JPH103672A - Optical disk device, signal generation method, and optical disk - Google Patents

Abstract

(57) [Problem] To provide both a tracking error signal and a track cross signal with sufficiently large amplitude even when lands and grooves of an optical disk are formed at the same width and high density. SOLUTION: An image of a main light beam is formed on a center portion of a track 3, an image of a sub light beam is formed on a position other than a center portion and a side edge of the track 3, and reflected light of each light beam is radially formed on the optical disk 2. It is divided into two and detected individually. A tracking error signal is generated from the push-pull signal of the main light beam and the push-pull signal of the two sub-light beams, and a track cross signal is generated from the push-pull signal of the two sub-light beams. Since the sub-beam is not focused on the center or side edge of the track 3, even if the land 4 and the groove 5 have the same width, the track cross signal TC
Is produced satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk device, a signal generating method, and an optical disk.

[0002]

2. Description of the Related Art At present, optical disks are used as large-capacity information recording media. As such an optical disk, for example, a read-only CD (Compact Disk) -ROM (R
ead Only Memory), CD-WO (Write Once)
Disk), rewritable CD-RAM (Random Access Memor)
y), etc. In the CD-ROM, information is recorded on a flat board surface by pits, and the pit rows serve as tracks. In a CD-WO or a CD-RAM, lands and grooves are formed on the board surface, and one of them is generally used as a track.

[0003] In order to increase the information amount of an optical disc, a format in which both lands and grooves are used for tracks has been proposed, and is called a land & groove. In addition, the above-mentioned various optical disks are all standards conforming to the CD, but at present, larger-capacity DVDs are used.
(Digital Video Disk) has also been developed. This is a medium that has been developed for the purpose of reproducing images, compared to a CD that has been developed for the purpose of reproducing music, and the track pitch and pit size are small in order to realize a large capacity. This DVD is also a read-only medium like a CD, but a DVD-RAM or a DVD-WO is planned to be developed like a CD.

The above-described optical disk apparatus for recording and reproducing information on and from an optical disk controls the position of an objective lens in a tracking direction and a focusing direction in order to properly record and reproduce information on a track of the optical disk. . Since focusing control is not related to the present invention, only tracking control will be described below.

Conventionally, a push-pull method and a three-beam method have been known as typical methods of tracking control.
In the push-pull method, one laser beam emitted from a laser light source is imaged as a spot of a predetermined diameter on a track of an optical disc by an objective lens, and the reflected light is detected by a light receiving element divided in a radial direction of the optical disc, A tracking error signal is generated by subtracting one detection signal from another detection signal.

In this case, if the center of the spot coincides with the track, the tracking error signal becomes "0". However, if the spot is displaced to the side of the track, the tracking error signal has a polarity corresponding to the displacement direction. Since the beam spot increases, if the position of the objective lens is controlled so that the tracking error signal becomes “0”, the beam spot follows the track.

In the three-beam method, a laser beam is divided into one main beam and two sub beams by a grating or the like.
The main beam is focused on the center of the track, and the two sub-beams are focused on the side edges of the track. The reflected light of these two sub-beams is individually detected by two light-receiving elements,
A tracking error signal is generated by subtracting one detection signal from another detection signal.

However, in the three-beam method, an offset occurs in the tracking error signal when the optical disk is tilted in the track direction, and in the push-pull method, an offset occurs in the tracking error signal when the optical disk is tilted in the radial direction. In order to solve these problems, a differential push-pull method has been developed.

In the differential push-pull method, similarly to the three-beam method, the laser beam is divided into one main light beam and two sub-light beams, and the main light beam is imaged at the center of the track. The auxiliary light beam is focused on the center of the gap between the adjacent tracks. For example, if the main light beam is imaged at the center of a certain land, the sub light beam is imaged at the center of a groove adjacent to the land. Similarly to the push-pull method, each of the three reflected lights is detected by a light receiving element which is bisected in the radial direction of the optical disk, and a tracking error signal is generated from these detected signals by a predetermined arithmetic processing. That is, the detection signal of the main light beam divided in the radial direction of the optical disc is represented by M
a, Mb, the detection signals of one sub-beam are S1a and S1b, the detection signals of the other sub-beam are S2a and S2b, and the predetermined constant is k,
Assuming that k ′, the tracking error signal TE is generated as TE = Ma−Mb−k (S1a−S1b) + k ′ (S2a−S2b).

In the three-beam method, an offset occurs in the tracking error signal when the optical disk is tilted in the track direction. In the push-pull method, an offset occurs in the tracking error signal when the optical disk is tilted in the radial direction. Does not occur in the differential push-pull method.

Incidentally, in a general optical disk device, a track cross signal is also generated separately from the tracking error signal. This is the signal that is maximal at the center of the track,
For example, it is used to count the number of tracks traversed when the optical head moves. For example, in an optical disc device of the differential push-pull method, a track cross signal is generated by adding two detection signals of a main light beam divided into two.

[0012]

When the tracking error signal is generated as described above, the spot can be made to follow the track of the optical disk, and when the track cross signal is generated, the track of the optical disk that the spot crosses can be detected. can do.

[0013] Like the above-mentioned DVD, there is still a demand for an increase in the capacity of the optical disk, and to achieve this, it is necessary to form tracks at a high density. However, since the spot is relatively enlarged in this case, the amplitude of the tracking error signal and the track cross signal becomes small,
The detection accuracy decreases.

In this regard, in the case of the differential push-pull method described above, the tracking error signal can be generated with a sufficiently large amplitude, but it is difficult to generate the track cross signal with a sufficient amplitude. In particular, in the case of the above-mentioned land & groove system, in order to maximize the recording capacity of the optical disk, it is necessary to form the land and the groove in a substantially one-to-one horizontal width. Extremely difficult.

In the case of a write-once or rewritable optical disc, the track on which information is not recorded and the track on which information is recorded have different reflection intensities. For this reason, for example, in the three-beam method or the differential push-pull method, when information is recorded with a main light beam on a track on which no information is recorded, the reflection intensities of the front sub light beam and the rear sub light beam differ, This occurs as an offset in the tracking error signal.

[0016]

According to a first aspect of the present invention, there is provided an optical disk apparatus, comprising: a disk drive section rotatably supporting an optical disk having tracks arranged at a predetermined pitch; a laser light source for emitting a laser beam; A light splitter that splits a laser beam into a main light beam and two sub light beams, and forms an image of the main light beam as a spot on the center of the track of the optical disc, and forms the sub light beam on the center and side edges of the track of the optical disc. An objective lens that forms an image as a spot at a position other than the center of the gap between tracks adjacent to the section, a main beam receiving section that divides reflected light of the main beam in the radial direction of the optical disc and individually detects the beam, and a sub beam A sub-beam light-receiving unit for dividing the reflected light in the radial direction of the optical disc and detecting the split light individually, and the main light when the spot of the main light flux follows the track of the optical disc. An error signal generating unit that generates a tracking error signal from a push-pull signal of a light receiving unit and a plurality of detection signals of the sub light beam receiving unit; and a sub light beam receiving unit when a main light beam spot crosses a track of the optical disc. And a cross signal generation unit for generating a track cross signal from the plurality of detection signals. Therefore, since the tracking error signal is generated by combining the push-pull signal of the main light beam and the detection signal of the sub light beam, even when the tracks are arranged densely and the spot diameter is relatively large,
A tracking error signal having a sufficiently large amplitude is generated. In addition, since the auxiliary light beam is arranged at a specific position with respect to the main light beam, when a track cross signal is generated,
A track cross signal having a sufficiently large amplitude is generated even if the width between the tracks is the same as the gap between the tracks. Here, the track means a position at which information is recorded or reproduced. For example, in the case of a reproduction-only optical disk on which information is recorded by pits, the pit train is a track. Similarly, in the case of a write-once or rewritable optical disk having a land and a groove formed thereon, a track is a land or a groove for recording information, and in the case of a land and groove optical disk, both a land and a groove are a track. It is. Since the track gap is the track gap as described above, for example, in the case of a read-only optical disk on which information is recorded by pits, the pit row gap is the track gap. In the case of an optical disk that records information on lands, the groove is a gap between tracks, and in the case of an optical disk that records information on a groove, the land is a gap between tracks. In the case of a land-and-groove optical disk, since a land serving as a track is directly adjacent to a groove, it is considered that there is no gap between tracks.

According to a second aspect of the present invention, in the optical disk apparatus of the first aspect, the displacement amount of the spot center portion of the main light beam and the sub light beam in the radial direction of the optical disk is Δd, the lateral width of the track is WT, and the predetermined width is WT. When the integer of m is m, the relationship of Δd △ WT / 4 + WT × m / 2 is satisfied. For example, when the sub light beam is sufficiently close to the main light beam, the amplitude of the tracking error signal is large, but the amplitude of the track cross signal is small. When the sub-beams are sequentially separated from the main beam, the amplitude of the tracking error signal decreases and the amplitude of the track cross signal increases. Therefore, if the main light beam and the sub light beam are arranged at positions satisfying the above relationship, both the tracking error signal and the track cross signal are generated with sufficiently large amplitude.

According to a third aspect of the present invention, in the optical disk device of the first or second aspect, the detection signal of the main light beam divided in the radial direction of the optical disk is Ma, Mb, and the detection signal of one of the sub light beams is S1a, Assuming that S1b, the detection signals of the other sub-beams are S2a and S2b, and the predetermined constants are k and k ', the error signal generation unit calculates the tracking error signal TE as TE = Ma-Mb + k (S1a + S2a) TE = Ma-Mb + k (S1a-S2b) TE = Ma-Mb + k (S1b + S2b) TE = Ma-Mb + k (S1b-S2a) TE = Ma-Mb + k (S1a-S1b) + k '(S2a-S2b) . Therefore, a tracking error signal having a sufficiently large amplitude is generated by a simple calculation.

According to a fourth aspect of the present invention, in the optical disk device of the third aspect, the error signal generating section includes detection signals Ma, M of the main luminous flux divided in a radial direction of the optical disk.
b is normalized by (Ma + Mb), the detection signals S1a and S1b of one sub-beam are normalized by (S1a + S1b), and the detection signals S2a and S2b of the other sub-beam are normalized by (S2a + S2b). Therefore, when recording information on a track of a write-once or rewritable optical disk with a main light beam, the signal intensity of each light beam is different, but the signal obtained by dividing each light beam is normalized by the overall intensity of each light beam. No offset occurs in the tracking error signal.

According to a fifth aspect of the present invention, in the optical disk device of the first or second aspect, the detection signals of one of the sub-beams divided in the radial direction of the optical disk are S1a, S1b,
The detection signals of the other sub-beams are S2a and S2b, and a predetermined constant is j.
Then, the cross signal generation unit calculates the track cross signal T
C is generated by one of a plurality of equations TC = S1a + S2b TC = S1a-S2a TC = S1b + S2a TC = S1b-S2b TC = S1a-S1b-j (S2a-S2b) Therefore, a track cross signal having a sufficiently large amplitude is generated by a simple calculation.

According to a sixth aspect of the present invention, there is provided a signal generating method, wherein an optical disk having tracks arranged at a predetermined pitch is rotatably supported, a laser beam is divided into a main beam and two sub beams, and the main beam is divided. An image is formed as a spot at the center of the track of the optical disc, and the sub-beam is formed as a spot at a position other than the center of the gap between the track and the side edge of the track of the optical disc. The reflected light is divided and detected individually in the radial direction of the optical disc,
The reflected light of the sub-beam is divided and detected individually in the radial direction of the optical disk, and a tracking error signal is generated from the detection signal of the main beam and the sub-beam when the spot of the main beam is made to follow the track of the optical disk. When the spot of the main light beam crosses the track of the optical disk, a track cross signal is generated from the detection signal of the sub light beam. Therefore, since the tracking error signal is generated by combining the push-pull signal of the main light beam and the detection signal of the sub light beam, even if the tracks are arranged at a high density and the spot diameter is relatively large, the tracking is sufficiently large. An error signal is generated. In addition, since the sub-beam is located at a specific position with respect to the main beam, when a track cross signal is generated, a track cross signal having a sufficiently large amplitude is generated even if the width between the tracks is the same. You.

An optical disk according to a seventh aspect of the present invention is an optical disk used in the optical disk device according to any one of the first to fifth aspects, wherein a recording mark to be overwritten with a recording mark is previously formed on a track. Therefore, when writing information as a recording mark on the track of the optical disk, the signal intensities of the sub-beams before and after the main beam become the same, and no offset occurs in the tracking error signal.

According to an eighth aspect of the present invention, there is provided an optical disk used in the optical disk apparatus according to any one of the first to fifth aspects, wherein the lands and the grooves are formed to have substantially the same lateral width. Therefore, since the land and the groove have substantially the same width, the recording capacity of the optical disk can be maximized in the case of a land and groove recording information on both the land and the groove. In the optical disk device according to any one of the first to fifth aspects, since the auxiliary light beam is arranged at a specific position with respect to the main light beam, even if the lands and the grooves of the optical disk have substantially the same width, the amplitude is sufficient. A large track cross signal can be generated.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, the optical disc device 1 according to the present embodiment executes recording and reproduction of information on the optical disc 2 as shown in FIG. As shown in FIG. 1, the optical disc 2 is formed in a land & groove system, and here, a land 4 and a groove 5, each of which is a track 3, are formed to have substantially the same lateral width.

The optical disk device 1 of the present embodiment has a disk drive (not shown) that rotatably supports the optical disk 2 as described above, and as shown in FIG. An optical head 11 is arranged at a position facing the optical disc 2 that is supported by the shaft. This optical head 11
Supported movably in the radial direction of the optical disc 2,
The optical disk device 1 is provided with a head seek mechanism (not shown) for controlling the position of the optical head 11 in this direction.

The optical head 11 has a semiconductor laser 12 as a laser light source.
A collimator lens 13, a grating 14 as a light splitter, a beam splitter 15, a quarter-wave plate 16, and an objective lens 17 are arranged in this order on the optical axis, and the reflected light path of the beam splitter 15 is The condenser lens 18 and the light receiving element unit 19 are arranged in order.

The grating 14 divides the laser beam into a main beam and two sub beams, and
As shown in FIG. 1, the main beam is focused on the center of the track 3 of the optical disk 2 as a spot, and the sub beam is spotted at a position other than the center and the side edge of the track 3 of the optical disk 2. As an image.

More specifically, the displacement amount of the center of the spot between the main light beam and the sub light beam in the radial direction of the optical disk 2 is expressed as
d, when the width of the track 3 is WT and a predetermined integer is m, the following relationship is satisfied: Δd ≒ WT / 4 + WT × m / 2. Here, since “m = 0” is set, spots of the main light beam and the sub light beam are arranged at positions satisfying Δd ≒ WT / 4, and these spots are located on one track 3. doing. The track 3 is actually a land 4 and a groove 5, but their widths WL and WG are substantially the same.

The objective lens 17 is supported so as to be displaceable in a tracking direction and a focusing direction.
An actuator 20 for controlling the position of the objective lens 17 in these directions is provided on the optical head 11. Since the focusing control is not related to the present invention as described above, it is omitted in the following description.

As shown in FIG. 3, the light receiving element unit 19 has one main light beam receiving portion 21 and two sub light beam receiving portions 22 and 23, and these light receiving portions 21 to 23 are provided.
Has two light receiving elements 24-29, respectively. These light receiving elements 24 to 29 include the light receiving sections 21 to 23, respectively.
Each of the differential amplifiers 30 to 32 is connected, and these differential amplifiers 30 to 32 and the light receiving elements 26 to 29 are
It is connected to the signal generation circuit 33. The signal generation circuit 33 is composed of a predetermined logic circuit, and here serves as both an error signal generation unit and a cross signal generation unit.

In other words, when the signal generating circuit 33 causes the spot of the main light beam to follow the track 3 of the optical disk 2, the push-pull signal of the main light beam receiving portion 21 and the plurality of light beams of the sub light beam receiving portions 22 and 23 are transmitted. A tracking error signal is generated from the detection signal, and a track cross signal is generated from a plurality of detection signals of the sub light beam receiving units 22 and 23 when the spot of the main light beam crosses the track 3 of the optical disk 2.

More specifically, the detection signals of the light receiving elements 24 and 25 of the main light beam receiving section 21 are Ma and Mb, and the detection signals of the light receiving elements 26 and 27 of the sub light beam receiving section 22 are S1a and S1a.
1b, assuming that the detection signals of the light receiving elements 28 and 29 of the sub-beam light receiving unit 23 are S2a and S2b and the predetermined constants are k and k ', the signal generation circuit 33 generates the tracking error signal TE
Is generated by the following equation: TE = Ma−Mb + k (S1a−S1b) + k ′ (S2a−S2b), and the track cross signal TC is generated by the following equation: TC = S1a−S1b−j (S2a−S2b).

A lens drive circuit 34 is connected to the signal generation circuit 33, and the lens drive circuit 34 is connected to the actuator 20. The signal generation circuit 33 outputs a tracking error signal to the lens drive circuit 34, and the lens drive circuit 34 controls the operation of the actuator 20 according to the tracking error signal.

A seek control circuit 35 is also connected to the signal generation circuit 33.
5 is connected to the head seek mechanism. The signal generation circuit 33 outputs a track cross signal to the seek control circuit 35, and the seek control circuit 35 controls the operation of the head seek mechanism according to the track cross signal.

In such a configuration, the optical disk device 1 of the present embodiment executes recording and reproduction of information on the optical disk 2 by a land & groove method. In this case, since recording and reproduction of information are performed by the spot of the main light beam on the track 3 of the optical disk 2 which is rotationally driven by the disk drive unit, the spot of the main light beam follows the track 3 which varies in the radial direction of the optical disk 2. Execute tracking control.

More specifically, the optical head 11 transmits the laser beam emitted from the semiconductor laser 12 to the collimator lens 13.
The light beam is split by the grating 14 into one main light beam and two sub light beams, and these three light beams are imaged on the surface of the optical disk 2 by the objective lens 17. In this case, as described above, the displacement amount Δd of the central portion of the spot between the main light beam and the sub light beam in the radial direction of the optical disk 2 △ d
Is one-fourth of the lateral width WT of the track 3. Therefore, as shown in FIG. 1, when the spot of the main beam is focused on the center of the track 3, The spot will be imaged.

The reflected light of the three light beams imaged on the track 3 of the optical disk 2 as described above is transmitted to the beam splitter 15.
And the light is condensed by the condensing lens 18 and is individually received by the three light receiving sections 21 to 23 of the light receiving element unit 19, so that the light receiving elements 24 to 29 of these light receiving sections 21 to 23 As shown in FIG. 4, the detection signal (Ma,
Mb), (S1a, S1b) and (S2a, S2b).

These detection signals are supplied to differential amplifiers 30 to 3
2, the push-pull signals (Ma-Mb), (S1a-S1
b) and (S2a-S2b) and input to the signal generation circuit 33. The signal generation circuit 33 calculates the tracking error signal as TE = Ma-Mb + k (S1a-S1b) + k '(S2a-S2b). Generate TE. Since the tracking error signal TE is output to the lens driving circuit 34, the lens driving circuit 34 controls the position of the objective lens 17 by the actuator 20 so that the tracking error signal TE becomes "0".

Push-pull signal (Ma-Mb) of main beam
Can be used as the tracking error signal TE as it is, but the optical disc 2 of the present embodiment
Are arranged at high density, the push-pull signal of the main beam has a small amplitude, and the tracking error signal T
When used for E, the detection accuracy is insufficient. If a signal having a small amplitude is amplified, the amplitude can be expanded. However, in this case, noise is also expanded, so that a decrease in detection accuracy cannot be solved.

Therefore, the optical disk device 1 of the present embodiment
Indicates that the push-pull signals (S1a-S1b) and (S2a-S2b) of the sub-beams for detecting the track 3 on both sides of the main beam are added to the push-pull signal of the main beam, and the tracking error signal TE
Therefore, as shown in FIG. 1C, a tracking error signal TE having a sufficiently large amplitude can be generated from three push-pull signals having small amplitudes, and tracking control can be performed with high accuracy. Can be. The generation of such a tracking error signal is essentially the same as that of the differential push-pull method described above, and no offset occurs due to the tilt of the optical disk 2.

When information is recorded or reproduced on the track 3 of the optical disk 2 as described above, the optical head 11 is first moved to the desired track 3 position. In this case, the track 3 of the optical disk 2 is optically detected by the optical head 11 moving in the seek direction, and the signal generation circuit 33 generates a track cross signal from the detection signal and outputs the track cross signal to the seek control circuit 35. The circuit 35 controls the operation of the head seek mechanism to stop the optical head 11 at a desired track 3 position.

More specifically, the two sub-beam receiving units 22,
Detection signals (S1a, S1b) of the 23 light receiving elements 26 to 29,
(S2a, S2b) are converted into push-pull signals (S1a-S1b) and (S2a-S2b) by the differential amplifiers 31, 32 and output to the signal generation circuit 33.
Is the difference "S1a-S" between the push-pull signals of the two sub-beams.
1b-j (S2a-S2b) "to generate the track cross signal TC.

As described above, the optical disc apparatus 1 of this embodiment uses the track cross signal as the difference between the push-pull signals (S1a-S1b) and (S2a-S2b) of the sub-beams for detecting both sides of one track 3. Since TC is generated, FIG.
As shown in (c), a tracking cross signal TC having a sufficiently large amplitude can be generated from two push-pull signals having a small amplitude, and seek control can be executed with high accuracy.

For example, in the conventional differential push-pull method,
The sum signal (Ma + Mb) of the main beam is converted to a track cross signal TC.
However, since the land 4 and the groove 5 are formed to have the same width in the optical disk 2 of the present embodiment, as shown in FIG. 4, the sum signal (Ma + Mb) of the main light flux is used.
It is difficult to generate the track cross signal TC from the Similarly, the sum signal of the sub-beams cannot be used for the track cross signal, but the optical disc apparatus 1 of the present embodiment has the sub-beams on both sides of one track 3 as described above, The track cross signal TC having a sufficiently large amplitude can be generated by the difference between the push-pull signals.

That is, the optical disk device 1 of the present embodiment
Can generate the tracking error signal TE with a sufficiently large amplitude even if the tracks 3 of the optical disk 2 are arranged at a high density. Even if the land 4 and the groove 5 of the optical disk 2 have the same width, the track cross The signal TC can be generated with a sufficiently large width. For this reason,
Both the tracking control and the seek control can be executed with high accuracy, and the optical disc 2 can be formed to have the maximum capacity.

The present invention is not limited to the above-described embodiment, but allows various modifications. For example, here, as the optimum value in which the amplitudes of both the tracking error signal TE and the track cross signal TC are sufficiently large, the displacement amount Δd of the spot center between the main light beam and the sub light beam is set to a quarter of the lateral width WT of the track 3. In this case, the spot center of the main beam is located at the center of the track 3 and the spot center of the sub beam is located at a location other than the center and the side edge of the track 3. Good.

Here, the push-pull signal of the sub-beam is set to "(S1
a−S1b) = A and (S2a−S2b) = B ″, the above-mentioned signals TE and TC are as follows: TE = Ma−Mb + kA + k′B TC = A−jB. The coefficient k and the like are assumed to be “1”. Then, “A + B” reflects the amplitude of the tracking error signal TE and “A−
B "reflects the amplitude of the track cross signal.

Therefore, when the width of the land 4 and the groove 5 of the optical disk 2 is the same as described above, the displacement Δd of the center of the spot between the main light beam and the sub light beam is set to the width WT of the track 3. When sequentially changed, as shown in FIG. 5, the position where the above-mentioned "A + B" and "AB" become the maximum and the position where the above becomes "0" coincide with each other.

For example, as in the conventional three-beam method, “△ d
= WT / 2 ”, the spot of the sub-beam is on track 3
Of the track cross signal T
The amplitude of C becomes the maximum, but the amplitude of the tracking error signal TE becomes “0”. If "す る と d = WT" as in the conventional differential push-pull method, the spot of the sub-beam will be located at the center of the tracks 3 on both sides, and the amplitude of the tracking error signal TE will be the maximum. However, the amplitude of the track cross signal TC becomes “0”.

That is, if the spot of the sub beam is arranged with respect to the spot of the main beam so as to avoid the above-mentioned position, the tracking error signal and the track cross signal can be satisfactorily generated. It is evident that it is other than the center and side edges of 3 and the optimal value at which the amplitudes of both signals are sufficiently large is "△ d = WT
/ 4 ".

Although the present embodiment has exemplified the case where three spots are formed on one track 3, the sub-beams are formed on the tracks 3 on both sides of the track 3 on which the main beam is formed. It is also possible. In this case as well, it is sufficient that the auxiliary light beam does not form an image on the center portion and the side edge portion of the track 3 as described above, and the optimal position is Δd = WT / 4 + WT × m / 2.

FIG. 4 shows examples of push-pull signals when the sub-beams are arranged as (S3a-S3b) and (S4a-S4b). Since these push-pull signals are equal to the inverted signals of the above-described push-pull signals (S2a-S2b) and (S1a-S1b), if they are inverted, a tracking error signal can be generated by the above-described formula.

That is, the tracking error signal T
K in the equation of E is an appropriate constant, and its sign changes depending on the position of the spot of the sub-beam. As described above, the case where the sub light beam is imaged on the same track 3 as the main light beam and the case where the sub light beam is imaged on the tracks 3 on both sides of the track 3 where the main light beam is imaged are as follows. Is inverted, the sign of the constant k is correspondingly inverted.

In this embodiment, both the lands 4 and the grooves 5 are used as the tracks 3 in order to maximize the capacity of the optical disk 2, but only one of them is used as the tracks 3. It is also possible.
For example, when the groove 5 is the track 3, the land 4
Is the track gap. In such a case, with the center of the spot of the main beam positioned at the center of the track 3,
The center of the spot of the sub-beam may be located at a position other than the center of the track 3, the side edge, and the center of the gap between the tracks 3. In other words, it is sufficient that the sub light beam is not formed on the boundary between the groove 5 and the land 4 or on the center of the land 4 while the main light beam is formed on the center of the groove 5.

Further, in the present embodiment, in order to maximize the capacity of the land & groove optical disc 2, the land 4
And the groove 5 are formed to have the same horizontal width. However, when the land 4 and the groove 5 are not formed to have the same horizontal width for reasons such as recording characteristics, or when the land 4 and the groove 5 are not formed.
When only one of the above is used as the track 3, it is preferable to increase the capacity of the optical disc 2 by forming only the track 3 wide. Even in such a case, with the center of the spot of the main beam positioned at the center of the track 3, the center of the spot of the sub beam is located at a location other than the center of the track 3, the side edge, and the center of the gap between the tracks 3. It just needs to be located.

In the present embodiment, the optical disc 2 is described as an example in which the lands 4 and the grooves 5 are formed and the information is rewritable. However, the lands 4 and the grooves 5 are not formed and the information is formed by the pit rows. It may be fixedly written. In this case, the pit row becomes the track 3, the gap between the pit rows becomes the gap between the tracks 3, and the image forming position of the main light beam and the sub light beam may be set as described above.

Further, in this embodiment, TE = Ma−Mb + k using all of the detection signals Ma and Mb of the main light beam, the detection signals S1a and S1b of the sub light beam, and the detection signals S2a and S2b of the sub light beam. Although the generation of the tracking error signal TE by the mathematical formula of (S1a-S1b) + k '(S2a-S2b) has been exemplified, TE = Ma-Mb + k (S1a + S2a) TE = Ma-Mb + k (S1a-S2b) TE = Ma- It is also possible to generate the tracking error signal TE by using an equation such as Mb + k (S1b + S2b) TE = Ma−Mb + k (S1b−S2a).

Similarly, it has been exemplified that the track cross signal TC is generated from all the detection signals of the sub-beams by the equation TC = S1a-S1b-j (S2a-S2b), but TC = S1a + S2b TC = S1a-S2a TC = S1b + S2a TC = S1b-S2b.

As described above, when only a part of the detection signal of the sub-beam is used, the light receiving elements 26 to 29 and the differential amplifiers 31 and 32 which are not used can be omitted. For example, as shown in FIG. 1D, when TE = Ma−Mb + k (S1a + S2a) TC = S1a−S2a, the light receiving elements 27 and 29 of S1b and S2b and the differential amplifiers 31 and 32 are omitted. And the structure can be further simplified.

As apparent from FIGS. 1 (c) and 1 (d),
When all the detection signals of the sub-beams are used, each signal T
Since the amplitudes of E and TC also become maximum, it is preferable that the above-mentioned several calculation methods be selected in consideration of various conditions. For example, when information is recorded on the track 3 of the optical disk 2 by the main light beam, it is preferable that the sub-light beam is not irradiated on the track 3. Therefore, when emphasizing this, TE = Ma−Mb + k (S1a−S2b) TC = S1a + S2b, and the inner sub-beams S1b and S2a may be shielded before the track 3 is irradiated.

Since the tracking error signal TE is generated from the detection signal of the reflected light of the optical disk 2 as described above, an offset occurs in the tracking error signal TE if the reflection intensity of the optical disk 2 is partially different.
For example, when information is sequentially recorded on the track 3 on which no information is recorded, the detection signals of the sub-beams at the front and rear of the main beam at which the information is recorded have different intensities. This is not a problem when the signals TE and TC are generated from all the detection signals as the push-pull signals as described above, but becomes a problem when only a part of the detection signal of the sub-beam is used.

If this is a problem, the detection signals Ma and Mb of the main light beam are normalized by (Ma + Mb), and the detection signals S1a and S1b of one of the sub light beams are converted to (S1a + S1b).
And the detection signals S2a and S2b of the other sub-beams are
It is preferable to normalize by (S2a + S2b). In this case, the divided signal of each light beam is normalized by the intensity of the entire light beam, so that the offset of the tracking error signal can be eliminated.

Even if the signal offset due to the intensity difference between the sub-beams before and after the main beam is eliminated, the signal offset due to the intensity difference between the right and left tracks 3 cannot be eliminated. For example, when the tracks 3 are arranged in the left-right direction, if information is sequentially recorded from the right to the left, the reflection intensity of the right and left tracks 3 of the track 3 on which information is recorded differs. This is not a problem when only one of the land 4 and the groove 5 records information, but becomes a problem when the land & groove 5 records information on both.

Therefore, if this poses a problem, it is preferable to form a recording mark on which the recording mark is to be overwritten on the track 3 of the optical disk 2 in advance. in this case,
Since the reflection intensity is uniform at the front, rear, left and right positions of the information recording position on the optical disk 2, no offset occurs in the tracking error signal, and it is not necessary to normalize each signal as described above.

[0065]

According to the optical disk apparatus of the first aspect of the present invention, the main light beam is formed as a spot on the center of the track of the optical disk as a spot, and the sub light beam is formed on the track adjacent to the center and the side edge of the track of the optical disk. An objective lens that forms an image as a spot at a position other than the center of the gap, a main light beam receiving unit that divides the reflected light of the main light beam in the radial direction of the optical disc and individually detects the reflected light, and a reflected light of the sub light flux of the optical disc. Tracking from the sub-beam light receiving section that is divided and detected individually in the radial direction, and from the push-pull signal of the main beam receiving section and the plurality of detection signals of the sub-beam receiving section when the spot of the main beam follows the track of the optical disk An error signal generating unit for generating an error signal; and a plurality of detection signals from the sub-beam receiving unit when the spot of the main beam crosses the track of the optical disk. And a cross signal generation unit for generating a cross signal, the tracking error signal is generated by combining the push-pull signal of the main light beam and the detection signal of the sub light beam, so that the tracks are arranged at high density and relatively Even when the spot diameter is large, it is possible to generate a tracking error signal having a sufficiently large amplitude, and since the position of the spot of the sub-beam is devised, even if the horizontal width between the tracks is the same, the amplitude is small. Can generate a track cross signal sufficiently large, and it is possible to execute both tracking control and seek control with high accuracy.

According to the second aspect of the present invention, when the displacement of the center of the spot between the main beam and the sub beam in the radial direction of the optical disk is Δd, the width of the track is WT, and a predetermined integer is m, Δd By satisfying the relationship of ≒ WT / 4 + WT × m / 2, it is possible to generate both the tracking error signal and the track cross signal with a sufficiently large amplitude.

According to the third aspect of the present invention, the detection signals of the main beam divided in the radial direction of the optical disk are Ma and Mb, the detection signals of one sub beam are S1a and S1b, and the detection signal of the other sub beam is S2a. , S2b, and the predetermined constants are k and k ',
The error signal generation unit calculates the tracking error signal TE as follows: TE = Ma−Mb + k (S1a + S2a) TE = Ma−Mb + k (S1a−S2b) TE = Ma−Mb + k (S1b + S2b) TE = Ma−Mb + k (S1b−S2a) TE = The tracking error signal having a sufficiently large amplitude can be generated by a simple calculation by using one of a plurality of mathematical expressions, Ma-Mb + k (S1a-S1b) + k '(S2a-S2b).

According to the fourth aspect of the present invention, the error signal generating section normalizes the detection signals Ma and Mb of the main light beam divided in the radial direction of the optical disk by (Ma + Mb), and detects the detection signal S1a and S1a of one sub light beam. S1b is normalized by (S1a + S1b), and the detection signals S2a and S2b of the other sub-beams are (S2a + S2
By normalizing according to b), since the divided signal of each light beam is normalized by the overall intensity of the light beam, even if the reflectance of the optical disk is partially different, it is possible to prevent the offset of the tracking error signal. it can.

According to the fifth aspect of the present invention, the detection signals of one of the sub-beams divided in the radial direction of the optical disk are provided as S1a, S1a,
Assuming that 1b, the detection signals of the other sub-beams are S2a and S2b, and the predetermined constant is j, the cross signal generation unit calculates the track cross signal TC as TC = S1a + S2b TC = S1a−S2a TC = S1b + S2a TC = S1b−S2b TC = S1a-S1b-j (S2a-S2b) By generating the signal by one of a plurality of equations, a track cross signal having a sufficiently large amplitude can be generated by a simple calculation.

According to the signal generation method of the present invention, the main light beam is formed as an image of a spot on the center of the track of the optical disk, and the sub-light beam is formed between the center of the track and the side edge of the optical disk. An image is formed as a spot at a position other than the center of the optical disk, and the reflected light of the main light beam is divided and detected individually in the radial direction of the optical disk, and the reflected light of the sub light beam is separately detected in the radial direction of the optical disk. A tracking error signal is generated from a detection signal of the main light beam and a sub light beam when the spot of the main light beam follows the track of the optical disk, and a tracking error signal is generated from the detection signal of the sub light beam when the spot of the main light beam crosses the track of the optical disk. By generating the track cross signal, the tracking error signal is generated by combining the push-pull signal of the main beam and the detection signal of the sub beam. Therefore, even when the tracks are arranged at high density and the spot diameter is relatively large, a tracking error signal with a sufficiently large amplitude can be generated, and the position of the spot of the sub light beam is devised. Even when the horizontal width between the tracks is the same, a track cross signal having a sufficiently large amplitude can be generated, and both the tracking control and the seek control can be performed with high accuracy.

An optical disk according to a seventh aspect of the present invention is an optical disk used in the optical disk device according to any one of the first to fifth aspects, wherein a recording mark on which a recording mark is to be overwritten is previously formed on a track. When information is recorded on a track of an optical disk by a main light beam, the two sub-light beams have the same signal intensity, so that an offset of a tracking error signal can be prevented.

An optical disk according to an eighth aspect of the present invention is an optical disk used in the optical disk apparatus according to any one of the first to fifth aspects, wherein the lands and the grooves are formed to have the same width. In the case of a land and groove recording information on both of them, the recording capacity of the optical disk can be maximized. According to any one of the optical disk devices,
A seek control can be executed by generating a track cross signal having a sufficiently large amplitude.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory diagrams of a signal generation method by an optical disk device according to an embodiment of the present invention, wherein FIG. 1A is a schematic longitudinal sectional view showing shapes of lands and grooves, which are tracks of an optical disk; () Is a schematic plan view showing the shapes of lands and grooves, (c) is a characteristic diagram showing a tracking error signal and a track cross signal, and (d) is a characteristic diagram showing a modification of each signal.

FIG. 2 is a schematic diagram showing a mechanism of the optical disk device.

FIG. 3 is a block diagram illustrating a part of a signal generation circuit.

FIG. 4 is a characteristic diagram showing various signals generated by the optical disc device.

FIG. 5 is a characteristic diagram showing a change in the amplitude of each signal with respect to a change in the amount of displacement between the main light beam and the sub light beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Optical disk 3-5 Track 4 Land 5 Groove 12 Laser light source 14 Light splitter 17 Objective lens 21 Main light beam receiving part 22, 23 Sub light beam receiving part

Claims (8)

[Claims] 1. A disk drive section for rotatably supporting an optical disk having tracks arranged at a predetermined pitch, a laser light source for emitting laser light, and a light for splitting the laser light into a main light beam and two sub light beams. A splitter for imaging the main light beam as a spot at the center of the track of the optical disc, and spotting the sub light beam at a position other than the center of the gap between the track center and the side edge of the optical disc track and an adjacent track. An objective lens that forms an image, a main light beam receiving unit that detects reflected light of the main light beam in the radial direction of the optical disc and detects the light beam individually, and splits the reflected light of the sub light beam in the radial direction of the optical disc and individually. A sub-beam light receiving unit to be detected, and a push-pull signal of the main light beam receiving unit and a plurality of detections of the sub-beam light receiving unit when the spot of the main light beam follows the track of the optical disc. An error signal generating section for generating a tracking error signal from the output signal; and a cross signal generating section for generating a track cross signal from a plurality of detection signals of the sub-beam receiving section when a spot of the main beam crosses a track of the optical disc. An optical disc device comprising: 2. When the displacement of the center of the spot between the main beam and the sub beam in the radial direction of the optical disk is Δd, the width of the track is WT, and a predetermined integer is m, Δd △ WT / 4 + WT × m. 2. The optical disk device according to claim 1, wherein the following relationship is satisfied. 3. A detection signal of the main light beam divided in the radial direction of the optical disk is Ma, Mb, a detection signal of one sub light beam is S1a, S1b, and a detection signal of the other sub light beam is S2a, S2b, a predetermined constant. Is k, k ′, the error signal generation unit calculates the tracking error signal TE as TE = Ma−Mb + k (S1a + S2a) TE = Ma−Mb + k (S1a−S2b) TE = Ma−Mb + k (S1b + S2b) TE = Ma− Mb + k (S1b-S2a) TE = Ma-Mb + k (S1a-S1b) + k '(S2a-S2
3. The optical disk drive according to claim 1, wherein the optical disk drive is generated by one of a plurality of mathematical expressions. 4. An error signal generating section outputs detection signals Ma and Mb of the main light beam divided in the radial direction of the optical disk to (Ma
+ Mb), and the detection signal S1 of one of the sub-beams
4. The optical disk apparatus according to claim 3, wherein a and S1b are normalized by (S1a + S1b), and the other sub-beam detection signals S2a and S2b are normalized by (S2a + S2b). 5. Assuming that S1a and S1b are detection signals of one sub-beam divided in the radial direction of the optical disc, S2a and S2b are detection signals of the other sub-beam, and j is a predetermined constant, the cross signal generation unit And the track cross signal TC is generated by one of a plurality of equations TC = S1a + S2b TC = S1a-S2a TC = S1b + S2a TC = S1b-S2b TC = S1a-S1b-j (S2a-S2b) The optical disk device according to claim 1. 6. An optical disk on which tracks are arranged at a predetermined pitch is rotatably supported, and a laser beam is divided into a main light beam and two sub-light beams, and the main light beam is formed as a spot at the center of the track of the optical disk. Imaging, the sub-light flux is imaged as a spot at a position other than the center of the gap between tracks adjacent to the center and side edges of the track of the optical disc,
The reflected light of the main light beam is divided and detected individually in the radial direction of the optical disc, the reflected light of the sub light beam is divided and detected individually in the radial direction of the optical disc, and the spot of the main light beam is detected on the track of the optical disc. When tracking, a tracking error signal is generated from detection signals of the main light beam and the sub light beam,
A signal generation method, wherein a track cross signal is generated from a detection signal of a sub-beam when a spot of a main beam crosses a track of the optical disc. 7. An optical disk for use in the optical disk device according to claim 1, wherein a recording mark on which the recording mark is to be overwritten is formed in a track in advance. 8. An optical disk used in the optical disk device according to claim 1, wherein lands and grooves are formed to have substantially the same lateral width.