JPH10198964A - Disc playback device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent the influence of crosstalk from increasing even if the track pitch is narrowed, and to realize higher density recording. SOLUTION: One or a plurality of detectors provided for receiving reflected light from a disk are divided into a plurality of light receiving areas in a light receiving direction corresponding to a disk radial direction. Then, the crosstalk removal arithmetic processing is performed on the detection outputs of the plurality of light receiving areas,
The arithmetically processed signal is decoded so that reproduced data is extracted. The crosstalk removal calculation processing
Calculation processing for giving a larger gain to the output of the light receiving area AR2 located on the center side in the light receiving direction corresponding to the radial direction among the plurality of divided light receiving areas, than to the outputs of the other light receiving areas AR1 and AR3; I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for decoding a signal optically read from a disk-shaped recording medium and reproducing the data.

[0002]

2. Description of the Related Art In recent years, in systems using recording media such as optical disks and magneto-optical disks, studies have been made on increasing the recording capacity and increasing the recording density for that purpose. For high-density recording, it is necessary to shorten the laser wavelength and set an appropriate NA (aperture ratio) of the objective lens. In addition, as a physical method on a disk for increasing the density, it is necessary to reduce the pit interval in the track direction (pit row direction) or to narrow the track pitch.

[0003]

Although reducing the track pitch is effective for increasing the recording density, reducing the track pitch after setting a certain laser wavelength and NA requires a certain track. When the beam spot scans, information on an adjacent track is also picked up, which leads to an increase in the so-called crosstalk problem. For example, assuming that the laser wavelength and beam spot size are set to a certain limit and the track pitch is set so that the influence of crosstalk is not so large, the track pitch is required to further increase the density. As the width becomes narrower, the crosstalk component becomes larger on the reproduction signal, and the quality of the reproduction signal deteriorates. In other words, the track pitch cannot be narrowed without lowering the quality of the reproduced signal.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is intended to prevent the influence of crosstalk from increasing even when the track pitch is reduced, thereby realizing higher density recording. The purpose is to do.

For this reason, in the reproducing apparatus, one or a plurality of detectors provided for receiving the reflected light from the disk-shaped recording medium are provided in a plurality of light-receiving directions corresponding to the radial direction of the disk-shaped recording medium. It should be divided into light receiving areas. Then, the detection output of the plurality of light receiving areas is subjected to a crosstalk elimination calculation process, and the signal subjected to the calculation process is decoded to reproduce data. Further, the crosstalk elimination calculation processing is performed for a plurality of divided light receiving areas.
The output of the light receiving area located on the center side in the light receiving direction corresponding to the radial direction is an arithmetic processing in which a larger gain is provided than the outputs of the other light receiving areas. By calculating the detection output of each light receiving area divided in the radial direction, that is, in the track pitch direction on the detector, the crosstalk component in the reproduction signal can be reduced.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a reproducing apparatus according to an embodiment of the present invention will be described in the following order. <1. Configuration Concept of Embodiment><2. Configuration of playback device><3. Configuration of Optical System><4. Specific circuit example for realizing the embodiment>

<1. Configuration Concept of Embodiment> FIG. 1 shows a configuration concept as an embodiment of the present invention. Arrow T
RD is a light receiving direction corresponding to a track line direction on the disk. A detector 4d for receiving light reflected by a laser spot that scans in the track direction is divided into light receiving areas AR1, AR2, and AR3 as shown in the figure. . The arrow RDD is the light receiving direction corresponding to the radial direction of the disk, that is, the detector 4d has three light receiving areas AR1, AR1 in the light receiving direction corresponding to the radial direction of the disk.
It is divided into AR2 and AR3. In this example, when the diameter of the received beam spot SP is d, the width of the central light receiving area AR2 in the direction corresponding to the radius is d / 10.

Assuming that the detection outputs photoelectrically converted by the respective light receiving areas are signals Iα, Iβ, and Iγ, the signals Iα, Iβ, and Iγ are subjected to predetermined arithmetic processing for obtaining a crosstalk noise canceling effect. Then, the data is output to the reproduction processing system. An example of a specific calculation process is Iα + Iβ + (Iγ × g). g is a predetermined coefficient.

FIG. 2 shows an image of a track on a disk, in which a land LD portion sandwiched between grooves GB is used as a recording track. And track pitch T
It is assumed that P = 0.85 μm and the pit width formed on the track is 0.62 μm. In this figure, it is assumed that the beam spot SP is currently passing on the track Tn as shown by the arrow, and the reflected light information leaking from the adjacent tracks Tn + 1 and Tn-1 during this scanning is considered as a crosstalk component. And

[0010] Assuming such a situation, further, as optical conditions, laser wavelength = 685 nm, A / W (tan) =
Assuming that 0.64 and A / W (rad) = 1.30 (A: aperture, W: laser width), the crosstalk removing effect by the arithmetic processing of the present example is as follows.

When a normal detector output, that is, an output corresponding to the amount of light received by the detector 4d is used as a reproduction signal as it is, considering the example of the divided detector of FIG.
The information of α + Iβ + Iγ becomes reproduction information. In this case, when the crosstalk level is calculated under the above conditions, -16.
4 dB. On the other hand, in this example, when the coefficient g in the above calculation is 1.5 and the calculation result is reproduction information, the crosstalk level in the reproduction information is-
It becomes 18.9 dB. That is, the central light receiving area AR2
Is weighted 1.5 times, the crosstalk is improved by 2.5 dB.

FIGS. 3 and 4 show the image of the improvement of the crosstalk level replaced with a model having a beam spot shape. 3 and 4, the horizontal axis shows the distance with the beam spot center set to 0, and the vertical axis shows the spot intensity level. That is, the curves SP1 and SP2 each represent the beam spot shape. Here, the curve SP1 represents the normal reproduction information detection method, that is,
+ Iβ + Iγ is the spot shape equivalent to the case where the reproduction information is used, while the curve SP2 is the spot shape equivalent to the reproduction information detection method of the present example, that is, the case where Iα + Iβ + (Iγ × 1.5) is used as the reproduction information. .

In the case of this embodiment, as can be seen from the spot shape model, an effect equivalent to the case where the spot diameter is reduced can be obtained. FIG. 5 is an enlarged view of a part of FIG. 4. In the beam spot shape, the reflected light becomes a region serving as information of the main track, a region corresponding to the groove GB, and a crosstalk component from an adjacent track. The area is shown. As can be seen from this figure, the curve SP2
Is smaller than that of the curve SP1, that is, represents an improvement of the crosstalk noise of 2.5 dB.

That is, in the present embodiment, the operation signals (Iα + Iβ) of the outputs of the three light receiving areas AR1, AR2, AR3 divided in the light receiving direction corresponding to the radial direction of the disk.
+ (Iγ × g)), an effect of canceling crosstalk noise can be obtained, which makes it easier to narrow the track pitch while maintaining the quality of the reproduced signal.

<2. Configuration of Reproducing Apparatus> A recording / reproducing apparatus employing the above-described detector configuration will be described with reference to the block diagram of FIG.

As the optical disk 1, a ROM disk in which the user area is entirely formed of embossed pits, a RAM disk in which the user area is a rewritable area capable of recording and reproduction, or an RO as the user area
Partial ROM where M area and rewritable area are mixed
It becomes a disk etc. It is to be noted that these discs employ a sample servo method, and therefore, a servo area is formed on a track for each predetermined segment unit, and servo pits formed of embossed pits are formed in the servo area. It is assumed that these disks adopt the zone CAV method.

The optical disk 1 is rotationally driven at a predetermined rotational speed for each zone by a spindle motor 2. The rotation speed servo control of the spindle motor 2 is performed by the spindle control unit 3. For example, the spindle control unit 3 detects the rotation speed of the spindle motor 2 based on an FG pulse (frequency signal synchronized with the rotation speed) from the spindle motor 2 and the like, and supplies the reference speed information SK from the controller 6 and the reference speed information SK. By comparing the rotation speed of the spindle motor 2 with the rotation speed of the spindle motor 2 and performing acceleration / deceleration of the spindle motor 2 based on the error information, a disk rotation operation at a required rotation speed is realized.

For the optical disc 1 being rotated,
Laser light from the optical pickup 4 is irradiated. The optical pickup 4 includes, for example, a laser light source 4c such as a laser diode or a laser coupler, an optical system 4e such as various lenses or a beam splitter, an objective lens 4a serving as an output end of a laser beam, and a detector 4d detecting reflected light from a disk. And a biaxial mechanism 4b for holding the objective lens 4a movably in the tracking direction and the focus direction. On / off of the laser output from the laser light source 4c and the output level in the optical pickup 4 are controlled by the laser control unit 5.

The recording / reproducing apparatus is connected to a host computer 90 by an interface unit 19, and data recording / reproducing operation is executed by the controller 6 receiving a recording request / reproducing request from the host computer 90. Will be. During recording, data to be recorded is supplied from the host computer 90 together with the recording request. The recording data D _REC is supplied from the interface unit 19 to the encoder 25, where necessary encoding processing is performed.

When the disk 1 is a RAM disk or a partial ROM disk, data can be magneto-optically recorded in the rewritable area.
Recording methods are roughly classified into an optical modulation method and a magnetic field modulation method.

In the light modulation method, an external magnetic field is applied in a fixed direction perpendicular to the disk recording surface,
This method modulates laser light with recording data. That is, when this method is adopted, at the time of recording, the controller 6 causes the magnetic head driver 26 to apply an external magnetic field of N or S from the magnetic head 27 to the disk recording surface.
Then, the recording data encoded by the encoder 25 is supplied to the laser control unit 5, and the laser control unit 5 turns on / off the laser output from the laser light source 4c according to the recording data. As a result, the portion irradiated with the laser has the polarity of the external magnetic field, and the recording data is recorded on the disk 1 as magnetic field information.

On the other hand, the magnetic field modulation system includes a simple magnetic field modulation system in which a magnetic field modulated based on recording data is applied to a disk recording surface and a laser beam is continuously irradiated with a constant light amount. While applying a magnetic field that is modulated based on the recording data,
There is a laser strobe magnetic field modulation method in which laser light is emitted in pulses.

When these magnetic field modulation methods are employed, during recording, the controller 6 controls the laser control unit 5 so that the laser output from the laser light source 4c is continuously emitted or pulsed. The recording data encoded by the encoder 25 is supplied to a magnetic head driver 26, and the magnetic head driver 26
Applies an N or S magnetic field from the magnetic head 27 according to the recording data. As a result, the recording data is recorded on the disk 1 as magnetic field information.

The data reading position of the optical pickup 4 is movable in the radial direction. Although not specifically shown, a sled mechanism is provided to allow the entire optical pickup 4 to move in the radial direction of the disc, thereby performing a large movement of the reading position, and moving the objective lens 4a to the biaxial mechanism 4b. As a result, a small reading position is performed by a tracking servo operation which is moved in the disk radial direction.

In place of the sled mechanism for moving the optical pickup 4, a mechanism for sliding the disk 1 together with the spindle motor 2 may be provided. Further, the focus control of the laser spot is performed by moving the objective lens 4a toward and away from the disk 1 by the biaxial mechanism 4b.

When the disk 1 is loaded by a loading mechanism (not shown), the rotation drive by the spindle motor 2 is started. When the disk 1 reaches a predetermined rotation speed, the reading position is controlled so that the optical pickup 4 reads data in the management information area formed on the inner or outer peripheral side of the disk 1. In this management information area, a necessary start-up process such as focusing is performed, and then a recording or reproducing operation according to a request from the host computer 90 is started.

As the detector 4d of the optical pickup 4, a detector necessary for extracting reproduction data, a servo error signal, and the like is provided. In order to extract the reproduction data, it is configured such that both information corresponding to the emboss pits of the disk 1 and information corresponding to the magnetic field pits can be obtained. That is, the magnetic field data (MO data) in the rewritable area is detected for each polarization component by the magnetic Kerr effect to obtain an RF signal as MO data and an RF signal as a light amount corresponding to the emboss pit.
A signal is obtained. A configuration example will be described later.

From each light receiving area of the detector 4d, a current signal S1 corresponding to the amount of received light is output, and these are supplied to the I / V conversion matrix amplifier 7. The I / V conversion matrix amplifier 7 performs current-to-voltage conversion on the received light amount signal S1, and outputs signals such as embossed pits and magnetic field pits by arithmetic processing of signals from the respective light receiving areas, and focus error signals FE and the like. Generate the required signals.

A focus error signal FE serving as focus state error information is supplied to the servo controller 8. The servo controller 8 is equipped with a focus phase compensation circuit, a focus driver, and the like as a processing unit of a focus system, and generates a focus drive signal based on the focus error signal FE and applies the signal to the focus coil of the two-axis mechanism 4b. As a result, a focus servo system for converging the objective lens 4a to the just focus point is formed.

From the I / V conversion matrix amplifier 7, an RF signal used for generating the servo clock SCK and the data clock DCK is output as a signal S2. This signal S2 becomes a signal digitized by the A / D converter 10 after the low frequency fluctuation of the RF signal is removed by the clamp circuit 9. This digital signal is supplied to the address decoder 18, PL
It is supplied to the L circuit 11 and the tracking error generator 16.

The PLL circuit 11 generates the servo clock SCK synchronized with the RF signal by controlling the oscillation frequency of the internal oscillator based on the phase error between the input signal and the oscillation output and performing a predetermined frequency division process. . The servo clock SCK is used as a sampling clock in the A / D converter 10 and is supplied to an address decoder 18 and a timing controller 17. The data PLL circuit 12 divides the frequency of the servo clock SCK to generate a data clock DCK. This data clock DCK is supplied to the timing controller 17, the A / D converter 14, and the laser control unit 5.

The timing controller 17 generates a necessary timing signal for each section based on the servo clock SCK and the data clock DCK. For example, a sampling timing Ps for extracting a servo pit for a tracking operation, a synchronization timing DSY for a decoding operation in the data detection unit 14, and the like are generated. It also instructs the address decoder 18 when to extract address information. The address decoder 18 decodes digital data from the A / D converter 10 using the servo clock SCK during the timing period, and extracts address data. The address data is supplied to the controller 6 and the data PLL circuit 12
The data PLL circuit 12 switches the frequency division ratio so as to switch the data clock DCK in accordance with the disk radial position (zone) which can be determined from the address data.

The timing controller 17 and the tracking error generator 16 generate a tracking error signal TE by, for example, three-phase tracking control and supply it to the servo controller 8. Although not described in detail, a tracking error signal is formed from a signal obtained according to a so-called servo pit on the disk 1.

From the I / V conversion matrix amplifier 7, R
At the time of reproducing the OM area, an RF signal used for extracting emboss pit data is output as a signal S3. When reproducing the rewritable area, M as magnetic field pit information is used.
The O signal is output as signal S3. This signal S3 is subjected to a low frequency fluctuation of the signal by the clamp circuit 13 to remove the signal A / A.
It is digitized by the D converter 14.

The digital signal is supplied to the data decoder 15. The data decoder 15 performs a decoding process based on the synchronization timing DSY generated by the timing controller 17 based on the data clock DCK, and obtains reproduction data D _PB . The reproduction data D _PB is transmitted to the host computer 90 via the interface unit 19.
Will be supplied.

<3. Configuration of Optical System> FIG. 6 shows an example of the configuration of an optical system in the optical pickup 4 of this recording / reproducing apparatus. In the optical pickup 4, a collimator lens 70, a beam splitter 71, and a half-wave plate 72 are provided as a configuration of an optical system 4e that guides a laser beam from a laser light source 4c to an objective lens 4a that is an output end.
The light reflected from the disk 1 travels from the objective lens 4a to the half-wave plate 72 and the beam splitter 71. The component reflected by the beam splitter 71 is guided to the polarization beam splitter 74, The component that has passed through 74 is condensed by a lens 75 and is irradiated on the detector 4d1. On the other hand, the component reflected by the polarization beam splitter 74 is condensed by the lens 76 and is irradiated on the detector 4d2.

Various examples of the configuration of the optical system are conceivable. For example, in such a configuration, the detector 4
d1 and 4d2 are detectors for extracting emboss pit information and magnetic field pit information. The detector 4d1 is divided into light receiving areas da, db, and dc, and the detector 4d2 is divided into light receiving areas d,
It is divided into d, de, and df. Arrow TRD in the figure is
The direction corresponding to the track direction on the disk 1 as the light receiving surface, and the arrow RRD indicates the direction corresponding to the radial direction on the disk 1 as the light receiving surface.
Each of d2 is divided into three in the direction corresponding to the radius. That is, each has the configuration described in FIG.

<4. Specific circuit example for realizing the embodiment>
FIG. 7 shows a configuration example of an I / V conversion matrix amplifier 7 for obtaining a signal for reproducing data, that is, a signal S3 from the signals detected from the detectors 4d1 and 4d2.
Shown in FIG. 7 shows only a part related to the processing of the signal S3 in the I / V conversion matrix amplifier 7, but as this circuit system, I / V conversion circuits 51, 52, 53, and 5
4, 55, 56, adders 57, 58, 59, 60, 6
1, a subtractor 62, multipliers 63 and 64, and a switch 65 are provided.

The detector 4d, that is, each light receiving area da, db, dc, d of the three divided detectors 4d1, 4d2
The photoelectric conversion current signals from d, de, and df are I
In the / V conversion circuits 51, 52, 53, 54, 55, 56, current-voltage conversion is performed. The information of the reflected light from the embossed pits of the disk 1 becomes information of the amount of light, and therefore becomes a sum signal of the outputs of the detectors 4d1 and 4d2. Speaking of light receiving areas, light receiving areas da, db, dc, dd,
It is the sum of the signals from de and df. On the other hand, the reflected light information from the magnetic field pits of the disk 1 is information obtained by detecting a polarization component due to the magnetic Kerr effect, and the detectors 4d1, 4d
2 is the difference signal. Speaking of the light receiving areas, the outputs of the light receiving areas da, db, dc are used to calculate the light receiving areas dd, d.
The output of e and df is a signal obtained by subtraction.

In the case of this example, an arithmetic circuit configuration for canceling crosstalk noise by calculating the output of each light receiving area divided into three in the direction corresponding to the radius is employed. That is, with respect to the detector 4d1, the adder 57 adds the signals of the light receiving areas da and dc. The multiplier 63 multiplies the signal in the light receiving area dB by a coefficient g (for example, g = 1.5), and the multiplication result and the output of the adder 57 are added by the adder 58. The output of the adder 58, ie, the output of the detector 4d1, is the result of the calculation of Iα + Iβ + (Iγ × g) described with reference to FIG.

As for the detector 4d2, the adder 59 adds the signals of the light receiving areas dd and df. Further, the multiplier 64 applies a coefficient g to the signal in the light receiving area de.
(For example, g = 1.5), and the result of the multiplication and the output of the adder 59 are added by the adder 60. The output of the adder 60, ie, the output of the detector 4d2, is the result of the calculation of Iα + Iβ + (Iγ × g) described with reference to FIG.

The output of the adder 60 is subtracted from the output of the adder 58 in the subtractor 62. The output of the subtracter 62 is subjected to the operation for canceling the crosstalk noise, and then the detector 4d1 is used. , 4d2. That is, it is reproduction information from a magnetic field pit recorded on a track that is scanning with a laser spot. The output of the adder 58 and the output of the adder 60 are added in the adder 61. The output of the adder 61 is
It becomes the sum signal of the outputs of the detectors 4d1 and 4d2 after the calculation for canceling the crosstalk noise is performed. In other words, it is the reproduction information from the embossed pits recorded on the track scanning with the laser spot.

The output of the subtracter 62 is supplied to the tM terminal of the switch 65, and the output of the adder 61 is the tR of the switch 66.
While being supplied to the terminal, it is output as a signal S2 as servo pit information. Switch 65 is for disk 1
The switch 41 is connected to the tM terminal when the area in which data is recorded by the magnetic field pit is reproduced by switching control by a signal indicating the distinction between the ROM area and the rewritable area. Thus, the output of the subtractor 64 is supplied to the circuit system after the clamp circuit 13 as the magnetic field pit reproduction signal S3, and is decoded. On the other hand, when the area in which data is recorded by the emboss pit is reproduced, the switch 41 is connected to the tP terminal, so that the output of the adder 61 is used as the emboss pit reproduction signal S3 as the circuit system after the clamp circuit 13. And decoded.

As described above, in this embodiment, the detectors 4d1 and 4d2 divided into three in the direction corresponding to the radial direction of the disk are provided.
Since the reproduction information is obtained after performing an operation that can reduce the crosstalk component with respect to the output of the laser, a narrow track pitch that is disadvantageous in terms of the crosstalk with respect to the laser spot size is set. However, the disadvantage of the crosstalk can be eliminated. That is, narrow track pitch can be easily promoted, and high density recording can be realized.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, but includes, for example, an arithmetic processing circuit, a setting example of a coefficient g, and a light receiving area division of a detector. More various examples are conceivable in the examples. Although the playback device is compatible with a CAV disk, the present invention is also suitable for a playback device compatible with a CLV disk.

[0046]

As described above, according to the present invention, the detector is divided into a plurality of light receiving areas in the light receiving direction corresponding to the radial direction of the disk-shaped recording medium. The crosstalk removal operation processing is performed, and the signal subjected to the operation processing is decoded to reproduce data. In the crosstalk removal calculation processing, a gain greater than the output of the other light receiving areas is given to the output of the light receiving area located on the center side in the light receiving direction corresponding to the radial direction among the plurality of divided light receiving areas. Calculation processing. With such a configuration, the crosstalk component on the reproduction signal from the disc can be reduced and the signal quality can be improved.
By reducing the crosstalk component in this manner, a narrower track pitch can be realized, which is suitable for a high-density recording system.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration concept according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a track configuration for describing an embodiment.

FIG. 3 is an explanatory diagram of a crosstalk canceling effect of the embodiment.

FIG. 4 is an enlarged view for explaining a crosstalk canceling effect of the embodiment.

FIG. 5 is a block diagram of the recording / reproducing apparatus according to the embodiment.

FIG. 6 is an explanatory diagram of an optical system of the recording / reproducing device of the embodiment.

FIG. 7 is a block diagram of an I / V conversion matrix amplifier according to a second embodiment.

[Explanation of symbols]

1 disc, 2 spindle motor, 3 spindle controller, 4 optical pickup, 4a objective lens, 4
b Biaxial mechanism, 4c laser light source, 4d, 4d1, 4D2
Detector, 4e optical system, 5 laser controller, 6
Controller, 7 I / V conversion matrix amplifier, 8
Servo controller, 9, 13 Clamp circuit, 10,
14 A / D converter, 11 PLL circuit, 12 data PLL circuit, 15 data decoder, 16 tracking error generator, 16a sample hold circuit, 16
b error signal generation circuit, 17 timing controller, 18 address decoder, 19 interface section, 25 encoder, 26 magnetic head driver, 2
7 magnetic head, 51-56 I / V conversion circuit, 57,
58, 59, 60, 61 Adder, 62 Subtractor, 6
3,64 multiplier, 65 switches

Claims (2)

[Claims] 1. A reproducing device for performing a predetermined decoding process on a signal read from a disk-shaped recording medium and reproducing data, wherein one or more devices provided for receiving reflected light from the disk-shaped recording medium are provided. A plurality of detectors are divided into a plurality of light receiving areas in a light receiving direction corresponding to a radial direction on the disk-shaped recording medium, and a crosstalk removal calculation process is performed on detection outputs of the plurality of light reception areas, and the calculation is performed. A disk reproducing apparatus characterized in that a processed signal is decoded and reproduced data is extracted. 2. The crosstalk elimination arithmetic processing is performed on the output of the light receiving area located on the center side in the light receiving direction corresponding to the radial direction among the plurality of divided light receiving areas, based on the output of the other light receiving areas. 2. The disk reproducing apparatus according to claim 1, wherein the arithmetic processing is performed to give a large gain.