JPH07192288A - Optical disk device - Google Patents

Abstract

PURPOSE:To highly accurately perform the tracking control of an optical disk provided with thew address area of a track recorded at the groove part or the land part of the track on the disk in the form of uneven pits at least. CONSTITUTION:Only the address area recording the output of a second track deviation detecting means 8 by a phase difference method in the form of uneven pits is sampled/held by a sample/hold means 9. Based on that output, a correct signal is prepared by a correct signal generating means 12, and a moving means 7 of an optical head 14 is controlled by correcting the output of a first track deviation detecting means 4 constituted by a push-pull method while using a synthesizing means 5. Thus, the component of tracking offset generated in the push-pull method is reduced.

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 for irradiating a focused light beam on an optical disk having a plurality of tracks to record or reproduce information.

[0002]

2. Description of the Related Art Conventionally, a light beam generated from a light source such as a semiconductor laser is focused on a rotating optical disk by a focusing lens or the like to irradiate information on the optical disk. 2. Description of the Related Art There is known an optical reproducing apparatus which reproduces a recorded signal or a recorded signal.

FIG. 13 schematically shows a recording surface of an optical disc used in such an optical reproducing apparatus. On the disk, a minute track 1000 having a width W of 0.6 μm and a pitch P of 1.6 μm (projection in the figure)
Are provided spirally or concentrically. Further, a mark indicating the address area 1100 of the track 1000 is formed on the track by a convex portion 1101 and a concave portion 1102. A recording film such as a phase change recording material is formed on the surface of the disk by a method such as sputtering. When recording information on a disc, focus control is performed so that the light beam spot is always located on the recording film, and tracking control is performed so that the light beam spot is located on the track, while By modulating the intensity according to the information to be recorded, the reflectance of the recording material changes and the information is recorded. When reproducing the recorded information, the focus control and the tracking control are similarly performed, and the change in the amount of light reflected from the disc is detected.

A signal indicating the amount of deviation of the focal position of the light beam spot from the recording film (hereinafter referred to as a focus error signal) is detected by a detection method generally called astigmatism method. Focus control is performed by driving the focusing lens in the direction orthogonal to the recording surface according to the focus error signal.

A signal representing the amount of deviation of the light beam spot from the track (hereinafter referred to as tracking error signal).
Is detected by a detection method generally called push-pull method. The tracking control is performed by driving the focusing lens in the direction orthogonal to the track according to the tracking error signal.

FIG. 14 shows an example of a tracking error signal by the push-pull method. When the light beam spot is located at the center of the track, the tracking error signal becomes zero, and when it shifts to the inner circumference side of the disc, it becomes a positive value.
If it shifts toward the outer circumference of the disc, it will be a negative value. Also, when the light beam spot is located between tracks, the tracking error signal becomes zero, and it has a negative value when it shifts to the inner circumference side of the disc, and has a positive value when it shifts to the outer circumference side of the disc. . That is, the polarities of the tracking error signals are opposite between the center of the track and the middle of the tracks. By the way, since the required band of the tracking control system is generally several kHz or less, a tracking error signal is input to a low pass filter having a cutoff frequency of several tens of kHz, and tracking control is performed based on the output signal of the low pass filter. . Since the concave-convex pit for the address is generally recorded at several MHz, if the tracking error signal is input to the low-pass filter having the cutoff frequency of several tens of kHz, the output signal of the low-pass filter in the address area has a low detection sensitivity. It becomes a signal indicating the amount of deviation of the light beam spot from the track.

By the way, there is a strong demand for increasing the capacity of each recording medium or reducing the size of the recording medium. In order to meet this demand, information is recorded not only on the tracks of the optical disk but also on the recesses between the tracks. A recording method has been proposed. As described above, in the push-pull method, the polarities of the tracking error signal in the convex portion and the concave portion are opposite,
By switching the polarity of the tracking error signal, it is possible to control so that the light beam spot is located in the recess. Below, the convex part is called the groove part track,
The recess is called a land track.

[0008]

However, in order to detect the tracking error signal detected by the push-pull method, the tilt of the disk (hereinafter referred to as tilt) and the deviation from the center of the optical beam of the lens optical axis (hereinafter referred to as the lens). Offset occurs due to factors such as shift.
On the other hand, when recording information on both the land and groove, it is necessary to reduce crosstalk from adjacent tracks, and conventional tracking detection realizes high-density recording because track deviation occurs due to offset. I couldn't.

The present invention solves the above problems in the conventional optical disk device, eliminates the influence of the offset generated in the tracking error signal, and provides a high density optical disk for recording information on the groove track and the land track. It is an object of the present invention to provide an optical disk device capable of performing suitable and highly accurate tracking control.

[0010]

In order to achieve the above object, the optical disk device of the present invention comprises a first track deviation detecting means for detecting a positional deviation between a light beam spot and a track by a push-pull method, Moving means for moving the position of the beam spot in a direction substantially perpendicular to the track direction of the disk, and control for controlling the moving means so that the light beam spot follows the track according to the output signal of the first track deviation detecting means. Means, a second track deviation detecting means for detecting a positional deviation between the light beam spot and the track by a phase difference method, and a sample hold signal generating means for changing the output each time the light beam spot passes through the track address area. And a sample and hold circuit for sampling and holding the output of the second track deviation detecting means in accordance with the output of the sample and hold signal generating means. Ruhorudo means and, first from the output of the sample-and-hold means generates an offset correction signal
And a correction signal generating means for correcting the output signal of the track deviation detecting means.

In addition to the above structure, the present invention further comprises polarity switching means for inverting the polarity of the output of the first track deviation detecting means at the groove portion and the land portion of the track.

[0012]

According to the present invention, with the above-described structure, the offset is corrected by detecting the address area of the track recorded in the form of concave and convex pits by a relatively stable phase difference method against tilt and lens shift. The influence of can be reduced.

The present invention can also be applied to a disc in which information is recorded / reproduced on both the groove portion and the land portion of the track by providing the polarity switching means.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk device according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an optical disk device for recording information on at least one of a groove track and a land track. Figure 1
In FIG. 1, 1 is a disc for recording information, 2 is a motor for rotating the disc 1, 3 is a photodetector for detecting reflected light from the light beam spot S irradiated on the disc 1, and 4 is a photodetector 3. From the output, the first track deviation detecting means for detecting the positional deviation between the light beam spot S and the track by the push-pull method, 5 is a combining means for combining the signals, and 6 is an output signal of the first track deviation detecting means 4. Control means for controlling the moving means 7 so that the light beam spot S follows the track in accordance with the
Is a moving means for moving the position of the track substantially perpendicularly to the track direction of the disk 1, and 8 is a second track deviation detecting means for detecting the positional deviation between the light beam spot S and the track from the output of the photodetector 3 by the phase difference method. , 9 are sample and hold means for sampling and holding the output of the second track deviation detecting means 8 according to an output from a sample and hold signal generating means 11, which will be described later, and 10 is an RF signal detection for detecting an RF signal from the photodetector 3. Means, 11 is a sample and hold signal generating means for changing the output from the output of the RF signal detecting means 10 every time the light beam spot S passes through the address area of the track, and 12 is an offset correction signal from the output of the sample and hold means 9. It is a correction signal generating means for generating and correcting the output of the first track deviation detecting means 4. Reference numeral 13 is a light source such as a semiconductor laser for irradiating the light beam spot S on the disk 1, and 14 is an optical head in which the light source 13 and the optical system and the photodetector 3 are integrated and driven by the moving means 7.

As shown in FIG. 2, the disk 1 is a disk in which an address area 1100 of a track recorded in the form of concave and convex pits is provided on at least one of the groove track 1101 and / or the land track 1102. Although an example provided on both sides is shown, in the present embodiment, the address area 11 is provided only on the groove track 1001.
An example in which 00 is provided will be described. Reference numeral 1200 is a data area in which data is recorded in the address area 1100.
The motor 2 is controlled so that the disk 1 rotates at a predetermined rotation speed. The reflected light emitted from the light source 13 to the disk 1 and reflected is received by the photodetector 3 divided into four, and is output from the output terminals 31, 32, 33, and 34, respectively. The outputs from the output terminals 31, 32, 33 and 34 are input to the input terminals 41, 42, 43 and 44 of the first track deviation detecting means 4, respectively. The first track deviation detecting means 4 is constructed by a tracking error detecting method generally called push-pull method. The tracking error signal is output from the output terminal 45,
It is inputted to the input terminal 61 of the control means 6 through the synthesizing means 5. The output terminal 62 of the control means 6 is connected to the input terminal 71 of the moving means 7, the optical head 14 is moved by the moving means 7, and the light beam spot S on the disk 1 is at the center of the groove track or land track. Tracking is controlled so that it is located at.

On the other hand, four output terminals 31 of the photodetector 3,
The outputs from 32, 33 and 34 are also input to the four input terminals 81, 82, 83 and 84 of the second track deviation detecting means 8. The second track deviation detecting means 8 is constructed by a tracking error detecting method generally called a phase difference method. The output terminal 85 of the second track deviation detecting means 8 is connected to the input terminal 91 of the sample hold means 9. Further, the RF signal detection means 10 inputs the outputs from the four output terminals 31, 32, 33 and 34 of the photodetector 3 to the input terminals 101, 102, 103 and 104, respectively, synthesizes them and outputs them to the output terminal 105. Output an RF signal. In addition, the sample and hold signal generating means 11 uses RF
The RF signal from the signal detecting means 10 is input to the input terminal 111, and the signal whose level changes in the address area is output to the output terminal 112. The output of the sample hold signal generating means 11 is connected to the control input terminal 93 of the sample hold means 9. Therefore, in the sample hold means 9, when the control input terminal 93 is at the high level, that is, the address area, the output level of the second track deviation detecting means 8 is sampled, and when the control input terminal 93 is at the low level, that is, other than the address area. , The sampled level is held and output from the output terminal 92. The output of the sample hold means 9 enters the input terminal 121 of the correction signal generating means 12, and the correction signal output is output from the output terminal 122. This correction signal generating means 12
Is combined with the output of the first track deviation detecting means 4 by the synthesizing means 5 to obtain the first track deviation detecting means 4
The offset caused by the tilt, lens shift, etc. generated in the output of 1 is canceled out, and the control means 6 and the moving means 7 enable highly accurate tracking.

Next, the operation of the optical disk device shown in FIG. 1 will be described in more detail. FIG. 3 shows in detail the part of the photodetector 3 divided into four in FIG. The outputs of the four photodetector units A, B, C, D are output terminals 31,
32, 33 and 34, respectively. FIG. 4 is a block diagram of the first track deviation detecting means 4 by the push-pull method. 4 input terminals 41, 42, 43, 4
Outputs of the photodetector 3 divided into four are connected to 4. By the resistors 401 and 402, the photodetectors A and D
Of the photo detectors B and C are combined by the resistors 403 and 404. Further, the combined two signals have high frequency components removed by capacitors 405 and 406, are input to a subtractor 407, and output to an output terminal 45. That is, a signal corresponding to the light amount difference (A + D) − (B + C) on the left and right of the photodetector divided into four parts is obtained at the output terminal 45.

FIG. 5 shows the relationship between the track deviation and the tracking error signal. When the light reflected from the disc 1 deviates from the center of the four-division photodetector 3 to the left and right, the output changes as shown in FIG. 5, and the track deviation can be detected. However, in such a push-pull method, an offset is likely to occur in the output due to tilt or lens shift, and tracking is likely to be unstable.

FIG. 6 is a block diagram of the second track deviation detecting means 8 by the phase difference method. Four input terminals 81,
Outputs of the photodetector 3 divided into four are connected to 82, 83, and 84, respectively. The signals at the input terminals 81 and 82 are combined at the resistors 801 and 802, and the signals at the input terminals 83 and 84 are combined at the resistors 803 and 804 and input to the comparators 805 and 806, respectively. The outputs of the two comparators 805 and 806 are input to the phase comparator 807. That is, the sum of the two diagonals of the photodetector 3 (A + B)
And (C + D) are binarized by comparators 805 and 806, respectively, and a phase comparator 807 detects the phase difference between the two signals.

FIG. 7 shows the relationship between the input and output of the phase comparator 807. When the light beam spot S is at the center of the track on the disk 1, the relationship between the input and the output is shown in FIG.
The output is 0 because there is no phase shift as shown in (a). Next, when the light beam spot S is outside the center of the track on the disk 1, the relationship between the input and the output is shown in FIG.
As shown in (b), a positive pulse proportional to the input phase difference is generated at the output. On the contrary, when the light beam spot S is located inside the center of the track on the disk 1, the relationship between the input and the output is as shown in FIG. 7C, and the output is proportional to the phase difference of the input. Negative pulse occurs. The output of this phase comparator 807 is the resistance 808 and the capacitor 8
Output terminal 8 through a low pass filter composed of
5, the signal proportional to the track deviation is obtained at the output terminal 85.

In this phase difference method, since the phase difference occurring in the output of the photodetector 3 when the light beam spot S passes through the concave and convex pits on the disk 1 is detected, the track shift is detected in the portion where there is no signal. Can not do it. However, even in the case of a recording / reproducing disc, it is possible to detect a track shift in the address area prerecorded in the form of uneven pits. Therefore, as shown in FIG. 8A, the sample hold signal generating means 11 of FIG.
Each time the optical head 14 passes through the address area 1100, as shown in FIG. 8B, a signal that changes to a high level is created, and the signal is added to the control input terminal 93 of the sample hold means 9 of FIG. The tracking output by is sample-held. Then, the output of the sample hold means 9 changes as shown in FIG. 8C following the track shift component due to the offset, and the correction signal generation means 12 uses the correction signal shown in FIG. 8D based on this signal. And the output of the first track deviation detecting means 4 configured by the push-pull method is corrected by the synthesizing means 5,
The offset amount of the push-pull method can be reduced as shown in FIG. The reason why the tracking control is not performed only by the sampled and held output of the phase difference method is that the frequency at which the address area 1100 passes through the optical head 14 is about several hundred Hz, so that the tracking control reaches several kHz. This is because the bandwidth cannot be secured.

Next, an optical disk device according to the second embodiment of the present invention will be described with reference to FIG. This embodiment is shown in FIG.
As shown in FIG. 5, this is an example of an optical disk device using a disk in which the address areas of the tracks to be recorded in the form of concave and convex pits are recorded in both the groove track 1001 and the land track 1002. This embodiment is the first shown in FIG.
The embodiment is different from the first embodiment in that the first track deviation detecting means 4
Since the polarity switching means 15 for reversing the polarity between the groove portion and the land portion is provided between the synthesizing means 5 and the synthesizing means 5,
The other same elements are given the same numbers, and the description of the configuration is omitted.

The output terminals 31, 32, 33 of the photodetector 3,
The outputs from 34 are input to the input terminals 41, 42, 43 and 44 of the first track deviation detecting means 4, respectively.
The tracking error signal output from the output terminal 45 of the first track deviation detecting means 4 is input to the input terminal 151 of the polarity switching means 15. The polarity switching means 15 inverts the polarity of the input signal when tracking the groove track 1001 of the disc 1 while keeping the polarity of the input signal and when tracking the land track 1002. Output to the output terminal 152. Polarity switching means 1
The output of 5 is input to the input terminal 61 of the control means 6 through the synthesizing means 5. The output of the control means 6 is connected to the input terminal 71 of the moving means 7, and the moving means 7 causes the optical head 1 to move.
4 is moved, the light beam spot S on the disc 1 becomes
Groove track 1001 or land track 1
Tracking control is performed so as to be located at the center of 002.

FIG. 10 shows the relationship between the tracks on the disk 1 and the output signals of the polarity switching means 15. Control means 6 for controlling the moving means 7 and performing tracking control
Is designed to pull in a negative gradient when the polarity of the signal applied to the input terminal 61 goes toward the outer circumference of the disk. Therefore, when the input / output relationship of the polarity switching means 15 is in the non-inverted state, tracking control is performed on the groove track 1001 of FIG.
By reversing the input / output relationship of No. 5, the land portion track 1002 shown in FIG. At this time, the polarity of the offset generation by the push-pull method is the same polarity as seen from the input terminal 61 of the control means 6 regardless of whether it is the groove track 1001 or the land track 1002. The output of the deviation detecting means 8 is sampled and held by the sample and hold means 9, the correction signal is generated by the correction signal generating means 12 based on the output, and the polarity switching means 15 is generated by the synthesizing means 5.
By correcting the output of No. 1, it is possible to reduce the offset amount of the push-pull method regardless of whether it is the groove track 1002 or the land track, and it is possible to perform highly accurate tracking control.

Next, the sample hold signal generating means 11 in this embodiment will be described with reference to FIG.
The sample and hold signal generating means 11 is the sample and hold signal generating means 1 in the first embodiment.
It is the same as 1. FIG. 12 shows the structure of the sector format of the disk used in this embodiment. 12
As shown in (a), one sector is composed of an address area and a data area. Further, the address area follows a sector mark indicating the beginning of a sector, and an address mark and ID a.
The nd CRC pair is written in triplicate. Therefore,
In FIG. 11, the start detecting means 113 detects the sector mark to detect the start of the address area, and the end detecting means 114, as shown in FIG.
The address mark located third from the sector mark is detected as shown in FIG. Then, by connecting the output of the start detection means 113 to the set input terminal of the RS flip-flop 115 and connecting the output of the end detection means 114 to the reset input terminal, the output of the RS flip-flop 115, that is, the sample hold. As an output of the signal generation means 11, FIG.
Can be obtained. By performing sample-holding by the sample-holding means 9 based on this signal, it is possible to detect the track shift signal in the address area recorded in the form of concave and convex pits.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and a phase change recording material was used as a recordable recording material. A mold recording material can also be used.

[0027]

As is apparent from the above-described embodiment, the present invention is carried out by detecting the positional deviation between the light beam spot for reproducing a signal from the recording surface of the disk or recording the signal and the track by the push-pull method. In contrast to normal tracking control, the positional deviation between the light beam spot and the track is corrected by generating an offset correction signal based on the signal detected by the phase difference method in the address area of the track recorded in the form of uneven pits. As a result, it is possible to reduce the effect of offset on tilt and lens shift.
Highly accurate tracking control is possible, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing tracks of an optical disc in the example.

FIG. 3 is a schematic diagram of a photodetector in the same example.

FIG. 4 is a block diagram of a first track deviation detecting means in the embodiment.

FIG. 5 is a signal waveform diagram showing a tracking error signal in the example.

FIG. 6 is a block diagram of a second track deviation detecting means in the embodiment.

FIG. 7 is a signal timing chart of essential parts of the second track deviation detecting means in the embodiment.

FIG. 8 is a signal timing diagram of main parts in the address area of the embodiment.

FIG. 9 is a block diagram of an optical disc device according to a second embodiment of the present invention.

FIG. 10 is a signal timing chart showing the output of the track of the optical disc and the polarity switching means in the embodiment.

FIG. 11 is a block diagram of sample hold signal generating means in the first and second embodiments of the present invention.

FIG. 12 is a sector structure and signal timing diagram of an optical disc according to a second embodiment of the present invention.

FIG. 13 is a schematic diagram showing tracks on an optical disc.

FIG. 14 is a signal waveform diagram showing a tracking error signal of an optical disc in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 disk 2 motor 3 photodetector 4 first track deviation detection means 5 combining means 6 control means 7 moving means 8 second track deviation detection means 9 sample hold means 10 RF signal detection means 11 sample hold signal generation means 12 correction Signal generating means 13 Light source 14 Optical head 15 Polarity switching means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kanji Tadashi Hirohiro 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Shinichi Yamada 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Within the corporation

Claims (3)

[Claims] 1. A first track deviation detecting means for detecting a positional deviation between a light beam spot for reproducing a signal from a recording surface of a disc or recording a signal and a track by a push-pull method, and a position of the light beam spot. And a control means for controlling the moving means so that the light beam spot follows the track according to the output signal of the first track deviation detecting means. Second track deviation detecting means for detecting a positional deviation between the light beam spot and the track by a phase difference method, and a sample hold signal generation for changing the output each time the light beam spot passes through the track address area. Means and the output of the second track deviation detecting means in response to the outputs of the sample and hold signal generating means. Optical disk apparatus comprising: a sample-and-hold means for Rudo, a correction signal generating means for correcting the output signal of the generator to the first tracking error detection means offset correction signal from the output of said sample-hold means. 2. An optical disk device for recording / reproducing information on / from both tracks of a groove portion and a land portion, wherein a positional deviation between a light beam spot for reproducing a signal from the recording surface of the disk or a signal and a track is recorded. A first track deviation detecting means for detecting by a push-pull method, a polarity switching means for inverting the polarity of the output of the first track deviation detecting means between a groove portion and a land portion, and a position of the light beam spot of the disc. Moving means for moving in a direction substantially perpendicular to the track direction, control means for controlling the moving means so that the light beam spot follows the track in accordance with an output signal of the polarity switching means, and the light beam spot A second track shift detecting means for detecting a position shift with respect to the track by the phase difference method and the light beam spot are detected. And a sample and hold signal generating means for changing the output every time when passing through the address area of the clock, and a sample and hold means for sampling and holding the output of the second track deviation detecting means in accordance with the output of the sample and hold signal generating means. An optical disc device comprising: a correction signal generation unit that generates an offset correction signal from the output of the sample hold unit and corrects the output signal of the polarity switching unit. 3. A sample hold signal generating means has a start address detecting means and an end detecting means of a track address area, and outputs a sample signal each time the track address area passes by the output of the start detecting means. 3. The optical disk device according to claim 1, wherein a hold signal is output by the output of the end detecting means.