JP3227803B2 - Reproduction method of optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for reproducing an optical recording medium, a playback method, especially high-density recording possible optical recording medium.

[0002]

2. Description of the Related Art An optical recording medium such as a constant angular velocity (so-called C
The pit format of an optical disc rotated and driven by AV (Constant Angular Velocity) is, for example, as shown in FIG.
The pit 71 which is 0.86 μm is 1.6 μm in the radial direction.
(Hereinafter referred to as a track pitch), and the format is such that the pitch 71 is aligned in the track direction. These dimensions are based on manufacturing restrictions, the size of the spot 72 on the recording surface of the reproduction laser beam, and the like.

In order to increase the recording density, it is conceivable to reduce the above-described track pitch, pitch length, and 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 pit, and the pit length is substantially shortened by so-called overwriting in which a pit to be formed next is overlapped with a part of the pit previously formed, thereby achieving high density. I have. That is, a magneto-optical disc having a higher recording density than a so-called compact disc, which is a read-only optical disc having the same diameter, is realized in the track direction.

[0004]

On the other hand, in order to increase the recording density in the radial direction of the disk, it is conceivable to narrow the track pitch, for example. Is also irradiated to the pits of the adjacent track, so-called crosstalk occurs, so-called S / N (Signal to Noise Ratio) deteriorates, and in the worst case, data cannot be reproduced.

Therefore, it is conceivable to reduce the track pitch and also reduce the spot size of the laser beam. The spot size is proportional to the wavelength of the laser beam, and the so-called aperture ratio of the objective lens (hereinafter referred to as NA: Numeri).
cal 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 NA.

[0006] Then, maintaining the spot size,
It is conceivable to increase the recording density by reducing the track pitch and reducing the pit width so that crosstalk does not occur. However, if the pit width is reduced, the production yield, for example, decreases, or the conventional so-called cutting is performed. There is a problem that the device cannot be used.

[0007] The present invention has been made in view of such circumstances, pit width, without changing the spot size of the pit length and the laser beam, a high-density recording method for reproducing possible optical recording medium It is intended to be provided.

[0008]

The reproduction method of the present invention is applied.
The recording medium to be recorded has a track pitch of 1 / n of the spot size of the laser beam on the recording surface , and is formed by a predetermined logical operation of the data recorded on the preceding N-1 tracks and the input data. The resulting data is recorded on the next track .

[0009] Also, at a track pitch of 1 / n of the spot size of the laser beam in serial Rokumen, obtained by a predetermined logical operation with the previous consecutive n-1 pieces of recorded data and the input data to the track Record the data on the next track .

A reproducing method for such a recording medium is as follows.
Irradiating a reproducing laser beam having n times the spot size of a track pitch on the recording surface of the optical recording medium, the light amount of the reflected light to the multi-level detection, play the data.

[0011] The reproducing laser beam having n times the spot size of Matato rack pitch is irradiated to the recording surface of the optical recording medium, based on the intensity distribution of the reflected light, play <br/> data.

According to the reproducing method of the present invention, a reproducing beam having a spot size of n times the track pitch is applied to the recording surface of the optical recording medium to perform reproducing scanning, and perform scanning by the m-th tracking center. The reproduction data for each of the tracks to be scanned obtained from the reflected light at that time, and the reproduction data for each of the tracks to be scanned obtained from the reflected light when scanning is performed by the (m + 1) th tracking center. And using
Confirmation of coincidence of reproduced data of the track to be scanned in both the scanning of the m-th tracking center and the scanning of the (m + 1) -th tracking center (that is, verify operation)
Is performed.

[0013]

In the optical recording medium according to the reproducing method of the present invention, data is recorded at a track pitch of 1 / n of the spot size of the laser beam.

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

As a reproducing method , data is reproduced by irradiating a recording surface of an optical recording medium with a reproducing laser beam having a spot size of n times the track pitch, detecting the amount of reflected light in multiple levels, and reproducing data.

Further, by irradiating a reproduction laser beam having n times the spot size of the track pitch in the recording surface of the optical recording medium, based on the intensity distribution of the reflected light, to reproduce the data.

According to the method of reproducing an optical recording medium of the present invention , the reproduction data of each track to be scanned obtained when a plurality of tracks are scanned by a reproduction laser beam having a spot size of n times the track pitch. When,
The verify operation is performed by comparing the reproduced data of the track to be scanned in both scans with the reproduced data of each track to be scanned next obtained by the next round scan.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an optical recording medium, an optical recording medium recording method and an optical recording medium reproducing method according to the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to an optical recording medium such as a constant angular velocity (so-called CAV: Constant Angul
FIG. 1 shows a format of pits formed on a recording surface of the optical disc, which is applied to a read-only optical disc which is driven to rotate by ar Velocity.

That is, 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 is recorded on the preceding n-1 consecutive tracks. A pit is formed based on data obtained by a predetermined logical operation of the input data and the input data.

More specifically, as shown in FIG. 1, for example, the diameter (spot size) of the spot 11 of the reproducing laser beam on the recording surface is made equal to that used in a so-called compact disc reproducing apparatus or the like. 1.5 to 1.6 μm
In this optical disk, the pits 12 having pit widths and pit lengths of 0.5 μm and 0.86 μm, respectively, like a compact disk which is a read-only optical disk, for example, have a track pitch of 1/1 of the spot size.
n, for example, 0.8 μm, which is １ ／. As shown in FIG. 1 described above, for example, when 1s continue as recording data, the pits 12 are combined with the adjacent pits on the same track, and the length thereof is a value proportional to the number of consecutive 1s. It is formed so that it becomes.

Further, track #i (i = 1, 2, 3 ‥)
The pit 12 recorded in ‥‥) corresponds to the previous track #
It is formed based on data obtained by a predetermined logical operation between the data recorded in i-1 and the input data, for example, a logical match (or an equivalent) which is a negative logic of exclusive OR.

For example, as shown in Table 1, each track #i
Are input to track # 0 as 1, 0,
1, 0, 1, 1, 0, 1, 0, 1, 0, and 0, 1, 1, 1, 0, 0, 0, 1, 1, 0 for track # 1,
For track # 2, 1, 1, 1, 0, 0, 0, 1,.
1, 1, 1 and 0, 0, 1,.
1, 1, 1, 0, 0, 0, 1 and the track # 0 is, for example, the innermost track, the recording data for the track # 0 is pit 1 inside (before) the innermost track.
Since No. 2 is not formed, the initial value of the recording data is set to, for example, 0, and the input data is used as it is as shown in Table 2. Next, as shown in Table 2 above, 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 this track # 1.
0, 0, 1, 0, 0, 1, 1). The recording data for track # 2 is, as shown in Table 2 above,
It is assumed that data (0, 0, 1, 1, 1, 0, 0, 0, 1, 1) obtained by a logical match between the recording data for the track # 1 and the input data for the track # 2.
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.

[0023]

[Table 1]

[0024]

[Table 2]

Thus, the recording capacity of this optical disk is:
For example, the pit width and the pit length are the same as those of a conventional compact disc, and are n times, for example, twice as large as a 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 logical sum, a logical sum, or the like.

Here, a method of reproducing data from an optical disk having the pit format as described above will be described.

An optical disk reproducing apparatus used for reproducing the optical disk is, for example, as shown in FIG. 2, an optical pickup for irradiating the optical disk 1 with a laser beam and detecting the amount of light reflected on the recording surface 1a. 20 and
A signal processing unit 30 for reproducing data from a reproduction signal from the optical pickup 20.

As shown in FIG. 2 described above, the optical pickup 20 includes a laser light source 21, a collimator lens 22 for converting the light emitted from the laser light source 21 into parallel light, and a collimator lens 22 for converting the parallel light from the collimator lens 22. An objective lens 23 for condensing and irradiating the recording surface 1a of the optical disc 1 with the collimator lens 22 and the objective lens 23;
A beam splitter 24 for separating light reflected on the recording surface 1a of the optical disc 1;
A photoelectric conversion element (hereinafter, referred to as a detector) 25 for detecting the amount of the reflected light separated in 4 is disposed between the beam splitter 24 and the detector 25, and the reflected light decomposed by the beam splitter 25 is collected. Condensing lens 26
And a preamplifier 27 that reproduces an RF signal based on the signal from the detector 25 and generates a servo error signal such as a tracking error signal.

That is, the optical pickup 20 has substantially the same configuration as that of a conventional optical pickup used in a compact disk reproducing apparatus or the like.
The track pitch of the optical disk 1 is, for example, の of the spot size of the laser beam, and the laser beam spot 11 simultaneously scans two adjacent tracks #i and # i-1 as shown in FIG. The tracking servo is applied as follows (the width scanned by the spot is referred to as a scanning track width).

On the other hand, as shown in FIG. 2, the signal processing unit 30 includes a signal discriminating circuit 31 for reproducing data from the RF signal from the preamplifier 27,
The so-called phase that reproduces the clock from the RF signal from
A controller 33 for performing tracking servo control and focus servo control based on a servo error signal from the preamplifier 27, and a controller 33 based on a clock from the PLL 32. It comprises a system controller 34 for controlling and a spindle motor 35 for driving the optical disc 1 to rotate.

In the optical disk reproducing apparatus, the optical disk 1 is driven to rotate at a constant angular velocity by the spindle motor 35. On the other hand, 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 makes the light emitted from the laser light source 21 incident on the beam splitter 24 as parallel light.

The beam splitter 24 is constituted by, for example, a so-called half mirror, and allows the light emitted from the laser light source 21 to pass through the objective lens 23.

The objective lens 23 has a so-called aperture ratio (hereinafter referred to as NA: Numerical Aperture) equivalent to that of a conventional optical pickup, condenses the light emitted from the laser light source 21 passing through the beam splitter 24, and Irradiate the recording surface 1a. Therefore, the spot size of the laser beam on the recording surface 1a is twice the track pitch.

The pits 12 are formed on the recording surface 1a of the optical disk 1 based on the recording data as shown in FIG. 1 described above. For example, as shown in FIG. , #I have no pits 12, the intensity distribution of the reflected light is left-right symmetric on the paper surface.
As shown in (b), when there is no pit 12 on the track # i-1 and there is a pit 12 on the track #i, the intensity distribution of the reflected light is When the pits 12 exist on the track # i-1 and the pits 12 do not exist on the track #i, for example, as shown in FIG. 3C, the intensity distribution of the reflected light is strong on the left side on the paper. For example, as shown in FIG. 3D, when the pits 12 exist on both tracks # i-1 and #i, the intensity distribution of the reflected light is symmetrical and the pits 12
Weaker than when there is no.

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, and then is incident on the beam splitter 24 again.
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 a so-called astigmatism method, and condenses reflected light on a light receiving surface of the detector 25.

The detector 25 has four light receiving regions 25a, 25b and 25 as shown in FIG.
c and 25d, the so-called far field pattern on the light receiving surface of the detector 25 is, for example, as shown in FIG.
As shown in (a), when there is no pit 12 in the track # i-1 and there is a pit 12 in the track #i, the areas 25a and 25b are bright, and the areas 25b and 25c are dark due to diffraction at the pit 12. (Indicated by diagonal lines). on the other hand,
For example, as shown in FIG. 5B, when the pit 12 is present on the track # i-1 and the pit 12 is not present on the track #i, the areas 25a and 25d are dark and the areas 25b and 25c are dark.
Becomes brighter. Also, for example, as shown in FIG.
When the pits 12 are present on both tracks # i-1 and #i, all the areas 25a, 25b, 25c and 25d become dark, and, for example, as shown in FIG. 1, when there is no pit 12 in #i, all areas 25a, 25b, 25c, 25d become bright.

The preamplifier 27 is composed of, for example, a plurality of differential amplifiers.
If the levels detected in the regions 25a, 25b, 25c, and 25d are A, B, C, and D, respectively, based on the levels detected in b, 25c, and 25d, a so-called focus error signal, tracking error signal, and RF The signals are obtained by equations 1, 2, and 3, respectively.

Focus error signal = (A + C) − (B + D) ‥‥‥ Equation 1

Tracking error signal = (A + D) − (B + C) ‥‥‥ Equation 2

RF signal = (A + B + C + D) ‥‥‥ Equation 3

The signal discriminating circuit 31 detects the level of the RF signal from the preamplifier 27, sets the value to 0 when the level is within a predetermined range, and sets the value to 1 when the level is outside the predetermined range. Play data with the same value as. Specifically, the spots are track # i-1 and track #i
Is performed so that the pits 12 do not exist in both tracks # i-1 and #i, and when the pits 12 exist in one of the tracks, the tracks # i-1 and #i 3 when there is a pit 12 in
In response to the two cases, for example, as shown in FIG.
The RF signal has three levels, for example, a high level (hereinafter, referred to as an H level), an M level, and an L level. So 2
By discriminating the level of the RF signal from the three threshold values, setting the value to 0 at the M level and setting the value to 1 at the H level and L level, data having the same value as the input data can be reproduced. For example, when reproducing the track # 1 shown in FIG. 1 described above, if the tracking servo control is performed so that the spot 11 simultaneously scans the track # 0 and the track # 1, the level of the reproduction signal from the preamplifier 27 becomes M level. , L level, H level, L level, M level, M level, M level, L level, H level, M level, where M level is 0, and L level and H level are 1
As a result, data having the same value as the input data shown in Table 1 (0, 1, 1, 1, 0, 0, 0, 1, 1,.
0) can be obtained. That is, by the multi-value detection of the RF signal, the spot size is set to, for example, 2 of the track pitch.
The data can be reproduced for each track by using the double reproduction laser beam. In other words, data can be reproduced without shortening the wavelength of the laser light source or increasing the NA of the objective lens as compared with a conventional compact disk reproducing apparatus. The beam position on the horizontal axis of the graph shown in FIG. 6A represents the position of the spot 11 in the track direction, as shown in FIG. 6B.

On the other hand, the PLL 32 reproduces a clock from the RF signal from the preamplifier 27 and supplies this clock to the system controller 34. The 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 so that these signals become zero so that these signals become zero.
Is controlled in the optical axis direction and the radial direction of the disk. That is, focus servo control,
Perform tracking servo control. Controller 3
Numeral 3 performs so-called spindle servo control, and controls the rotational speed of the spindle motor 35 to be constant at an angular speed. Also, control is performed to slide the entire biaxial device 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 that of 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 multi-level detection, for example, ternary detection of the level of the RF signal proportional to the amount of reflected light.

Here, a reproducing method different from the above-described embodiment will be described. 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.

In this optical disk reproducing apparatus, for example, the level (A + D) obtained by the preamplifier 27 and the level (B +
The data is reproduced based on C). Specifically, the reproduction signal RFa obtained by the region 25a and the region 25d of the detector 25, the region 25b, and the region 25d
c is compared with a predetermined threshold value, and when the level is equal to or less than the threshold value, if the reproduction data is set to 1, the reproduction data has the same value as the recording data shown in Table 2 above for two tracks. And are played back simultaneously. Therefore,
When playing track #i, the spot is track #
Tracking is performed so that i-1 and #i are simultaneously scanned, and recording of reproduction data reproduced from track # i-1 (reproduction signal RFa) and reproduction data reproduced from track #i (reproduction signal RFb). By obtaining a logical operation corresponding to the logical operation used at the time, for example, a logical match, data for the track #i can be reproduced. For example, as shown in FIG. 1 described above, the reproduction data obtained when the spot 11 scans the track # 0 and the track # 1 at the same time, the reproduction data from the track # 0 is 1, 0,
1, 0, 1, 0, 1, 0, 1, 0, and track # 1
From 0, 0, 1, 0, 0, 1, 0, 0,
1, 1 and these reproduction 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 disc 1 in which the pits 12 having the same shape as that of a compact disc are recorded at a track pitch of 1 / n of the spot size of the reproducing laser beam, the intensity distribution of the reflected light Is detected by the detector 25 that divides the light receiving area into a plurality of parts, so that data can be reproduced for each track.

By the way, reproduction scanning by the laser beam spot 11 in the present embodiment, in FIG. 8 R _1, R ₂ ··
In this case, one track is always reproduced and scanned at least twice (when n = 2). Then, as described above, if data is reproduced based on the intensity distribution of the reflected light, the recording data of two adjacent tracks are simultaneously extracted by one scan. Therefore, when the influence of crosstalk due to pits in other tracks is considered, the verify operation can be performed with reference to data obtained by the previous scan.

The track # 1 of the reproduction information obtained by scanning R ₁ in FIG. 8, for example, from the track # 1 of the reproduction information obtained by the scanning R _2, completely determines the reproduction information of the track # 1. Also determines the track # 2 for reproducing information obtained by scanning R _2, and a track # 2 reproduction information obtained by scanning R _3, the reproduction information of the track # 2. By performing such a verify operation, a data reproduction error can be reduced or eliminated.

[0051] Namely, when explaining the track # 1 as an example, by scanning R _1, but pit information by the track # 0 and the track # 1 is obtained as the RF signal as described above in Table 2, the time signal The discrimination circuit 31 temporarily stores the recorded data reproduced. Then, although not pit information by similarly track # 1 and track # 2 by the next scanning R ₂ is obtained, and recording data of the track # 1 obtained at this time, scanning R ₁ which has been stored Is compared with the recording data of the track # 1 to confirm the coincidence.

The verify operation is similarly performed for the other tracks, and when it is confirmed that the recorded data is correctly reproduced, the input data as shown in Table 1 is reproduced by a predetermined logical operation. I do. of course,
If data mismatch (reproduction failure) is detected by the verify operation, the track may be scanned again.

By executing such a verify operation, data reproduction can be performed by canceling crosstalk, so that the track pitch can be set substantially narrower. That is, further high-density recording is realized.

In the case of a reproducing method in which the recording data of the two tracks to be scanned are simultaneously reproduced by one scan performed simultaneously on the two tracks, such a verify operation is performed by the tracking control. It is not necessary to perform the change or the reproduction scan by the same tracking center twice or more. Therefore, for example, as described above, the reproduction signal RFa by the region 25a and the region 25d of the detector 25 is used.
It is very suitable to employ this together with a reproduction method for obtaining reproduction data from the reproduction signal RFb by the regions 25b and 25c. In addition, in addition to this, the sum signal (regions 25a, 2a)
5b, 25c, 25d), ie, the reproduced signal RF
And the push-pull signal, that is, (the output of the area 25a + 25b)-(the output of the area 25c + 25d), the recorded data of two tracks can be reproduced at the same time.

For example, in a paired track of track #i and track # i-1 as shown in FIG.
If it is possible to distinguish between the case of FIG. 5A and the case of FIG. 5B, four patterns can be distinguished by one scan. In each case of FIGS. 5A and 5B, push-pull is performed. The diffraction levels obtained as signals have ± reverse values. Therefore, when the diffraction level by the RF signal and the push-pull signal is shown as a numerical model, the RF signal is “1” in FIGS. 5A to 5D.
"1", "2" and "0", and the push-pull signal becomes "-"
Since they are "1", "+1", "0", and "0", the pit pattern of the adjacent track can be determined by the combination of the RF signal and the push-pull signal, that is, the recording data of two tracks can be extracted at the same time.

Next, a method for recording an optical disk having a pit format as shown in FIG. 1 will be described.

Here, a method for producing a read-only optical disk will be briefly described. The manufacturing process of a read-only optical disk can be roughly classified into a so-called mastering process (mastering process) and a disc-forming process (replication process). The mastering process is a process until a metal master (a so-called stamper) used in the disc making process is completed, and the disc making process is a process of mass-producing an optical disc, which is a replica of the metal master, using the stamper. Specifically, in the mastering step, a photoresist is applied to a polished glass substrate, and data (information) is recorded on the photosensitive film by exposure with a laser beam. That is, so-called cutting is performed. The data to be recorded must be prepared in advance, and this preparation step is also called so-called premastering. Then, when the cutting is completed, after performing a predetermined process such as a phenomenon, the information is transferred onto the metal surface by, for example, so-called electroforming,
Create the stamper needed to duplicate the optical disk.

Next, by using this stamper, information is transferred onto a resin substrate by, for example, a so-called injection method or the like, a reflection 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 of the optical recording medium according to the present invention is applied to the above-described premastering and cutting.

More specifically, as shown in FIG. 7, for example, the cutting apparatus comprises a photoresist-coated glass substrate 41.
An optical unit 40 for irradiating the glass substrate 41 with a laser beam to perform cutting, and a driving unit 50 for rotationally driving the glass substrate 41
And a signal processing unit 60 that converts the input data into recording data and controls the optical unit 40 and the driving unit 50.

Further, as shown in FIG. 7, the optical section 40 includes a laser light source 42 and an optical modulator 43 for modulating the light emitted from the laser light source 42 based on the recording data.
A prism 44 for bending the optical axis of the modulated beam from the optical modulator 43, and an objective lens 45 for condensing the modulated beam reflected by the prism 44 and irradiating the photoresist surface of the glass substrate 41 with the objective lens 45. Be composed.

As shown in FIG. 7, the driving section 50 includes a motor 51 for driving the glass substrate 41 to rotate.
An FG 52 for generating a pulse (hereinafter referred to as an FG pulse) for detecting the rotation speed of the motor 51; a slide motor 53 for moving (sliding) the glass substrate 41 in the radial direction; And a servo controller 54 for controlling the rotation speed of the slide motor 53, the tracking of the objective lens 45, and the like.

Further, the signal processing section 60 performs the processing shown in FIG.
As shown in FIG. 2, a formatting circuit 61 for forming input data by adding, for example, an error correction code or the like to source data from a computer, and performing a predetermined logical operation on the input data from the formatting circuit 61 to record data. A logical operation circuit 62 to be formed; a driving circuit 63 for driving the optical modulator 43 based on the recording data from the logical operation circuit 62;
And the like, and a system controller 65 for controlling the servo controller 54 and the like based on the 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 control 54 controls the motor 51 so that the glass substrate 41 rotates at a constant angular velocity, and sets the feed pitch in the radial direction to be equal to the spot size of the reproduction laser beam.
/ N, for example, 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, a so-called 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 through the prism 44 and the objective lens 45 on the photoresist of the glass substrate 41. Irradiate the surface. As a result, the photoresist is exposed based on the recording data. Specifically, the wavelength of the light emitted from the laser light source 42 and the NA of the objective lens 45 are set such that the spot size of the converged modulated beam becomes 1 / n of the spot size of the reproduction laser beam on the photoresist surface. Assuming that the spot size of the reproduction laser beam is 1.6 μm and n is 2, as described above, the photoresist is exposed with a 0.8 μm width.

On the other hand, the formatting circuit 61 divides source data from, for example, a computer into selectors and segments, and adds selector and segment addresses, error correction codes, and the like to form input data. It is supplied to the logical operation circuit 62. In addition, the formatting circuit 61 includes focusing,
A so-called servo byte for tracking is supplied to the logical operation circuit 62.

The logical operation circuit 62 has a built-in memory having a capacity for recording, for example, n-1 tracks of recording data, and sequentially stores the recording data recorded on the previous consecutive n-1 tracks. As described above, the recording data to be recorded on the next track is formed by a predetermined logical operation of the stored recording data and the input data, and the 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. For example, an exposed portion corresponding to the pit 12 as shown in FIG. It is formed. Thereafter, development, electroforming and the like are performed to complete the stamper. 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 reproducing laser beam, and the recording density of a conventional compact disk having the same radius can be obtained. Can be doubled. 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 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, the rewriting rewrites the data recorded on the other tracks as in the case of the conventional overwriting. However, for example, the music in PCM recording of music is completely separated from the music, and the rewriting area is one. In an application such as music, there is no problem caused by overwriting, and the recording capacity can be increased as compared with a conventional magneto-optical disk. Further, it is needless to say that the present invention can be applied to an optical recording medium such as a memory card in which tracks are configured in parallel. Of course, the verify operation in the reproducing method of the present invention can be applied at the time of recording.

[0070]

As is apparent from the above description, the optical recording medium according to the present invention has a track pitch of 1 / n of the spot size of the laser beam on the recording surface, and has n-1 consecutive continuous tracks. Since the data obtained by a predetermined logical operation of the data recorded on the track and the input data is recorded on the next track, the pit width, the pit length and the spot size of the reproduced laser beam can be changed without changing the pit width. The recording capacity can be increased n times as compared with, for example, a compact disk having the same size.

Further, in the recording method for an optical recording medium according to the present invention, the data recorded on the preceding continuous n-1 tracks are input at a track pitch of 1 / n of the spot size of the laser beam on the recording surface. By recording the data obtained by a predetermined logical operation with the data on the next track, the pit width, pit length and spot size of the reproduction laser beam can be changed without changing the pit width, the pit length and the reproducing laser beam spot size. Thus, the recording capacity can be increased n times. Further, a conventionally used cutting device for a compact disc, for example, can be used, and a new cutting device is not required.

In the reproducing method for an optical recording medium according to 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 multi-valued. Then, by reproducing the data, 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.

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

Further, since one track is scanned a plurality of times, it is possible to perform a verify operation by comparing reproduced data obtained in a plurality of scans for each track, and particularly to execute such a verify operation. Then, data reproduction can be performed by canceling the crosstalk, so that the track pitch can be set to be substantially narrower, and there is an effect that higher density recording is realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a format of a pit formed on a recording surface of an optical disc according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an optical disc reproducing apparatus that reproduces an optical disc according to an embodiment.

FIG. 3 is an explanatory diagram of an intensity distribution of reflected light at a pit of the optical disc of the embodiment.

FIG. 4 is an explanatory diagram of a configuration of a light receiving surface of a detector in a reproducing apparatus for the optical disc of the embodiment.

FIG. 5 is an explanatory diagram of a far field pattern of reflected light on a light receiving surface of a detector in a reproducing apparatus for an optical disc according to an embodiment.

FIG. 6 is an explanatory diagram of an RF signal level in the reproducing method according to the embodiment.

FIG. 7 is a block diagram of a configuration of a cutting device for an optical disc according to the embodiment.

FIG. 8 is an explanatory diagram of a reproducing method using a verify operation of the embodiment.

FIG. 9 is an explanatory diagram of a format of a pit formed on a recording surface of a conventional compact disc.

[Explanation of symbols]

 11 spots 12 pits

Claims (1)

(57) [Claims] 1. A laser beam spot on a recording surface.
Has a track pitch of 1 / n of the size,
data recorded on n-1 tracks and input data
The data obtained by the specified logical operation of
Playback method for playing back an optical recording medium recorded on a disc.
Thus, a playback video having a spot size of n times the track pitch
Irradiates the recording surface of the optical recording medium with the beam to perform reproduction scanning
Together, their upon performing scanning by the tracking center of the m
Each track that was scanned from the reflected light
Data and the (m + 1) th tracking center
Scan pair obtained from the reflected light when scanning by
Using the playback data for each track
Scanning of the m-th tracking center and the (m + 1) -th tracking center.
Scanned in both scanning of the center
Confirmation of matching of track playback data
A method for reproducing an optical recording medium.