JP2001312831A - Tracking method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the detection of tracking error signals by the PDD method for various optical disks each having a different track pitch, with a single optical pickup and to permit the radiation of the optimum laser beam to each optical disk. SOLUTION: A laser irradiation position switching circuit 14 controls an actuator 15 for adjusting a PU position in accordance with the track pitch of an optical disk 3, and rotates the optical pickup 10 at a prescribed angle relative to the disk surface of the optical disk 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk tracking method and an optical disk recording / reproducing apparatus.
In particular, the present invention relates to an optical disk tracking method and an optical disk recording / reproducing apparatus that enable one optical pickup to perform appropriate tracking on various optical disks having different track pitches.

[0002]

2. Description of the Related Art There are various methods for detecting a tracking error of an optical disk, and a DPP method (Differential Push Pull) is known as a typical tracking error detection method used for a writable optical disk.

In the DPP method, as shown in FIG. 6, three beam spots are arranged on a recording surface of an optical disk at positions in the front-back direction of a track and shifted by 1/2 track pitch in the left-right direction of the track at linear and equal intervals. Then, the reflected light of the main spot m1 located on the track is detected by the 4-split photodetector, and the sub spot s1 and the main spot m1 located on the inner land adjacent to the track where the main spot m1 is located are located. The reflected light of the sub-spot s2 located on the land on the outer peripheral side adjacent to the track is detected by the two-segment photodetector, and the detection signals are added and subtracted for each of the four-segment photodetector and the two-segment photodetector, thereby obtaining three push-pull signals. , And use a predetermined arithmetic expression to cancel these offsets. Calculates and is obtained to detect the tracking error signal.

The above three beam spots divide one laser beam emitted from a laser diode into at least three laser beams of 0th-order diffracted light and ± 1st-order diffracted light by a diffraction grating, and irradiate the laser beam to an optical disk. Therefore, the arrangement interval of the three beam spots is uniquely determined by the wavelength of the laser beam emitted from the laser diode and the grating interval of the diffraction grating.

By arranging the diffraction grating in the optical pickup with its grating direction inclined at a predetermined angle with respect to the radial direction of the disk, the laser beam emitted from the optical pickup can form three beam spots formed on the optical disk. Are arranged linearly at a predetermined angle with respect to the tangent direction of the track, and as a result, are shifted by 1/2 track pitch in the left-right direction of the track at positions in the front-back direction of the track.
One beam spot can be obtained.

Incidentally, there are various optical disks having different track pitches, such as a CD and a DVD, for example.

[0007]

However, in the conventional optical disk recording / reproducing apparatus, the diffraction grating is fixedly arranged in the optical pickup at a predetermined angle corresponding to the track pitch of the predetermined optical disk. A tracking error signal of another type of optical disc could not be detected.

For example, in an optical pickup in which a diffraction grating is fixedly arranged at an angle corresponding to a track pitch of a CD (1.6 μm), the arrangement of three laser spots formed by a laser beam on an optical disk is the same as that of a DVD track. It cannot respond to the pitch (0.74 μm), and cannot detect a DVD tracking error signal.

Therefore, in the conventional optical disk recording / reproducing apparatus, in order to enable tracking of various optical disks having different track pitches by the above-mentioned DPP method,
A plurality of optical pickups respectively corresponding to a plurality of types of optical discs are prepared, or a diffraction grating is arranged at an angle at which three beam spots are arranged at intervals corresponding to an intermediate value of the track pitch of the plurality of types of optical discs. Measures such as using an optical pickup.

However, the method of using a plurality of optical pickups is not a preferable method because it leads to a significant increase in cost. In addition, the method of arranging laser spots at intervals corresponding to intermediate values of the track pitches of a plurality of types of optical discs is difficult. Optimal tracking cannot be performed for each optical disc, and the tracking performance deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and enables a single optical pickup to detect a tracking error signal by the PDD method for various optical disks having different track pitches. ,
An object of the present invention is to improve the tracking performance of an optical disk recording / reproducing apparatus for recording / reproducing various optical disks having different track pitches by enabling each of the optical disks to be irradiated with an optimal laser beam.

[0012]

In order to achieve the above-mentioned object, the present invention provides a main laser beam for forming a main beam spot on a track of an optical disk, and a straight line extending in the track direction with respect to the main beam spot. The optical disk is irradiated with two sub-laser beams forming two sub-beam spots located at equal and equal intervals on the optical disc, and the main laser beam and the sub-laser beam reflected from the optical disc are received as reflected light signals. In a tracking method for generating a tracking error signal based on a tangential direction of a line connecting a center of the main beam spot and a center of the sub beam spot corresponding to a track pitch of the optical disk and a track irradiated by the main laser beam. And the angle formed by the angle is changed.

That is, the present invention provides a three-beam method and a D-beam method.
The present invention relates to a tracking error signal detection method based on a differential push pull (PP) method.

According to such a method, the irradiation position of the laser beam can be changed so that the main beam spot and the sub beam spot are arranged at the optimum positions for the individual optical disks with respect to various optical disks having different track pitches. Therefore, it is possible to detect an appropriate tracking error signal for any optical disc.

According to the present invention, there is provided a main laser beam forming a main beam spot on a track of an optical disk, and two sub-beam spots positioned linearly and equidistantly from the main beam spot back and forth and right and left in the track direction. A tracking device that irradiates the optical disc with two sub-laser beams that form a laser beam and generates a tracking error signal based on a light receiving signal of reflected light of the main laser beam and the sub-laser beam from the optical disc,
An optical pickup for irradiating the main laser beam and the sub-laser beam onto the optical disc; and a line segment connecting a center of the main beam spot and a center of the sub-beam spot corresponding to a track pitch of the optical disc; A beam irradiation position adjusting means for adjusting the position of the sub-beam spot by changing an angle between a track irradiated by a laser beam and a tangential direction of the track is provided.

Here, the following two means can be applied as the beam irradiation position adjusting means.

1) Optical pickup rotation control means for adjusting the position of the sub-beam spot by rotating the entire optical pickup parallel to the optical disk surface at an angle corresponding to the track pitch of the optical disk.

That is, by changing the angle of the entire optical pickup with respect to the optical disk, the angle between the grating direction of the diffraction grating fixed to the optical pickup and the radial direction of the optical disk is adjusted. The irradiation position of the laser beam to the laser beam.

2) The diffraction grating for forming the main laser beam and the sub laser beam in the optical pickup is rotated about an optical axis thereof at an angle corresponding to a track pitch of the optical disk, thereby forming the sub beam. Diffraction grating rotation control means for adjusting the spot position.

That is, the diffraction grating is disposed in the optical pickup so as to be rotatable about its optical axis, and the angle of the diffraction grating in the direction of the grating with respect to the radial direction of the optical disk is changed so that the laser beam is transmitted to the optical disk. Change the irradiation position.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an optical disk tracking method and apparatus according to an embodiment of the present invention;

FIG. 1 is a block diagram showing an overall configuration of a first embodiment of an optical disk recording / reproducing apparatus according to the present invention.

In FIG. 1, this optical disk recording / reproducing apparatus includes an optical pickup 10, a CPU 20, a focus control circuit 11, a tracking control circuit 12, a feed control circuit 13, a laser irradiation position switching circuit 14, a PU position adjusting actuator 15, a spindle motor. Control circuit 16, RF
It comprises an amplifier 21, a signal processing circuit 22, a ROM 23 and the like.

The optical pickup 10 has a focus function controlled by a focus control circuit 11 and a tracking function controlled by a tracking control circuit 12. The optical pickup 10 is controlled by a feed control circuit 13. The optical disk 3 is configured to be slidable in the radial direction of the optical disk 3, and irradiates a laser beam following a desired track to record information on the optical disk 3 or read information recorded on the optical disk 3.

Various information read from the optical disk 3 by the optical pickup 10 is applied to a signal processing circuit 22 via an RF amplifier 21. Here, information read from the optical disc 3 by the optical pickup 10 includes a focus error signal (FE), a tracking error signal (TE), and an EFM (Eight to Fourteen Modulatio).
n) Signals, subcodes, etc. are included.

Among them, the focus error signal (FE)
And the tracking error signal (TE) are R
It is applied to a focus control circuit 11 and a tracking control circuit 12 via an F amplifier. The focus control circuit 11 and the tracking control circuit 12
The focus function and the tracking function of the optical pickup 10 are controlled based on the focus error signal (FE) and the tracking error signal (TE) added from 1.

The EFM signal of the information read from the optical disk 3 is subjected to error correction by the signal processing circuit 22, and then demodulated and output.

The subcode of the information read from the optical disk 3 is input to the CPU 20 via the RF amplifier 21 and the signal processing circuit 22.

FIG. 2 shows a schematic configuration of an optical system of the optical pickup 10 shown in FIG.

In FIG. 2, a laser beam emitted from a laser diode 101 is converted into a parallel beam by a collimator lens 102, enters a diffraction grating 103, and is split into at least three beams of 0-order diffracted light and ± 1st-order diffracted light. .

The light beam split by the diffraction grating 103 is
The beam enters the beam splitter 104, of which the 0th-order diffracted light is used as a main beam for recording and reproducing information, and the ± 1st-order diffracted light is used as a sub-beam for tracking control.

The light beam transmitted through the beam splitter 104 converges on the recording surface of the optical disk 3 via the objective lens 105, and three spots arranged linearly and at equal intervals by the 0th-order diffracted light and ± 1st-order diffracted light form the recording surface. Formed on top.

The light beam reflected on the recording surface contains the information recorded on the recording surface in its optical characteristics, enters the objective lens 105 again, becomes parallel light, and is reflected by the beam splitter 104 in the direction of 90 degrees. Then, in the photodetector 107 which forms an image on the photodetector 107 via the condenser lens 106, the EFM signal, the focus error signal,
The tracking error signal is converted into an electric signal and output to the RF amplifier 21 in FIG.

The optical disk recording apparatus according to this embodiment enables tracking of various optical disks having different track pitches. When the optical disk 3 is inserted into the optical disk recording / reproducing apparatus shown in FIG. The optical pickup 10 reads the value of the track pitch unique to the optical disk 3 recorded in, for example, a subcode, or the type information of the optical disk 3 from the optical disk 3 and transmits the read information to the CPU 20.

The optical pickup 10 includes an objective lens 105
The position of the optical disk 3 with respect to the disk surface is adjusted by the PU position adjusting actuator 15 so as to be able to irradiate an appropriate laser beam corresponding to the track pitch of various optical disks. .

The laser irradiation position switching circuit 14 is an optical pickup 1 whose arrangement angle is adjusted to an angle (reference position) corresponding to an optical disk having a reference track pitch.
Based on 0, the optical pickup 15 is controlled to rotate stepwise according to the value of the track pitch of the inserted optical disc or the type information.

The ROM 23 stores the rotation angle from the reference position of the optical pickup 10 with respect to the type of the optical disk and the value of the track pitch.

The CPU 20 determines the rotation angle of the optical pickup 10 from the reference position based on the value of the track pitch unique to the optical disk 3 read from the optical disk 3 by the optical pickup 10 or the type information of the optical disk 3. Obtained from the ROM 23.

Next, the CPU 20 outputs the rotation angle from the reference position acquired from the ROM 23 to the laser irradiation position switching circuit 14, and the laser irradiation position switching circuit 14
The PU position adjusting actuator 15 is controlled based on the rotation angle input from the optical disk 20 to rotate the optical pickup 10 about the optical axis of the objective lens 105 to adjust the angle of the optical pickup 10 with respect to the disk surface of the optical disk 3. I do.

FIG. 3 shows that the optical pickup 10 is rotated by a predetermined angle about the optical axis of the objective lens 105 so that the optical pickup 10 is rotated by a predetermined angle.
FIG. 9 is a diagram showing a state in which the arrangement of main spots m1 formed by second-order diffracted lights and sub-spots s1 and s2 formed by ± first-order diffracted lights on the recording surface of the optical disc 3 is changed.

In FIG. 3, an optical pickup 10 enables tracking of two types of optical discs having different track pitches, for example, a CD-R (reference disc) and a DVD-R (high-density disc). 10
5 is provided in the recording / reproducing apparatus so as to be rotatable in two stages of a reference position a and a position b corresponding to a high-density disc with the optical axis 5 as a center. The rotation operation of the optical pickup 10 can be realized, for example, by employing a piezoelectric element for the PU position adjustment actuator 15.

If the inserted optical disk 3 is a reference disk, the optical pickup 10 is held at the reference position a,
Spots in the row a corresponding to the reference disc are formed on the optical disc 3.

When the inserted optical disk 3 is a high-density disk, the optical pickup 10 operates the laser irradiation position switching circuit 1 via the PU position adjusting actuator 15.
4 to be rotated and held at the position 10b.

Then, as shown in FIG. 3 (b), the laser beam emitted from the optical pickup 10 emits a main spot m1 and a sub spot s formed on the recording surface of the optical disk.
When the main spot m1 is located on the center of the track with respect to the high-density disc, the sub-spots s1 and s2 become the main spot m1. Are located on the center of the land on both sides of the track where the track is located.

Since the CD-R and the DVD-R have different disk thicknesses and different wavelengths of the laser beam to be used, the objective lens 105 must be used to share the optical pickup 10.
And the laser diode 101 need to be switched. That is, the optical pickup 10 has an objective lens and a laser diode corresponding to a CD-R (a disc thickness of 1.2 mm and a used laser wavelength of 780 nm), and a DVD-R (a disc thickness of 0.6 mm and a used laser wavelength of 635 to 660 nm). It is necessary to provide an objective lens and a laser diode, respectively, and switch between them depending on the optical disk used. The switching of the objective lens and the switching of the laser diode can be easily realized by switching the circuit in the optical pickup 10 or the like.

Further, development of a high-density CD-R (HD-CD-R) which enables recording at a higher density than a CD-R while keeping the disc thickness and the used laser wavelength at the CD standard is currently in progress. However, if the HD-CD-R is compatible with the CD-R, it is not necessary to switch between the objective lens and the laser diode, and one optical pickup can handle the difference in recording density, that is, the difference in track pitch. The effect of the present invention that can be achieved is great.

In the above description, the optical pickup that rotates in two stages corresponding to two types of optical disks has been described. However, the optical pickup 10 is configured to be rotatable in multiple stages according to the type of optical disk. May be.

FIG. 4 is a block diagram showing an overall configuration of a second embodiment of the optical disk recording / reproducing apparatus according to the present invention.

In FIG. 4, the optical disk recording / reproducing apparatus is the same as the optical disk recording / reproducing apparatus shown in FIG.
Instead of the position adjustment actuator 15, a diffraction grating position adjustment actuator 17 is provided inside the optical pickup 10.

In this embodiment, as shown in FIG.
Diffraction grating 103 constituting optical system of optical pickup 10
Is rotated by the diffraction grating position adjusting actuator 17, and the diffraction grating 1 for the optical system of the optical pickup 10 is rotated.
By changing the diffraction direction of the transmitted laser light by changing the grating direction of 03, the irradiation position of the laser light on the optical disk can be changed as shown in FIG. Such a rotation operation of the diffraction grating 103 can be realized, for example, by employing a piezoelectric element as the diffraction grating position adjusting actuator 17.

[0051]

As described above, according to the present invention, in the detection of the tracking error signal by the DPP method, three laser beams emitted from the optical pickup corresponding to the track pitch of the inserted optical disk are detected. Since the irradiation position on the recording surface was changed,
For various optical disks having different track pitches, when the main beam irradiates a track, two sub-beams irradiate lands adjacent to the track, respectively. With a single optical pickup, and it is also possible to irradiate various types of optical discs with an optimal laser beam.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an optical disk recording apparatus according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of an optical pickup that includes a diffraction grating and emits a plurality of laser beams.

FIG. 3 is a diagram showing a relationship between rotation of the entire optical pickup and a laser irradiation position.

FIG. 4 is a block diagram showing a second embodiment of the optical disc recording apparatus according to the present invention.

FIG. 5 is a diagram illustrating a state in which a diffraction grating is rotated.

FIG. 6 is a diagram illustrating a method of generating a tracking error signal.

[Explanation of symbols]

 Reference Signs List 10 optical pickup 11 focus control circuit 12 tracking control circuit 13 feed control circuit 14 laser irradiation position switching circuit 15 PU position adjustment actuator 16 spindle motor control circuit 17 diffraction grating position adjustment actuator 21 amplifier 22 signal processing circuit 23 ROM 3 optical disk 101 laser diode 102 Collimator lens 103 Diffraction grating 104 Beam splitter 105 Objective lens 106 Condenser lens 107 Photodetector

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hironobu Shimizu 6-16-20 Ueno, Taito-ku, Tokyo Inside Taiyo Denki Co., Ltd. (72) Inventor Shinsei Sekiguchi 6-16-20, Ueno, Taito-ku, Tokyo No. Taiyo Denki Co., Ltd. (72) Inventor Isao Matsuda 6-16-20 Ueno, Taito-ku, Tokyo F-term in Taiyo Denki Co., Ltd. (reference) EB13 EC41 FA05 JA22 JA51 LB07

Claims (4)

[Claims] 1. A main laser beam for forming a main beam spot on a track of an optical disk and two sub beam spots linearly and equidistantly positioned with respect to the main beam spot back and forth and right and left in the track direction. A tracking method for irradiating the optical disk with a sub-laser beam and generating a tracking error signal based on a light receiving signal of reflected light of the main laser beam and the sub-laser beam from the optical disk; And changing an angle between a line segment connecting the center of the main beam spot and the center of the sub-beam spot and a tangent direction of a track irradiated by the main laser beam. . 2. A main laser beam for forming a main beam spot on a track of an optical disk and two sub beam spots linearly and equidistantly positioned in front and rear and right and left of the main beam spot in a track direction. A tracking device that irradiates the optical disk with the sub-laser beam and generates a tracking error signal based on a reception signal of reflected light of the main laser beam and the sub-laser beam from the optical disk. An optical pickup that irradiates a main laser beam and the sub-laser beam; and a line segment connecting a center of the main beam spot and a center of the sub-beam spot corresponding to a track pitch of the optical disc, and the main laser beam irradiates. By changing the angle between the track and the tangential direction, Tracking apparatus characterized by comprising a beam irradiation position adjusting means for adjusting the spot position. 3. The optical pickup rotating means for adjusting the position of the sub-beam spot by rotating the entire optical pickup parallel to the optical disk surface at an angle corresponding to the track pitch of the optical disk. 3. The optical disk recording / reproducing apparatus according to claim 2, further comprising control means. 4. The beam irradiation position adjusting method according to claim 1, wherein a diffraction grating for forming the main laser beam and the sub-laser beam in the optical pickup has an angle corresponding to a track pitch of the optical disc with its optical axis as a center. 3. The optical disk recording / reproducing apparatus according to claim 2, further comprising: a diffraction grating rotation control unit that adjusts the position of the sub-beam spot by rotating.