JP2003272188A - Optical disk apparatus and method for deciding emission position of sub-beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disk apparatus for reproducing a DVD-R/RW and a DVD-RAM. <P>SOLUTION: A P<SB>1</SB>is a track pitch of a first disk, a P<SB>2</SB>is a track pitch of a second disk, an L<SB>1</SB>=P<SB>1</SB>/2+P<SB>1</SB>×N<SB>1</SB>is a tentative distance between a main beam spot and a sub beam spot in a radial direction of the first disk, and an L<SB>2</SB>=P<SB>2</SB>/2+P<SB>2</SB>×N<SB>2</SB>is a tentative distance between the main beam spot and the sub beam spot in a radial direction of the second disk. Then N<SB>2</SB>is an integer selected such that the L<SB>1</SB>is closest to the L<SB>2</SB>. Further, an L is an intermediate value between the L<SB>1</SB>and L<SB>2</SB>and a ΔL<SB>1</SB>is a difference between the intermediate value L and the L<SB>1</SB>. The value N<SB>1</SB>minimizing the absolute value of the ΔL<SB>1</SB>is decided and the N<SB>1</SB>is assigned to the L<SB>1</SB>=P<SB>1</SB>/2+P<SB>1</SB>×N<SB>1</SB>to decide the intermediate value L. The sub beam is placed so that the distance between the main beam spot and the sub beam spot in the radial direction of the first or second disk is L. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device and a sub-beam irradiation position determining method, and more particularly, for example, a first optical disk and a second optical disk having different track pitches.
Record or play information on an optical disc,
The present invention relates to an optical disk device and a sub-beam irradiation position determination method using a differential push-pull method for tracking control.

[0002]

BACKGROUND OF THE INVENTION There is a DVD (Digital Versatile Disk) family as a recording medium capable of recording and reproducing a large amount of information. This DVD family includes DVD-ROM,
There are DVD-R / RW and DVD-RAM. D
VD-ROM is used only for reading, but DVD-
R / RW is suitable for continuous recording such as video information, and DVD-RAM is suitable for external memory of a computer because it can be randomly accessed to record in discontinuous areas. There is.

Although these recording media have different suitable applications, it is desired by the user that all of them can be reproduced by a DVD-ROM drive device that reproduces a previously read-only optical disc.

[0004]

Since the recorded optical disc of DVD-R / RW is defined by the standard so as to be almost the same as DVD-ROM, the DVD-R / RW is a DVD-ROM drive device. It's easy to play. However, DVD-RAM and DVD-R
The physical format such as the track pitch is completely different from that of the OM. For example, DVD-R / RW is groove recording, and its track pitch is 0.74 μm, which is the same as DVD-ROM, but DVD-RAM is land / groove recording, and its track pitch is 0.615 μm.
m. Therefore, it is impossible to reproduce the DVD-RAM as it is without modifying the DVD-ROM drive device.

Therefore, the main object of the present invention is to
An object of the present invention is to provide an optical disc device capable of reproducing both VD-R / RW and DVD-RAM.

[0006]

A first invention is an optical disk which records or reproduces information on a first optical disk and a second optical disk having different track pitches and uses a differential push-pull method for tracking control. A device for irradiating a track to be tracked with a main beam, and a sub-beam to a position where the deviation from the center of the track is minimized regardless of whether the track is irradiated with the first optical disc or the second optical disc. The optical disk device is provided with a second irradiating means.

A second aspect of the present invention is an optical disc apparatus that records or reproduces information on a first optical disc and a second optical disc having different track pitches and uses a differential push-pull method for tracking control. First irradiating means for irradiating the main beam onto the track to be recorded, second irradiating means for irradiating the primary sub-beam for the first optical disc, and 2 for the second optical disc.
The optical disk device includes a third irradiation unit that irradiates the next sub beam.

A third aspect of the invention is a sub-beam irradiation position in an optical disc apparatus that records or reproduces information on the first optical disc and the second optical disc having different track pitches and uses a differential push-pull method for tracking control. The determination method is as follows: (a) The track pitch of the first optical disk is P _1, and (b) the second
The track pitch of the optical disc is set to P _2, and (c) a temporary distance between the spot of the main beam and the spot of the sub beam in the radial direction of the first optical disc

[0009]

[6] _{L 1 = P 1/2 +} P 1 × N 1 (N 1 is an integer), and the tentative distance in a second radial direction of the optical disc of (d) and the main beam spot and sub-beam spots

[0010]

Equation 7] _{L 2 = P 2/2 +} P 2 × N 2 (N 2 is an integer) and, (e) N ₂ is an integer such L ₁ is closest to L _2, and (f) L ₁ Let L be the intermediate value with L ₂ , (g) be the difference between the intermediate values L and L ₁ be ΔL _1, and (h) determine the intermediate value L based on N _{1 at} which the absolute value of ΔL ₁ is the minimum. And (i) the sub-beam irradiation position determining method, in which the sub-beams are arranged such that the distance between the spot of the main beam and the spot of the sub-beam in the radial direction of the first optical disc or the second optical disc is L.

A fourth aspect of the invention is a sub-beam irradiation position in an optical disc apparatus which records or reproduces information on the first optical disc and the second optical disc having different track pitches and uses a differential push-pull method for tracking control. A method of determination, (a) 1
The two main sub-beams, the two primary sub-beams and the two secondary sub-beams are irradiated to the positions where the secondary sub-beams are located outside the main beam and the primary sub-beam to form a straight line, and (b) the spots of the primary sub-beams And a tentative angle formed by the straight line formed by the spot of the main beam and the tangent of the track irradiated with the main beam is θ ₁ , (c)
The provisional angle formed by the straight line formed by the spot of the secondary sub-beam and the spot of the main beam and the tangent of the track irradiated with the main beam is θ _2, and (d) the track pitch of the first optical disc is P _1, and ( e) The track pitch of the second optical disc is P ₂ , (f) the distance between the spot of the main beam and the spot of the primary sub-beam is R, and
(G) The distance between the main beam spot and the secondary sub-beam spot is 2R, and (h) the distance between the main beam spot and the primary sub-beam spot in the radial direction of the first optical disc.

[0012]

Equation 8] _{L 1 = R × sinθ 1 =} P 1/2 + P 1 × N 1 (N 1 is an integer), and, (i) a main beam spot and the second optical disk in the radial direction of the spot of the secondary sub-beams Distance

[0013]

Equation 9] _{L 2 = 2 × R × sinθ} 2 = P 2/2 + P 2 × N 2
(N ₂ is an integer), (j) N ₂ is an integer such that θ ₂ is closest to θ ₁ , and (k)

[0014]

[Formula 10] L ₂ ′ = 2 × R × sin θ ₁ , (l) The difference between L ₂ ′ and L ₂ is ΔL _2, and (m) Δ
Θ ₁ and θ ₂ based on N ₁ when the absolute value of L ₂ is minimum
, And (n) the spot of the primary sub-beam, 2
The primary sub-beam and the secondary sub-beam are arranged so that the angle θ formed by the straight line formed by the spot of the next sub-beam and the spot of the main beam and the tangent of the track irradiated with the main beam is θ ₁ ≦ θ ≦ θ _2. This is a method for determining the irradiation position of the sub beam.

[0015]

In the first invention or the fifth invention, when irradiating the sub-beam, either the first optical disk or the second optical disk having different track pitches is irradiated,
The sub beam is applied to the position where the deviation from the center of the track is minimal.

More specifically, the track pitch of the first optical disk is P ₁ , the track pitch of the second optical disk is P _2, and the spot of the main beam and the spot of the sub beam are provisional in the radial direction of the first optical disk. Distance

[0017]

And Equation 11] _{L 1 = P 1/2 +} P 1 × N 1 (N 1 is an integer), the tentative distance in the radial direction of the second optical disc and the spot of the spot and sub-beams of the main beam

[0018]

Equation 12] _{L 2 = P 2/2 +} P 2 × N 2 (N 2 is an integer) to.

N ₂ is an integer such that L ₁ is closest to L ₂ . The intermediate value between L ₁ and L ₂ is L, and the difference between this intermediate value L and L ₁ is ΔL ₁ (intermediate value L
And the difference between L ₂ is the same). Then, N _{1 at} which the absolute value of ΔL ₁ is minimized is determined, and this N ₁ is

[0020]

Determining an intermediate value L by substituting the Equation 13] _{L 1 = P 1/2 +} P 1 × N 1.

The sub-beams are arranged such that the distance between the spot of the main beam and the spot of the sub-beam in the radial direction of the first optical disk or the second optical disk is L.

By doing so, the deviation of the spot of the sub beam from the track center is almost eliminated in both the first optical disc and the second optical disc.

In the third invention or the sixth invention, two kinds (four in total) of sub-beams are used for each of the first optical disk and the second optical disk having different track pitches. In this case, due to the structure of the optical pickup, the spot of the sub-beam, the spot of the primary sub-beam (two) and the spot of the secondary sub-beam (two) are arranged on a straight line. Further, the distance from the spot of the sub beam to the spot of the primary sub beam and the distance from the spot of the primary sub beam to the spot of the secondary sub beam are substantially equal.

More specifically, the temporary angle formed by the straight line formed by the spot of the primary sub-beam and the spot of the main beam and the tangent of the track irradiated with the main beam is θ _1, and the spot of the secondary sub-beam is set. Let θ ₂ be a tentative angle formed by the straight line formed by the spot of the main beam and the tangent of the track irradiated with the main beam. Also,
The track pitch of the first optical disk is P ₁ , the track pitch of the second optical disk is P ₂ , and the distance between the main beam spot and the primary sub-beam spot is R,
The distance between the spot of the main beam and the spot of the secondary sub-beam is 2R.

Then, the distance between the spot of the main beam and the spot of the primary sub-beam in the radial direction of the first optical disk is

[0026]

Equation 14] _{L 1 = R × sinθ 1 =} P 1/2 + P 1 × N 1 (N 1 is an integer), and the second distance in the radial direction of the optical disk and the spot of spot and secondary sub-beams of the main beam

[0027]

Equation 15] _{L 2 = 2 × R × sinθ} 2 = P 2/2 + P 2 × N
₂ (N ₂ is an integer).

Here, N ₂ is an integer such that θ ₂ is closest to θ ₁ .

When the angle formed by the straight line formed by the main beam spot and the secondary sub-beam spot and the tangent line of the track irradiated with the main beam is θ ₁ ,
The radial distance of the second optical disc between the main beam spot and the secondary sub beam spot

[0030]

## EQU16 ## Let L ₂ '= 2 × R × sin θ ₁ . Then, the difference between L ₂ 'and L ₂ is ΔL ₂ .

N ₁ when the absolute value of ΔL ₂ has a minimum value is obtained, and θ ₁ and θ ₂ are determined based on N ₁ . The angle θ formed by the straight line formed by the spot of the primary sub-beam, the spot of the secondary sub-beam and the spot of the main beam and the tangent of the track irradiated with the main beam is θ ₁ ≦ θ
The primary sub-beam and the secondary sub-beam are arranged so that ≦ θ ₂ holds.

By doing so, the primary sub-beam is irradiated to approximately the center of the track of the first optical disk, and the secondary sub-beam is irradiated to approximately the center of the track of the second optical disk.

As will be described in detail later, if the positional deviation of the light receiving sensor in the optical pickup and the deviation of the spot of the sub-beam from the center of the track occur at the same time, a focus error (hereinafter , FE) signals cannot completely remove the influence of disturbance (offset occurs).

When reproducing the first optical disc and the second optical disc having different track pitches by the conventional optical disc apparatus, since the track pitches are different, the spot of the sub beam deviates from the center of the track on either of the optical discs. If the light receiving sensors are misaligned, the FE signal is affected by the disturbance. Therefore, the first optical disc and the second optical disc having different track pitches cannot be reproduced by one optical disc device.

[0035]

According to the present invention, it is possible to eliminate the influence of disturbance on the FE signal, which is a barrier when reproducing two optical disks having different track pitches by one optical disk apparatus, so that, for example, DVD-s having different track pitches can be eliminated. R / R
W and DVD-RAM can be reproduced by one optical disk device.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an optical disk device 10 of this embodiment uses, for example, D as a recording medium for reproducing a signal.
Optical disc 1 such as VD-R / RW, DVD-RAM
2 is used. In FIG. 1, only the outer shape of the optical disc 12 is shown by an imaginary line in order to clearly show the components below the optical disc 12. The optical disk 12 is held by the holding unit 14 and is rotated by the spindle motor 16. An optical pickup 18 for recording a signal on the optical disc 12 and reproducing a signal from the optical disc 12 is provided below the optical disc 12.
Are held by the shaft 20 so as to be movable in the axial direction of the shaft 20. The shaft 20 is held by the shaft holder 22, and the shaft holder 2
2 is fixed on the chassis 24 together with the spindle motor 16.

The above-mentioned spindle motor 16 is fixed on a spindle motor chassis 26, and the spindle motor chassis 26 and the shaft holder chassis 24 are connected by a support shaft 28.

The laser light emitted from the optical pickup 18 is focused on the optical disc 12 rotated by the spindle motor 16 to form a minute spot. The optical pickup 18 moves along the shaft 20 by a driving unit (not shown). Therefore, the spot can scan the optical disk 12 two-dimensionally. As a result, the signal is recorded on the optical disc 12 and the signal is reproduced.

The optical system to which the present invention is applied is slightly different depending on various recording / reproducing systems. In describing the embodiments, the optical system of DVD-R / RW is used as an example, but the present invention is not limited to this.

Next, the flow of laser light will be described with reference to FIG. First, laser light is radially emitted from the laser diode 30. This laser light is a spherical wave, and when passing through the diffraction grating 32, it is divided into three spherical waves each having a virtual light source. One is 0th-order light whose source is the laser diode 30 on the optical axis of the collimator lens 38 for converting emitted light into parallel light, and the rest is symmetric with respect to the optical axis, and the yz plane is centered on the z-axis. They are + first-order light and -1st-order light, which have virtual light sources in the slightly rotated y'z 'plane.

The 0th-order light becomes a main beam having a large light quantity and is used for recording and reproducing a signal. The ± first-order light becomes a sub-beam with a small light quantity, and is used for tracking servo called a differential push-pull method.
Since this signal is a well-known technique and is not directly related to the present invention, description thereof will be omitted here together with the ± 1st order light paths. Therefore, only the flow of zero-order light will be described.

The polarization beam splitter 34, which reflects or transmits light depending on its polarization, has a P wave (polarization parallel to the normal of the reflecting surface) component of the light at a predetermined ratio, for example, 9 :.
At 1, the light is split into transmitted light and reflected light, and the S-wave (polarized light perpendicular to the normal of the reflecting surface) component is split at a predetermined ratio, for example 0:10, into transmitted light and reflected light.

In this optical system, since the polarization plane of the linearly polarized light of the laser diode 30 is arranged parallel to the zx plane, all the light emitted from the laser diode 30 becomes P waves. Therefore, the polarization beam splitter 3
One-tenth of the total light amount is reflected by 4 and enters the front monitor 36 that detects the light amount, and the rest is transmitted. The light incident on the front monitor 36 is converted into an electric signal and used for automatic power control. That is, the current supplied to the laser diode 30 is controlled so that the electric signal output from the front monitor 36 is maintained at a predetermined value. As a result, the power of the main beam emitted from the objective lens 44 is maintained at a predetermined intensity.

The light transmitted through the polarization beam splitter 34 is converted from a spherical wave into a plane wave by a collimator lens 38.
In other words, the emitted light is converted into parallel light. The direction of parallel light is a direction parallel to the optical axis.

The parallel light converted by the collimator lens 38 is incident on the quarter wave plate 40, and linearly polarized light is converted to circularly polarized light. Then, the circularly polarized light is changed in direction by the reflection mirror 42 and enters the objective lens 44. Then, the light transmitted through the objective lens 44 forms an image on the signal surface of the optical disc 12 and is reflected. Due to this reflection, the phase of the light is reversed, so that the rotation direction of the circularly polarized light is reversed. The light reflected on the signal surface follows the outward path in the reverse direction, and is first converted into parallel light by the objective lens 44, and then the quarter-wave plate 40.
Pass through. At this time, the circularly polarized light is converted into the linearly polarized light, but unlike the forward path, the circularly polarized light has the opposite direction, so the polarization plane of the returned linearly polarized light is the S wave plane in the polarization beam splitter 34, that is, the yz plane. Become parallel.

Next, the collimator lens 38 converts the parallel light into focused light, and the converted focused light enters the polarization beam splitter 34. Since this incident light is linearly polarized into an S wave, the polarization beam splitter 34 produces 100
%, The light is redirected to the direction of the light receiving sensor 48 that converts the light into an electric signal, and enters the cylindrical lens 46 that generates astigmatism. The ridgeline of the cylindrical lens 46 is inclined in a direction forming an angle of 45 degrees with the xy plane with the optical axis as the x-axis direction. Therefore, the image forming position on the optical axis in this cross section does not coincide with the image forming position in the cross section perpendicular to this cross section. What causes such astigmatism is
This is because the astigmatism method is used for focus servo.
Since the principle of the astigmatism method is well known, its explanation is omitted here.

The light is condensed on the optical axis near the light receiving sensor 48 by the collimator lens 38 and the cylindrical lens 46. The light receiving sensor 48 is arranged at approximately the center position of each image forming point in the two cross sections defined by the cylindrical lens 46.

The light emitted from the cylindrical lens 46 is the four-division sensor 4 arranged at the optical axis position shown in FIG.
It is focused on 8a, 48b, 48c and 48d.
These sensors simultaneously reproduce the recorded signal,
Although it is divided into four parts for use in focus servo, its operation is well known, and therefore its explanation is omitted here. Incidentally. The focus error signal (hereinafter, FE signal) used for focus servo is detected by the sensor 48.
The outputs of a, 48b, 48c and 48d are A,
When expressed as B, C and D, it is given by Equation 17.

[0050]

FE = (A + C) − (B + D) In DVD-RAM, random access frequently occurs. When the astigmatism method, which is a simple and general method, is used in focusing control, the spot irradiated on the optical disk 12 causes a diffraction phenomenon by the track groove when the track groove is traversed during random access. This diffraction phenomenon becomes a disturbance to the FE signal.

Since the DVD-R / RW rarely needs random access, it is not important to take measures against the disturbance generated when the track groove is traversed. Therefore, the DVD-R / RW drive apparatus takes measures against the disturbance. Absent. for that reason,
In order to reproduce the DVD-RAM with the DVD-R / RW drive device, it is necessary to take measures against this disturbance.

Therefore, the gist of the present invention is to reduce the influence of disturbance on the FE signal generated when the spot traverses the track, and DVD-RAM having different track pitches.
To be reproducible by a DVD-R / RW drive device.

When the differential push-pull (DPP) method is used as the tracking control method, the arrangement position of the sub-beams is defined by the track pitch (strictly speaking, the groove pitch). Therefore, when reproducing a DVD-R / RW and a DVD-RAM having different track pitches, the position of the sub beam must be changed strictly.

In order to explain the arrangement of sub-beams, first,
The land and groove will be briefly described. Guide grooves are formed in advance on the recording optical disk 12. As shown in FIGS. 4 and 5, the groove is a groove that is convex when viewed from the optical pickup 18 that performs recording and reproduction, and the land is a groove that is concave.

Irradiation positions are different between the main beam and the sub beam. In DVD-R / RW, the main beam is applied to the groove and the sub-beam is applied to the land. In the DVD-RAM, recording is performed on both the land and the groove. Therefore, when the main beam irradiates the groove, the sub beam irradiates the land, and when the main beam irradiates the land, the sub beam irradiates the groove. In the conventional optical disk device, as shown in FIGS. 4 and 5, the main beam and the sub beam are applied to the land and groove adjacent to each other. Therefore, the distance from the main beam to the sub beam in the radial direction of the optical disc 12 is DVD-
In R / RW, 0.37, which is half of the groove pitch of 0.74 μm
μm, and for DVD-RAM, groove pitch is 1.23 μm
Since it is 0.615 μm which is half of m, the difference is large.

Therefore, DVD-R / RW and DVD-R
If the position of the sub beam is not changed in case of AM, D
The location of the sub-beam of the VD-RAM deviates from the center of the land or groove in the width direction, which is the position of the circle originally drawn by the dotted line (see FIG. 5).

As will be described later in detail, when the position of the sub beam is displaced from the center of the land or groove in the width direction, and when the displacement of the light receiving sensor 48 is further overlapped, the influence on the FE signal due to disturbance can be eliminated. Can not.

The case where a disturbance occurs will be described below.

Disturbance in ideal state (no displacement of light receiving sensor, proper beam position) FIGS. 6A to 6C show a state in which light is imaged on the optical disk 12 together with the objective lens 44. FIG. 3 is a schematic diagram showing a parallel light far-field pattern (hereinafter, FFP) for a main beam and a sub beam when a spot moves from left to right in the optical disc radial direction (crosses tracks by random access or the like). It is assumed that the center of the FFP intensity of the parallel light incident on the objective lens 44 substantially coincides with the optical axis of the objective lens 44. The groove (land) on the optical disk 12 acts like a diffraction grating to generate n-th order diffracted light. It is the ± first-order light that actually overlaps the zero-order light and affects the FFP. The guide groove of the recording optical disk 12 is designed to have a depth of about ⅙ to ⅛ of the wavelength of light so that a push-pull (hereinafter, PP) signal can be easily obtained. When 0 and the zero-order light are superposed on each other, the light amount is attenuated. As a result, the shaded area in FIG. 6 becomes darker than the surrounding area.

FIG. 6A shows the case where the spot is located to the left of the center of the track width, and the dark part of the FFP of the main beam is asymmetric with respect to the track center axis (horizontal direction). Split sensor (sensors 48a, 48b,
48c and 48d) are vertically symmetrical.
Therefore, the FE signal becomes "0" and no disturbance occurs (see FIG. 3 and Equation 1).

FIG. 6B shows the case where the spot is located at the center of the track width, and the dark portion of the FFP of the main beam is symmetrical with respect to the track center axis. Therefore, F
The E signal becomes "0" and no disturbance occurs (see equation 1).

FIG. 6C shows the case where the spot is located to the right of the center of the track width, and the dark portion of the FFP of the main beam is vertically symmetrical with respect to the 4-division sensor. Therefore, the FE signal becomes "0" and no disturbance occurs.

As described above, when the light receiving sensor is not displaced and the beam position is appropriate, the FE signal is not affected by the track crossing.

In the four-division sensor, the difference in the amount of light divided into left and right on the center axis of the track is reflected in the PP signal, and a PP signal resembling a sine wave is generated as the spot crosses the track groove. To do.

Disturbance in the state where the light receiving sensor is misaligned FIGS. 7A to 7C show the case where the light receiving sensor 48 is vertically misaligned when the optical pickup 18 is assembled. .

FIG. 7A shows the case where the spot is located closer to the left than the center of the track width, and the dark part of the FFP of the main beam is asymmetrical in the vertical and horizontal directions of the four-division sensor, so the FE signal is It does not become "0".

FIG. 7B shows the case where the spot is located at the center of the track width, and the dark portion of the FFP of the main beam is symmetrical in the left-right direction in the four-division sensor.
The E signal becomes "0".

FIG. 7C shows a case in which the spot is located closer to the right than the center of the track width, and the dark portion of the FFP of the main beam is asymmetrical in the vertical and horizontal directions of the 4-division sensor, so the FE signal is It does not become "0".

Thus, when the spot crosses the track from left to right, a signal similar to a sine wave is superimposed on the FE signal. This becomes a disturbance. However, in this case, the disturbance can be removed by using the differential astigmatism method.

As shown in FIG. 8, the light receiving sensor for receiving the reflected light of the sub beam on the optical disk is also divided into four.
Then, the FE signal can be detected in the same manner as the main beam, and the disturbance is applied to the output of the four-division sensor for the sub-beam when the track is crossed.

In FIGS. 7A and 7C, the FFP of the main beam and the FFP of the sub beam are bilaterally symmetrical. Therefore, the sign of the output of each FE signal is opposite. Therefore, the FE of the sub-beam
If the signal is appropriately amplified and the FE signal of the main beam and the FE signal of the sub beam are added, the FE signal becomes "0". That is, even if the spot crosses the track from left to right, the disturbance is canceled and the FE signal is not disturbed. This is the differential astigmatism method.

Although the case where the light receiving sensor 48 is displaced in the vertical direction has been described here, the same applies to the case where the position is displaced in the horizontal direction.

Disturbances when the sub-beam position is not appropriate FIGS. 9 (A) to 9 (C) are the same as FIGS. 6 (A) to 6 (B), except that the optical disc 1 with the main beam and the sub-beam is used.
This is the case when the radial distance of 2 is not arranged at half the groove pitch, that is, when the sub-beam spot is not located at the center of the track. In this case, there is a difference between the left-right non-uniformity of the sub-beam FFP and the left-right non-uniformity of the main beam FFP.

FIG. 9A shows the case where the spot is located to the left of the center of the track width, and the dark portion of the FFP of the main beam is symmetrical in the left-right direction in the 4-division sensor. Therefore, the FE signal becomes "0".

FIG. 9B shows the case where the spot is located at the center of the track width, and the dark portion of the FFP of the main beam is symmetrical vertically and horizontally in the four-division sensor. Therefore, the FE signal becomes "0".

FIG. 9C shows the case where the spot is located to the right from the center of the track width, and the dark portion of the FFP of the main beam is vertically symmetrical in the four-division sensor. Therefore, the FE signal becomes "0".

As described above, when the position of the sub-beam is not appropriate, even if the spot crosses the track groove, it does not affect the FE signal.

Disturbances when the sub-beam position is not proper and the light receiving sensor is misaligned. In FIGS. 10A to 10C, the distance between the main beam and the sub-beam in the radial direction of the optical disk 12 is a groove. This is a case where the light receiving sensor 48 is not arranged at half the pitch (the spot of the sub beam is not arranged in the center of the track) and the light receiving sensor 48 is displaced in the vertical direction. There is a difference between the left-right non-uniformity of the FFP of the sub-beam and the left-right unevenness of the FFP of the main beam.

FIG. 10A shows the case where the spot is located to the left from the center of the track width, and the dark portion of the FFP of the main beam is asymmetrical in the vertical and horizontal directions in the 4-split sensor. Therefore, the FE signal does not become "0".

FIG. 10B shows the case where the spotlight is located at the center of the track width, and the FF of the main beam is used.
The dark portion of P is symmetrical in the left-right direction in the 4-division sensor. Therefore, the FE signal becomes "0".

FIG. 10C shows the case where the spot is located to the right from the center of the track width, and the dark portion of the FFP of the main beam is asymmetric in the vertical and horizontal directions in the four-division sensor. Therefore, the FE signal does not become "0".

From the above, when the spot crosses the track from left to right, a signal similar to a sine wave is superimposed on the FE signal. This is a disturbance. To remove this disturbance, we try to use the previously mentioned differential astigmatism method.

In FIGS. 10A and 10C, the main beam FFP and the sub-beam FFP are not symmetrical. However, each FE signal is almost the opposite, so amplify the sub-beam FE signal appropriately,
The main beam and the sub beam are added. Then FE
Although the disturbance oscillation from the signal can be removed, the individual DC components are added and an offset occurs in the FE signal.

As described above, when the arrangement of the sub-beams is largely deviated from the center of the track, if the light-receiving sensor 48 further shifts due to misalignment or some reason after assembly, an offset occurs in the FE signal. When the offset occurs, the spot cannot be narrowed down on the optical disc 12, and the recording and reproducing performance deteriorates. Therefore, the DVD-R / RW and the DVD-RAM cannot be reproduced by one disk device.

Therefore, the optical disk device 10 of this embodiment is
Then, in order to avoid the above-mentioned problem, a measure is taken so that the irradiation position of the sub beam does not largely deviate from the center of the track regardless of whether the track pitch is DVD-R / RW or DVD-RAM. . By doing so, even if the light receiving sensor 48 is misaligned, the FE
The disturbance generated in the signal can be removed by using the differential astigmatism method.

Specifically, the position of the spot of the sub beam is gradually separated from the spot of the main beam in the radial direction of the optical disc 12, and the DVD-R / RW and DVD-R are read.
In both of AM and AM, the position where the spot of the sub beam is not largely separated from the center of the track width is specified.

In the case of DVD-R / RW, as shown in FIG. 11, the main beam is irradiated on the groove, and the sub-beam is adjacent to the groove irradiated by the main beam as represented by the dotted circle. Previously, the land was irradiated. In this case, the radial distance L of the optical disc 12 between the spot of the main beam and the spot of the sub beam on one side is L.
₁ is 0.74 μm / 2 = 0.37. Here, the spot of the sub beam is changed from the spot of the main beam to N ₁
If the distance is set to be the groove pitch of the book, the distance L ₁ is
Given in.

[0088]

In the case of L ₁ = 0.37 + 0.74 × N ₁ DVD-RAM, as shown in FIG. 12, when the main beam is applied to the groove, the sub-beams are as shown by the dotted circles. Previously, the land adjacent to the groove irradiated with the main beam was irradiated. In this case, the radial distance L of the optical disc 12 between the spot of the main beam and the spot of the sub beam on one side is L.
₂ is 0.165 μm. Here, assuming that the spot of the sub beam is separated from the spot of the main beam by the groove pitch of N ₂ lines, the distance L ₂ is given by Formula 19. Here, the pitch means a distance from a groove to a next groove or a land to a next land.

[0089]

[Formula 19] L₂  = 0.615 + 2 x 0.615 x N₂ Where N₂Is L₂Is L₁An integer that is closest to
Choose. And L₁And L ₂In between (the main beam
The sub-beam at a distance L) from the
It At this time, the main beam spot and the sub beam
The distance to the spot is L. And L and L₁Difference from
ΔL₁And L and L₂And the difference is ΔL₂And

Here, N ₁ and N ₂ are changed to find a value that minimizes the absolute value of ΔL _{1 and} the absolute value of ΔL ₂ . The absolute value of ΔL _{1 and} the absolute value of ΔL ₂ are the same.
Each value of the time went to N ₁ is changed are shown in Table 1, shows the deviation from the track of the sub-beams when changing the N ₁ in FIG.

[0091]

[Table 1]

As N ₁ is increased, the two sub-beams spread to the outer circumference side and the inner circumference side of the optical disk 12, so that the number of tracks that the main beam cannot access increases at the outermost circumference and the innermost circumference. . Further, as N ₁ is increased, ΔL ₁ and ΔL ₂ periodically fluctuate as shown in Table 1 and FIG. Therefore, it is preferable to _first select N ₁ that minimizes the absolute value of ΔL _{1 and} the absolute value of ΔL ₂ .

As a result, N ₁ = 2, N ₂ = 1 and ΔL ₁ =
A value of 0.0025, ΔL ₂ = −0.0025 is obtained. According to this result, in the case of DVD-R / RW, the sub-beam is about the groove pitch 2 from the main beam.
The main part will be located in a distant place, DVD-RA
In the case of M, the sub beam is located at a place separated from the main beam by one groove pitch. And
In both cases of DVD-R / RW and DVD-RAM, the deviation of the track width of the sub beam from the center is 0.0.
It becomes as small as 025 μm.

Therefore, DVs having different track pitches
In both the D-R / RW and the DVD-RAM, since the sub-beams are arranged at the center of the track width, even if the optical sensor is displaced for some reason,
As described above, since the disturbance can be canceled by using the differential astigmatism method, the FE signal becomes “0”,
The signal is unaffected by disturbances. Therefore, an offset does not occur in the FE signal, and the offset does not deteriorate the recording and reproducing performance. Therefore, with one drive device, DVD-R / R
Both W and DVD-RAM can be played.

In the optical disk device 10 of the next embodiment, D
A dedicated sub-beam is used for each of the VD-R / RW and the DVD-RAM. That is, four sub-beams are generated by the diffraction grating 32, and, for example, the ± first-order light is used as a sub-beam for DVD-R / RW, and the ± second-order light is D.
It is a sub beam for VD-RAM. In this case, the sensor included in the light receiving sensor 48 is configured as shown in FIG. As shown in this figure, the ± first-order light reflected on the recording surface of the DVD-R / RW is converted into E1, F1, G1 and H
± 2 received at 1 and reflected at the recording surface of DVD-RAM
The next light is received by E2, F2, G2 and H2.

When using four sub-beams, FIG.
And as shown in FIG. 16, due to the structure of the optical pickup 18 (due to the diffraction grating 34), the spot of the main beam,
The spots of the primary sub-beams (± primary light) and the spots of the secondary sub-beams (± secondary light) are arranged on a straight line.
Further, the distance between the main beam spot and the primary sub beam spot and the distance between the primary sub beam spot and the secondary sub beam spot are substantially equal. Therefore, if the angle θ formed by the straight line formed by the main beam spot and the sub beam spot and the tangent line of the track irradiated with the main beam is determined, the position of the sub beam spot is determined.

Referring to FIG. 15, first, the DVD-R / R
The case of W will be described. In the conventional optical disk device, the sub-beams are applied to the lands on both sides of the groove on which the main beam is applied, as indicated by the dotted circles in the figure. In this case, the radial distance L ₁ of the optical disc 12 between the spot of the main beam and the spot of the sub beam on one side is 0.74 / 2 = 0.37 μm.

Sub Beam (Primary Sub Beam: DVD-R
/ The position of the spot of sub-beam) for RW, and the distance from the main beam spot as it is as shown in FIG. 15, N ₂ from the groove in which the main beam is irradiated
When distanced by the groove pitch for the main line (drawing an arc), the radial distance L ₁ between the spot of the main beam and the spot of the sub beam in the radial direction of the optical disk 12 is given by Equation 20.

[0099]

[Formula 20] L ₁ = R × sin θ ₁ = 0.37 +
0.74 × N ₁ where R is the distance between the main spot and the sub-spot θ ₁ : The angle formed by the straight line connecting the main spot and the sub-spot and the tangent to the groove irradiated with the main beam Next, referring to FIG. The case of a DVD-RAM will be described with reference to FIG. In the conventional optical disk device, the sub-beam is applied to the land or the grooves adjacent to both sides of the land to which the main beam is applied, as depicted by a dotted circle in the drawing. In this case, the optical disc 12 having the spot of the main beam and the spot of the sub beam on one side
The radial distance L ₂ is 0.615 μm.

Sub-beam (Secondary sub-beam: DVD-R
As shown in FIG. 16, the position of the spot of the sub beam for AM is moved away from the land or groove irradiated with the main beam by a groove pitch of N ₂ while keeping the distance from the spot of the main beam as it is ( In the case of drawing a circular arc), the radial distance L ₂ between the main beam spot and the sub beam spot is ₂
Can be obtained at.

[0101]

[Equation 21] L ₂ = 2 × R × sin θ ₂ = 0.61
5 + 2 × 0.615 × N ₂ However, 2 × R: distance between main spot and sub-spot θ ₂ : straight line connecting main spot and sub-spot and tangent to land or groove irradiated with main beam Angle Here, N ₂ is an integer such that θ ₂ is closest to θ ₁ .

[0102] and was placed the sub-beam (second-order sub-beams) for the DVD-RAM in θ ₁ instead of θ _2. At this time, the distance between the spot of the main beam and the spot of the sub beam in the radial direction of the optical disk 12 is L ₂ [θ ₁ ] (= 2 ×
R × sin θ ₁ ), and the difference between L ₂ [θ ₁ ] and L ₂ is ΔL ₂
And

Then, N ₁ is changed to specify θ ₁ that minimizes this ΔL ₂ . Each value of the time went to N ₁ is changed are shown in Table 2, shows the deviation from the track of the sub-beams when changing the N ₁ in FIG.

[0104]

[Table 2]

As N ₁ is increased, the sub-beam spreads to the outer and inner circumferences of the optical disk 12, so that the number of tracks that the main beam cannot access increases in the outermost and innermost areas. Also, when N ₁ is increased,
As shown in Table 2 and FIG. 17, ΔL ₂ changes periodically. Therefore, it is preferable to _first select N ₁ which gives the minimum absolute value of ΔL ₂ .

As a result, N₁= 4, N₂= 5, θ₁= 1
0.481, θ₂= 10.643, ΔL ₂= 0.105
The value is obtained. According to this result, the main bee
Spot, primary sub beam spot and next sub beam
The straight line formed by the beam spot and the main beam
The angle formed by the tangent to the track being tracked is 10.481.
It is deg.

When θ = θ ₁ , the primary sub-beam is D
The secondary sub-beam is irradiated to the center of the VD-R / RW track and the secondary sub-beam is 0.10 from the center of the DVD-RAM track.
Irradiation is performed at a position shifted by 5 μm.

In the case of DVD-R / RW, the sub beam is located at a position four groove pitches away from the main beam, and in the case of DVD-RAM,
The spot of the sub-beam is located at a position separated from the spot of the main beam by about 5 groove pitches.

When θ = θ ₂ , the primary sub-beam is 0.105 from the center of the DVD-R / RW track.
The secondary sub-beam is irradiated on the position shifted by μm
It is irradiated to the center of the D-RAM track.

Unless the performance of either the DVD-R / RW or the DVD-RAM is emphasized, θ may be set to a value between θ ₁ and θ ₂ .

As described above, DVs having different track pitches are used.
In both of the D-R / RW and the DVD-RAM, the sub-beams are arranged at almost the center of the track width. Therefore, even if the optical sensor is displaced for some reason,
As described above, since the disturbance can be canceled by using the differential astigmatism method, the FE signal becomes “0” and the FE signal is not affected by the disturbance. Therefore, an offset does not occur in the FE signal, and the offset does not deteriorate the recording and reproducing performance.
Therefore, the DVD-R / RW and the DVD-RAM can be reproduced by one drive device.

The embodiment described above can be modified in various ways. For example, in the above example, the ± 1st order light is used for DVD-R / RW, and the ± 2nd order light is used for the DVD-RAM.
However, on the contrary, ± 1st order light is used for DVD-RAM,
The secondary light may be for DVD-R / RW.

[Brief description of drawings]

FIG. 1 is an illustrative view showing the overall configuration of an embodiment of the present invention.

FIG. 2 is an illustrative view showing an example of an optical pickup.

FIG. 3 is an illustrative view showing one configuration example of a light receiving sensor.

FIG. 4 is an illustrative view showing spot positions on a DVD-R / RW.

FIG. 5 is an illustrative view showing spot positions on a DVD-RAM.

FIG. 6 is an illustrative view showing a far field pattern.

FIG. 7 is an illustrative view showing a far field pattern.

FIG. 8 is an illustrative view showing one configuration example of a light receiving sensor.

FIG. 9 is an illustrative view showing a far field pattern.

FIG. 10 is an illustrative view showing a far field pattern.

FIG. 11 is an illustrative view showing spot positions of a DVD-R / RW.

FIG. 12 is an illustrative view showing spot positions on a DVD-RAM.

FIG. 13 is an illustrative view showing a track shift of a sub beam.

FIG. 14 is an illustrative view showing one configuration example of a light receiving sensor.

FIG. 15 is an illustrative view showing spot positions of DVD-R / RW.

FIG. 16 is an illustrative view showing spot positions on a DVD-RAM.

FIG. 17 is an illustrative view showing a track shift of a sub beam.

[Explanation of symbols]

10 ... Optical disk device 18 ... Optical pickup 30 ... Laser diode 32 ... Diffraction grating 34 ... Polarizing beam splitter 36… Front monitor 38 ... Collimator lens 40 ... Quarter wave plate 42 ... Reflective mirror 44 ... Objective lens 46 ... Cylindrical lens 48 ... Light receiving sensor

Continued front page    F-term (reference) 5D118 AA14 AA26 BA01 CA23 CF06                       CG03 CG05 CG14 CG24 CG33                       CG36 CG44 CG47 DA33 DA35                 5D119 AA41 BA01 CA16 EB14 EC45                       EC46                 5D789 AA41 BA01 CA16 EB14 EC45                       EC46

Claims (6)

[Claims] 1. An optical disc device for recording or reproducing information on a first optical disc and a second optical disc having different track pitches, and using a differential push-pull method for tracking control, the main optical disc being a track to be tracked. An optical disc including a first irradiating unit for irradiating a beam and a second irradiating unit for irradiating the sub-beam to a position where the deviation from the center of the track is minimized regardless of whether the first optical disc or the second optical disc is irradiated. apparatus. 2. The optical disk device according to claim 1, wherein the minimum position is a position closest to the track irradiated with the main beam. 3. An optical disk device for recording or reproducing information on a first optical disk and a second optical disk having different track pitches, and using a differential push-pull method for tracking control, which is a main optical disk for a track to be tracked. An optical disk device comprising: a first irradiation means for irradiating a beam, a second irradiation means for irradiating a primary sub-beam for the first optical disk, and a third irradiation means for irradiating a secondary sub-beam for the second optical disk. 4. The second irradiating means forms an angle θ between a straight line formed by the spot of the main beam and the spot of the primary sub-beam and a tangent line of the track irradiated with the main beam, and the track of the primary sub-beam. The primary sub-beam is irradiated at a position where the deviation from the center is minimal, and the third irradiation means causes the straight line formed by the spot of the main beam and the spot of the secondary sub-beam and the tangent of the track on which the main beam is irradiated. 4. The optical disk device according to claim 3, wherein the angle is θ, and the secondary sub-beam is irradiated at a position where the deviation of the secondary sub-beam from the center of the track is minimal. 5. A method for determining the irradiation position of a sub-beam in an optical disk device, wherein information is recorded on or reproduced from a first optical disk and a second optical disk having different track pitches, and a differential push-pull method is used for tracking control. (A) the track pitch of the first optical disk is P ₁ , (b) the track pitch of the second optical disk is P _2, and (c) the main beam spot and the sub-beam spot of the first optical disk. the temporary distance in the radial direction is ## EQU1 ## _{L 1 = P 1/2 +} P 1 × N 1 (N 1 is an integer), (d) of the second optical disc with the main beam spot and the sub-beam spot and the temporary distance in the radial direction Equation 2] _{L 2 = P 2/2 +} P 2 × N 2 (N 2 is an integer), (e) N ₂ is L ₁ is the L ₂ It is an integer such that (f) the intermediate value between L ₁ and L ₂ is L, (g) the difference between the intermediate values L and L ₁ is ΔL _1, and (h) the absolute value of ΔL ₁ The intermediate value L is determined on the basis of N _{1 at} which is minimized, and (i) the distance between the spot of the main beam and the spot of the sub beam in the radial direction of the first optical disc or the second optical disc is L. A method for determining the irradiation position of a sub-beam, wherein the sub-beam is arranged in the. 6. A method for determining a sub-beam irradiation position in an optical disk device, wherein information is recorded on or reproduced from a first optical disk and a second optical disk having different track pitches, and a differential push-pull method is used for tracking control. (A) Irradiating one main beam, two primary sub-beams and two secondary sub-beams to a position where the secondary sub-beam is located outside the main beam and the primary sub-beam to form a straight line. (B) The provisional angle formed by the straight line formed by the spot of the primary sub-beam and the spot of the main beam and the tangent of the track irradiated with the main beam is θ _1, and (c) of the secondary sub-beam. A straight line formed by a spot and the spot of the main beam and a track irradiated with the main beam Of the tangent line to θ ₂ , (d) the track pitch of the first optical disk is P ₁ , (e) the track pitch of the second optical disk is P _2, and (f) the main beam The distance between the spot and the spot of the primary sub-beam is R, (g) the distance between the spot of the main beam and the spot of the secondary sub-beam is 2R, (h) the spot of the main beam and the primary sub-beam the Equation 3] the length of the first optical disk in the radial direction _{L 1 = R × sinθ 1 =} P 1/2 + P 1 × N 1 (N 1 is an integer), and, (i) the main beam spot spot with the the length of the second optical disk in the radial direction of the spot of the second sub-beams and Equation 4] _{L 2 = 2 × R × sinθ} 2 = P 2/2 + P 2 × N 2
(N ₂ is an integer), (j) N ₂ is an integer such that θ ₂ is closest to θ ₁ , and (k) ## EQU5 ## L ₂ '= 2 × R × sin θ _1, and (l) The difference between L ₂ 'and L ₂ is ΔL _2, and (m) θ ₁ and θ ₂ are determined based on N ₁ when the absolute value of ΔL ₂ is a minimum, and (n) the primary sub-beam Of the primary sub-beam and the spot of the secondary sub-beam and the spot of the main beam and the tangent to the track irradiated with the main beam, the angle θ is θ ₁ ≦ θ ≦ θ ₂ A method for determining an irradiation position of a sub-beam, wherein a sub-beam and the secondary sub-beam are arranged.