JPH0954954A - Information recording / reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a reproducing error rate of recorded information by discriminating whether a track is a land or a groove from a polarity of its tracking error signal. SOLUTION: The tracking error signal is provided with a positive relation with a drive current in land tracking, and a negative relation with the drive current in groove tracking. Then, the land track is discriminated from the groove track from the relation. In such a case, an actuator drive signal and the tracking error signal are eliminated in a low frequency signal unnecessary for discrimination by high-pass filters 51, 52 to be inputted to a phase comparator 53. The phase comparator outputs a positive value when an input is an equal phase, and outputs a negative value when the input is an inverse phase. Thus, the land track is discriminated from the groove track by the output of the phase comparator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing apparatus, and more particularly to a land / groove recording optical disk recording / reproducing apparatus for recording on both lands and grooves.

[0002]

2. Description of the Related Art An optical disk capable of storing information at high density is expected to expand its market as a large capacity external memory. The recorded portion of the recording layer of the optical disc is called a mark. An area in which these marks are continuously arranged is called a track. To increase the recording density, it is necessary to arrange the tracks in order, and for that purpose, it is necessary to guide the laser beam along the tracks. That is, a guide for tracking is required, and this guide is generally formed in the shape of a concave or convex groove in a spiral shape from the inner circumference to the outer circumference of the disk. This groove is called a guide groove.

The guide groove is a portion which is concave when viewed from the optical pickup, that is, a portion which is far from the optical pickup is called a land, and a portion which is convex when viewed from the pickup, that is,
The part near the optical pickup is called a groove. Information is recorded on either the land or groove. Recording on a land is called a land recording method, and recording on a groove is called a groove recording method. A route for recording information is called a track. The distance from the track center to the adjacent track center is called the track pitch. Usually the track pitch is about 1.6 μm.

In order to record information on an optical disc, as described above, the laser beam is narrowed down to a diameter of about 1 micron, and the recording layer of the optical disc is irradiated with the laser beam for a predetermined period of time. It is performed by raising and lowering the temperature and causing melting, phase change, magnetization direction change, etc. at that time. Such recording mainly by thermal energy is called heat mode recording. In order to accurately reproduce the information recorded on the heat mode recording optical disc, first, when forming the mark in the recording stage, it is necessary to set the irradiation laser beam intensity to an optimum value and form the mark accurately. . Therefore, the recording / reproducing apparatus generally has an optimum recording laser beam intensity value as a recording power table, and when recording is performed, the recording laser beam intensity is set based on this table.

The optimum laser beam intensity for recording depends on the linear velocity of the optical disk. Since the optical disc is generally used at a constant rotation speed, the linear velocity differs depending on the radial position of the disc. Therefore, the optimum laser beam intensity for recording also differs depending on the radial position. Therefore, in the recording / reproducing apparatus, the optimum recording laser beam intensity for each area divided into a plurality of areas in the radial direction of the optical disk is stored in the recording power table, and the recording power is recorded for each area based on the value of this table. The laser beam intensity is set.

Also, since the optical capacity of an optical disk differs depending on its structure, the optimum recording laser beam intensity differs from optical disk to optical disk. Therefore, information about the recording laser beam intensity is recorded in advance on the optical disc, and the recording / reproducing apparatus first reproduces this information on the optical disc, and rewrites the optimum recording laser beam intensity based on the value to match the optical disc. , Record with the optimum laser beam intensity.

By the way, to increase the recording density,
Various approaches have been proposed because the advantages of the optical disk will be further increased. The proposal to narrow the track pitch to 1.4 μm, 1.2 μm, 1.0 μm, etc. is one example. However, when a semiconductor laser beam with a wavelength of 780 to 830 nm is focused by an objective lens with a numerical aperture (NA) of 0.5 to 0.6, if the track pitch is made smaller than 1.4 μm, the information recorded on the adjacent track at the time of reproduction is recorded. There is a problem in that the leakage (referred to as crosstalk) becomes extremely large, the tracking error signal necessary for the tracking operation becomes extremely small, and the tracking accuracy decreases. A semiconductor laser with a wavelength of 630 to 690 nm has been developed in order to reduce these problems as much as possible, but there is a problem in practicality because of its low output and high price.

Therefore, the land / groove recording method has been proposed as another approach to increasing the density. This is a method of recording data on both the land and the groove, which has been conventionally recorded on the land or the groove. In this method, the land width and the groove width are made the same in order to read the data recorded in the land and the data recorded in the groove with the same C / N value. For example, if the track pitch is 1.4 μm,
The land width and groove width are both 0.7 μm.

This method is extremely effective for high density because it is possible to minimize crosstalk between adjacent grooves and lands (crosstalk free) by appropriately selecting the groove depth. is there. By the way, when manufacturing an optical disc, a recording layer is formed at the same time for a land portion and a groove at the same time. Therefore, the characteristics of the recording layer in the land and the characteristics of the recording layer in the groove portion are considered to be the same. Therefore, there is no difference between the optimum recording laser beam intensity of the land and the optimum laser beam intensity of the groove of the land / groove recording type optical disc.
It was thought that one recording power table should be used for land recording and one for groove recording.

[0010]

However, when land recording and groove recording are performed by using a common single power table, the reproduction error rate of the recorded information becomes high in either the land or the groove. There is.
SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a highly reliable recording / reproducing apparatus with a low reproduction error rate in both land recording and groove recording.

[0011]

DISCLOSURE OF THE INVENTION The inventors of the present invention discriminate in the recording / reproducing apparatus whether the track being tracked is a land or a groove based on the polarity of the tracking error signal, and the land is responded accordingly. If so, if the recording power table for land recording is used, and if it is a groove, the recording power table for groove recording is used,
In either case, it was found that an optimum recording laser beam intensity can be set, and a highly reliable recording / reproducing apparatus with a low reproduction error rate can be provided, and the present invention has been completed.

Therefore, a first aspect of the present invention is a recording / reproducing apparatus for recording / reproducing information on / from an optical disk having guide grooves in a concentric circle shape or a spiral shape and having information recording tracks in both lands and grooves. A means for detecting a tracking polarity, a means for determining whether the land is being tracked or a groove is being tracked based on the tracking polarity, and a recording power table (land) for recording information on the land track. Recording power table for recording) and a recording power table for recording information on the groove track (recording power table for groove), and secondly "tracking on land". Whether or not you are tracking the groove. The information recording / reproducing apparatus according to claim 1, wherein the recording power table for land and the recording power table for groove are selected and used according to the result. Thirdly, "recording power table for land and groove" 4. The information recording / reproducing apparatus according to claim 1, wherein the recording power table for recording records the recording laser beam intensity for each of a plurality of areas according to the radial position of the optical disc. 2. The information recording / reproducing according to claim 1, wherein the land recording power table and the groove recording power table are created by reproducing information on the recording laser beam intensity which is pre-recorded on the optical disc. Equipment.

As a result of research conducted by the present inventors, it has been found that there is a non-negligible difference in the optimum recording laser beam intensity even between adjacent lands and grooves. Therefore, in the case of the land / groove recording method, if the recording laser beam intensity is set by the recording power table common to the land and the groove, the recording is performed with the laser beam intensity which is not optimal for either the land or the groove. In this case, the mark is not formed at a predetermined position or a predetermined length, and reproducing such a mark increases the error rate.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0015]

First, a magneto-optical disk having a diameter of 130 mm is prepared. This disc has a width of 0.7 μm and a depth of 90 nm.
Has a guide groove in a spiral shape with a pitch of 1.4 μm. That is, the convex portions and the concave portions are both 0.7 μm wide and are alternately formed in the radial direction. As described above, the portion far from the optical pickup is the land and the portion near the optical pickup is the groove. The depth of the guide groove is a value that achieves crosstalk free. In addition, the preformat information is in the form of concave and convex pits and is a condition that crosstalk with adjacent tracks is free. The shape of the recording layer surface of this magneto-optical disk is shown in FIG. 4, and the state of the tracks is shown in FIG. Here, 2 is a land, 3 is a groove, 41 is an uneven pit, 42 is a mark, 43 and 45 are address parts, and 44 and 46 are data parts.

Next, a magneto-optical recording / reproducing device is prepared. This will be described with reference to FIG. This equipment consists of a semiconductor laser 5 that emits a beam with a wavelength of 830 nm and an objective lens with a numerical aperture of NA 0.55.
The optical pickup 4 comprises a detector 6, a detector 8, a track actuator 11, a positioner 12, and a focus actuator 13. The beam emitted from the semiconductor laser 5 passes through the polarization beam splitter 7 and the objective lens.
It is focused by 6 and connects a spot to the recording layer of the magneto-optical disk. The beam reflected by the recording layer again passes through the objective lens 6 and the polarization beam splitter 7 and enters the detector 8 where it is converted into an electric signal, and then enters the processing circuit 9. The processing circuit 9 processes the electric signal and outputs a track error signal (TE), a focus error signal (FE), a phase pit signal (PPS), and a magneto-optical signal (MOS). The track error signal and the focus error signal are processed by the servo controller 10 and converted into a tracking signal, a positioning signal, and a focusing signal. The positioning signal positions the beam spot near the target track by moving the optical pickup 4 in the radial direction of the disk by the positioner 12. The tracking signal positions the beam spot on the target track by moving the objective lens 6 in the radial direction of the disk by the track actuator 11. The focusing signal moves the objective lens 6 in the optical axis direction by the focus actuator 13 to focus the beam spot on the target track.

On the other hand, the phase pit signal and the magneto-optical signal are input to the system controller 20. The system controller 20 communicates with the host computer 30 about commands and recording / playback information. Further, a control signal is created based on the phase pit signal and the magneto-optical signal and sent to the system controller 20. Information recording is performed as follows. The processing circuit 9 modulates the drive current of the semiconductor laser 5 in accordance with the information to be recorded sent from the host computer 30 to the system controller 20. As a result, the intensity of the emitted beam of the semiconductor laser 5 is modulated according to the information to be recorded, and the information is recorded as a magneto-optical mark on the medium. At this time, the system controller 20 obtains the recording radius position of the disc from the address information designated by the host computer 30, sets the optimum recording laser beam intensity according to the land recording power table 14 or the groove recording power table 15, and The processing circuit 9 accordingly sets the drive current of the semiconductor laser.

Erasing the informed information is performed as follows. The system controller 20 determines the recording radial position from the phase pit signal, determines the optimum constant intensity of the erasing laser beam intensity based on the recording power table 14 or 15, and the processing circuit 9 sets the driving current of the semiconductor laser accordingly. . The external magnetic field 16 is arranged in the direction of FIG. 1 at the time of recording and in the direction of NS at the time of erasing so as to be opposite to that of FIG. 1, and generates a recording magnetic field and an erasing magnetic field in the disk recording layer, respectively.

Next, the control will be described in more detail with reference to FIG. The tracking error signal is input to the land track control circuit 31 and the groove track control circuit 32. The control circuits have the same control constants but opposite signal polarities. The switch circuit 17 controls the track actuator 11 by selectively producing an open state, 31 and closed state, 32 and closed state, and a track actuator forced drive circuit 54 and closed state by the signal of the system controller 20 and the tracking polarity detection circuit 50. To do. On the other hand, a part of the track actuator control signal controls the positioner via the positioner control circuit 19.

The focus error signal controls the focus actuator 13 via the focus control circuit 16 and the switch circuit 18. Similarly, the switch circuit 18 is controlled to be in an open state and a closed state by a signal from the system controller. The phase pit signal enters the address detection circuit 21, the address is detected, and the magneto-optical signal is reproduced by the information reproduction circuit 22 and sent to the host computer.

Next, referring to FIG. 7, the change in the polarity of the tracking error signal when tracking the land and when tracking the groove will be described. First,
(A) shows the movement of the optical pickup in the radial direction, d is a land track, e is a groove track, and f is a boundary between the two. (B) shows a change in reflectance. Further, (c) shows a tracking error signal in tracking error detection by the push-pull method, which shows a positive polarity in the land tracking and a negative polarity in the groove tracking. Then, FIG. 8 shows a method of distinguishing the land and the groove from the polarity of the tracking error signal. (A) shows the movement of the optical pickup in the radial direction, d is a land track, and e is
Represents a groove track, and f represents a boundary between the two. (B) shows the drive current of the track actuator. Further, (c) shows a tracking error signal in tracking error detection by the push-pull method, which has a positive relationship with the drive current in the land tracking and a negative relationship with the drive current in the groove tracking. Therefore, the land track and the groove track can be identified from this relationship. FIG. 9 shows a discrimination circuit for the land track and the groove track. High-pass filter for actuator drive signal and tracking error signal
Low-frequency signals unnecessary for identification are removed by 51 and 52 and enter the phase comparator 53. The phase comparator outputs a positive value when the inputs have the same phase and a negative value when the inputs have the opposite phase. Therefore, the land track and the groove track can be identified by the output of the phase comparator.

The recording power table is created based on the information of the optimum recording laser beam intensity for the lands and grooves prerecorded at the predetermined positions of the magneto-optical disk. For example, during land tracking, the address portion of the land track is reproduced to recognize the position of the optical pickup. In this state, when an instruction to record information in a predetermined sector is received from an external host computer, it is determined whether the sector instructed to be recorded exists in a land track or a groove track. Then, the relative position difference between the current head position and the position of the sector which received the recording instruction is obtained. Next, the tracking servo is set to an open loop, and the movement is started in the direction of the sector which received the recording instruction. At this time, the tracking condition is set to a condition (for example, groove track) of the track in which the sector that has received the read instruction exists. While counting the number of tracks to be traversed, the tracking servo is set to a closed loop when a sector having a recording instruction reaches a track. The track address part of the tracked track is reproduced to detect the track address. It is confirmed that the detected track address is a groove track and that the sector for which the recording instruction is received exists. If they are different, the same operation is performed again.

Next, the information already recorded in the sector which has received the recording instruction is erased by the following procedure. First, the external magnetic field 16 is directed toward the erasing direction, and a magnetic field in the erasing direction is applied to the recording layer of the magneto-optical disk. The optimum recording power at that radial position is read from the recording power table according to the track address that received the recording instruction. For example, if the track that has received the erase instruction is a groove, the recording power table for groove recording is used. Irradiate the data section of the erase-instructed sector with an intensity 1.2 times the optimum recording laser beam intensity.

Next, recording is performed in the data portion of the sector which received the recording instruction in the following procedure. First, the direction of the external magnetic field 16 is directed to the recording direction, and a magnetic field in the recording direction is applied to the recording layer of the magneto-optical disk. When the beam spot reaches the data portion of the target sector, the laser beam intensity is modulated according to the information to be recorded (see FIG. 10). Pw is the optimum recording laser beam intensity of the recording power table for groove recording.
0.9 times, and Pb is set to 0.1 times the optimum recording laser beam intensity of the recording power table for groove recording.
When the recording is completed, the intensity of the semiconductor laser is returned to the reproduction intensity, and the host computer waits for an instruction.

[0025]

As described above, according to the present invention,
Whether recording on land or groove,
It is possible to set the recording laser beam intensity to an optimum value according to the recording sensitivity difference and the recording radial position of each medium, and to provide a highly reliable recording / reproducing apparatus with a low reproduction error rate of recorded information. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing pits of a conventional CD.

FIG. 3 is an explanatory diagram showing a recording layer surface of a conventional magneto-optical disk.

FIG. 4 is an explanatory view showing a recording layer surface of a magneto-optical disk used in the present invention.

FIG. 5 is an explanatory diagram showing a track configuration of a magneto-optical disk used in the present invention.

FIG. 6 is an explanatory diagram showing details of control according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a change in polarity of a tracking error signal.

FIG. 8 is an explanatory diagram showing a principle of distinguishing a land from a groove based on a polarity of a tracking error signal.

FIG. 9 is an explanatory diagram showing an embodiment of a discrimination circuit for a land track and a groove track.

FIG. 10 is a conceptual diagram of the time change of the laser beam intensity with which the recording layer of the optical disc is irradiated during recording.

[Explanation of symbols]

 Description of parts 1 ... Magneto-optical disk 2 ... Land track 3 ... Groove track 4 ... Optical pickup 5 ... Semiconductor laser 6 ... Objective lens 7 ... Polarization beam splitter 8 ... Detector 9 ... Processing circuit 10 ... Servo controller 11 ... Track actuator 12 ... Positioner 13 ... Focus actuator 14 ... Land recording power table 15 ... Groove recording power table 16 ... ..External magnetic field 17 ... switch circuit 18 ... switch circuit 19 ... positioner control circuit 20 ... system controller 21 ... address detection circuit 22 ... information reproduction circuit 24 ... sequence controller 30・ ・ ・ Host computer 31 ・ ・ ・ Land track control circuit 3・ ・ ・ Groove track control circuit 41 ・ ・ ・ Phase pit 42 ・ ・ ・ Magneto-optical mark 43 ・ ・ ・ Address part 44 ・ ・ ・ Data part 45 ・ ・ ・ Address part 46 ・ ・ ・ Data part 50 ・ ・ ・ Tracking polarity Detection circuit 51 ... High-pass filter 52 ... High-pass filter 53 ... Phase comparator 54 ... Track actuator forced drive circuit

Claims (4)

[Claims] 1. A concentric circular or spiral guide groove is provided,
A recording / reproducing apparatus for recording / reproducing information on / from an optical disc having information recording tracks on both the land and the groove, the means detecting the polarity of tracking, and tracking the land on the basis of the tracking polarity or the groove. A recording power table (land recording power table) for recording information on the land track, and a recording power table (recording power for groove) for recording information on the groove track. An information recording / reproducing apparatus having a table). 2. A land recording power table and a groove recording power table are selected and used according to a determination result by means for determining whether a land is being tracked or a groove is being tracked. The information recording / reproducing apparatus according to claim 1. 3. The land recording power table and the groove recording power table are recorded with recording laser beam intensities for each of a plurality of areas corresponding to the radial position of the optical disk. Information recording / reproducing device. 4. The land recording power table and the groove recording power table are created by reproducing the information about the recording laser beam intensity prerecorded on the optical disk, respectively. Information recording / reproducing apparatus.