JPH0554410A - Tracking device - Google Patents

Abstract

PURPOSE:To facilitate stable tracking operation by discriminating the direction of positional deviation between irradiated light and a guiding groove based upon meandering information and the reflected light, and then by relatively controlling a position between the guiding groove and the reflected light according to the discriminating result so as to reduce the offset of tracking signal. CONSTITUTION:A photodetector provided with photoelectric conversion elements A, B, C and D converts the light reflected on an optical disk into electrical signal and, by an adder 22 and a subtractor 23, obtains a sum signal HF and a difference signal TE, respectively. The TE is inputted into a wobbling separation means consisting of a BPF 25 and a comparator 26 and is separated from a wobbling content so as to output a meandering information ATIP. The HF and the ATIP are arithmetically processed in the interrelation with the LIF and the TE by a BPF 24, a multiplier 27 and an integrator 28. The comparator 29 discriminates the direction of positional deviation between an irradiated light and a guiding groove and then controls a relative position between the guiding groove and the irradiated light through a U/D counter 30 based upon the discriminating result. So, the affection from an offset is reduced and stable operation is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention focuses light on a track such as a pit row or a guide groove formed on a recording medium such as an optical disk, irradiates the track with a light spot, and the light spot tracks the track. However, the present invention relates to a tracking device that controls the track and the light spot so that the track and the light spot move relative to each other.

[0002]

2. Description of the Related Art The push-pull method is already known as a method for detecting the positional deviation between a light spot and a track. This system irradiates a two-divided photodetector that converts the light in which one set of the first-order component of the diffracted light by the track is superimposed on the zero-order component of the reflected light from the recording medium into an electric signal, to form a light spot and a track. The change in the balance of one set of primary components due to the positional relationship of is converted into an electric signal, and tracking control is performed by the difference signal. In this method, the center axis of the reflected light from the recording medium is displaced from the boundary of the two-divided photodetector because the lens tracks the track or the recording medium and the irradiation term axis to the recording medium are not perpendicular.

[0003]

Since the conventional tracking device using the push-pull method operates as described above, when the central axis of the reflected light is displaced from the boundary of the two-division photodetector, a light spot is generated. An electric signal irrelevant to the positional relationship with the track is generated, and an offset is superimposed on the difference signal that is the control signal. If tracking control is performed using this difference signal, the light spot is irradiated at a position deviated from the track due to the offset, and the original intended light spot cannot be irradiated to the track.

The present invention has been made to solve the above problems, and a tracking device capable of reducing the influence of an offset superimposed on a tracking signal by a push-pull method or the like in an optical disk and performing a stable tracking operation. Bet on the purpose of getting.

[0005]

A tracking device according to the present invention is a tracking device in which a track and irradiation light meander relative to each other, and photoelectric conversion means for converting light reflected from a recording medium into an electric signal. A separating means for separating the wobbling component from the electric signal from the photoelectric converting means and outputting the meandering information; a judging means for judging the direction of the positional deviation between the irradiation light and the guide groove from the meandering information and the reflected light; The driving means is provided for controlling the relative position of the guide groove and the irradiation light according to the result.

[0006]

The separating means in the present invention separates the wobbling component from the electric signal from the photoelectric converting means and outputs the meandering information, and the judging means judges the direction of the positional deviation between the irradiation light and the guide groove based on the meandering information and judges the position. Since the relative position between the guide groove and the irradiation light is controlled according to the result, when the irradiation light is deviated from the track, the deviation can be corrected.

[0007]

【Example】

Example 1. FIG. 1 shows a CD-type of a write-once optical disc.
It is a sectional view of an unrecorded disc for WO. In the figure, 1 is a base material made of polycarbonate, 2 is a recording layer that is deformed by temperature rise, 3 is a reflection layer that reflects light, 4 is a protective film, 5 is a guide groove, 6 is a base material 1, recording layer 2, and reflection Layer 3,
It is a disk made of the protective film 4. FIG. 2 is a plan view of the disk 6 of FIG. The disc 6 is irradiated with convergent light, and the irradiation light causes the recording layer 2 to rise in temperature.
When the information is recorded by deforming, the converged light traces the guide groove, and the information is spirally recorded. In FIG. 2, the guide groove 5 is pre-recorded in a spiral shape with respect to the center of the disk 6, and is about 22.05 kHz.
It is recorded in the form of wobbling in the radial direction at a substantially constant frequency of z.

FIG. 3 is a block diagram of a pickup which irradiates the focused light of the disc 6 and converts the reflected light from the disc 6 into an electric signal. In the figure, 10 is a laser diode which is a light source of convergent light, and 11 is a laser diode
A first lens for collimating the divergent light from the laser beam into a parallel light beam, a second lens 12 for converging the parallel light beam onto the disk 6, and a reference numeral 13 for moving the second lens 12 in the radial direction of the disk 6 to guide the focused light beam. A coil that biases the second lens to follow the groove 5, 14 is a semi-reflecting mirror that reflects the reflected light from the disk 6 and changes the direction, and 15 is a third mirror that focuses the reflected light on the photodetector described below. A lens 16 is a photodetector in which a photoelectric conversion element for converting reflected light into an electric signal is divided into four parts A, B, C, and D. The pickup is configured as described above and has the guide groove 5
In principle, the so-called tracking signal indicating the relative positional relationship between the photoelectric conversion element A and the converged light is obtained by the push-pull method.
And the sum of the signals from B and the sum of the signals from photoelectric conversion elements C and D.

FIG. 4 shows a part of a recording device for recording information on the disc 6 by using the pickup shown in FIG.
This is a tracking device that controls the second lens 12 by supplying power to the coil 13 based on an electric signal from the photodetector 16 so that the focused light tracks the guide groove 5. In the figure, 20 and 21 are adders for adding the electric signals from the photoelectric conversion elements A and B, and C and D, respectively, and 22 is a signal corresponding to the total reflected light amount, which is obtained by adding the signals from the adders 20 and 21. HF) is output by an adder 23 is a subtractor by which a difference between signals from the adders 20 and 21 is calculated and a tracking signal (TE) is output.
Is a band pass filter having a center frequency of 22.05 kHz for separating the components of HF and TE corresponding to the above wobbling, 26 is a comparator for discriminating whether the signal from the band pass filter 25 is positive or negative, and outputting an ATIP signal, 27 is A
A multiplier that multiplies TIP and TE, 28 is an integrator that integrates the signal from the multiplier 27 in synchronization with a change in ATIP, 29 is a comparator that determines whether the output signal of the integrator 28 is positive or negative, and 30 is ATIP , A counter in which the output numerical value sequentially rises and falls in accordance with the output signal of the comparator 29, 31 is a DA converter (DAC) that converts the numerical value from the counter 30 into an analog signal (TEC), 32
Is an adder for adding the signal from the DAC and TE, and 33 is an amplifier for feeding the coil 13. FIG. 5 is a signal state diagram showing signals of respective parts of the tracking device.

Next, the operation of this embodiment will be described with reference to FIGS. 1, 2, 3, 4, and 5. The signal HF obtained by collecting the reflected light from the disk 6 on the photodetector 15 changes depending on the position of the focused light on the disk 6 with respect to the guide groove 5. This change depends on the shape of the guide groove 5 and the like, and is not always constant. The value of the HF signal when the focused light is applied to a position on the disk 6 far from the guide groove 5 is Il, and the HF when the focused light is applied to the center of the guide groove 5.
The value of the signal is defined as Ig, and the degree of the above change is defined as the radial contrast (RC), which is defined by the following equation. RC = 2
(Il-Ig) / (Il + Ig) (1) RC of the CD-WO disc 6 in this embodiment is 0.
Let's say 01. That is, when the focused light is at the center of the guide groove 5, the signal intensity is lower than in other cases.

Conventionally, the tracking control is performed so that the focused light tracks the guide groove 5 by using only the TE signal without using the signal from the DAC in this embodiment. In this case, the TE signal is offset as described above, and the focused light is at a position displaced from the center of the guide groove 5 in the radial direction of the disk 6. In this state, the TE signal is the original tracking signal (TEI) indicating the positional deviation between the focused light and the guide groove 5.
The above offset (OFS) and the wobbling of the guide groove 5 cause the TE signal to have a small amplitude of about 22.0.
Wobbling component (TEW) that changes at a speed of 5 kHz
It is obtained as the sum of the three. The band pass filter 25 separates and extracts the wobbling component in the TE signal. The separated wobbling component TEW is a logic signal type AT when the comparator 26 determines whether it is positive or negative.
It becomes an IP signal.

On the other hand, the signal intensity of the HF signal changes depending on whether the converged light is close to the center of the guide groove 5 due to the RC described above. Since the guide groove 5 is wobbled, the HF signal is affected by the TE signal as well as the TE signal, but the receiving method is different from the TE signal. FIG. 6 is a diagram showing an HF signal when the focused light changes its position with respect to the wobbling guide groove 5.

Returning to FIGS. 1 to 5, the description will be continued. It is assumed that the focused light is at a position shown in FIG. 2 which is slightly offset from the center of the guide groove 5 to the outside in the radial direction of the disk 6 with respect to the guide groove 5. The ATIP signal is almost unaffected by the slight deviation described above, and a normal signal indicating whether the guide groove 5 meanders outward or inward in the radial direction of the disk 6 by wobbling can be obtained. .. The signal intensity of the HF signal changes corresponding to FIG. 6 as the focused light approaches or moves away from the center of the guide groove 5 due to the wobbling of the guide groove 5. The bandpass filter 24 changes the HF signal that is affected by wobbling from the wobbling fundamental frequency component signal (HFW).
Are separated and extracted. In the case of FIG. 2, HFW and TEW
Are in the same phase, but when the focused light is inside the center of the guide groove 5, the phase between them is opposite. That is, one of the spirits of the present invention is that, due to the phase relationship between the two,
It is to determine whether the focused light is inside or outside the center of the desired track or guide groove 5.

The HFW signal is multiplied by the ATIP signal in the multiplier 27. When the focused light shown in FIG. 2 is slightly outside the center of the guide groove 5 and HFW and TEW are in phase, the multiplication result is positive, and when it is inside, it is negative. In principle, it is possible to determine whether it is inside or outside based on only the multiplication result, but in reality, the multiplication result may change irrespective of the physical relationship between the focused light and the guide groove 5 due to noise or the like. is there. In the present embodiment, as one method of reducing this effect, a method of making a determination based on the result of integration over one period of the ATIP signal is shown.

The integrator 28 is initialized at the rising edge of the ATIP signal and starts integration of the above multiplication result. The comparator 29 determines whether the integration result of the integrator 28 is positive or negative.
When the focused light shown in FIG. 2 is slightly outside the center of the guide groove 5, the integration result is positive and the comparator 29 indicates
H "is output. At the next rising edge of the ATIP signal,
The counter 30 responds to the signal from the comparator 29
In the case of "H", the numerical value is increased by 1 count, and in the case of "L", the numerical value is decreased by 1 count. In the present embodiment, the numerical value is increased by 1. The DAC 31 converts the numerical value from the counter 30 into an analog electric signal (TEC). Since the value of the counter 30 has increased by 1 count, the TEC signal slightly increases.

The adder 32 adds the TEC signal and the TE signal including the offset, and adds the TE signal to the coil 13 via the amplifier 33.
Since the power is supplied to the coil 13, the power supply intensity to the coil 13 increases by one count, and the lens 12 is urged to guide the convergent light to the guide groove 5.
A little closer to the center of. Further, the discrimination between the focused light and the guide groove 5 is started with the rising edge of the ATIP signal as a starting point, and the converged light is slightly moved closer to the center of the guide groove 5 at the next rising edge of the ATIP signal. After that, by repeating this operation, the focused light comes to be positioned substantially in the center of the guide groove 5. As mentioned above, TE
Normal tracking operation can be performed even when the signal includes an offset.

Embodiment 2. In the first embodiment described above, although the converged light is deviated from the center of the guide groove 5 due to the influence of the offset, a case where the tracking operation is performed for the time being is shown. However, the tracking operation may not be performed depending on the amount of offset. As a method of reducing or eliminating the influence of offset in the initial pull-in of the tracking operation, an optical disk called an optical disk drive (ODD) has already been put to practical use in an apparatus used as an external storage device of a computer. Specifically, when the focused light sequentially traverses the guide groove 5 due to the eccentricity of the disk without performing the tracking operation, the TE signal becomes a signal that vibrates at its maximum amplitude in response to the traversing. If the tracking operation is performed with the center value (TEM) of the highest value and the lowest value of the vibration signal as the control center, the good tracking operation can be performed at least for a certain period. Following the initial pull-in operation in the ODD, the value of the TEM signal is given as the initial value of the TEC signal, and thereafter, the tracking operation is performed according to the first embodiment. Good tracking operation is possible.

Example 3. In the above-mentioned first and second embodiments, the tracking device for the disk having the guide groove accompanied by wobbling is shown. The following describes a tracking device for a disc that does not have wobbling in the guide groove or the information track, such as a read-only CD disc. As described in the first embodiment, one of the spirits of the present invention is that the TE signal and the HF signal change in synchronization with the wobbling due to the relative wobbling of the focused light and the guide groove or the track, and the two have the same phase. The purpose is to determine the positional relationship between the focused light and the desired tracking track depending on whether the change occurs in or in the opposite phase. Therefore, it is clear that the same effect can be obtained if both are relatively wobbling. FIG. 7 is a block diagram of a tracking device in a reproducing device which reproduces a CD disc whose information tracks are not wobbled by a pickup based on the principle of the push-pull method.

In the figure, 40 is a sine wave signal (SIN).
41 is a phase shifter that changes the phase of the SIN signal, and 42 is a bandpass filter whose center frequency matches the frequency of the SIN signal. The SIN signal is
The TE signal is added by the adder 32, and power is supplied to the coil 13 via the amplifier 33, and the lens 12 is slightly vibrated in the radial direction of the disk 6 in accordance with the SIN signal to cause relative wobbling between the focused light and the track. .. The phase of this wobbling operation differs from the phase of the SIN signal due to the weight of the lens 12 and the like. By correcting the phase shift by the phase shifter 41, the ATIP signal which is the output signal of the comparator 26 and the bandpass filter 42 are corrected.
ATIP whose relationship with the signal HFW from FIG.
The relationship between the signal and the HFW signal is the same. Similar to the first embodiment, a good tracking operation can be performed by vibrating the lens 12.

[0020]

The tracking device according to the present invention is a tracking device in which a track and irradiation light intentionally relatively wobble, and photoelectric conversion means for converting the reflected light from the recording medium into an electric signal. , A separating means for separating the wobbling component from the electric signal from the photoelectric converting means and outputting the meandering information, a judging means for judging the direction of the positional deviation between the irradiation light and the guide groove from the meandering information and the reflected light, and the judgment result. According to the above, since the guide groove and the driving means for controlling the relative position of the irradiation light are provided, there is an effect that a stable tracking operation becomes possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a CD-WO disc.

FIG. 2 is a plan view of a CD-WO disc.

FIG. 3 is a configuration diagram of a pickup.

FIG. 4 is a block diagram showing a tracking device according to an embodiment of the present invention.

5 is a signal state diagram of the block diagram of FIG. 4. FIG.

FIG. 6 is a response diagram of an HF signal with respect to wobbling.

FIG. 7 is a block diagram of a tracking device according to another embodiment of the present invention.

[Explanation of symbols]

 1 Base Material 2 Recording Layer 3 Reflection Layer 5 Guide Groove 6 Disk 12 Lens 13 Coil 16 Photodetector 20, 21, 32 Adder 23 Subtractor 24, 25 42 Bandpass Filter 26, 29 Comparator 27 Multiplier 28 Integrator 30 Counter 31 DAC 33 Amplifier 40 Oscillator 41 Phase shifter

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[Procedure amendment]

[Submission date] May 21, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction content]

[0005]

[Means for Solving the Problems] Claim 1 of the present invention
The tracking device in the system is intentionally wobbled.
The light is focused on a recording medium having a guide groove
In order for the irradiation light to follow the guide groove, the phase of the guide groove and the irradiation light
It is a tracking device equipped with an optical system that performs relative position control.
Photoelectric conversion that converts the reflected light from the recording medium into an electrical signal.
And a wob from the electric signal from the photoelectric conversion means.
Separation means that separates ring components and outputs meandering information
Direction of misalignment of irradiation light and guide groove from row information and reflected light
Discriminating means for discriminating between the guide groove and the irradiation depending on the discrimination result.
Having drive means for controlling relative position with respect to light
Is. Further, the tracking device according to claim 2 of the present invention.
Is the first and second photoelectric conversion means according to claim 1.
2 photoelectric conversion elements are provided,
Subtraction means for outputting a difference component as a difference signal, and the above-mentioned two elements
Adder that outputs the sum component of the electrical signal from
And the meandering information is calculated by calculating the correlation between the sum signal and the difference signal.
The correlation means for outputting is provided with a discrimination means. Well
The tracking device according to claim 3 of the present invention is
The light is condensed and applied to the recording medium having a rack, and the above-mentioned illumination is performed.
The light illuminates the information track to track it.
A tracking device equipped with an optical system for controlling the relative position with respect to the incident light.
The illuminating light is a small snake in the lateral direction of the information track.
Output a meandering signal to perform wobbling
The meandering means and the light reflected from the recording medium are converted into electrical signals.
Photoelectric conversion means and the electric signal from the photoelectric conversion means
Separating hand that separates the wobbling component from each other and outputs the meandering information
From the step, the meandering information and the reflected light, the irradiation light and the information track
A discriminating means for discriminating the direction of the positional deviation, and
Drive to control the relative position between the information track and the irradiation light.
And means for moving. Also, the claims of the present invention
The tracking device in claim 4 is the amount of reflected light according to claim 3.
Of the electric signal and the meandering signal from the photoelectric conversion means corresponding to
The correlating means for calculating the correlation and outputting the meandering information is called the discriminating means.
And prepared for it. Further, claim 5 of the present invention
The tracking device in claim 1 to claim 4.
The relative position control between the information track and the irradiation light by the difference signal of
Control loop and the determination result of the above determination means.
Applying means for gradually applying a signal to the difference signal according to the result
It is equipped with and.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

The photoelectric conversion means according to claim 1 of the present invention.
Converts the reflected light from the recording medium into an electrical signal and separates it.
The stage is wobbled from the electric signal from the photoelectric conversion means.
The components are separated and the meandering information is output.
Determines the direction of positional deviation between the irradiation light and the guide groove from the reflected light
However, the driving means determines the phase of the guide groove and the irradiation light according to the determination result.
Performs relative position control. Further, in claim 2 of the present invention
The subtraction means in the present invention includes a first photoelectric conversion element and a second photoelectric conversion element.
The difference component of the electric signal from the two elements of the photoelectric conversion means is transmitted.
Signal, and the adding means outputs the electric signal from the above two elements.
The sum component of the sum signal is output as a sum signal, and the correlating means outputs the sum signal
And the difference signal is calculated to output the meandering information. Also,
In the meandering means according to claim 3 of the present invention, the irradiation light is
A small meandering (wobbling) is performed in the lateral direction of the information track.
It outputs a meandering signal so that the photoelectric conversion means is a recording medium.
It converts the reflected light from the
Separation of wobbling component from electric signal from conversion means
The meandering information is output, and the discrimination means is based on the meandering information and the reflected light.
Determine the direction of positional deviation between the irradiation light and the information track, and
The moving means determines the phase of the information track and the irradiation light according to the discrimination result.
Performs relative position control. Further, in claim 4 of the present invention
Is the discrimination means in the photoelectric conversion means corresponding to the amount of reflected light?
Calculate the correlation between the electric signal and the meandering signal, and output the meandering information.
Force Furthermore, the control rule according to claim 5 of the present invention.
The phase difference between the information track and the irradiation light depends on the difference signal.
Performs a relative position control, and the applying means is the above-mentioned determining means.
A signal is gradually applied to the above difference signal according to the discrimination result.
It

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

In the figure, 40 is a sine wave signal (SIN).
41 is an oscillator for generating the SIN signal in the TE signal.
A phase shifter for changing the phase of the signal component, the center frequency of 42 is SI
It is a bandpass filter that matches the frequency of the N signal. The SIN signal is added to the TE signal by the adder 32, and is fed to the coil 13 via the amplifier 33. The lens 12 is slightly vibrated in the radial direction of the disk 6 according to the SIN signal, and the focused light and the track are relatively moved. Cause selective wobbling. The phase of this wobbling operation differs from the phase of the SIN signal due to the weight of the lens 12 and the like.
By correcting this phase shift by the phase shifter 41, the relationship between the ATIP signal, which is the output signal of the comparator 26, and the signal HFW from the bandpass filter 42 is the ATIP signal and the HFW signal shown in the first embodiment. Is the same as the relationship. Similar to the first embodiment, a good tracking operation can be performed by vibrating the lens 12.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (5)

[Claims] 1. A relative position between the guide groove and the irradiating light so that the irradiating light tracks the guide groove by converging and irradiating the recording medium having the intentionally wobbling guide groove. A tracking device provided with an optical system for controlling, wherein photoelectric conversion means for converting light reflected from a recording medium into an electric signal and wobbling component separated from the electric signal from the photoelectric conversion means, and meandering information is output. Separation means, discrimination means for discriminating the direction of positional deviation between the irradiation light and the guide groove based on the meandering information and the reflected light, and a driving means for controlling the relative position of the guide groove and the irradiation light according to the discrimination result. A tracking device characterized by being provided. 2. The photoelectric conversion means includes first and second photoelectric conversion elements, the subtraction means outputting a difference component of the electric signals from the two elements as a difference signal, and the sum of the electric signals from the two elements. The tracking device according to claim 1, further comprising: an addition unit that outputs the component as a sum signal and a correlation unit that calculates the correlation between the sum signal and the difference signal and outputs the meandering information. .. 3. A tracking provided with an optical system for condensing light onto a recording medium having an information track and irradiating the recording medium to control the relative position of the information track and the irradiation light so that the irradiation light tracks the information track. A device, a meandering means for outputting a meandering signal so that the irradiation light performs a small meandering (wobbling) in the lateral direction of the information track, and a photoelectric conversion means for converting the reflected light from the recording medium into an electric signal. Separation means for separating the wobbling component from the electric signal from the photoelectric conversion means and outputting the meandering information, judgment means for judging the direction of the positional deviation between the irradiation light and the information track from the meandering information and the reflected light, and the judgment result. A tracking device comprising: a drive unit that controls the relative position of the information track and the irradiation light accordingly. 4. The correlation means for calculating the correlation between the electric signal from the photoelectric conversion means corresponding to the amount of reflected light and the meandering signal and outputting the meandering information is provided as the discriminating means. Tracking device. 5. A control loop for controlling the relative position of the information track and the irradiation light by the difference signal, and an applying means for gradually applying a signal to the difference signal in accordance with the result of the judgment by the judging means. The tracking device according to any one of claims 1 to 4, wherein: