JP3500184B2 - Optical disc playback device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 3-beam type optical disc reproducing apparatus.

[0002]

2. Description of the Related Art In a three-beam type optical disk reproducing apparatus consisting of a main beam and two sub-beams, if the main beam is on-track, it can be obtained from each sub-beam. The three beams are strictly fixed and arranged with respect to the optical pickup so that the amounts of reflected light become equal. Specifically, the sub-beams are arranged at positions of 1/4 track pitch Tp at equal intervals above and below the main beam across the track, and the main beam and the two sub-beams are tracked. Is strictly fixed and arranged so as to be on a straight line forming a predetermined angle with. In such a 3-beam type optical disc reproducing apparatus, tracking control is performed by forming a tracking servo as described below.

<Tracking servo> Each sub-beam
The amount of reflected light obtained from the optical system is converted into an electric signal by a photodetector and amplified by a differential amplifier. I'm feeding back. In this tracking servo, the positions of the two sub-beams on the optical disk are set so that the output from the differential amplifier becomes zero, that is, the amount of reflected light obtained from each sub-beam becomes equal. Is controlled. In the conventional 3-beam type optical disc reproducing apparatus, a gain fixing circuit is usually connected to the output side of the differential amplifier in order to secure the gain of the tracking servo.

[0004]

However, the above-mentioned conventional 3-beam type optical disk reproducing apparatus has the following problems. As described above, the main beam and the two sub beams are strictly fixed and arranged with respect to the optical pickup. As shown in FIG. 7A, the line connecting the two sub-beams E and F and the main beam M becomes a straight line L,
Further, they are fixed and arranged so that the angle formed by the tangential direction T of the track and the straight line L is always a constant value Θ (the angle at which the maximum tracking error signal is obtained).

Incidentally, the tracking control includes tracking control for moving the optical pickup in the radial direction of the optical disk, in addition to the tracking control for sequentially following the tracks as described above. In that case, even if the optical pickup 1 moves on the optical disc 7 from the inner circumference side to the outer circumference side as shown in FIG. −
If the frame M) is on the straight line L ₀ passing through the center O of the optical disk 7, no problem will occur. However, since the optical pickup usually has a mounting error (deviation of the optical axis), for example, if the optical axis is deviated by α due to the mounting error, the optical pickup 1 will be on the straight line L ₃ on the inner peripheral side. Position, and on the straight line L _{2 in} the middle of the optical disk 7,
On the outer peripheral side, it is in a state of being located on the straight line L ₁ .
Then, as shown in FIG. 7C, when the optical pickup 1 is located on the inner peripheral side, a straight line L connecting the sub beam E and the sub beam F with the main beam M and a tangential direction T of the track.
The angle between the line L and the tangential direction T is always Θ ₃ and the angle Θ ₂ is midway on the optical disk 7 and the angle Θ ₁ is on the outer peripheral side. Will not be possible. Straight line L and tangential direction T
If the angle formed by and deviates from the constant value Θ, the positions of the sub-beams E and F will deviate from the point of 1/4 track pitch, and the level of the tracking error signal obtained will fluctuate (decrease). , The detection sensitivity of the tracking error signal fluctuates (decreases), and the gain of the tracking servo fluctuates (decreases).

The gain of the tracking servo may be neither too large nor too small. It is necessary to put it in a proper range. If it is too large, the tracking servo becomes sensitive to noise (disturbance that should not be followed, etc.), and if it is too small, errors due to track disturbance, disk eccentricity, etc. will be large. The problem arises that the value becomes larger than the allowable amount. In particular, when the angle formed by the straight line L and the tangential direction T changes from the constant value Θ, the detection sensitivity of the tracking error signal becomes low and the gain of the tracking servo decreases. When the gain is reduced, the amount of noise due to the disturbance to be followed increases as described above, so it is necessary to correct the reduction in the gain. However, since the gain of the tracking servo is fixed in the conventional 3-beam type optical disk reproducing apparatus, it is not possible to deal with the fluctuation of the gain in the tracking servo such as the decrease of the gain. There is a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical disk reproducing apparatus capable of suppressing the fluctuation of the gain of the tracking servo and stably reproducing. I am trying.

[0008]

In order to achieve the above object, an optical disk reproducing apparatus (1) according to the present invention is provided with a main window.
-Optical pickup consisting of two sub-beams
In a 3-beam type optical disc reproducing apparatus equipped with
The gain adjusting means for adjusting the gain of the tracking servo and the tracking servo with the tracking servo closed
The two Sabubi - and phase difference measuring means for measuring the phase difference between the beam is determined based on the phase difference measured by the phase difference measuring means, the attachment error of the optical pickup
So as to compensate for the decreased amount of the detection sensitivity of the tracking error signal due to the tracking service by controlling the gain adjustment means - Bol - it is characterized by comprising a signal processing apparatus for adjusting the gain of the flop .

Optical disk reproducing apparatus (2) according to the present invention
The optical disc reproducing apparatus (1) is provided with a reproducing position calculating means for calculating a reproducing position from the data read from the optical disc and the linear velocity of the optical disc, and the reproducing means calculates two lines at a plurality of reproducing positions by the phase difference measuring means. Subby
The phase difference between the frames is measured, and the relational expression between the reproduction position and the tracking servo gain is obtained based on the phase difference.
Gain control means for adjusting the gain of the tracking servo by obtaining the gain of the tracking servo at an arbitrary reproducing position on the basis of the relational expression.

Optical disc reproducing apparatus (3) according to the present invention
Is characterized in that, in the optical disc reproducing device (1) or the optical disc reproducing device (2), an average value circuit is interposed between the phase difference measuring means and the signal processing device.

Optical disk reproducing apparatus (4) according to the present invention
In the optical disc reproducing device (1) or the optical disc reproducing device (2), an average value circuit and a peak value detection circuit are provided in parallel between the phase measuring means and the signal processing device, and the average value circuit is provided. It is characterized in that it is provided with a computing means for computing the output of the circuit and the output of the peak value detection circuit.

[0012]

Optical disk reproducing apparatus (5) according to the present invention
Is any one of the optical disk reproducing devices (1) to (4)
In tracking service - injecting disturbances into flop - Bol
Equipped with a disturbance injection means, disturbance to the tracking servo
Two Sabubi when injected with - tracking based on the phase difference between the arm support - Bol - obtained by adjusting the gain of the flop
It is characterized that you have configured so that.

[0014]

If the angle between the straight line L connecting the sub-beam E and the sub-beam F and the tangential direction T of the track is kept at a strictly constant value Θ at any position on the optical disk, in other words, in other words. , And if the sub-beam E and the sub-beam F are located exactly at 1/4 track pitch (= where the detection sensitivity of the tracking error signal is maximized) across the track, the sub-beam E The phase difference between the beam E and the sub beam F is 180 °. However, when the angle changes, the phase difference becomes (180 ° ± δ), and the phase difference shifts by δ, so that the detection sensitivity of the tracking error signal decreases.
A constant relational expression holds between the phase difference δ and the detection sensitivity of the tracking error signal (gain of the tracking servo).

Optical disk reproducing apparatus (1) having the above structure
In this case, the sub-beam E and the sub-beam E with the tracking servo closed are provided by the phase difference measuring means.
The phase difference with the frame F is measured, and by the signal processing device,
The optical pickup, which is obtained based on the measurement result,
The gain adjusting means is controlled so as to compensate the decrease in the detection sensitivity of the tracking error signal due to the mounting error of the tracking servo, and the gain of the tracking servo is adjusted. That is, when the deviation δ of the phase difference between the sub-beam E and the sub-beam F from 180 ° is measured, the signal processing device controls the gain adjusting means based on the relational expression, and the tracking servo is performed. The gain of the volume is increased.

Optical disk reproducing apparatus (2) having the above structure
In this case, the phase difference between the sub-beam E and the sub-beam F is measured at two or more reproduction positions, and the reproduction position and the gain of the tracking servo are calculated based on these phase differences. A relational expression is required. Then, the gain of the tracking servo at an arbitrary reproducing position is adjusted based on the relational expression. Therefore, even if the phase difference δ between the sub-beam E and the sub-beam F is not measured at each reproduction position,
By measuring the phase difference at the two or more reproducing positions, it is possible to adjust the gain of the tracking servo at all reproducing positions.

Optical disk reproducing apparatus (3) having the above structure
In this case, since the average value circuit is interposed between the phase difference measuring means and the signal processing device, the amount of reflected light obtained from the sub beam E and the sub beam F varies due to rattling of the optical pickup. Even if the measured value of the phase difference δ in the phase difference measuring means fluctuates, it is possible to almost eliminate the influence of the fluctuation on the signal processing device. As a result, the tracking processing is performed in the signal processing device.
It is possible to reliably perform the signal processing related to the gain adjustment of the loop.

Optical disk reproducing apparatus (4) having the above structure
In this case, an average value circuit and a peak value detection circuit are interposed in parallel between the phase difference measuring means and the signal processing device, and the output of the average value circuit and the peak value detection circuit The output means is provided with a calculating means. When the optical disc has an eccentricity, the phase difference measurement value varies depending on the rotation angle of the optical disc. In the optical disk reproducing apparatus (4), the phase difference δ is obtained by calculating the output from the average value circuit and the output from the peak value detecting circuit by the calculating means, and the mounting error amount of the optical pickup is calculated. , It is not affected by the fluctuation of the measured value of the phase difference δ, the error amount can be obtained more accurately, and the gain of the tracking servo can be adjusted with certainty. .

[0019]

Optical disk reproducing apparatus (5) having the above structure
In this case, a disturbance such as a sine wave is injected into the loop with the tracking servo closed, and the phase difference δ between the sub beam E and the sub beam F is measured. The gain of the tracking servo is adjusted based on the measurement result.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk reproducing apparatus and a tracking servo gain adjusting method according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing an optical disc reproducing apparatus 100 according to the first embodiment. The optical disc reproducing apparatus 100 is the optical disc reproducing apparatus (1) described in "Means for Solving Problems".
Is specifically shown.

In the figure, reference numeral 1 denotes an optical pickup, which is an objective lens 4 and a tracking coil 2.
And the focus coil 3 and the like. The optical pickup 1 is connected to an amplifier 22 forming a differential amplifier 21 via a sub beam E signal line 2a, and
The sub-beam F signal line 2b is connected to the amplifier 23 that constitutes the differential amplifier 21. The optical pickup 1 is connected to a matrix amplifier 31 via a main beam M signal line 3a composed of four signal lines of A signal, B signal, C signal and D signal. One output side of the matrix amplifier 31 is connected to the clock recovery circuit 41, and the other output side is feedback connected to the focus coil 3 via the equalizer amplifier 32. The optical pickup 1 (focus coil 3), the matrix amplifier 31, the equalizer amplifier 32, and the like constitute a focus servo group 30. The reproduced clock is output from one output side of the clock recovery circuit 41, and the data is output from the other output side.
The one output side and the other output side are both connected to the phase comparison circuit 42. A crystal oscillator 43 is connected to the phase comparison circuit 42, and the phase comparison circuit 42 is connected to a disk rotation motor 6 for rotating the optical disk 7 via an equalizer amplifier 44.

On the other hand, the amplifier 2 which constitutes the differential amplifier 21
2 and the output side of the amplifier 23 are connected to the subtracter 24 that constitutes the phase difference measuring device 11 and the differential amplifier 21.
4 is connected to the gain adjusting circuit 25, and the phase difference measuring device 11
Is also connected to the gain adjusting circuit 25 via the signal processing device 14. The gain adjustment circuit 25 is the equalizer amplifier 2
It is feedback-connected to the tracking coil 2 via the tracking coil 20 by the optical pickup 1 (tracking coil 2), the differential amplifier 21, the gain adjusting circuit 25 and the equalizer amplifier 26.
Is configured. Further, the equalizer amplifier 26 is connected via an equalizer amplifier 27 to a slide motor 5 for moving the optical pickup 1 in the radial direction of the optical disk 7.

The optical disc reproducing apparatus 100 configured as described above operates as follows. The data read from the optical disk 7 by the main beam M is transmitted to the matrix amplifier 31 via the main beam M signal line 3a composed of four signal lines. In the matrix amplifier 31, a data signal (A + B + C + D) obtained by adding all the signals (A to D) input through the four signal lines,
The signals input from the four signal lines are divided into two groups of (A + C) and (B + D), and a focus error signal [(A + C)-(B + D)] is created by taking the difference between the groups. To be done. The focus error signal is amplified by the equalizer amplifier 32, then fed back to the focus coil 3, and the data signal is input to the clock recovery circuit 41.

The clock reproduction circuit 41 reproduces a clock from the data signal. The regenerated clock is input to the phase comparison circuit 42 together with the data signal and compared with the reference frequency input from the crystal oscillator 43. The comparison result is amplified by the equalizer amplifier 44 and then transmitted to the disk rotation motor 6 to control the rotation of the optical disk 7.

On the other hand, the signals obtained by the two sub-beams are respectively the amplifier 22 via the sub-beam E signal line 2a and the amplifier 2 via the sub-beam F signal line 2b.
3 is input and amplified. Amplifier 22 and amplifier 23
The output of is input to the subtractor 24 and is subtracted, (EF)
Tracking error signal is generated. The tracking error signal is input to the gain adjusting circuit 25. The outputs of the amplifier 22 and the amplifier 23 are input to the phase difference measuring device 11, and the phase difference measuring device 11 measures the phase difference δ between the sub-beam E signal and the sub-beam F signal. The measured phase difference δ is input to the signal processing device 14. The signal processing device 14 calculates the mounting error amount of the optical pickup 1 and the detection sensitivity of the tracking error signal based on the phase difference δ. Then, the signal processing device 14 controls the gain adjusting circuit 25 so as to increase the gain of the tracking servo 20 by the amount that the detection sensitivity of the tracking error signal decreases due to the amount of the mounting error. The gain increased by the gain adjusting circuit 25 (EF)
After being amplified by the equalizer amplifier 26, one of them is fed back to the tracking coil 2 and the other is amplified by the equalizer amplifier 27, and then the slide motor 5 for moving the optical pickup 1 in the radial direction. To be fed back.

As described above, in the optical disc reproducing apparatus 100 according to the first embodiment, the phase difference measuring device 11 measures the phase difference δ between the sub-beam signal E and the sub-beam signal F, and the phase difference δ is measured. Since there is a phase difference δ and the detection sensitivity of the tracking error signal is reduced, the tracking servo 20
Since the signal processing device 14 controls the gain adjustment circuit 25 so as to increase the gain of the optical pickup 1,
Even if the detection error of the tracking error signal is lowered due to the attachment error, the angle formed by the straight line L formed by the three beams and the tangential direction T of the track changes depending on the reproducing position, and the tracking error is compensated for. -It is possible to prevent a decrease in gain in the loop 20. This allows stable reproduction.

Next, an optical disk reproducing apparatus 200 according to the second embodiment will be described with reference to FIG. The optical disc reproducing apparatus 200 is a concrete example of the optical disc reproducing apparatus (2) described in the "Means for Solving the Problem". The configuration of the optical disc reproducing apparatus 200 is different from that of the optical disc reproducing apparatus 100 shown in FIG.
The signal processing device 14 serves as the signal processing device 15, and the signal processing device 15 receives the linear velocity of the optical disk 7 and the data signal output from the clock reproducing circuit 41. Other configurations are the same.

The optical disc reproducing apparatus 200 configured as described above operates as follows, but only the points different from the operation of the optical disc reproducing apparatus 100 will be described here. In the signal processing device 15, the reproduction position is calculated based on the linear velocity of the optical disk 7 and the time information contained in the data signal input from the clock reproduction circuit 41. Then, the phase difference δ between the sub-beam E signal and the sub-beam F signal is measured at two or more reproducing positions. From these phase differences, the relationship between the phase difference δ and the gain of the tracking servo and the phase difference δ and the reproduction position (optical disc 7
The radius) and the gain of the tracking servo are obtained. Then, the gain of the tracking servo at an arbitrary reproducing position is calculated based on the relationship. When reproducing an arbitrary reproducing position, the gain of the tracking servo 20 is adjusted (the gain adjusting circuit 25 is controlled) based on the gain calculated by the above relationship.

As described above, in the optical disc reproducing apparatus 200 according to the second embodiment, the relation between the reproducing position and the gain of the tracking servo 20 is obtained, and based on the above relation at any reproducing position. Since the gain adjusting circuit 25 is controlled by the gain adjusting circuit 25, the gain of the tracking servo 20 can be adjusted without obtaining the phase difference δ between the sub beam E signal and the sub beam F signal for each reproduction position. it can. This allows stable reproduction.

Next, an optical disk reproducing apparatus 300 according to the third embodiment will be described with reference to FIG. The optical disc reproducing apparatus 300 is a concrete example of the optical disc reproducing apparatus (3) described in the "Means for Solving the Problem". The configuration of the optical disc reproducing apparatus 300 is different from that of the optical disc reproducing apparatus 100 shown in FIG.
The only difference is that the average value circuit 12 is interposed between the phase difference measuring device 11 and the signal processing device 14. Average value circuit 12
Even if the optical pickup 1 rattles and the measured value of the phase difference δ by the phase difference measuring device 11 fluctuates, the signal processing device 1 outputs the measured value signal with the fluctuation suppressed.
4 can be transmitted. Thereby, the signal processing device 1
In No. 4, the signal processing can be performed without being affected by the rattling, and the gain of the tracking servo 20 can be adjusted reliably. This allows
Stable reproduction can be performed.

Next, an optical disk reproducing apparatus 400 according to the fourth embodiment will be described with reference to FIG. The optical disc reproducing apparatus 400 is a concrete example of the optical disc reproducing apparatus (4) described in the section “Means for Solving the Problems”. The configuration of the optical disc reproducing apparatus 400 is different from that of the optical disc reproducing apparatus 100 shown in FIG.
The signal processing device 14 becomes the signal processing device 16, and the average value circuit 12 and the peak value detection circuit 13 are interposed in parallel between the phase difference measuring device 11 and the signal processing device 16. Other configurations are the same. In the signal processing device 16, the phase difference δ between the sub beam signal E and the sub beam signal F is calculated by calculating the output from the average value circuit 12 and the output from the peak value detection circuit 13. Desired. By thus calculating the phase difference δ, even if the phase difference δ measured by the phase difference measuring device 11 fluctuates due to the eccentricity of the optical disk 7 or the like, an accurate phase difference value can be obtained without being affected by the fluctuation. Signal processing can be performed. As a result, the gain of the tracking servo 20 can be adjusted reliably, and stable reproduction can be performed.

The optical disk reproducing apparatus 100 described above
The optical disc reproducing apparatus 400 shows a case where the gain of the tracking servo 20 is adjusted by measuring the phase difference δ between the two sub-beams while reproducing all of them. The measurement of may be performed during reproduction.
When the tracking servo is applied, the tracking error signal becomes close to zero, so the tracking servo is in the open state or the tracking servo except when reproducing or reading data. If the phase difference is measured in the state where the disturbance is injected into the loop, the phase difference δ at the reproducing position can be measured more reliably, and the gain of the tracking servo 20 can be adjusted. . A method for adjusting the gain of the tracking servo 20 by measuring the phase difference between the two sub-beams other than during reproduction will be described below with reference to FIGS.

FIG. 5 is a block diagram schematically showing an optical disc reproducing apparatus 150 according to the first reference example . The optical disc reproducing apparatus 150 is the optical disc reproducing apparatus 10 shown in FIG.
The tracking servo 20 at 0 is provided with a loop switch 51. However, since the loop switch 51 is always provided in the tracking servo, the optical disk reproducing device 150 and the optical disk reproducing device 100 are substantially the same. The means for turning on / off the loop switch 51 may be the signal processing device 14 or the optical disk reproducing device 1
It may be another control device that controls 50.

The loop switch 51 is opened at the time of start-up of the optical disk reproducing device 150 or when it is desired to perform stable and reliable reproduction by strictly adjusting the gain of the tracking servo 20 even during reproduction. Two sub-bye
Tracking servo 20 by measuring the phase difference between
Adjust the gain of. Normally, the optical disc 7 has a factor of error generation such as eccentricity. Therefore, when the tracking servo 20 is opened and the optical disc 7 is rotated, a large tracking error signal is generated, and the phase difference measuring device 11 causes the two discs It becomes easy to measure the phase difference δ between the sub-beams.
If the phase difference signal is used, the processing in the signal processing device 14 can be surely and stably performed, and the gain of the tracking servo 20 at the reproduction position where the loop switch 51 is opened can be surely adjusted. be able to.

The method of adjusting the gain of the tracking servo 20 by opening the loop switch 51 to obtain the phase difference δ between the two sub-beams is not limited to the optical disk reproducing apparatus 100. It can be applied to any of the optical disc reproducing apparatus 200, the optical disc reproducing apparatus 300, and the optical disc reproducing apparatus 400 described above.

FIG. 6 is a block diagram schematically showing the optical disk reproducing apparatus 151 according to the fifth embodiment , and the optical disk reproducing explained in the section "Means for Solving the Problems".
It is a figure for demonstrating an apparatus (5) . The optical disc reproducing apparatus 151 is configured by connecting a disturbance injection means 61 such as a sine wave oscillator to the tracking servo 20 of the optical disc reproducing apparatus 100 shown in FIG.

In the case of the optical disk reproducing device 151, a disturbance such as a sine wave having a small amplitude is injected into the loop with the tracking servo 20 closed, and the phase difference δ between the two sub-beams. Is measured to adjust the gain of the tracking servo 20. Disturbance injection means 61
By superimposing a sine wave having a small amplitude on the tracking servo 20, the generation level of the tracking error signal can be increased and the phase difference δ between the two sub-beams in the phase difference measuring device 11 can be increased. Will be easier to measure.
As a result, the measurement of the phase difference δ in the phase difference measuring device 11 can be ensured, and the gain adjustment of the tracking servo 20 can be surely adjusted.

The disturbance injecting means 61 is not limited to the optical disc reproducing apparatus 100, and any one of the tracking servo 20 of the optical disc reproducing apparatus 200, the optical disc reproducing apparatus 300 and the optical disc reproducing apparatus 400 already described.
You may connect to. Also, tracking servo 2
As the disturbance to be injected into 0, the objective lens 4 may be slightly vibrated by the radius method of the optical disk 7 in addition to superimposing the sine wave.

[0040]

As described in detail above, in the optical disc reproducing apparatus (1) according to the present invention, the tracking servo is
The gain of the tracking servo can be adjusted by measuring the phase difference δ between the two sub-beams in the closed state, and the tracking servo due to the optical pickup mounting error can be adjusted. It is possible to compensate for the decrease in the gain of the amplifier.

In the optical disk reproducing apparatus (2) according to the present invention, the sub beam is reproduced at two or more reproducing positions without measuring the phase difference δ between the two sub beams for each reproducing position. By measuring the phase difference between the beams, the relationship between the reproduction position at an arbitrary reproduction position and the phase difference δ between the sub-beams and the relationship between the reproduction position and the gain of the tracking servo by the control means. Can be asked. Thus, even if the phase difference δ is not measured for each reproduction position, when the reproduction position is calculated by the reproduction position calculation means, the phase difference between the sub-beams at an arbitrary reproduction position is obtained from the relationship. Therefore, the gain of the tracking servo can be adjusted.

In the optical disc reproducing apparatus (3) according to the present invention, in the optical disc reproducing apparatus (1) or the optical disc reproducing apparatus (2), an average value is placed between the phase difference measuring means and the signal processing apparatus. Since the circuit is interposed, even if the optical pickup or the like rattles and the measured value of the phase difference δ in the phase difference measuring means fluctuates, the measured value signal in which the fluctuation is suppressed is transmitted to the signal processing device. You can As a result, the operation of the signal processing device relating to the control of the gain adjusting means can be made stable and reliable, and the gain of the tracking servo can be adjusted reliably.

In the optical disk reproducing apparatus (4) according to the present invention, in the optical disk reproducing apparatus (1) or the optical disk reproducing apparatus (2), the average value between the phase difference measuring means and the signal processing apparatus is set. A circuit and a peak value detection circuit are interposed in parallel, and the output of the average value circuit and the peak
Since the calculation means for calculating the output of the black value detection circuit is provided, the phase difference δ between the two sub-beam signals can be obtained by the calculation. As a result, even if the measured value of the phase difference δ in the phase difference measuring means fluctuates due to an error such as eccentricity of the optical disc, the signal processing device can obtain an accurate phase difference value without being affected by the fluctuation. The gain of the tracking servo can be adjusted with certainty.

In the optical disk reproducing apparatus (5) according to the present invention
In this case, the generation level of the tracking error signal can be increased and the phase difference measuring means can easily measure the phase difference. As a result, the phase difference can be measured with certainty, and the tracking servo gain can be adjusted with certainty.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing an optical disk reproducing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram schematically showing an optical disk reproducing device according to a second embodiment of the present invention.

FIG. 3 is a block diagram schematically showing an optical disk reproducing device according to a third embodiment of the present invention.

FIG. 4 is a block diagram schematically showing an optical disk reproducing device according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram schematically showing an optical disk reproducing device according to a first reference example .

FIG. 6 is a block diagram schematically showing an optical disk reproducing device according to a fifth embodiment of the present invention.

7 (a) to 7 (c) are diagrams used to explain "problems to be solved by the invention".

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-61-165831 (JP, A) JP-A 64-50241 (JP, A) JP-A 62-266780 (JP, A) JP-A-6- 347214 (JP, A) JP-A-6-325395 (JP, A) JP-A-6-44569 (JP, A) JP-A-2-297726 (JP, A) JP-A-2-56743 (JP, A) JP-A 64-50247 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B ^7/ 00-7/0013 G11B 7/095

Claims (5)

(57) [Claims] 1. A main beam and two sub-beams
In a three-beam type optical disc reproducing apparatus equipped with an optical pickup, gain adjusting means for adjusting the gain of the tracking servo, and the above-mentioned two devices with the tracking servo closed. of Sabubi - and phase difference measuring means for measuring the phase difference between the beam, determined based on the phase difference measured by the phase difference measuring means
Caused by the mounting error of the optical pickup.
That way compensate for the decreased amount of the detection sensitivity of a tracking error signal, by controlling the gain adjusting means and the tracking service - optical disk reproduction, characterized in that a signal processing apparatus for adjusting the gain of the up - Bol apparatus. 2. A reproducing position calculating means for calculating a reproducing position from the data read from the optical disk and the linear velocity of the optical disk, and two sub-beams by the phase difference measuring means at two or more reproducing positions. The phase difference between the two is measured, the relational expression between the reproduction position and the gain of the tracking servo is obtained based on the phase difference, and the tracking servo at the arbitrary reproduction position is calculated based on the relational expression. 4. A gain control means for calculating a gain and adjusting the gain of a tracking servo.
The optical disk reproducing apparatus described. 3. An average value circuit is interposed between the phase difference measuring means and the signal processing device.
Alternatively, the optical disk reproducing apparatus according to claim 2. 4. An average value circuit and a peak value detection circuit are provided in parallel between the phase difference measuring means and the signal processing device, and the output of the average value circuit and the peak value detection circuit are provided. The optical disk reproducing apparatus according to claim 1 or 2, further comprising arithmetic means for computing the output and the output. 5. A disturbance injection means for injecting a disturbance into the tracking servo is provided, and the tracking servo is based on a phase difference between two sub-beams when the disturbance is injected into the tracking servo. -It is constituted so that the gain of a -Volume can be adjusted.
5. The optical disc reproducing device according to any one of items 4 to 4.