only to the above-mentioned read-only optical disk but also to, for example, a rewritable magneto-optical disk. In this case, rewriting rewrites data recorded on other tracks as in the case of conventional overwriting.
In applications such as PCM recording of music where the music is completely separated and the area to be rewritten is one music, there is no problem due to overwriting, and the recording capacity is higher than that of a conventional magneto-optical disk. Can be increased. Needless to say, the first embodiment of the present invention can be applied to an optical storage medium such as a memory card in which tracks are configured in parallel.

As is clear from the above description, the optical recording medium according to the first embodiment of the present invention has a track pitch of 1 / n of the spot size of the laser beam on the recording surface, and has the previous continuous ( n-1) Since data obtained by a predetermined logical operation of the data recorded on one track and the input data is recorded on the next track,
Without changing the pit width, pit length, and spot size of the reproducing laser beam, the recording capacity can be increased n times as compared with a conventional compact disk having the same size as the conventional one. In the method for recording an optical recording medium according to the first embodiment of the present invention, recording is performed on the preceding (n-1) consecutive tracks at a track pitch of 1 / n of the spot size of the laser beam on the recording surface. By recording data obtained by a predetermined logical operation of data and input data on the next track, without changing the pit width, pit length and spot size of the reproduction laser beam,
The recording capacity can be increased n times as compared with a conventional compact disk of the same size, for example. Further, a conventionally used cutting device such as a compact disc can be used, and a new cutting device is not required.

Further, in the reproducing method of the optical recording medium according to the first embodiment of the present invention, a reproducing laser beam having a spot size of n times the track pitch is irradiated on the recording surface of the optical recording medium, and the reflected light of the laser beam is reflected. By reproducing the data by detecting the light amount in multiple values, the data can be reproduced for each track using a reproduction laser beam having a spot size of n times the track pitch. That is, data can be reproduced without shortening the wavelength of the laser light source or increasing the NA of the objective lens. By irradiating the recording surface of the optical recording medium with a reproducing laser beam having a spot size of n times the track pitch and reproducing the data based on the intensity distribution of the reflected light, the spot size becomes n times the track pitch. Data can be reproduced track by track using a reproduction laser beam. That is,
The wavelength of the laser light source can be shortened or the aperture ratio N of the objective lens can be reduced.
Data can be reproduced without increasing A.

Embodiments of a method for recording an optical recording medium, an optical recording medium, and a method for generating a tracking error signal according to a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the present invention is applied to an optical recording medium, for example, an optical disk of a sample servo control system.
FIG. 9 is a block diagram showing a circuit configuration of a main part of an optical disk device for recording and reproducing data on and from this optical disk. FIG. 9 is a diagram showing a format of servo pits formed on a recording surface of the optical disk.

The format of a servo pit previously formed on the recording surface of the optical disk will be described. As shown in FIG. 9, the format of the servo pits is such that servo pits 131 are previously formed at positions A and C on track #A _i (i = 1, 2, 3,...), And on track #B _i the servo pits 131 are previously formed on the position B and the position a, the track #C _i servo pits 131 are previously formed at a position C and the position B, they are a format repeated at three tracks cycles. Also,
These tracks #A _i, # B _i, the track pitch is the distance # C _i is ½ of the spot size of the laser beam on the recording surface. Therefore, the recording density in the radial direction of this optical disc is two times that of the conventional optical disc.
Doubled.

More specifically, when the spot size of the laser beam on the recording surface is set to 1.5 μm to 1.6 μm, which is the same as that used in a compact disk reproducing apparatus or the like, the pit width of the servo pit 31 is reduced. The pit length is, for example, 0.
5. μm, 0.86 μm, and the track pitch is 0.8 μm, which is の of the spot size.

Next, a description will be given of a main part of an optical disk apparatus for recording or reproducing data on or from an optical disk having servo pits of the above-described format. As shown in FIG. 8, the main part of this optical disk device is
An optical pickup 111 for irradiating the optical disc 101 with a laser beam and detecting the amount of reflected light reflected on the recording surface
And an amplifier 112 for amplifying the RF signal from the optical pickup 111, a phase locked loop (PLL) 113 for reproducing a clock from the RF signal amplified by the amplifier 12, and a clock from the PLL 13. Controller 114 that generates a sampling clock and the like, and an amplifier 11 using the sampling clock from the timing controller 114.
A sample-and-hold circuit 115 for sampling the RF signal from the second and a three-phase signal from the sample-and-hold circuit 115, and a tracking error for generating a tracking error signal by periodically switching and selecting these difference signals. It includes a signal generation circuit 120 and a phase compensation circuit 116 for compensating the phase of the tracking error signal from the tracking error signal generation circuit 120.

In this optical disc apparatus, as shown in FIG. 9, servo pits formed on adjacent tracks, for example, track #A and track #B, track #B and track #C, or track #C and track #B The tracking servo control is performed by using 131 to record or reproduce data. Specifically, the optical pickup 111
Are, for example, a laser light source, a collimator lens that collimates the light emitted from the laser light source, an objective lens that collects the parallel light from the collimator lens and irradiates the recording surface of the optical disc 101, and is reflected by the recording surface. A beam splitter that separates the reflected light, a detector that detects the amount of reflected light separated by the beam splitter, a so-called two-axis device that drives an objective lens in the optical axis and in the radial direction of the optical disc 101, and the like. The spot size of the laser beam on the surface is, for example, the same as that used in a compact disk reproducing device or the like.

Therefore, the optical pickup 111
Since the track pitch of the optical disc 101 is の of the spot size as described above, the laser beam irradiates two tracks simultaneously, and an RF signal based on the amount of reflected light is sent to the amplifier 112. Output. The amplifier 112 amplifies the RF signal, and
And a sample and hold circuit 115.

The PLL 113 reproduces a clock based on, for example, a component corresponding to the servo pit 131 formed at the position B of the RF signal amplified by the amplifier 112,
The reproduced clock is supplied to the timing controller 114. Note that the clock reproduction by the PLL 113 may be performed based on an RF signal component corresponding to a data pit instead of the servo pit 131 when data has already been recorded. The timing controller 114 generates a sampling clock at a timing corresponding to the positions A, B, and C shown in FIG. 9 based on the clock, and supplies the sampling clock to the sample and hold circuit 115. The sample and hold circuit 115 samples and holds the RF signal from the amplifier 112 using the sampling clock from the timing controller 114, and supplies the obtained three-phase signals having different phases to the tracking error signal generation circuit 120.

For example, when a track jump is performed and the spot of the laser beam scans (seeks) obliquely across the track, the sample hold circuit 115
For example, as shown in FIG. 10, an RF signal RFA obtained by sampling and holding at a timing corresponding to a position A and a position B
, And an RF signal RFC obtained by sampling and holding at a timing corresponding to the position C is output.

Tracking error signal generation circuit 120
Is a sample and hold circuit 115 as shown in FIG.
Amplifiers 121a, 121b, 121 for respectively calculating the difference between the RF signals RFA, RFB, and RFC from
c and these differential amplifiers 121a, 121b, 121
A multiplexer 122 for switching and selecting each output of c
And comparators 123a, 123 which respectively detect the polarities of the outputs of the differential amplifiers 121a, 121b, 121c.
3b, 123c and these comparators 123a, 1
A logical operation circuit 124 that controls the multiplexer 22 by a predetermined logical operation of each output of 23b and 123c.

The differential amplifier 121a generates a tracking error signal TRA (shown by a broken line) by subtracting the RF signal RFB from the RF signal RFC, as shown in FIG. The tracking error signal TRB (shown by a broken line) is generated by subtracting the RF signal RFC from the signal RFA, and the differential amplifier 121c subtracts the RF signal RFA from the RF signal RFB to generate the tracking error signal TRC (shown by a broken line). Generate. Therefore,
These tracking error signals TRA, TRB, TR
C is a sine wave having a phase different from each other by 120 degrees and a signal whose phase is advanced by 90 degrees with respect to the RF signals RFA, RFB, and RFC, respectively. The tracking error signals TRA, TRB, TRC generated in this manner are supplied to the multiplexer 122 and the comparators 123a, 1a.
23b and 123c. Note that the dynamic range of these tracking error signals TRA, TRB, TRC is, as shown in FIG.
This is due to the diffraction at 31 and can be a large value compared to a conventional optical disc. In other words, a tracking error signal with a good S / N can be obtained.

The comparators 123a, 123b, 123
c detects the respective polarities of the tracking error signals TRA, TRB, and TRC, as shown in FIG. 10C. For example, when the level is positive, the polarity signals PA, PB, and PC which become logic "1" are detected. To form these polarity signals PA,
PB and PC are supplied to the logical operation circuit 24. As shown in FIG. 10D, the logical operation circuit 24 controls the control signals C having phases different from each other by 120 degrees based on the following Expressions 4 to 6.
A, CB, and CC are calculated. When the control signal CA is “1”, the tracking error signal TRA is selected. When the control signal CB is “1”, the tracking error signal TRB is selected. 1 ", the multiplexer 12 selects the tracking error signal TRC.
2 is controlled.

[0077]

(Equation 4)

[0078]

(Equation 5)

[0079]

(Equation 6)

In these equations (4) to (6), the signals “∧” and “INV ()” mean AND and negative logic, respectively.

The multiplexer 122 outputs a tracking error signal obtained by periodically switching the three-phase tracking error signals TRA, TRB, TRC having different phases from each other, as shown by the solid line in FIG. This tracking error signal is supplied to the phase compensation circuit 116. The phase compensation circuit 116 performs phase compensation in the servo loop, compensates the phase of the tracking error signal from the multiplexer 122, and supplies the phase-compensated tracking error signal to the optical pickup 111. The optical pickup 111 moves the spot of the laser beam in the radial direction of the optical disc 101 by the above-described biaxial device so that the tracking error signal becomes “0”.

As described above, a loop in servo control is formed, and tracking servo control is performed.
Then, in a state where the tracking servo control is performed in this manner, that is, as shown in FIG. 9, in a state where the spot 32 of the laser beam scans the center of the adjacent track, each track #A _i , #B _i , #C _i servo area 130 in which servo pit 131 is formed in advance
The data is recorded in the data area 133 between the servo area 130 and the next servo area 130, or the recorded data is reproduced.

The tracking error signal output from the tracking error signal generation circuit 120 is shown in FIG.
As shown in FIG. 23, there is no portion corresponding to the range 62 other than the range 61 in which the tracking servo can be stably performed as described with reference to FIG. 23, and the stable tracking servo can always be applied. If the tracking error signal shown in FIG. 10B is, for example, a signal obtained when the laser beam is sought from the inner circumference to the outer circumference, when the laser beam is sought from the outer circumference to the inner circumference, the time axis goes back. In the seek from the inner circumference to the outer circumference, the level always increases in a range where the level changes continuously, and conversely, the level always decreases in the seek from the outer circumference to the inner circumference. Therefore, the moving direction of the spot of the laser beam can be detected from the changing direction of the level in the range where the level changes continuously. In other words, in this optical disc device, a tracking error signal including information on the seek direction can be obtained. Further, the optical disk device does not require a divider or a memory used in a conventional device to generate a tracking error signal, and can have a simple circuit configuration.

The above-described tracking error signal generation circuit 1
20 will be described below. Note that FIG.
The circuits having the same functions as those of the tracking error signal generation circuit 120 shown in FIG. The tracking error signal generation circuit 120 is configured as shown in FIG.
As shown in FIG.
Differential amplifiers 121a, 121b, and 121c for calculating the differences between the signals RFA, RFB, and RFC, respectively, and the RF signals RFA and RF from the sample and hold circuit 115.
B and RFC, and a differential amplifier 1 that subtracts the output of the adder 141 from the RF signals RFA, RFB and RFC from the sample and hold circuit 115, respectively.
42a, 142b, 142c and differential amplifiers 121a,
An analog / digital converter (hereinafter referred to as an A / D converter) that converts each output of the respective 121b and 121c into a digital signal.
143a, 143b, 143c) and A / D converters 144a, 1 for converting the outputs of the differential amplifiers 142a, 142b, 142c into digital signals, respectively.
44b, 144c and A / D converters 143a, 143
b, 143c, 144a, 144b, 144c, a read-only memory (hereinafter referred to as ROM) 145 for outputting a tracking error signal by using each output as an address;
D / D for converting a tracking error signal supplied as a digital signal from the ROM 145 into an analog signal.
A converter 146 and differential amplifiers 121a, 121b, 1
Comparator 123a, 123b, 123c for detecting the polarity of each output of 21c, and a logical operation circuit 12 for controlling ROM 145 by a predetermined logical operation of each output of these comparators 123a, 123b, 123c.
And 4.

The differential amplifiers 121a, 121b, 121c
Is a sine wave having a phase difference of 120 degrees from each other as shown in FIG.
A, RFB, and RFC generate tracking error signals TRA, TRB, and TRC whose phases are advanced by 90 degrees, respectively, and these tracking error signals TRA and TRC are generated.
B, TRC are converted to A / D converters 143a, 143b, 143.
c and the comparators 123a, 123b, 123c. A / D converters 143a, 143b, 143c
Converts the tracking error signals TRA, TRB and RFC into digital signals, respectively, and converts the tracking error signals TRA and TR converted into these digital signals.
B and TRC are supplied to the ROM 145 as addresses.

On the other hand, the adder 141 adds the RF signals RFA, RFB, and TRC from the sample-and-hold circuit 115 and, as shown in FIG. 10A, an RF signal which is a three-phase AC signal. RFA, RFB, RF
The average value of C (the center value and a constant) C is calculated by the differential amplifier 14.
2a, 142b and 142c. Differential amplifier 14
2a, 142b, 142c are RF signals RFA, RF
This average value C is subtracted from B and RFC, that is, the RF signals RFA, RFB and R are obtained by shifting the RF signals RFA, RFB and RFC by the average value C in a DC manner and removing the DC component.
The FC is supplied to A / D converters 144a, 144b, 144c. A / D converters 144a, 144b, 144c
Are the RF signals RFA, RFB, R from which the DC component has been removed.
FC are converted into digital signals, and RF signals RFA, RFB, RF converted into these digital signals are converted.
C is supplied to the ROM 145 as an address.

Thus, the tracking error signals TRA and TR converted into digital signals are stored in the ROM 145.
B, TRC and RF signals RFA, RFB, RFC. The ROM 145 contains tracking error signals TRA, TRB, TRC and RF signals RFA, RF
A table that satisfies a predetermined relationship with B and RFC is stored in advance.
RFB and RFC are used as addresses, and a tracking error signal indicated by a solid line in FIG. 10E is output. Specifically, for example, the displacement of the spot of the laser beam from the tracking center is x, the track pitch is p, the RF signal RFA from the sample servo circuit 115 is V _QA, and this V _QA is represented by the following equation 7. And the output v _QA of the differential amplifier 142a is obtained by the following equation 8.

[0088]

(Equation 7)

[0089]

(Equation 8)

On the other hand, the tracking error signal TRA from the differential amplifier 121a has a phase that is 90
The tracking error signal TRA
_{Assuming PA} , this _vPA is represented by the following equation 9.

[0091]

(Equation 9)

It is assumed that K ₂ / K ₁ = 1. From these Expressions 8 and 9, the signal v _x indicating the displacement x is obtained by Expression 10.

[0093]

(Equation 10)

By the way, this signal v _x is expressed as | x | <(p
/ 4) is proportional to the displacement x in principle.
In the range of | x | <(3p / 2),
A value (table) on a straight line obtained by extending a straight line in the range of | x | <(p / 4) is stored, and the digitized tracking error signal TRA (v _PA ) and RF signal RF
By looking up this table using A (v _QA ), a tracking error signal TRA ₁ indicated by a broken line in FIG. 10C is obtained. Also, tables for the other tracking error signals TRB ₁ and TRC ₁ are stored in the same manner, and are stored using the digitized tracking error signal TRB and RF signal RFB or the tracking error signal TRC and RF signal RFC. Tracking error signal TRB ₁ ,
To read the TRC _1.

In the ROM 145, as the read control signals, the above-mentioned control signals CA,
Control signals for switching between the normal mode and the lock mode are supplied via terminals 147 and CB and CC (shown in FIG. 10D). In the normal mode, when the control signal CA is “1”, the tracking error When the signal TRA ₁ is selected and the control signal CB is “1”, the tracking error signal TRB ₁ is selected, and when the control signal CC is “1”,
Select a tracking error signal TRC _1, the above-mentioned FIG. 1
0 (e), as indicated by the solid line, three-phase tracking error signals TRA ₁ , TRB ₁ , TRC having different phases from each other.
Outputs a tracking error signal in which ₁ is switched periodically. In the lock mode, regardless of the control signals CA, CB and CC, the tracking error signals TRA ₁ , TR
One of B ₁ and TRC ₁ is selected and output.

The tracking error signal read from the ROM 145 as described above is output to the D / A converter 146.
After being converted into an analog signal in the optical pickup 1 in the same manner as in the above-described embodiment, the optical pickup 1
11 is supplied. As a result, in the normal mode, the tracking error signal includes a range 6 other than the range 61 in which the tracking servo control can be stably performed, as in the above-described embodiment.
2 (see FIG. 23), and stable tracking servo control can always be performed. Also,
A tracking error signal including seek direction information can be obtained.

Next, the operation of the track jump will be described. For example, in a state where the track #A _i rests tracking, when the track jump from the track #A _i to the track #B _i, and supplies the control signal through the terminal 147, forcibly track read from ROM145 Switching from the error signal TRA ₁ to the tracking error signal TRB ₁ and the control signals CA,
The lock mode is set so that the tracking error signal is not switched regardless of CB and CC. Specifically, as shown in FIG. 13, when tracking is applied to the track #A _i , the spot of the laser beam becomes the tracking error signal T in the range where the control signal CA is “1”.
Located in track center of the track #A _i corresponding to zero cross point X _A of RA _1. In this state, when reading from the ROM 145 is switched to the tracking error signal TRB ₁ irrespective of the control signals CA, CB and CC, a signal of a level L is output from the ROM 145 and the optical pickup 111 has a low level L. so that the track #B _i the spot of the laser beam, which corresponds to the tracking error signal zero crossing point of the TRB ₁ X _B
And the track jump is completed.

As described above, in this optical disk device,
A track jump can be performed while keeping the tracking servo control in a closed loop state, and there is no need to once open a tracking servo control loop as in a conventional device. In other words, there is no need for an electric component for opening the loop of the tracking servo control, and the cost can be reduced. Further, as described above, by providing the lock mode, it is possible to widen the capture range in the tracking servo control, for example, a tracking error signal TRB from the tracking error signal TRA _1
After switching to ₁ and setting the lock mode, even if some disturbance occurs, there is a margin as shown in FIG. 3 (e), and a stable track jump can be performed.
Further, the servo pit 131 shown in FIG.
It can be formed using a conventional compact disk cutting device or the like, and does not require new capital investment. That is, in the conventional cutting apparatus, the laser beam can be easily formed by halving the feed pitch of the laser beam in the radial direction of the disk. Also,
The tracking servo control circuit of this optical disk device
It can also be used as a tracking servo circuit of a conventional magneto-optical disk device.

It is needless to say that the present invention is not limited to the above-described embodiment, but can be applied to an optical recording medium such as a memory card having tracks arranged in parallel.

As is clear from the above description, in the second embodiment of the present invention, tracking servo control is performed by using pits formed on adjacent tracks as servo pits for obtaining a tracking error signal.
Data can be recorded by performing stable tracking servo control. Further, an optical recording medium using such tracking servo control does not require a wobble pit for obtaining a conventional tracking error signal,
The track pitch can be reduced, and the recording density in the track pitch direction can be increased.

In the second embodiment of the present invention, a recording medium is irradiated with a laser beam, and an RF based on the amount of reflected light is used.
3 obtained by sampling the signal at the servo pit position
By calculating the difference between the phase signals and periodically switching and selecting these difference signals to generate a tracking error signal, a tracking error signal capable of performing stable tracking servo control can be obtained. Further, a track jump can be performed while the tracking servo control is being performed, and a stable track jump can be performed. Also, at the time of a track jump, the retraction range can be widened.

In the first embodiment, in order to improve the recording density, an information signal is recorded and formed on an optical disk so that the track width is 1.6 μm and the track pitch is 0.8 μm. The information signal recorded on the optical disk as described above is read based on the signal level of the sum signal of the detector 25 that detects the reflectance of the laser beam applied to the optical disk. However, the signal obtained by taking the sum of the respective light receiving areas of the detector 25 has a state where there is a pit on either the left or right of the tracking center as shown in FIG. 5 (FIGS. 5A and 5B). In the state where there are pits on both sides of the line (FIG. 5C), although the cycle of the sum signal is constant,
The amplitude of the sum signal changes. As a result, the sum signal from the detector 25 is the MT signal when a pit exists on one side of the tracking center as shown in FIGS. 5 (a) and 5 (b).
There are two MTF curves, an F curve and an MTF curve in the case where pits exist on both sides of the tracking center.
It becomes impossible to specify the characteristics of a single MTF (Modulation Transfer Function). When the sum signal of the detector 25 is supplied to the equalizer circuit in such a state, there is a problem that the eye pattern of the sum signal is broken.

Therefore, a third embodiment of the present invention for solving this problem will be described with reference to FIG. FIG.
FIG. 4 shows a part of the reproducing circuit according to the third invention of the present invention. The detector 25 shown in FIG. 14 has four light receiving regions 25a, 25b, 25c, as described in the first embodiment.
25d. Of the four light receiving regions, two light receiving regions 25a, 2
In the third embodiment, the first light receiving area 251 made of 5d and the second light receiving area 252 made of the remaining two light receiving areas 25b and 25c are handled. In practice, a signal obtained by summing the respective detection outputs from the light receiving areas 25a and 25d and a signal obtained by summing the respective detection outputs from the light receiving areas 25b and 25c are equalizer circuits described later. 201 and 202.

Reference numerals 201 and 202 denote equalizer circuits to which output signals from the first light receiving area 251 and the second light receiving area 252 are supplied. These equalizer circuits 201, 2
Numeral 02 corrects the output signals from the first light receiving area 251 and the second light receiving area 252 so as to raise the middle part of the MTF spatial frequency. Reference numeral 206 denotes a subtraction circuit that operates the output signals from the equalizer circuits 201 and 202. As a result of the subtraction circuit 206 subtracting the output signals from the first light receiving area 251 and the second light receiving area 252 via the equalizer circuits 201 and 202, a push-pull signal is obtained. 207 is an equalizer circuit 2
01 and an adder circuit for calculating the sum of output signals from the equalizer circuit 202. The first light receiving region 25 via the equalizer circuits 201 and 202 by the adding circuit 207
As a result of adding the output signals from the first and second light receiving regions 252, a sum signal is obtained. A variable resistor 203 is connected in parallel with the subtraction circuit 206 at a stage preceding the subtraction circuit 206, and the equalizer circuit 201 supplied to the subtraction circuit 206 by adjusting the resistance value of the variable resistor 203.
, And the ratio of the output signal from 202 can be adjusted. Reference numerals 204 and 205 denote variable resistors for adjusting the gain of the adding circuit 207.

Output signals from the first light receiving area 251 and the second light receiving area 252 of the detector 25 are supplied to the subtraction circuit 206 and the addition circuit 207 via the equalizer circuits 201 and 202. As a result, the subtraction circuit 20
6 can obtain a push-pull signal as shown in FIG. 15A, and the adder circuit 207 can obtain a sum signal as shown in FIG. The sum signal from the adding circuit 207 is supplied to the signal discriminating circuit 31 via the preamplifier 27 shown in FIG. The signal level is determined.

In the reproducing circuit shown in FIG. 14, equalizer circuits 201 and 202 are used before subtracting and adding output signals from the first light receiving area and the second light receiving area sandwiching the tracking center of the detector 25. The correction of the characteristic is performed by the above. In other words,
Since the output signal from the first area 251 of the detector 25 is a result of detecting a pit arranged on one side of the tracking center, the MTF characteristic is not determined as described above. Since the output signal from the second light receiving area is also a result of detecting a pit arranged on the other side of the tracking center, the characteristic of the MTF is specified as a single signal similarly to the detection output from the first light receiving area. can do. As a result, the sum signal obtained from the adder circuit 207 is corrected by the equalizer circuits 201 and 202, and then a signal having a constant period and a constant amplitude can be obtained.

In the first embodiment, a signal obtained by summing the detection outputs from the respective light receiving areas 25a, 25b, 25c, 25d of the detector 25, that is, the sum signal is used as an RF signal, The information signal recorded on the optical disk 1 is read based on the signal level of the information signal. However, as in the first embodiment, a signal obtained by summing the output signals from the respective light receiving areas of the detector 25 is represented by R
When used as the F signal, various conditions of the optical system of the optical pickup 20 and in-phase components in the sum signal caused by changes in the reflectance of the optical disk 1 fluctuate. As a result, in the first embodiment, the information recorded on the optical disc 1 is read based on the signal level of the sum signal. Therefore, when the in-phase component in the sum signal changes, the sum signal also changes. Therefore, there is a possibility that an erroneous detection is performed when determining the level of the read signal.

A fourth embodiment of the present invention for solving this problem will be described below. In the fourth embodiment, a push-pull signal obtained as a result of the subtraction of the subtraction circuit 206 of the reproducing circuit shown in the third embodiment is used as an RF signal. In the case of the fourth embodiment of the present invention, the third embodiment
As in the first embodiment, the detector 25 includes four light receiving regions 25a, 25b, 25c, and 25 as described in the first embodiment.
d. Of the four light receiving areas, two light receiving areas 25a and 25d sandwiching the tracking center
First light receiving region 251 composed of
It is treated as a second light receiving area 252 composed of 5b and 25c.

FIG. 16 is a parin showing the relationship between the spot formed on the light receiving area of the detector 25 and the pits of the tracks # i-1 and #i of the optical disk 1 with respect to the formed spot. Is shown. This FIG.
Are obtained as a result of the simulation. The waveforms of the sum signal and the push-pull signal generated based on the detection output from the detector 25 corresponding to FIG. 16 are as shown in FIG. 17 and FIG. FIG.
Is based on the pattern shown in FIG.
This shows the waveform of the sum signal when 0.55 and the pit phase depth = λ / 6. In FIG. 17, the horizontal axis indicates the beam position as viewed from the center of the spot on the detector 25 in the direction of arrow U in FIG. 16, and the vertical axis indicates the signal level of the sum signal. The sum signal shown in FIG. 17 is normalized between 0 and 1. In FIG. 17, 1.0 is a high (H) level, 0.6 is a middle (M) level, and 0.35 is a low (L) level. FIG. 18 shows the waveform of the push-pull signal when the numerical aperture NA = 0.55 and the pit phase depth = λ / 6 for the pattern shown in FIG. The push-pull signal shown in FIG. 18 is normalized in the range of -0.5 to +0.5. +
A value of 0.2 or more is a high (H) level, 0.0 is a middle (M) level, and -0.2 or less is a low (L) level. (When the intermediate (M) level is set to 0, the high (H) level can be treated as "+" and the low level (L) can be treated as "-".) FIG. 18 is similar to FIG. The beam position when viewed from the center of the spot on the detector 25 in the U direction in FIG. 16 is taken, and the signal level of the push-pull signal is taken on the vertical axis.

Since the pit phase depth of the optical disk is λ / 6 as shown in FIGS. 16, 17, and 18,
Both the sum signal and the push-pull signal can be obtained. Good.

In the fourth embodiment of the present invention, information recorded on the optical disc 1 as shown in FIG. 1 is read using the sum signal and the push-pull signal as shown in FIGS. That is, similarly to the first embodiment, the laser beam from the optical pickup 20 is irradiated so as to extend over two tracks such as the track # 0 and the track # 1 as shown in FIG. The resulting reflected light from the optical disk 1 is received by the detector 25 and
5, a signal obtained by taking a difference between output signals from the first light receiving region 251 and the second light receiving region 252, that is, a push-pull signal is used as an RF signal. As a result, by using a signal obtained by taking a difference between output signals from the first light receiving area 251 and the second light receiving area 252 of the detector 25, various conditions of the optical system of the optical pickup 20 and the optical disk 1 can be obtained. Since the in-phase component in the sum signal caused by the change in the reflectance of the optical disk 1 is canceled, errors are suppressed when determining the level of the FR signal as a result of reading the optical disc 1 by the change in the in-phase component. . However, even when the reflectance of the optical disk changes and the signal level of the detection output signal from the detector 25 itself decreases, it is not possible to read information recorded on the optical disk 1 based on the push-pull signal as the RF signal. Although it is possible, the first light receiving region 251 and the light receiving region 25
The sum signal obtained by summing the output signals from the two is also used. In this case, the information recorded on the optical disc 1 is read in the form of a matrix of the push-pull signal and the sum signal.

Table 3 is a matrix for reading an optical disk as shown in FIG. 1 by using a push-pull signal as an RF signal and using a sum (RF) signal as an auxiliary.

[0113]

[Table 3]

In Table 3, the row has the polarity of the push-pull signal, and the column has the signal level of the sum signal. This Table 3
When the sum signal is H and the polarity of the push-pull signal is "+" or "-", there is no pit in the spot of the detector 25 shown in FIG. Since there is no push-pull signal, the state of the push-pull signal cannot be "+" or "-". Therefore, a state where the sum signal is H and the polarity of the push-pull signal is “+” or “−” cannot exist.

When the sum signal is H and the push-pull signal is “0”, it means that a pit exists in one of the spots of the first and second light receiving areas of the detector 25. In this case, Since the push-pull signal always occurs, there is no possibility that the push-pull signal is "0".
Therefore, a state where the sum signal is H and the push-pull signal is “0” cannot exist. When the sum signal is H and the push-pull signal is “+” or “−”, it means that pits exist in the spots of both the first and second light receiving areas of the detector 25. No pull signal is obtained. Therefore, the state where the sum signal is L and the push-pull signal is “+” or “−” cannot exist. Therefore,
As shown by a circle in Table 3, when the sum signal is M and the push-pull signal is “+”, when the sum signal is H or L and the push-pull signal is “0”, the sum signal is M and the push-pull signal The information recorded on the optical disc 1 can be read out and determined based on the four states when is "-". However, in the fourth embodiment, since the push-pull signal is treated as an RF signal, focusing on the push-pull signal, the state of the push-pull signal is “+” and the sum signal is M, and the state of the push-pull signal is “0” and the sum signal is Can be regarded as three states, that is, a state of H or L, and a state where the push-pull signal is “−” and the sum signal is M. As a result, as in the first embodiment, 3
Multi-value detection of values can be performed.

Preferably, as shown in the third embodiment,
Output signals from the first light receiving area 251 and the second light receiving area 252 of the detector 25 are supplied to a subtraction circuit 206 and an addition circuit 207 via equalizer circuits 201 and 202, respectively, to generate a sum signal and a push-pull signal. The signals are supplied to the signal discriminating circuits as in the first embodiment using the signals, and the push-pull signal is supplied to R as shown in the fourth embodiment.
It is desirable to read the information recorded on the optical disc 1 by taking a matrix of both signals with the aid of the F signal and the sum signal.

The above-described embodiment is a specific example.
Although the optical recording medium has been described using an optical disk as an example, the optical recording medium of the present invention is not limited to the optical disk, but can be applied to other optical recording media such as a magneto-optical disk.
In the above-described example, the case where exclusive logic is used as the logical processing when data is recorded or reproduced by irradiating a laser beam with the formation of track pits has been described. The present invention is not limited to logical processing, and any other logical processing can be applied.

[0118]

As is clear from the above description, the optical recording medium according to the first embodiment of the present invention has a track pitch of 1 / n of the spot size of the laser beam on the recording surface, and has The pit width, pit length, and spot size of the reproduction laser beam are changed because data obtained by a predetermined logical operation of the data recorded on the n-1 tracks and the input data is recorded on the next track. Thus, the recording capacity can be increased n times as compared with a conventional compact disk having the same size as the conventional one.

Further, in the recording method for an optical recording medium according to the first embodiment of the present invention, a laser beam spot size of a laser beam on a recording surface is 1 / n and a track pitch of 1 / n is used.
-1) By recording data obtained by a predetermined logical operation of the data recorded on one track and the input data on the next track, the pit width, pit length and spot size of the reproduction laser beam can be changed. The recording capacity can be increased n times as compared with a conventional compact disk having the same size. Further, a conventionally used cutting device such as a compact disc can be used, and a new cutting device is not required.

Further, in the method for reproducing an optical recording medium according to the first embodiment of the present invention, a recording surface of the optical recording medium is irradiated with a reproducing laser beam having a spot size of n times the track pitch, and the amount of reflected light is Is detected by multi-value detection and the data is reproduced, so that the spot size becomes n of the track pitch.
The data can be reproduced for each track by using the double reproduction laser beam. That is, without shortening the wavelength of the laser light source or increasing the NA of the objective lens,
Data can be played.

By irradiating the recording surface of the optical recording medium with a reproducing laser beam having a spot size of n times the track pitch, and reproducing the data based on the intensity distribution of the reflected light, the spot size becomes equal to the track pitch. Data can be reproduced for each track by using n times the reproduction laser beam. That is, data can be reproduced without shortening the wavelength of the laser light source or increasing the numerical aperture NA of the objective lens.

As is clear from the above description, according to the first embodiment of the present invention, the tracking servo is performed by using the pits formed on the adjacent tracks as the servo pits for obtaining the tracking error signal, thereby achieving a stable operation. Data can be recorded by performing a tracking servo. In addition, in an optical recording medium using such a tracking servo, the track pitch can be narrowed without the need for a conventional wobble pit for obtaining a tracking error signal, and the recording density in the track pitch direction can be increased. it can.

In the first embodiment of the present invention, a recording medium is irradiated with a laser beam, and an RF signal based on the amount of reflected light is sampled at a servo pit position to obtain a difference between three-phase signals. By periodically switching and selecting these difference signals to generate a tracking error signal, a tracking error signal capable of performing stable tracking servo can be obtained. Also, a track jump can be performed while the tracking servo is applied, and a stable track jump can be performed. Also, at the time of a track jump, the retraction range can be widened.

According to the third and fourth embodiments of the present invention, equalization is performed for each one-channel signal of the detector, and thereafter, a push-pull signal subjected to differential operation is generated, and this push-pull signal is used as the main RF signal. By using the (sum) signal, the stability in reproduction and multi-level detection in the optical recording media of the first and second embodiments is improved.

By combining the above-described first to fourth embodiments of the present invention, it is possible to stably reproduce data recorded on an optical recording medium capable of performing multi-value detection more stably with high density. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing a format of a pit formed on a recording surface of an optical disc to which a first embodiment of the present invention has been applied.

FIG. 2 is a block diagram showing a configuration of an optical disk reproducing device for reproducing the optical disk.

FIG. 3 is a diagram showing an intensity distribution of reflected light at pits of the optical disc.

FIG. 4 is a diagram illustrating a configuration of a light receiving surface of a detector included in the optical disc reproducing apparatus.

FIG. 5 is a diagram showing a far-field pattern of reflected light on a lecture surface of a detector constituting the optical disk reproducing apparatus.

FIG. 6 is a diagram illustrating a level of an RF signal.

FIG. 7 is a block diagram illustrating a configuration of a cutting device.

FIG. 8 is a block diagram illustrating a circuit configuration of a main part of an optical disk device to which a second embodiment of the present invention has been applied.

FIG. 9 is a diagram showing a servo pit format of an optical disc to which the present invention is applied.

FIG. 10 is a time chart for explaining the operation of the optical disk device.

FIG. 11 is a block diagram illustrating a specific circuit configuration of a tracking error signal generation circuit included in the optical disc device.

FIG. 12 is a block diagram showing another specific circuit configuration of the tracking error signal generation circuit that constitutes the optical disc device.

FIG. 13 is a diagram showing a time chart for explaining a track jump of the optical disk device.

FIG. 14 is a circuit diagram of a reproducing circuit according to a third embodiment of the present invention.

FIG. 15 is a signal waveform diagram of a push-pull signal and a sum signal generated in the reproduction circuit shown in FIG.

FIG. 16 is a diagram showing a pit pattern used in the simulation.

17 is a waveform diagram of a sum signal based on the pit pattern of FIG.

18 is a waveform diagram of a push-pull signal based on the pit pattern of FIG.

FIG. 19 is a diagram showing a format of a pit formed on a recording surface of a conventional compact disc.

FIG. 20 is a diagram showing a format of a servo pit of a conventional optical disc.

FIG. 21 is a waveform diagram of a tracking error signal obtained from a conventional optical disc.

[Explanation of symbols]

 11 spot 12 pit 101 optical disk 111 optical pickup 114 sample hold circuit 120 tracking error signal generation circuit 201, 202, equalizer 206, deviation calculation amplification circuit 207 ·· Sum calculation amplifier circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 7/09-7/095

Claims (8)

(57) [Claims] 1. A predetermined logical operation of input data and a data recorded on a preceding (n-1) consecutive tracks, having a track pitch of 1 / n of a spot size of a laser beam on a recording surface. An optical recording medium characterized in that data obtained by the above is recorded on the next track. 2. A reproducing method for reproducing an optical recording medium according to claim 1, wherein a reproducing laser beam having a spot size of n times a track pitch is irradiated on a recording surface of the optical recording medium, and a reflected light of the laser beam is reflected. A method for reproducing data from an optical recording medium, comprising reproducing data by detecting a multi-valued light amount. 3. A reproducing method for reproducing an optical recording medium according to claim 1, wherein a reproducing laser beam having a spot size of n times the track pitch is applied to a recording surface of the optical recording medium, and the reflected light of the laser beam is reflected. A method for reproducing data from an optical recording medium, comprising reproducing data based on an intensity distribution. 4. The method according to claim 1, wherein the track pitch is 1 / n of the spot size of the laser beam on the recording surface, and the n-th consecutive
A recording method for an optical recording medium, comprising recording data obtained by a predetermined logical operation of data recorded on one track and input data on a next track. 5. A predetermined logical operation between input data and data recorded on the preceding (n-1) consecutive tracks, having a track pitch of 1 / n of the spot size of the laser beam on the recording surface. Is obtained on the next track, and n signals are detected from the optical recording medium characterized in that the pit depth is formed in the range of λ / 4 to λ / 8, and these detected signals are detected. A reproduction method characterized by the following. 6. A reproducing method according to claim 5 , wherein a differential operation of said equivalent signal is performed to generate a push-pull signal. 7. The reproducing method according to claim 6 , wherein said push-pull signal is provided as a main RF signal. 8. The reproducing method according to claim 5 , wherein a sum of said equivalent signals is calculated and provided as a sub main signal.