JPH11339293A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the effects of eccentricity at recording and reproducing by detecting the eccentricity components of an optical disk and by accurately compensating the eccentricity. SOLUTION: When tracking error signals are observed as compression waves in one revolution period of an optical disk 10, cosine or sine wave signals are detected for two waves per one revolution period making to coincide with fluctuation in the coarse density and the modulation components of the tracking error signals caused by the eccentricity of the disk contained in the signals are detected to simply and surely extract the eccentricity components of the disk 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus which detects an eccentric component of an optical disk and eliminates the influence of eccentricity during recording / reproducing by accurate eccentricity correction.

[0002]

2. Description of the Related Art In an optical disk apparatus for recording or reproducing an optical disk, it is necessary to cause an optical head to accurately follow the track of the optical disk. A tracking control system for that purpose controls the recording / reproduction accuracy along with a focusing control system. This is an important servo technology. However, if the optical disc is eccentrically mounted on the turntable, a deviation occurs between the center of rotation of the optical disc and the center of the track circle on the optical disc. As a result, the track pitch (several μm 100) which is several hundred times larger than
A track vibration of a low frequency (3 to 100 Hz) of 500 μm occurs. As a result, the tracking accuracy of the light spot with respect to the target track is degraded, and the light spot can follow the slight shock vibration applied from the outside due to the deterioration of the signal recording / reproducing quality or the deterioration of the track following performance. Has been found to cause extreme recording and reproduction errors.

[0003] Further, with the recent increase in the speed of optical disk devices, higher recording / reproducing accuracy has been required. Emphasis has been placed on the eccentricity correction technology for canceling the eccentricity of the rotating system, and attempts have been made to further improve the tracking accuracy by introducing such a technology. FIG. 4 is a block diagram of a main part showing an example of a conventional optical disk device, FIG. 5 is a signal waveform diagram of each block shown in FIG. 4, and FIG. 6 is an eccentricity of the optical disk device shown in FIG. It is a flowchart for explaining a detection operation.

As shown in FIG. 4, a conventional optical disk apparatus has a configuration in which a tracking control circuit 1b controls the attitude of an optical head 1a that scans an optical disk 10 in a tracking direction. , An eccentricity detection signal indicating the eccentricity of the optical disk 10 is supplied. Optical disk 1
The pulse generator 2 that generates a pulse in synchronization with the rotation of the rotor is connected to the spindle motor 9 that drives the zero, and this pulse is used as a speed pulse for speed control. On the other hand, a waveform shaper 3 is connected to the optical head 1a, and a tracking error signal indicating a track shift of a light spot irradiated on the optical disk 10 is shaped into a rectangular wave by the waveform shaper 3.

The waveform shaper 3 is connected to a rectangular wave width detector 4 for detecting the width of an output rectangular wave. The rectangular wave width detector 4 further stores a memory 5 for sequentially storing the rectangular wave width.
And a first computing unit 6 for obtaining the maximum rectangular wave width of the rectangular wave width stored in the memory 5. First computing unit 6
Is connected to a second computing unit 7, and the first computing unit 6
The center value of the rectangular wave having the maximum rectangular wave width obtained by the calculation is calculated, and an intermediate value of the width from at least two waves to the rectangular wave stored before m waves and the rectangular wave stored after m waves is calculated. Further, a third computing unit 8 is connected to the second computing unit 7, and the third computing unit 8 is connected to the output pulse of the pulse generator 2 and the intermediate value obtained by the second computing unit 7. Of the eccentricity from the width of the eccentricity, and outputs this as an eccentricity detection signal.
Thus, the tracking control circuit 1b performs the tracking correction corresponding to the eccentric phase based on the eccentricity detection signal supplied from the third computing unit 8.

A tracking error signal indicating a track shift of a light spot irradiated from the optical head 1a is sliced based on a slice level indicated by a dashed line in FIG. 5A, for example, as shown in FIG. As shown in (B), the tracking error signal is shaped into a rectangular wave. W (M) indicates the width of the rectangular wave having the maximum width in the rectangular wave signal, and W (M-1) indicates the width of the immediately preceding rectangular wave. S indicates the width from the end of the rectangular wave W (M−10) to W (M + 10) of 10 waves before and after the rectangular wave having the maximum width. The pulse generator 2 is synchronized with the rotation of the spindle motor 9 and each time the spindle motor 9 makes one rotation, the pulse generator 2 shown in FIG.
The rotation pulse shown in (C) is output. The cycle T (N) of the rotation pulse is the time required for the optical disc 10 to make one rotation. T (L) represents a time width from the leading edge of the rotation pulse to an intermediate value of the period S.

The above-mentioned conventional optical disk device 1 operates according to a flowchart schematically shown in FIG. When the optical disk 10 rotates, the pulse generator 2 outputs a rotation pulse shown in FIG. 5C at a rate of one pulse per rotation. First, in step (101), it is determined whether or not it is the first rotation pulse (first rotation pulse) that defines the beginning of the rotation cycle. Next, as shown in step (103), the width W of each rectangular wave is determined until the supply of the next rotation pulse (second rotation pulse) defining the end of the rotation cycle is determined in the following step (102). (N) are sequentially stored in the memory 5. That is, each width W (n) of the tracking error signal shaped into a rectangular wave is detected by the rectangular wave width detector 4, and the rectangular wave width is sequentially stored in the memory 5.

Next, in step (104), the first
The width W (M) of the largest rectangular wave is detected from the rectangular waves stored in the memory 5 by the computing unit 6 of FIG. Further, in the following step (105), the maximum rectangular wave width W
The second computing unit 7 obtains intermediate values of m (where M ≧ 2, here, 10) rectangular wave widths before and after (M). Further, in the next step (106),
The third calculator 8 obtains a time width T (L) from the first rotation pulse to the intermediate point.

Further, in the following step (107), the width from the first rotation pulse to the second rotation pulse, that is, the sum T of the rectangular wave width groups stored in the memory 5,
(N) is required. Lastly, in step (108), the width T from the first rotation pulse to the intermediate value T
From the (L) and the sum T (N) of the rectangular wave width groups, an eccentric phase T is obtained according to a calculation formula of T = 360 ° × T (L) / T (N). 8 to tracking control circuit 1
b.

[0010]

The conventional optical disk apparatus 1 has a pulse detection system including a pulse generator 2, a waveform shaper 3, and a rectangular wave width detector 4, and first to third arithmetic units 6, 7. , 8 and the memory 5 are indispensable, and the first computing unit 6 has to find the maximum rectangular wave width of the rectangular wave width stored in the memory 5, and the second computing unit 7
It is necessary to find an intermediate value of the width from the rectangular wave stored at least two waves before the rectangular wave having the maximum rectangular wave width obtained by the first computing unit 6 to the rectangular wave stored after the same wave number. Further, the third computing unit 8 must determine the eccentric phase from the width between the second rotation pulse output from the pulse generator 2 and the intermediate value determined by the second computing unit 7, The operation required for the computer was very complicated. Further, since the rectangular wave widths are stored in order, a large-capacity storage device is required for the memory 5. Further, even if the eccentric phase of the optical disk 10 can be detected, the eccentric amount cannot be calculated. However, there is a problem that the tracking control cannot be strictly corrected in accordance with the above.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk apparatus capable of correcting eccentricity of an optical disk with a simple configuration and improving tracking accuracy.

[0012]

To achieve the above object, the present invention relates to an optical disk apparatus for recording or reproducing a signal by scanning an optical disk with an optical head, wherein a tracking error signal obtained from the optical head is compressed. Detection means for detecting and converting to a signal corresponding to the coarse density of the compressional wave, eccentricity component extraction means for extracting the eccentricity component of the optical disc from the output of the detection means, and eccentricity component extraction means And a tracking control means for performing eccentricity correction tracking control based on the extracted eccentricity component.

In the present invention, the detection means may be an FM detector, or the eccentricity component extraction means may add a negative sign to the square root of the arithmetic output of the detection output output by the detection means and 1. And an arithmetic circuit for extracting an eccentric component.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of an optical disk apparatus according to the present invention. FIG. 2 is a signal waveform diagram of each block shown in FIG.
5 is a flowchart for explaining the eccentricity correction operation shown in FIG.

The optical disk device 11 shown in FIG. 1 has the same configuration as the conventional one in which the spindle motor 12 drives the optical disk 10 to rotate. However, the tracking error signal Te is applied to the closed loop including the optical head 1a and the tracking control circuit 1b by the FM. An FM detector 13 for detection, and an eccentricity component δ of the optical disc 10 based on the FM detection output d of the FM detector 13
It is characterized in that the arithmetic circuit 14 for extracting is externally connected. The FM detector 13 detects the tracking error signal Te obtained from the optical head 1a as a compression wave and converts it into a signal corresponding to the coarse density of the compression wave. On the other hand, the arithmetic circuit 14 functions to extract the eccentric component δ by adding a negative sign to the square root of the arithmetic output of the detection output d of the FM detector 13 and 1 based on the operation principle described later. That is, assuming that the rotation angle of the optical disk 10 is θ, an operation of δ = − [(1 + d) / 2] ^1/2 is performed.

The detection output d of the FM detector 13 is shown in FIG.
As shown in (C), the value is 1 at the position where the coarse density of the tracking error signal Te is maximum, and is -1 at the position where the coarse density of the tracking error signal Te is minimum. Further, at a point where the coarse density of the tracking error signal Te takes an intermediate value, the FM detector 13
The detection output d becomes 0. Therefore, the eccentric optical disk 1
When 0 rotates once by the spindle motor 12, FM
The detection output d of the detector 13 shows a change of d = cos2θ. Here, the angle θ represents the rotation angle of the optical disk 10 and when the optical disk 10 makes one rotation, θ = 360
°.

By the way, when the rotation angle of the optical disc 10 is θ
, The eccentric component δ shows the change shown in FIG. This change is represented by -cosθ. From the expansion formula of the trigonometric function, cos θ = [(1 + cos 2θ) / 2] ^1/2 is satisfied. Therefore, between the eccentric component δ and the FM detection output d, δ = −cos θ = − [(1 + cos 2θ) / 2] ^1/2 = − [(1 + d) / 2] ^1/2 . Based on such a relationship, the arithmetic circuit 14 according to the present embodiment extracts the eccentric component δ by adding a negative sign to the square root of the arithmetic output of the detection output d of the FM detector 13 and 1 as described above. I do.

The optical disk device 11 having the above configuration is similar to that of FIG.
The eccentricity correction tracking control is performed according to the flowchart shown in FIG. First, when the optical disc 10 is rotated by driving the spindle motor 12 to rotate, in step (201) shown in the figure, the optical head 1a sends the tracking error signal Te indicating the track deviation of the light spot to the tracking control circuit 1b and the FM detection. To the vessel 13. FM detector 13 receiving the tracking error signal Te
In step (202), the tracking error signal Te is FM-detected to obtain an FM detection output d. The FM detection output d obtained here is supplied to the arithmetic circuit 14, and in step (203), the eccentric component δ is calculated by the calculation of δ = − [(1 + d) / 2] ^1/2 .

The eccentricity component δ calculated by the arithmetic circuit 14 needs to be supplied to the tracking control circuit 1b as a signal -δ of the opposite polarity for the purpose of eccentricity correction. As shown in step (204), an eccentricity correction signal −δ of −δ = [(1 + d) / 2] ^1/2 is supplied to the tracking control circuit 1b. Thus, an accurate eccentricity correction signal can be extracted based only on the tracking error signal Te output from the optical head 1a.

As described above, the optical disk device 11
When the tracking error signal is observed as a compression wave in one rotation cycle of the optical disc 10, two cosine or sine wave signals per rotation cycle are detected in accordance with the fluctuation of the coarse density and are included in this signal. By detecting the modulation component of the tracking error signal due to the eccentricity of the optical disk, the eccentricity component of the optical disk 10 can be easily and reliably extracted. The eccentricity is calculated using the eccentricity correction data one cycle before, as in the conventional optical disc apparatus in which the eccentricity phase is detected based on the phase of several waves centered on the maximum width of the rotor in the rotation cycle of the rotor. There is no need to correct, it is possible to perform eccentricity correction in real time,
More accurate eccentricity correction can be performed, and tracking accuracy can be greatly improved. In addition, the tracking error signal is sliced at the reference level and the waveform is shaped and all the rectangular waves are stored. A complicated circuit configuration is used, or a storage device (memory) for storing the rectangular waves and the rotation of the rotor of the spindle motor are synchronized. Since there is no need for a pulse generator or the like for generating a pulse, the entire apparatus can be simply configured.

Further, by observing the tracking error signal as a compression wave whose frequency transition repeats periodic fluctuations due to eccentricity, the FM detector 13 adjusts the fluctuation of the compression density of the compression wave, which is an FM wave, per rotation period. Two cosine or sine wave signals can be detected, so that information on eccentricity can be obtained simply and accurately without the help of the rotor rotation phase of the spindle motor 12.

When the rotation angle of the optical disk 10 is θ, the detection output d is obtained as cos 2θ, so that the eccentric component δ (= −cos θ) is − [(1 + cos 2).
θ) / 2] ^1/2, that is, − [(1 + d) / 2] ^1/2 , and the eccentricity component can be calculated strictly and accurately to assure high-accuracy tracking control. Therefore,
Calculation of the maximum rectangular wave width (first calculation), calculation of the intermediate value of several waves sandwiching the maximum rectangular wave width before and after (second calculation), and calculation of the phase of the maximum width rectangular wave in one rotation cycle of the rotor ( Third
A complicated method such as detecting the eccentric phase from the above is unnecessary, and if the calculation for extracting the eccentric component δ from the detection output d is tabulated, the amount of calculation can be greatly reduced. It is possible.

In the above embodiment, the case where the FM detector 13 is used as the detecting means is taken as an example. However, the tracking error signal is detected as a compressional wave, and converted into a signal corresponding to the coarse density of the compressional wave. If it does, another circuit can be used instead.

[0024]

As described above, according to the present invention, according to the present invention, a tracking error signal obtained from an optical head is detected as a compression wave and converted into a signal corresponding to the density of the compression wave. Then, the eccentricity component of the optical disc is extracted from the converted output, and the eccentricity correction tracking control is performed based on the eccentricity component. Therefore, when the tracking error signal is observed as a compression wave in one rotation cycle of the optical disc. In addition, two cosine or sine wave signals are detected per rotation cycle in accordance with the variation in the coarse density.
By detecting the modulation component of the tracking error signal accompanying the eccentricity of the optical disk included in this signal, the eccentricity component of the optical disk can be easily and reliably extracted. Uses the data of the eccentricity correction one cycle before as in the conventional optical disk device where the eccentricity phase is detected based on the phase of several waves centered on the maximum width of the obtained rectangular wave in the rotation cycle of the rotor. There is no need to perform eccentricity correction, and eccentricity correction can be performed in real time, more accurate eccentricity correction can be performed, tracking accuracy can be greatly improved, and tracking error signal It has a complicated circuit configuration that stores all the square waves whose waveforms have been sliced at the reference level and shaped, or a storage device (memory) or memory for square wave storage. Since no such in synchronism with the rotation of the Dorumota the rotor requires a pulse generator or the like for generating a pulse, an excellent effect such as can be easily configure the entire apparatus.

Further, in the present invention, since the detection means is constituted by an FM detector, the tracking error signal is observed as a compression wave whose frequency transition repeats a periodical change due to eccentricity, so that the FM compression wave can be obtained. The FM detector can detect two cosine or sine wave signals per one rotation cycle in accordance with the variation of the coarse density, thereby enabling eccentricity without the help of the rotor rotation phase of the spindle motor. There is an effect that information on the information can be easily and accurately obtained.

Further, according to the present invention, an eccentric component extracting means is provided by an arithmetic circuit for extracting an eccentric component obtained by adding a negative sign to the square root of the arithmetic output and the detection output output from the detecting means. Since the detection output d is obtained as cos 2θ when the rotation angle of the optical disc is θ, the eccentric component δ (= −cos θ) is − [(1 + cos 2θ) /
2] ^1/2, that is,-[(1 + d) / 2] ^1/2 , which can calculate the eccentricity component strictly and accurately, assure high-accuracy tracking control, and calculate the maximum rectangular wave width. (First operation), calculation of the intermediate value of several waves sandwiching the maximum rectangular wave width before and after (second operation), and calculation of the phase of the maximum width rectangular wave occupying one rotation cycle (third operation) A troublesome method such as detecting the eccentric phase from the above is unnecessary. Particularly, if the calculation for extracting the eccentric component δ from the detection output d is tabulated, the amount of calculation can be greatly reduced. Qin effect.

[Brief description of the drawings]

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

FIG. 2 is a signal waveform diagram of each section of the block shown in FIG.

FIG. 3 is a flowchart for explaining an eccentricity correction operation of the optical disk device shown in FIG. 1;

FIG. 4 is a block diagram showing an example of a conventional optical disk device.

FIG. 5 is a signal waveform diagram of each section of the block shown in FIG. 4;

6 is a flowchart for explaining an eccentricity correction operation of the optical disk device shown in FIG.

[Explanation of symbols]

 1a Optical head 1b Tracking control circuit 10 Optical disk 11 Optical disk device 12 Spindle motor 13 FM detector 14 Operation circuit

Claims (3)

[Claims] 1. An optical disk apparatus for recording or reproducing a signal by scanning an optical disk with an optical head, detecting a tracking error signal obtained from the optical head as a compression wave, and converting the tracking error signal into a signal corresponding to the coarse density of the compression wave. A detecting means for converting, an eccentric component extracting means for extracting an eccentric component of the optical disk from an output of the detecting means, and performing eccentricity correction tracking control based on the eccentric component extracted by the eccentric component extracting means. An optical disk device comprising: a tracking control unit. 2. The optical disk device according to claim 1, wherein said detection means is an FM detector. 3. The eccentric component extracting means comprises an arithmetic circuit for extracting a eccentric component by adding a minus sign to the square root of the arithmetic output of the detection output and the detection output from the detecting means. 2. The optical disk device according to claim 1, wherein: