JPH06223380A - Optical disk and method for recording/reproducing optical disk - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an optical disc capable of improving the recording density. [Structure] A plurality of spiral tracks 2a and 2b on a disk surface are arranged in parallel with each other. Wobble pits 3a in the servo areas of adjacent tracks 2a and 2b,
The 3b and the wobble pits 5a and 5b are arranged at different time positions in the circumferential direction of the optical disc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk which is a target for recording and reproducing information using a light beam such as a laser beam, and a recording and reproducing method for the optical disk.

[0002]

2. Description of the Related Art With the rapid increase in the amount of information processing in an information processing system, as a recording medium with a large recording capacity,
Optical discs have recently received a great deal of attention. This optical disc is rotated by a disc drive, and information is recorded and reproduced by irradiating the disc surface with a light beam such as a laser beam emitted from a semiconductor laser. However, due to various factors, the track formed on the surface of the disk has a slight track deviation as the disk rotates. Therefore, in order to accurately record and reproduce information, tracking control for causing the irradiation of the light beam to follow the track shake is required.

By the way, the tracking control of an optical disk is roughly classified into the following two methods. One is called a sampled servo (hereinafter referred to as "SS") system, and the other is a continuous composite servo (hereinafter referred to as "CCS"). ) Is called a method. C. C. In the S method, a track groove having a predetermined depth and width is concentrically or spirally provided on the disk surface, and tracking control is performed by detecting diffracted light at this track groove portion. There is.

On the other hand, S. In the S method, a track groove is not provided and a clock pit previously embedded in the substrate is detected to generate a synchronization signal, and the synchronization signal is used to generate a tracking error signal and a timing signal for recording / reproduction. It is like this. For example, a tracking error signal is a light reflected from a wobble pit provided in a servo area, which is an area for producing the tracking error signal, that is, a pair of pits provided in a zigzag pattern at left and right adjacent positions sandwiching the track center. Is detected by using a synchronization signal, and the magnitudes thereof are compared to detect the amount of deviation from the track center. In addition, this S. In the S method, the servo area and the data area, which is an area for reading and writing data, are completely separated from each other, and wobble pits and clock pits are embedded in the servo area.

Currently, C.I. C. Tracking control by the S method is the mainstream, but if the track density is increased to further increase the density, C.I. C. In the S method, the quality of the information signal level deteriorates due to the influence of the groove, and it becomes difficult to form a stamper that is a mold for manufacturing an optical disc. For this reason, the S. The S method is drawing attention. Hereinafter, S. A conventional optical disc that performs tracking control by the S method will be described. Prior to the description, common terms used in this specification will be defined. That is, a signal obtained by photoelectrically converting the total light amount of the light beam reflected from the disk surface and returning to the optical head is called an Rf (+) signal. The Rf (+) signal includes a wobble signal and a clock signal which are amplitude-modulated by wobble pits and clock pits which are prepits in the servo area.
The binarized wobble signal and clock signal are called wobble pulse and clock pulse.

FIG. 8 shows the S. In an explanatory view of the arrangement of servo areas in a conventional optical disc that performs tracking control by the S method, when the optical disc 51 is rotated at a constant rotation speed (hereinafter referred to as “CAV method”), the same time interval is applied in the circumferential direction of the optical disc 51. The clock pits and the wobble pits are arranged in a servo area 53 that extends in a fan shape from the apex 52 of the track. Then, such a state is expressed as that the servo areas 53 are arranged at the same time position in the circumferential direction of the disk. The address area and the data area are also arranged at the same time position in the circumferential direction of the disk.

FIG. 9 shows the S. FIG. 3 is an explanatory diagram illustrating a pit arrangement in a servo area and a method of extracting a clock signal in a conventional optical disc that performs tracking control by the S method. In a spiral track 55, a servo area 53 and a data area 56 are alternately arranged. Are located in each servo area 5
3 has a pair of wobble pits 57a and 57b and a clock pit 58 embedded therein. The adjacent distance d ₁ between the tracks 55 is 1.6 μm. FIG. 9A shows an Rf (+) signal in a state where only focus is applied. A pair of wobble signals 59a and 59b is obtained corresponding to the pair of wobble pits 57a and 57b, and corresponds to the clock pit 58. Then, the clock signal 60 is obtained. FIG. 9B is a signal obtained by differentiating the Rf (+) signal in the state where only focus is applied and binarizing it, and a pair of wobble signals 59a and 5a.
A pair of wobble pulses 61a and 61b are obtained corresponding to 9b, and a clock pulse 6 corresponding to clock signal 60.
2 is obtained. The time interval between the wobble pulse 61b and the clock pulse 62 is a unique interval that does not appear in other places, and is called a unique distance UD.

In the tracking control, first, in order to extract the clock pulse 62, a pulse obtained by differentiating and binarizing the Rf (+) signal in the focused state shown in FIG. 9B. Each time, the gate is opened at the time interval of the unique distance UD to try to extract the clock pulse 62. For example, the gate signal generated by the wobble pulse 61a is as shown in FIG. 9C, and the gate signal generated by the wobble pulse 61b is as shown in FIG. 9D. That is, since only the wobble pulse 61b and the clock pulse 62 have a time interval equal to the unique distance UD among the time intervals of the pulse train shown in FIG. Of the gate signals generated based on the corresponding pulse, only the gate signal generated based on the wobble pulse 61b can extract the clock pulse 62, and the other gate signals cannot extract any pulse. The clock pulse 62 thus obtained is locked by a phased lock loop circuit (hereinafter referred to as "PLL"), and is output to a variable control oscillator (hereinafter referred to as "VCO") incorporated in the PLL. A reference clock signal is generated based on the reference clock signal, and a gate signal as shown in (e) of FIG. 9 for extracting the wobble signal 59a and a (f) of FIG. 9 for extracting the wobble signal 59b from the reference clock signal. Wobble signal 5 with a gate signal such as
9a and 59b are extracted, and these two wobble signals 5
The amplitudes of 9a and 59b are peak-held, and a tracking error signal is generated from the difference between the two.

As described above, it is important to accurately extract the clock pulse 62 in order to perform all synchronization using the reference clock signal. The conventional optical disk 5
In No. 1, since the adjacent distance d ₁ between the tracks 55 is wide, there is almost no crosstalk from the wobble pits 57a and 57b and the clock pit 58 of the adjacent tracks.
It does not affect the tracking error signal.

On the other hand, FIG. 10 shows the relationship between the position of the laser beam and the polarity of the tracking error signal. The laser beam undergoes amplitude modulation at the wobble pits 57a and 57b, but the way of receiving the modulation differs depending on the position of the laser beam. The Rf (+) signals when the laser beam is at the positions of a, b, and c in FIG. 10 are Rf ₁ (+) and Rf, respectively.
₂ (+) and Rf ₃ (+). Wobble pit 57a
The wobble signal amplitude-modulated by A ₁ and the wobble signal amplitude-modulated by the wobble pit 57b by A ₁ .
_If it is ₂ , the difference between A ₁ and A ₂ is amplified, and the tracking error signal TE = α · (A ₁ −A ₂ ) is generated. Note that α is an amplification factor. Further, when A ₁ -A ₂ is positive, the polarity is defined as positive (+), and when A ₁ -A ₂ is negative, the polarity is defined as negative (-). Rf
₁ (+) has a positive polarity, and Rf ₃ (+) has a negative polarity.
Rf ₂ (+) becomes zero when A ₁ = A ₂ . When the polarity is positive, a force acts on the objective lens of the optical head in the direction of arrow e toward the track center d, and when the polarity is negative, the objective lens of the optical head moves toward the track center d by arrow f.
A force acts in the direction, and the objective lens is driven so that the center of the laser beam is located at the track center d, and tracking control is performed. The magnitude of the force is proportional to the amplitude of the tracking error signal, and its polarity determines the direction in which the force acts. That is, when the laser beam is at the position a in FIG. 10, that is, when the polarity is positive, a force acts on the objective lens of the optical head in the direction indicated by the arrow e, and the laser beam moves to the position c in FIG. In some cases, that is, when the polarity is negative, a force acts on the objective lens of the optical head in the direction indicated by arrow f.

FIG. 11 is a schematic configuration diagram of an actuator that drives an objective lens based on a tracking error signal, and FIG. 12 is an enlarged perspective view of the same main portion. This actuator is included in an optical head. The objective lens 64 is held by a holder 65, and the holder 65 has a driving coil 66a for tracking in the radial direction, that is, for tracking.
66b is attached. The drive coils 66a and 66b slidably penetrate into the protruding portions of the yokes 67a and 67b, and the drive coils 66a and 66b are attached to the yokes 67a and 67b.
Magnets 68a, 68b, 68c, 68d are mounted so as to sandwich b. Magnets 68a, 68b, 68c, 68d
Of the magnetic flux crosses the drive coils 66a and 66b in the vertical direction of FIG. Therefore, since a force is applied to the objective lens 64 in the left-right direction of FIG. 11 according to Fleming's law, the objective lens 64 can be controlled so that the center of the laser beam is located at the track center d. The left-right direction in FIG. 11 corresponds to the radial direction, that is, the radial direction of the optical disc, and corresponds to the directions of arrows e and f in FIG. When a current is applied to the drive coils 66a and 66b in the a ₁ direction of FIG. 12, a magnetic flux is formed in the direction of arrow g. Therefore, a force is applied to the drive coils 66a and 66b by f ₁ according to Fleming's law.
Join in the direction of. The magnitude F of the force is F = B · I · L, which is proportional to the current I. B is the magnetic flux density in the air gap,
I is the current flowing through the drive coils 66a and 66b, and L is the coil length at which the drive coils 66a and 66b are linked to the magnetic flux in the air gap. Further, the air gap means the magnets 68a, 68b, 6
The gaps between 8c and 68d and the drive coils 66a and 66b. When an electric current is applied in the a ₂ direction of FIG. 12, the drive coil 66
A force is applied to a and 66b in the direction of f ₂ . That is, the direction of moving the objective lens 64 can be controlled by the direction of the current flowing through the drive coils 66a and 66b. Therefore, the force directions f ₁ and f ₂ are always directed toward the track center d,
Polarity of tracking error signal and drive coils 66a, 6
Tracking can be controlled by determining the relationship with the direction of the current flowing through 6b. For example, the laser beam is located at a in FIG. 10, and the force f applied to the objective lens 64 is
_{Assuming that} the direction of _{1 and} the direction of arrow e are the same, the direction of the current flowing through the drive coils 66a and 66b is a
You can set it to ₁ .

[0012]

However, in the above-mentioned conventional optical disk 51, when the track width is narrowed, the wobble signal due to the wobble pits of the adjacent tracks leaks due to the crosstalk, so that the pair of wobble signals 5
The difference between the amplitudes of 9a and 59b cannot be accurately extracted, and the quality of the tracking error signal deteriorates, making it difficult to apply servo. This also means that the clock pulse 62
It also causes a mistake in the extraction of. Further, since the pre-pits are close to each other, it is difficult to form the pits, and it is difficult to form the stamper. From the above, there is a problem that the recording density cannot be improved.

Further, the above-mentioned conventional recording / reproducing method has a problem that recording / reproducing cannot be performed by utilizing the space between adjacent tracks, and the recording density cannot be improved. The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical disc and a recording / reproducing method for the optical disc, which can improve the recording density.

[0014]

According to a first aspect of the present invention, in an optical disc for which tracking control is performed by a sampled servo system, a plurality of spiral tracks are arranged in parallel with each other, and servos of adjacent tracks are arranged. The wobble pits of the area are arranged at different time positions in the circumferential direction.

According to a second aspect of the present invention, in an optical disc which performs tracking control by a sampled servo system, a plurality of spiral tracks are arranged in parallel with each other, and the servo areas of adjacent tracks are circumferentially arranged. The feature is that they are arranged at different time positions. Claim 3
The invention is characterized in that the unit distances in the servo areas of adjacent tracks are set to different time intervals.

The invention according to claim 4 is characterized in that among the prepits arranged at a common time position in the circumferential direction in a plurality of tracks, at least the prepits of one track are left and the others are omitted. The invention of claim 5 is characterized in that the address area is made common to a plurality of tracks by making the track width of the address area wider than the track widths of the data area and the servo area.

According to a sixth aspect of the present invention, in a recording / reproducing method of an optical disc for recording / reproducing information on / from the optical disc while performing tracking control by the sampled servo system, the light beam moves to the center position of the track based on the tracking error signal. By reversing the polarity of the current for driving the lens of the optical head as described above, information is recorded / reproduced in the middle of tracks adjacent to each other.

[0018]

According to the invention of claim 1, the plurality of spiral tracks are arranged in parallel with each other. The wobble pits of the servo areas of adjacent tracks are arranged at different time positions in the circumferential direction. In the invention of claim 2, the plurality of spiral tracks are arranged in parallel with each other. The servo areas of adjacent tracks are
They are arranged at different time positions in the circumferential direction.

In the third aspect of the invention, the unit distances in the servo areas of adjacent tracks are set at different time intervals. In the invention of claim 4, the pre-pits arranged at the time positions common to the plurality of tracks in the circumferential direction are omitted except for the pre-pits of at least one track.

In the invention of claim 5, the track width of the address area is set wider than the track widths of the data area and the servo area, and the address area is shared by a plurality of tracks. According to the invention of claim 6, the polarity of the current for driving the lens of the optical head is reversed so that the light beam moves to the center position of the track on the basis of the tracking error signal, so that the tracks of the tracks adjacent to each other are reversed. Recording and reproducing information on.

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings. (Embodiment 1) FIG. 1 is an explanatory view of tracks on a disk surface of an optical disk according to Embodiment 1 of the present invention. Two spiral tracks 2a and 2b are juxtaposed on the disk surface of the optical disk 1. . Ie truck 2a,
The 2b are adjacent to each other with a very small interval over the entire length.

FIG. 2 is an explanatory view for explaining the pit arrangement in the servo area of the optical disc and the method for extracting the clock signal in the first embodiment of the present invention. A pair of wobble pits 3a, 3b and a clock are provided on the track 2a. The pits 4 are arranged at predetermined time intervals, and the track 2b has a pair of wobble pits 5a, 5b and clock pits 6 arranged at predetermined time intervals. The track pitch d ₂ is 1.
0 μm, wobble pits 3a, 3 of track 2a
b and the clock pit 4, the wobble pits 5a and 5b of the track 2b, and the clock pit 6 are arranged at different time positions in the circumferential direction of the optical disc 1. 2A shows the Rf (+) signal of the track 2a, and the wobble signals 7a and 7b are the wobble pits 3.
Corresponding to a and 3b, clock signal 8 is clock pit 4
The wobble signals 9a and 9b correspond to the wobble pits 5a and 5b of the track 2b, and the clock signal 10 corresponds to the clock pit 6 of the track 2b. That is, the wobble signals 9a and 9b and the clock signal 10
Is due to crosstalk from the adjacent track 2b. 2B shows the Rf (+) signal of the track 2b, and the wobble signals 11a and 11b are the track 2a.
Clock signal 1 corresponding to wobble pits 3a, 3b of
Reference numeral 2 corresponds to the clock pit 4 of the track 2a, wobble signals 13a and 13b correspond to the wobble pits 5a and 5b, and clock signal 14 corresponds to the clock pit 6. That is, the wobble signals 11a and 11b and the clock signal 12 are due to crosstalk from the adjacent track 2a. 2C is a signal obtained by differentiating and binarizing the Rf (+) signal of the track 2a. The wobble pulses 15a and 15b correspond to the wobble signals 7a and 7b, and the clock pulse 16 becomes the clock signal 8. It corresponds. 2D is a signal obtained by differentiating the Rf (+) signal of the track 2b and binarizing it.
Reference symbols a and 17b correspond to the wobble signals 13a and 13b, and clock pulse 18 corresponds to the clock signal 14.
Unique distance UD of track 2a, which is the time interval between wobble pulse 15b and clock pulse 16
₁ , the unique distance U of the track 2b, which is the time interval between the wobble pulse 17b and the clock pulse 18
D ₂ is a value different from each other.

FIG. 3 is an explanatory diagram of a track format of the optical disc according to the first embodiment of the present invention.
(C) is a format of the track 2a, in which an address area 20 is arranged at the head of each sector, and thereafter, servo areas 21 and data areas 22 are alternately arranged. The wobble pits 3a and 3b are provided in the address area 20.
Pre-pits such as sector marks are embedded in addition to the clock pits 4, and wobble pits 3a and 3b and clock pits 4 are embedded in the servo area 21. 3B and 3D are formats of the track 2b, and the address area 2 is provided at the head of each sector.
4 are arranged, and the servo areas 25 and the data areas 26 are arranged alternately after that, but prepits such as sector marks other than the wobble pits 5a and 5b and the clock pit 6 are embedded in the address area 24. Absent. Wobble pits 5a and 5b and a clock pit 6 are embedded in the servo area 25. Truck 2a
The servo area 21 and the servo area 25 of the track 2b are arranged at different time positions in the circumferential direction.

FIG. 4 is an explanatory diagram for explaining the pit arrangement in the address area of the optical disk and the method of extracting sector marks and the like in the first embodiment of the present invention. In the address area 20 of the track 2a, a plurality of prepits such as sector marks are formed. Although 27 are embedded, pre-pits such as sector marks are not embedded in the address area 24 of the track 2b. FIG. 4A shows Rf (+) of the track 2a.
4B is a signal, and FIG. 4B shows Rf (+) of the track 2b.
It is a signal. These Rf (+) signals are differentiated, binarized, and then input to a modulator (not shown) to generate a pulse such as a sector mark. Although the pre-pits 27 are not embedded in the track 2b, since the track density is high, the sector mark or the like can be sufficiently detected due to the leakage of the pre-pits 27 of the track 2a.

Next, the operation will be described. For example, truck 2a
When recording on, Rf with focus applied
The (+) signal is as shown in (a) of FIG. Then, this Rf (+) signal is differentiated and binarized to produce a pulse train as shown in FIG. The clock pulse 16 is extracted from this pulse train using the unique distance UD ₁ . Then, a reference clock signal is generated based on this clock pulse 16, and the amplitude difference between the pair of wobble signals 7a and 7b is detected by using the reference clock signal to generate a tracking error signal. At this time, the adjacent track 2b
Wobble signals 9a, 9b and clock signal 10 from
, But the amplitude of the wobble signals 7a and 7b is not affected because they are temporally displaced from the wobble signals 7a and 7b and the clock signal 8. Further, as indicated by a broken line in FIG. 2C, even when the wobble signals 9a and 9b and the clock signal 10 from the adjacent tracks 2b are binarized by mistake, the wobble pulse 17a which is erroneously detected is detected. , 17b and clock pulse 18 are
Since the unique distance UD ₂ is not equal to the unique distance UD _{1 of the} track 2a, the extraction of the clock pulse 16 is not affected.

Since the sector mark and the like are common to the track 2a and the track 2b, the sector mark and the like of the track 2b are set to the track 2a as described above.
You can substitute the sector mark. In this way, since the time positions in the circumferential direction of the wobble pits 3a, 3b and the wobble pits 5a, 5b of the adjacent tracks 2a, 2b are different from each other, the track pitch d ₂ between the tracks 2a, 2b is 10 μm. Wobble signals 7a, 7 even if narrow
Since b, 9a, and 9b are not affected by the crosstalk, the tracking error signal can be accurately generated.
That is, for example, the wobble pit 3a of the track 2a,
While reading 3b and clock pit 4,
The optical spots do not hit the wobble pits 5a and 5b and the clock pit 6 of the adjacent track 2b, and it is difficult for the optical spots to enter as a crosstalk. Therefore, the wobble signal 7
Since the amplitudes of a and 7b can be accurately detected, tracking control is stabilized. In addition, adjacent tracks 2a and 2b
Since the unique distances UD ₁ and UD ₂ are different from each other, it is possible to favorably prevent the detection of the clock pits 4 and 6 of the adjacent tracks. Also, since the pre-pits corresponding to the sector marks of the track 2b are omitted,
The density can be increased and the stamper can be easily manufactured. That is, when the track width is narrowed, the wobble pits 3a, 3b, 5a, 5b and the clock pits 4, 6 do not overlap because the prepit time positions are different, but
Since the other pre-pits 27 of the address areas 20 and 24 overlap, the track width is determined accordingly. Therefore, by omitting the pre-pits 27 such as sector marks in the address area 24, the track width can be narrowed and information can be recorded at high density. (Embodiment 2) As shown in FIG. 5, the address areas 20 of the tracks 2a and 2b may be shared. That is, in the second embodiment, the servo areas 21, 25 and the data areas 22,
The track width of 26 is half the track width of the address area 20. Since the pre-pits in the address area 20 are common to the tracks 2a and 2b, there is no inconvenience even if they are shared.

As described above, if the address areas 20 of the tracks 2a and 2b are shared, the density can be increased and the stamper can be easily manufactured. That is, when the track width is narrowed, the servo areas 21 and 25 do not overlap because the prepit time positions are different, but the address area 2
Since the other 0 pre-pits overlap, the track width is determined accordingly. Therefore, by sharing the address area 20, the track width can be narrowed and information can be recorded at high density. (Embodiment 3) FIG. 6 is a schematic configuration diagram of a main part of a recording / reproducing apparatus adopting a recording / reproducing method for an optical disk according to a third embodiment of the present invention. This recording / reproducing apparatus includes an objective lens, an actuator, etc. (not shown). Optical head 31 including, current / voltage conversion circuit 32, servo circuit 33, polarity switching circuit 3
4, a current / voltage conversion circuit 35, and a control circuit 36 including a microcomputer. Optical head 31
Is the laser beam 38 on the disc surface of the optical disc 37.
Irradiate. The current / voltage conversion circuit 32 is used for the optical disk 3
The current from the optical head 31 corresponding to the reflected light from the disk surface of No. 7 is converted into a voltage. Servo circuit 33 is
A tracking error signal is generated based on the voltage from the voltage conversion circuit 32. The polarity switching circuit 34 is the control circuit 3
Based on the command from 6, the polarity of the tracking error signal from the servo circuit 33 is switched. The current / voltage conversion circuit 35 converts the voltage of the tracking error signal from the polarity conversion circuit 34 into a current and supplies it to the optical head 31. It should be noted that although a large number of other constituent elements are actually provided, they are not directly related to the gist of the present invention, and a description thereof will be omitted. Further, the structure of the actuator of the optical head 31 is the same as the actuator in the conventional optical head shown in FIGS. 11 and 12.

FIG. 7 is an explanatory diagram of the pit arrangement in the servo area of the optical disc 37 according to the third embodiment of the present invention. One spiral track is arranged on the disc surface of the optical disc 37, and the track is A large number of pairs of wobble pits 41a and 41b and clock pits 42 are embedded. Wobble pits 41 on adjacent tracks
The a and 41b and the clock pit 42 are arranged at the same time position in the circumferential direction.

Next, the outline of the operation of the recording / reproducing apparatus in the third embodiment will be described. The laser beam 38 emitted from the optical head 31, reflected by the disk surface of the optical disk 37 and returned to the optical head 31 is received by a photodetector (not shown) included in the optical head 31 and converted into an electric current. It The current from the optical head 31 is converted into a voltage by the current / voltage conversion circuit 32, and Rf
A (+) signal is produced. The servo circuit 33 extracts a clock signal from the Rf (+) signal from the current / voltage conversion circuit 32, creates a clock pulse from the clock signal, creates a timing signal from the clock pulse,
From the timing signal, wobble pits 41a, 41b
The position where the laser beam 38 is modulated is detected by, the amplitude difference between the wobble signals modulated by the pair of wobble pits 41a and 41b is extracted, and this is amplified to generate a tracking error signal. The above operation is similar to that of the conventional recording / reproducing apparatus. The tracking error signal from the servo circuit 33 is supplied to the current
The current / voltage conversion circuit 35 is supplied to the voltage conversion circuit 35.
Is converted into a voltage by and supplied to the actuator of the optical head 31. As a result, the objective lens is driven, and tracking control is performed so that the center of the laser beam 38 is fixed to the track center. Here, if the user operates a switch (not shown), the control circuit 36
The polarity switching circuit 34 supplies a polarity switching command to the polarity switching circuit 34, and the polarity switching circuit 34 inverts the polarity of the tracking error signal from the servo circuit 33 and supplies it to the current / voltage conversion circuit 35.

When the polarity of the tracking error signal is not inverted by the polarity changing circuit 34, for example, when the laser beam 38 is at the position shown by the solid line in FIG.
A force acts on the objective lens in the direction of arrow g, and the laser beam 38 moves in the direction of arrow g. Conversely, when the laser beam 38 is at the position shown by the broken line in FIG. 7A, a force acts on the objective lens in the direction of arrow h, and the laser beam 38 moves in the direction of arrow h. And finally the laser beam 38
The objective lens is controlled so that the center of is located at the track center k. The operation in this case is similar to that of the conventional recording / reproducing apparatus shown in FIGS.

When the polarity of the tracking error signal is reversed by the polarity switching circuit 34, the direction of the current flowing through the actuator of the optical head 31 is in the opposite direction, so that the direction of the force acting on the objective lens is in the opposite direction. For example, when the laser beam 38 is at the position shown by the solid line in FIG. 7A, a force in the direction of arrow h acts on the objective lens, and the laser beam 38 moves further away from the track center k. Then, assuming that the laser beam 38 reaches the position shown by the solid line in FIG. 7B, the wobble pits 41a and 41b of the adjacent tracks are detected, a force in the arrow i direction acts on the objective lens, and the laser beam 38 is emitted. Move in the direction of the original track. Then, finally, as indicated by an imaginary line in FIG. 7B, the objective lens is controlled so that the center of the laser beam 38 is located at the center of the track center k of the adjacent tracks. That is, if the polarity of the tracking error signal is reversed, the laser beam 38 moves in a direction away from the track center k, which is the opposite direction to the normal case, so tracking is performed in a direction away from the track center k of the adjacent track. As a result of the control, the objective lens is driven so that the center of the laser beam 38 is located at the center of the adjacent tracks.

As described above, the optical head 31 including the objective lens and the actuator, and the current / voltage conversion circuit 3 are provided.
2, the servo circuit 33, the polarity switching circuit 34, the current
A voltage conversion circuit 35 and a control circuit 36 including a microcomputer are provided, and the polarity of the current for driving the lens of the optical head is inverted so that the light beam moves to the center position of the track based on the tracking error signal. Thus, if information is recorded / reproduced in the middle of the tracks adjacent to each other, another track is newly formed at the center of the adjacent tracks, so that the recording density is doubled and the wobble pits 41a, It is possible to increase the recording density without narrowing the track interval of the tracks in which 41b and the clock pit 42 are arranged.

[0033]

As described above, according to the present invention, a plurality of spiral tracks arranged in parallel with each other are provided,
In an optical disc that performs tracking control by the sampled servo method, wobble pits in the servo areas of adjacent tracks are arranged at different time positions in the circumferential direction, so that the wobble signal crosses even if the track pitch is narrow. Since it is not affected by the talk,
The tracking error signal can be generated accurately and the recording density can be increased.

Further, in an optical disc which performs tracking control by the sampled servo system, a plurality of spiral tracks are arranged in parallel with each other, and the servo areas of adjacent tracks are arranged at different time positions in the circumferential direction. By arranging it, as above, even if the track pitch is narrow, the wobble signal is not affected by crosstalk, so a tracking error signal can be accurately generated,
The recording density can be increased.

If the unit distances in the servo areas of the adjacent tracks are set to different time intervals, it is possible to favorably prevent the detection of the clock pits of the adjacent tracks and to accurately perform the tracking control. It can be carried out. Further, among the prepits arranged at the same time position in the circumferential direction on a plurality of tracks, if the prepits of at least one track are left and the others are omitted, the stamper can be easily manufactured. Since the limit of the track interval caused by the circumstances can be solved, the density can be increased.

Further, by making the track width of the address area wider than the track widths of the data area and the servo area so that the address areas are shared by a plurality of tracks, the stamper can be manufactured easily and the density can be increased. .
Further, in the optical disk recording / reproducing method of recording / reproducing information on / from the optical disk while performing tracking control by the sampled servo system, the lens of the optical head is moved so that the light beam moves to the center position of the track based on the tracking error signal. If the information is recorded / reproduced in the middle of the tracks adjacent to each other by reversing the polarity of the current for driving, another track is newly formed in the center of the adjacent tracks. Is doubled, and the recording density can be increased without narrowing the track interval of the tracks in which wobble pits and clock pits are arranged.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of tracks on a disc surface of an optical disc according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a pit arrangement in a servo area of an optical disc and a clock signal extraction method according to a first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a track format of the optical disc according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating a pit arrangement in an address area of an optical disc and a method of extracting a sector mark or the like according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a track format of an optical disc according to a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a main part of a recording / reproducing apparatus that employs an optical disk recording / reproducing method according to a third embodiment of the present invention.

FIG. 7 is an explanatory diagram of pit arrangement in a servo area of an optical disc according to a third embodiment of the present invention.

FIG. 8 is an explanatory diagram of the arrangement of servo areas in a conventional optical disc that performs tracking control by a sampled servo method.

FIG. 9 is an explanatory diagram illustrating a pit arrangement in a servo area and a method of extracting a clock signal in a conventional optical disc that performs tracking control by a sampled servo method.

FIG. 10 is an explanatory diagram illustrating a pit arrangement in a servo area and a wobble pit detection signal in a conventional optical disc that performs tracking control by a sampled servo method.

FIG. 11 is a schematic configuration diagram of an actuator in a conventional optical disc recording / reproducing apparatus.

FIG. 12 is an enlarged perspective view of a main part of an actuator in a conventional optical disk recording / reproducing apparatus.

[Explanation of symbols]

 1 optical disk 2a, 2b track 3a, 3b wobble pit 5a, 5b wobble pit 20 address area 21 servo area 22 data area 24 address area 25 servo area 26 data area 27 prepit 31 optical head 34 polarity switching circuit

Claims (6)

[Claims] 1. In an optical disc for performing tracking control by a sampled servo system, a plurality of spiral tracks are arranged in parallel with each other, and wobble pits in the servo areas of adjacent tracks are formed.
An optical disc, which is arranged at different time positions in the circumferential direction. 2. In an optical disc for performing tracking control by a sampled servo system, a plurality of spiral tracks are arranged in parallel with each other, and servo areas of adjacent tracks are arranged at different time positions in the circumferential direction. An optical disc characterized by being arranged. 3. The optical disk according to claim 1 or 2, wherein the unit distances in the servo areas of adjacent tracks are set to different time intervals. 4. The prepits of at least one track among the prepits arranged at a common time position in the circumferential direction on a plurality of tracks, and the others are omitted. An optical disc according to any one of 1. 5. The address area is shared by a plurality of tracks by making the track width of the address area wider than the track width of the data area and the servo area. An optical disc according to claim 2. 6. A recording / reproducing method of an optical disc for recording / reproducing information on / from the optical disc while performing tracking control by a sampled servo system, wherein an optical head is arranged so that a light beam moves to a center position of a track based on a tracking error signal. A method for recording / reproducing information on / from an optical disc, wherein information is recorded / reproduced in the middle of tracks adjacent to each other by reversing the polarity of a current for driving the lens.