JPH1079130A - Optical disc device and tracking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a recording capacity by raising a track density in the diametrical direction of a disc while allowing the control of tracking. SOLUTION: In an address segment and a data segment, a servo area with a length of 24SCK (servo clock) is provided and a segment mark and a track mark are formed in the servo area by emboss working or the like. Marks 1 are formed at 11th and 12th positions and marks 2 at 16th and 17th positions. The marks 1 and 2 are arranged diametrically at a cycle of two tracks while being differentiated by 180 deg. in phase. Even tracks and odd tracks are identified based on a push/pull signal obtained by a division photo detector. Thus, an accurate control of tracking is accomplished even when the polarity of a tracking error signal is inverted between the even tracks and the odd tracks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk apparatus for recording / reproducing, for example, computer data on / from an optical disk, and a tracking method for controlling a track on an optical disk so that a reading position is correctly traced.

[0002]

2. Description of the Related Art An optical disk is used as an external storage device of a computer, taking advantage of the ability to store a large amount of digital data. As a tracking servo system for an optical disk, a continuous groove system and a sample servo system are known. In the continuous groove system, grooves are provided on both sides of a track, and when a main beam for data recording / reproduction scans the track, two sub-beams located before and after the main beam in the track direction respectively scan the groove. , The reading position of the main beam is controlled so that the reading outputs of the two sub beams become equal.

In the sample servo method, servo areas including three pits provided in advance by embossing or the like are provided at regular intervals. One pit is provided at a position coinciding with the center of each track, and two pits provided before and after the track in the track direction are at a fixed distance in the disk radial direction with respect to the track center and in the opposite direction. Each is provided at a separated position. These pits are also called wobbling pits. The reading position is controlled so that the levels of the reading signals generated when the recording / reproducing laser beam scans the two pits are equal to each other. Further, a reproduction clock can be stably generated by using a read signal of a pit formed on the track center.

[0004] The present invention relates to an optical disk employing a sample servo system. In the case where a servo area is provided in each of the minimum units (referred to as segments) of physical data units obtained by dividing a track, the applicant of the present application has proposed to arrange a servo area having a configuration shown in FIG.
In the example of FIG. 12, the servo area is 24 SCK (SCK
Means a servo clock generated based on the read signal of the servo area). Positions defined by the servo clock are first, second, third,
.., Expressed in the 24th position, a segment mark is formed using the third position to the seventh position, the mark 1 is formed in the 11th and 12th positions, and the 16th and 17th positions are formed. Mark 2 is formed at the position of. These marks 1 and 2 are called track marks.

The mark 1 is １ ／ · Tp in one direction (for example, inward) in the disk radial direction with respect to the track center.
The mark 2 is formed by embossing at a position shifted by (Tp: track pitch), and the mark 2 is １ ／ · T in the other direction (eg, outside) in the disk radial direction with respect to the track center.
It is formed by embossing at a position shifted by p (Tp: track pitch). These marks 1 and 2 are wobbling pits. Therefore, by controlling the reading position of the laser beam so that the level of the reproduction signal when the laser beam crosses these marks becomes equal, the reading position can be made coincident with the track center.

One frame is composed of a plurality of segments, for example, 14 segments, one of the 14 segments is an address segment in which address data is recorded in advance, and the other 13 segments are data recordable. It is a data segment. One sector has a predetermined size, for example, 2 Kbytes, and one sector is composed of a plurality of address segments and data segments. The segment mark is used to identify the type of the segment, if the data segment is at the beginning of the sector, if the data segment is at the end of the sector,
It is provided to distinguish it from other cases. That is, as shown in FIG. 12, in order to distinguish between them, emboss pits having a length of two clocks are provided at positions shifted by one clock from the third position to the seventh position. .

In the servo area shown in FIG. 12, no clock pit is provided at a position corresponding to the track center. This makes it possible to shorten the length of the servo area and increase the recording data amount. The clock can be recovered by a differential detection method. That is, as shown in FIG.
The amplitude of both shoulders of the reproduced signal RF of the
Sampling positions tb1, tb2, tc based on CK
1 and tc2, the sampling output levels b1 and b2 are equal to each other, and the level c
The phase of the servo clock is controlled so that 1, c2 are equal to each other. The levels b0 and c0 obtained at the sampling positions tb0 and tc0 are used for tracking servo. That is, tracking servo is applied so that these levels b0 and c0 become equal.

Further, the above-described differential detection method is used to detect the position of a segment mark. In this way, address segments are intermittently arranged,
By providing a segment mark in each segment, it is possible to eliminate the need to record a sector number and a tracking address in sector units.

[0009]

As described above, the track mark is provided on each track. One method of increasing the data capacity of an optical disk is to reduce the distance (track pitch Tp) in the disk radial direction of the track center between adjacent tracks, thereby increasing the track density. However, in the method of providing the track marks on each track, the distance between the track marks in the disk radial direction becomes small,
It becomes difficult to detect a tracking error based on a reproduction signal of a track mark.

FIG. 14 shows the relationship between radial spatial frequency (horizontal axis) and MTF (Modulation Transfer Function) (vertical axis). This graph shows that the wavelength of the laser beam is 680.
[Nm] shows a change when an optical pickup having an aperture ratio NA of the objective lens of 0.55 is used. In FIG. 14, the track pitch Tp is (Tp = 1.6 μm, Tp =
(1.2 μm, Tp = 0.8 μm) are shown. For example, when the track pitch of 1.2 μm is reduced to 0.8 μm, as can be seen from FIG. 14, the MTF is reduced to about ８. MT
Since F represents the transfer characteristic of the amplitude, when the MTF is small, the level of a signal generated when a track mark is read becomes small, and normal tracking servo becomes difficult.

Accordingly, it is an object of the present invention to provide an optical disk apparatus and a tracking method capable of performing normal tracking servo when the track density is increased and increasing the recording capacity.

[0012]

According to a first aspect of the present invention, digital information is optically recorded on or formed from concentrically or spirally formed tracks on an optical disk medium. In an optical disk device designed to read, the optical disk medium is
In each of the tracks, a servo area is provided intermittently in the track direction and at a position aligned in the disk radial direction. A second mark is provided, wherein the first and second marks are:
Each of the marks is provided at a two-track cycle in the radial direction of the disk and the phases of the first and second marks in the radial direction of the disk are different from each other. An optical pickup that generates a read output by detection and generates a push-pull signal by a split optical detector whose split position is substantially the same as the center of the track and a read position of the optical pickup in the disk radial direction The level of the output corresponding to the first and second marks in the read output is compared with the tracking means for displacing the read and output signals, a tracking error is detected based on the comparison result, and an adjacent level generated based on the push-pull signal is detected. The direction of the tracking error is determined based on the information identifying the track. And, to the tracking error to zero, an optical disk apparatus characterized by comprising a tracking control means for controlling the reading position.

According to a sixth aspect of the present invention, there is provided an optical disk apparatus for optically recording digital information on or reading digital information from a track formed concentrically or spirally on an optical disk medium. In the tracking method of (1), the optical disk medium is provided with a servo area in each track intermittently in the track direction and at a position aligned in the disk radial direction, and the servo area is separated by a predetermined distance in the track direction. First and second marks physically formed in advance are provided, and the first and second marks are provided at a two-track cycle in the disk radial direction, respectively, and the first and second marks in the disk radial direction are provided. The mark 2 has a different phase and is irradiated onto the optical disk medium. A step of generating a read output by detecting reflected light of the laser beam and generating a push-pull signal by a split optical detector which is split into two and the split position substantially coincides with the center of the track; And the level of the output corresponding to the second mark is detected, a tracking error is detected based on the comparison result, and the direction of the tracking error is determined based on information for identifying an adjacent track generated based on the push-pull signal. And controlling the reading position so that the tracking error is reduced to zero.

A mark 1 and a mark 2 constituting a track mark are formed with two tracks in the radial direction of the disk, and the phases of the mark 1 and the mark 2 in the radial direction of the disk are different. Therefore, the spatial frequency in the radial direction of the track mark for detecting the tracking error decreases, and the tracking error can be detected even when the track density is increased. Furthermore, since the track being scanned is identified from the push-pull signal,
There is no need to add marks (pits) and addresses for identification.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, an optical disk medium according to this embodiment will be described. The optical disk is, for example, an MO (magneto-optical) disk having a diameter of 3.5 inches and having a spiral track formed on one surface thereof. The present invention is not limited to the MO disk, but can be applied to other types of optical disks such as a phase change optical disk, and the tracks may be formed concentrically. Further, the present invention provides a recordable optical disc,
The present invention is also applicable to a read-only optical disk, an optical disk having an area recordable on one surface of one optical disk and a read-only area independently, a double-sided optical disk, and the like.

One embodiment of the present invention employs a sample servo system and a zone CAV (Constant Angular Ve
locity) type optical disc. In addition, the zone CAV
The method is an example, and the CAV method, CLV (Constant
The present invention can be applied to an optical disk of the Linear Velocity type.

As shown in FIG. 1, the optical disk according to one embodiment of the present invention has a plurality of areas defined in the radial direction. GCP (Gray Code Par)
t) area (736 tracks), buffer tracks (2 tracks), control tracks (5 tracks), buffer tracks (2 tracks), test tracks (5 tracks), user zone 0, user zone 1,.
User zone 15, test track (5 tracks), buffer track (2 tracks), control track (5 tracks), buffer track (2 tracks), G
Each CP area (820 tracks) is defined. As an example, if the number of tracks in user zone 0 is 84
8, the number of tracks in the user zone 1 is 864,...

The zone CAV makes the recording density of each zone substantially constant by rotating the optical disc at a constant speed and changing the clock frequency of the data recorded in each zone, thereby facilitating the control of the disc rotation. And increases the recording capacity as compared with the simple CAV method. That is, since the linear velocity of the optical disk is higher on the outer peripheral side, the frequency of the data clock DCK is also higher on the outer peripheral side. Servo clock S
CK has a constant frequency irrespective of the zone, and the data clock DCK has a frequency multiplied by M / N of the servo clock SCK. As described above, the frequency of the data clock DCK in the outermost zone 0 is the highest, and the frequency of the data clock DCK in the innermost zone 15 is the lowest.

No user data is recorded in the GCP area, control track, and buffer track. Gray-coded media information (media type, format, etc.) is recorded in a predetermined number of segments of the GCP area. In the control track, information indicating the number of segments per track, information on the start track number of each zone, information on the total track number of each zone, information on the number of segments per sector, and the like are recorded.

FIG. 2 shows a sector structure, in which a black band represents an address segment. On the optical disk, an address segment and a servo area are provided for each track at positions intermittent in the track direction and aligned in the disk radial direction. In this embodiment, the amount of user data in one sector is defined as 2 Kbytes (2,048 bytes). Although the sector size is constant, the number of bytes per segment (the data byte capacity that can be recorded in the data area of one data segment) differs depending on the zone, and thus the number of segments constituting one sector differs depending on the zone. For example, in zone 0, one segment has 46 bytes, and one sector has 53 segments. In the zone 14, one segment has 22 bytes and one sector has 110 segments.

When a sector starts from a certain segment and the number of segments constituting one sector ends, the sector ends, and even if there is a surplus byte in the last segment, the surplus byte is used as the next sector. Without using,
Start the next sector from the next segment. Therefore, at the beginning of the zone, sector 0 starts from segment 0 of the 0th frame. As described above, at the start position of each zone, the start position of sector 0 is a position that matches in the radial direction, but otherwise, the start position of the sector does not match. Therefore, it is necessary to know the starting position of the sector for access.

FIG. 3 shows a physical data structure of this embodiment. As shown in FIG. 3, one track is composed of 100 frames (frame 0 to frame 99), and each frame is composed of 14 segments (one address segment and 13 data segments). Therefore, one frame is 1400 segments. The beginning of each frame is an address segment,
The remaining 13 segments are data segments.
One track includes 1300 data segments of data segment 0 to data segment 1299, and 100
Address segments.

The address segment is composed of the servo clock S
It has a length of 216 SCK with respect to CK.
The servo area (24 SCK) is located at the beginning of the segment, the next 10 SCK is blank, and the next 84 SCK
CK is an address area, and an ALPC (Automatic Laser Power Control) area (98SCK) is provided at the end of the address segment. The address segment is formed on the disk in advance by embossing or the like. The ALPC area is used to control the reading laser power to a predetermined value.

The data segment also has the same length (216 SCK) as the address segment, and a servo area (24 SCK) formed by embossing or the like is located at the top. If the data clock is represented by DCK after the servo area, a pre-write area PR having a length of 12 DCK, a data area, and a post-write area PO having a length of 4 DCK are arranged. Since the frequency of the data clock DCK differs depending on the zone, data of 176 DCK to 368 DCK is recorded in the data area.

The pre-write area PR secures a distance necessary for preheating the disk to a stable temperature for data recording and functions as a clamp area for suppressing DC fluctuation due to birefringence or the like. The post-write area PO is provided in order to eliminate the remaining unerased recorded data at the time of overwriting and to secure a distance to avoid data interference caused by the edge of the groove. The grooves are not used for tracking control, but for reducing adverse effects on disk molding, and have a depth of, for example, λ / 8 (λ: laser wavelength).

FIG. 4 shows a sector format. As the data of each sector, 2,048 bytes of user data and an error correction code redundant code (256 bytes)
Error detection CRC code (8 bytes) and user defined data (40 bytes)
Contains 2 bytes. And before the data area, 6
Six bytes of reference data are added, and one sector has a size of 2,418 bytes.

The reference data includes a 4-byte 8T pattern and a 1-byte pattern to indicate the waveform of the reproduced RF signal.
A 2-byte 2T pattern is repeated four times, and a 2-byte pattern of all `0's is provided as a margin for setting detected information. This reference data is recorded by the zone CAV method, similarly to the user data. The 2T pattern has a DC
This is used to correct a typical pit position shift during reproduction. The 8T pattern is used to set a threshold at the time of ternary detection by a partial response.

The servo area will be described with reference to FIG. FIG. 5A shows a servo area provided in the address segment, and FIG. 5B shows a servo area provided in the data segment. As described above, for both segments, the servo area has a length of 24 SCK. In the case of the address segment shown in FIG. 5A, the post-write area P of the data segment is placed before the servo area.
O (4DCK) is located, and a blank area (10SCK) of the address segment is located after the servo area. Up to the post write area PO, data is recorded on the basis of the data clock DCK. In the servo area, pits are formed in advance on the basis of the servo clock SCK. Address codes after the blank area are also based on the servo clock SCK. Pits are formed in advance.

In the case of the data segment shown in FIG. 5B, the post-write area PO (4DCK) of the data segment is located before the servo area, and the pre-write area (12D) of the data segment is located after the servo area.
CK) is located. Up to the post write area PO, data is recorded on the basis of the data clock DCK. In the servo area, pits are formed in advance on the basis of the servo clock SCK, and after the prewrite area, the pits are formed on the basis of the data clock DCK. The data is recorded. The groove is provided in the data recordable area in parallel with the track.

The address segment and the data segment have the same servo area configuration. That is, when defining the position in the servo area as the first position to the 24th position based on the servo clock SCK, the third position
The segment mark is recorded from the position to the seventh position,
Mark 1 is recorded at the eleventh and twelfth positions,
The mark 2 is recorded at the sixth and seventeenth positions. These marks 1 and 2 form a track mark. The track mark is used for detecting a tracking error and reproducing a clock, similarly to the optical disk (see FIG. 12) proposed earlier. The segment mark is defined in the same manner as the previously proposed optical disc. That is, the address segment and the data segment are distinguished, and the head of the sector, the end of the sector,
Distinguish other data segments. FIG. 5B shows the even and odd tracks of each of these data segments.

The reason why the lengths of the marks 1 and 2 are two servo clocks is to reduce the number of mirror portions where no pits are formed, thereby making it difficult for ghost pits to occur during disk molding. ,
This is for stably obtaining a reproduction RF signal corresponding to the pit. Moreover, by setting the interval between the mark 1 and the mark 2 at a predetermined interval, for example, 5 SCK or more, the interference between each pit and the corresponding reproduction RF signal can be reduced.

In one embodiment of the present invention, in the radial direction of the disk, an intermediate position between the track center of the adjacent first track (referred to as even-numbered track) and the track center of the second track (referred to as odd-numbered track). In addition, the marks 1 and 2 are formed so that the direction of the shift is different from the center of each of the even track and the odd track. In the example of FIG. 5, the mark 1 has an amount of ず れ · Tp (Tp: track pitch) with respect to the even-numbered track, and has a deviation in a direction, for example, inward (downward in the drawing) of the disk. 2 is an amount of ・ · Tp, and has a deviation in a direction, for example, outside (upper side in the drawing) of the disk. On the other hand, for odd tracks, mark 1
Has a displacement in the direction of, for example, the outside (upper side in the drawing) of the disc by an amount of ・ · Tp, and the mark 2 has an amount of ・ · Tp in the direction of the inside of the disc (lower side in the drawing). It has a misalignment.

The relationship between the even track and the odd track and the mark 1 and the mark 2 is common regardless of the address segment and the data segment. In addition, a servo area is formed so that the above-described relationship is established for all tracks on the optical disc that require tracking control. However, for all tracks on the optical disk, mark 1 and mark 2
It is not necessary to make the relationship between the even track and the odd track the same. In other words, this relationship may be reversed depending on an identifiable region, for example, a zone. Specifically, the relationship may be reversed between the even-numbered zone and the odd-numbered zone.

In the present invention, each of the mark 1 and the mark 2 is repeated with a period of two tracks in the radial direction of the disk, and the phases of the repetitions are different by 180 °. Conventionally, each track requires a pair of wobbling pits. Therefore, mark 1
The repetition period of each of the marks 2 in the radial direction of the disk was one track. According to the present invention, since the repetition period of the mark 1 and the mark 2 in the disk radial direction can be set to two tracks, the spatial frequency in the disk radial direction can be reduced when the track pitch Tp is the same as the conventional one. Therefore, the present invention can increase the MTF. Further, when the MTF is set to be substantially the same as that of the conventional method, the track pitch Tp can be further reduced. That is, the track density can be increased.

The tracking servo controls the reading position of the optical pickup so that the level of the read signal of the mark 1 and the level of the read signal of the mark 2 become equal, as in the prior art. According to the present invention, as described above, since the track mark is formed, the direction of the tracking error and the polarity of the detected tracking error signal are opposite between the even track and the odd track. Therefore, it is necessary to distinguish between even-numbered tracks and odd-numbered tracks in order to correctly pull in a target track. As described later, in the present invention, a push-pull signal is output from an optical pickup that reads an optical disc,
Based on this push-pull signal, an even track and an odd track are identified. Therefore, the present invention does not require a special pit or address for identification.

The address code of the address segment will be described with reference to FIG. FIG. 6 shows the entire address segment. As described above, the segment mark and the track mark are formed in the first servo area having a length of 24 SCK. After that, 10SC
There is a blank interval of length K, followed by 8
An address code having a length of 4 SCK is recorded. Following the address code, an ALPC area having a length of 98 SCK is provided.

The address code is recorded in advance by embossing or the like, and indicates position information in the track direction. The address code has an address code enlarged in FIG. The address code is further divided into an access code (AM, A2, A3, AL, parity) and a frame code (FM, FL).

AM, A2, A3, and AL are obtained by dividing a 16-bit track address into 4 bits and encoding each 4 bits as a Gray code. That is, a 16-bit address is divided into 4 bits at a time from the upper side, and each 4 bits is encoded as a Gray code,
Pits are recorded as pits at the first to twelfth positions specified by the servo clocks. A parity having a length of 12 SCK is added to the track address. This parity is an even parity for the same four bits of the track address. The track address gives position information of a track on the disk. Therefore, it is also possible to identify an even track and an odd track from the track number indicated by the track address.

FM and FL are frame codes. The frame code is obtained by dividing an 8-bit frame address by 4 bits, encoding each 4 bits as a Gray code, and recording pits at the first to twelfth positions specified by the servo clock. is there.
The frame address indicates a frame (frame 0 to frame 99) in the track.

FIG. 7 shows an example of a method of encoding 4-bit data into a Gray code and recording it at 12 positions. 0 to F are 4-bit code values, and a pit corresponding to this value is formed in a section of 12 SCK as shown in the figure. The access code, frame code,
The additional address is encoded into a Gray code according to the table shown in FIG.

The above-described format is applicable to both recordable discs (erasable discs and write-once discs) and read-only discs. FIG. 8 shows the configuration of an optical disk device when the present invention is applied to an MO disk.

In FIG. 8, reference numeral 1 denotes an optical disk having the format described above. The optical disc 1 is rotated at a constant rotation speed (for example, 2400 rpm) by the spindle motor 2 and the spindle control unit 3. The optical disk 1 is irradiated with laser light from the optical pickup 4. Although not shown, the optical pickup 4 includes an optical system such as a laser source, an objective lens, and a beam splitter, and a detector that detects light reflected by the optical disc 1. The amount of laser light from the laser source is controlled by the laser controller 5.

In this embodiment, since the optical disk 1 is an MO disk and employs a magnetic field modulation system, a magnetic head 6 is provided, and recording data is supplied to a magnet driver 7 for driving the magnetic head 6. Is done. The recording data is generated by the data encoder 9. Interface from external host computer 10 such as SC
The data transferred via the SI is supplied to the data encoder 8 via the controller 9. Commands such as write and read are also supplied from the host computer 10 to the controller 9. Then, the recording data is recorded by the magnetic head 6 in the NRZI system.

As a method of recording a digital signal on an MO disk, there are an optical modulation method and a magnetic field modulation method. The light modulation method is a method of modulating laser light with recording data while an external magnetic field is applied in a certain direction.
As a magnetic field modulation method, a simple magnetic field modulation method in which an external magnetic field is modulated with recording data while irradiating a fixed amount of laser light, and a laser strobe that modulates a magnetic field with recording data and emits a pulse of laser light. There is a magnetic field modulation method. The present invention can use any of these recording methods.

The reading position by the optical pickup 4 is
It can be displaced in the radial direction. Specifically, there are a coarse adjustment unit that handles a large radial displacement and a fine adjustment unit that handles a small displacement. A coarse adjustment means is constituted by a linear motor or the like, and a fine adjustment means (tracking means) is constituted by a rotating mirror, a movable objective lens or the like. Further, a tracking means for fixing the position of the optical pickup 4 and displacing the optical disc 1 may be employed. Further, a focusing means for adjusting the facing distance between the optical disc 1 and the optical pickup 4 is also provided so that the laser beam from the optical pickup 4 is correctly focused on the disc.

When the optical disk 1 is loaded by a loading mechanism (not shown), the rotation drive by the spindle motor 2 starts, and when the optical disk 1 reaches a specified rotation speed, the optical pickup 4 moves the inner or outer circumference of the optical disk 1. The reading position is controlled so as to read the GCP area. In this GCP area, the focus is drawn, and thereafter, a recording or reproducing operation is performed.

The reproduced RF signal detected by the detector of the optical pickup 4 is supplied to the IV conversion and matrix operation unit 11. Since the output signal of the detector is generated as a current, a voltage output is formed by the IV conversion. Further, by performing a matrix operation, a sum signal RFs, a difference signal RFd, a push-pull signal PP, a focus error signal FE, and the like are generated. The focus error signal FE is supplied to the servo control unit 12.
The servo control unit 12 generates a signal for driving a focusing unit in the optical pickup 4 in order to properly focus the laser light.

FIG. 9 shows an example of an optical detector provided in the optical pickup 4. The laser light reflected by the optical disk 1 is incident on the microprism 31, the straight light is irradiated on the photodetector 32, and the reflected light at 45 ° is irradiated on the photodetector 33. Photo detector 32
Is divided into two by a center line (indicated by a one-dot chain line) substantially coincident with the track center, and each divided region is divided into three in a direction orthogonal to the center line. The pairs of regions that are in contact with each other with the center line interposed therebetween are denoted by (A1, A2), (B1, B2), (C
1, C2). The photodetector 33 is divided into three parts in a direction orthogonal to the center line.
The symbols E and F are attached and shown. The broken-line circles drawn on the photodetectors 32 and 33 represent the spots of the return beam when the laser beam scans the track center.

The detection signals of the respective regions of the photodetectors 32 and 33 are taken out independently, and if the regions and the detection signals are indicated by the same reference numerals, the signals are generated by the following calculation. Where A = A1 + A2, B = B1 + B2, C
= C1 + C2. Sum signal RFs = (A + B + C) + (D + E + F) Difference signal RFd = (A + B + C)-(D + E + F) Focus error signal FE = (A + CB)-(D + FE) Push-pull signal PP = B1-B2 RF signal The photodetector for extracting the data is not limited to the configuration shown in FIG.

Returning to FIG. 8, the sum signal RFs
Is supplied to the A / D converter 14 via the clamp circuit 13, and the output signal of the A / D converter 14 is supplied to the PLL unit 15. The PLL unit 15 includes a servo clock SCK synchronized with a reproduction signal of a track mark in the servo area,
A data clock DCK synchronized with the recording data is generated. Servo clock SCK and data clock DCK
Is supplied to the timing generator 22. Further, the servo clock SCK is supplied to the A / D converter 14 as a sampling clock.

The difference signal RFd is supplied to the A / D converter 17 via the clamp circuit 16. A data clock DCK is supplied as a sampling clock of the A / D converter 17, and an output signal of the A / D converter 17 is output to the data detector 1.
8 is supplied. The data detection unit 18 is supplied with the data synchronization signal DSY from the timing generation unit 22. The data detector 18 performs a waveform equalization process using a digital equalizer, and corrects an error in the detection signal by Viterbi decoding. In the data detector 18, demodulation of digital modulation is performed, and the demodulated output is binarized. The reproduction data taken out from the output of the data detection unit 18 is transferred to the host computer 10 through the controller 9.

Further, the push-pull signal PP is supplied to the A / D converter 20 via the clamp circuit 19. The low frequency fluctuation of the reproduction signal is removed by the clamp circuits 13, 16 and 19. The output of the A / D converter 20 is supplied to the polarity discrimination unit 21. The polarity determining unit 21 generates an identification signal for identifying an odd track and an even track based on the push-pull signal PP. Polarity discriminator 2
1 is supplied with a track mark sampling signal from the timing generation unit 22.

The polarity determining operation in the polarity determining section 21 will be described with reference to FIG. FIG. 10A is an enlarged view of a track mark portion of the servo area shown in FIG. As described above, each of the mark 1 and the mark 2 is repeated with a period of two tracks in the radial direction of the disc, and the phases of the repetitions are different by 180 °. Therefore, when the beam spot 34a scans the even track, the push-pull signal PP shown in FIG. 10B is obtained. That is, a signal having a negative polarity corresponding to the mark 1 and a signal having a positive polarity corresponding to the mark 2 is obtained. If the beam spot 34b scans an odd track, the polarity of the push-pull signal PP is inverted from that shown in FIG. 10B. The push-pull signal PP includes a DC (direct current) offset due to optical lens movement and disk skew.

A track mark sampling pulse shown in FIG. 10C is supplied to the polarity discriminating section 21. With this pulse, the levels L1 and L2 of the push-pull signal respectively corresponding to the center of the mark 1 and the center of the mark 2 are sampled and held. further,
To remove the DC offset, the level L3 near the mark 1 or mark 2 is sampled / held.

The polarity discriminating section 21 calculates the levels L1 'and L2' from which the DC offset has been removed as follows. L1 '= L1-L3 L2' = L2-L3

An identification signal is generated from the polarities of the corrected levels L1 'and L2'. That is, (L1 ′ =
−, L2 ′ = +) (in the case of FIG. 10), it is determined that scanning is performed on an even-numbered track, and (L1 ′ = +, L2 ′).
If =-), it is determined that scanning is being performed on an odd track.

As another example of the polarity discriminating section 21, there is one that generates an identification signal based on the difference (Ld = L1-L2) between the sampling levels L1 and L2 of the push-pull signal PP. That is, if (Ld =-), it is determined that scanning is performed on even-numbered tracks, and if (Ld = +), scanning is performed on odd-numbered tracks. In this other example, since the difference Ld is formed, the influence of the DC offset can be canceled, and there is no need to detect the level L3.

Referring again to FIG. 8, a digital output of the identification signal and the sum signal RFs from the polarity discriminating unit 21 generated as described above is supplied to the tracking error generating unit 23. The sampling pulse from the timing generator 22 is supplied to the tracking error generator 23. Tracking error generator 23
Samples the level of the reproduction signal (sum signal RFs) of the track mark (mark 1 and mark 2) in the servo area, and performs the tracking error signal TE on the difference between the amplitudes of the reproduction signals corresponding to the mark 1 and mark 2 Output.

The tracking error signal TE is supplied to the servo control section 12. Servo control unit 1
2 so that the tracking error signal TE becomes 0,
A tracking drive signal for driving a tracking means in the optical pickup 4 is generated. Further, the tracking error generator 23 also generates a track position error signal TPE. The track position error signal TPE is supplied to a controller 24 that controls the entire operation of the optical disk device.

The track position error signal TPE is a signal indicating that the identification signal output from the polarity discriminating section 21 has changed, that is, that the track to be scanned has moved to an adjacent track. FIG. 11 shows the operation of the controller 24. When the track position error signal TPE is received, the control operation starts (step ST1). Whether the mode is the recording mode (meaning a recording operation or a recording verification operation) is determined in step ST2. If it is not the recording mode, the control is not performed, and the routine goes to the end step ST4.

If it is determined in step ST2 that the mode is the recording mode, the process proceeds to step ST3, and the laser power is reduced from write power to read power. At the same time, the application of the magnetic field by the magnetic head 6 is stopped. The recording operation is immediately stopped by the control in step ST3. Thereby, it is possible to prevent a malfunction in which data on an unintended track is erroneously rewritten.

[0062]

According to the present invention, since two marks for detecting a tracking error are formed at a period of two tracks in the radial direction of the disk, the radial frequency of the marks in the radial direction can be reduced. Accordingly, the track density can be increased, and the recording capacity can be increased. Further, according to the present invention, since the track being scanned is identified by the push-pull signal of the track mark, there is an advantage that it is not necessary to add a special mark (pit) and address for identification.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining area division in an embodiment of an optical disk medium according to the present invention.

FIG. 2 is a schematic diagram for explaining a sector structure of an embodiment of an optical disk medium according to the present invention.

FIG. 3 is a schematic diagram for explaining a data structure in one embodiment of the present invention.

FIG. 4 is a schematic diagram used for describing a sector structure and a reference signal in one embodiment of the present invention.

FIG. 5 is a schematic diagram showing a configuration of a servo area in one embodiment of the present invention.

FIG. 6 is a schematic diagram used for explaining an address segment and an address code.

FIG. 7 is a schematic diagram used for explaining data conversion when an address code and an additional address are encoded into a Gray code.

FIG. 8 is a block diagram of an embodiment of an optical disk device to which the present invention is applied.

FIG. 9 is a schematic diagram illustrating a photodetector that can be used in one embodiment of the present invention.

FIG. 10 is a waveform chart for explaining the operation of the polarity discriminating unit in one embodiment of the present invention.

FIG. 11 is a flowchart for explaining a control operation based on a track position error signal in one embodiment of the present invention.

FIG. 12 is a schematic diagram showing a configuration of a servo area of an optical disk proposed earlier.

FIG. 13 is a schematic diagram for explaining a method of reading pits of an optical disk proposed earlier.

FIG. 14 is a schematic diagram illustrating a relationship between a spatial frequency in a disk radial direction and an MTF.

[Explanation of symbols]

1 ... optical disk, 4 ... optical pickup, 6 ...
-Magnetic head, 15 ... PLL unit, 21 ... polarity discrimination unit, 23 ... tracking error generation unit

Claims (6)

[Claims] 1. An optical disk device, wherein digital information is optically recorded on a track formed concentrically or spirally on an optical disk medium, or digital information is optically read from the track. In the medium, a servo area is provided in each of the tracks intermittently in the track direction and at a position aligned in the disk radial direction. The servo area is physically separated in advance by a predetermined distance in the track direction. First and second formed
The first and second marks are provided at a two-track cycle in the radial direction of the disk, and the phases of the first and second marks in the radial direction of the disk are different. By detecting reflected light of the laser beam irradiated onto the optical disk medium, a read output is generated, and the optical disk medium is divided into two, and the push-pull is performed by a divided optical detector whose division position substantially coincides with the track center. An optical pickup for generating a signal; a tracking means for displacing a reading position of the optical pickup in a disk radial direction; and an output level corresponding to the first and second marks in the read output. , Detecting a tracking error based on the comparison result, Tracking control means for determining the direction of the tracking error based on the information for identifying the adjacent track generated based on the information and controlling the reading position so as to make the tracking error zero. Optical disk device. 2. The optical disk device according to claim 1, wherein the phases of the first and second marks are different from each other by approximately 180 °. 3. The push-pull signal according to claim 1, wherein the first signal and the second signal in the push-pull signal are sampled, respectively, based on a polarity of a sampling output of each of the first signal and the second signal. An optical disk device for identifying adjacent tracks. 4. The method according to claim 1, wherein the first signal and the second signal in the push-pull signal are sampled, respectively, and a differential signal of a sampling output of each of the first signal and the second signal is obtained. An optical disk device formed and identifying an adjacent track based on the polarity of the difference signal. 5. The recording apparatus according to claim 1, wherein a change in the information for identifying the adjacent track during a recording operation is detected, a track position error signal is generated, and the recording operation is stopped by the track position error signal. An optical disk device characterized by performing control as follows. 6. A tracking method for an optical disk device in which digital information is optically recorded on a track formed concentrically or spirally on an optical disk medium, or digital information is optically read from the track. In the optical disk medium, a servo area is provided in each of the tracks intermittently in a track direction and at a position aligned in a disk radial direction, and the servo area is separated by a predetermined distance in the track direction. First and second physically formed first
The first and second marks are provided at a two-track cycle in the radial direction of the disk, and the phases of the first and second marks in the radial direction of the disk are different. By detecting reflected light of the laser beam irradiated onto the optical disk medium, a read output is generated, and the optical disk medium is divided into two, and the push-pull is performed by a divided optical detector whose division position substantially coincides with the track center. Generating a signal, comparing the output levels corresponding to the first and second marks in the read output, detecting a tracking error based on the comparison result, and detecting a tracking error based on the push-pull signal. The direction of the tracking error is determined based on the generated information for identifying the adjacent track. Racking error to zero, the tracking method of the optical disk apparatus characterized by comprising the step of controlling the reading position.