JP2003257034A - Wobble signal extraction circuit and optical disk recording / reproducing device - Google Patents

Abstract

(57) [Problem] To provide a wobble signal extraction circuit and an optical disk recording / reproducing device which can reduce a noise component included in a wobble signal component and can cope with high-speed writing. SOLUTION: In a wobble signal extraction circuit for extracting a wobble component from an optical disk having a wobble formed in a guide groove during data recording, a write level signal is sampled in parallel with a first sample and hold circuit 14 for sampling a read level signal. Is provided, and the output signals of these two sample-and-hold circuits are added by an adder 24, and a wobble corresponding to the wobble formed in the guide groove based on the output of the adder 24 is provided. Extract signal components. As a result, the in-phase wobble signal components are simply added, and the out-of-phase wobble signal components are averaged, so that the ratio of the noise components to the wobble signal components is reduced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a CD-R and a CD-R.
The present invention relates to a wobble signal extraction circuit for extracting a wobble signal from a guide groove of an optical disc capable of writing data such as RW, and an optical disc recording / reproducing device.

[0002]

2. Description of the Related Art In optical discs such as CD-R and CD-RW, a guide groove called a pregroove, which serves as a guide when a light beam traces, is preliminarily formed in a spiral shape. Wobbles are formed in the grooves as the address information of the optical disc during recording.

The structure of the guide groove and wobble of the CD-R is shown in FIG. The wobble 3 is formed by making the guide groove 2 of the optical disc 1 meander in the width direction, and when recording data on the optical disc 1, absolute time information (ATIP: Absolute Time In Pregroo) indicating the current position of the light beam.
ve). The wobble signal corresponding to the wobble 3 is FM-modulated so that the modulation width is ± 1 kHz with respect to the carrier frequency of 22.05 kHz when the optical disc 1 is rotated at the standard speed.

In the optical disk recording / reproducing apparatus, as shown in FIG.
As shown in FIG.
The reflected light of the light beam 5 is received by the photodetector 4 which is composed of four light receiving surfaces A, B, C, and D which are divided into four in the direction along.
Generation of the tracking error signal, focus error, and wobble signal extraction are performed based on the difference between the outputs of the photodetectors (A + D) and (B + C). Based on the extracted wobble signal, the speed of the spindle motor is controlled so that the optical disc 1 rotates based on the carrier signal of 22.05 kHz.

In this way, for example, CL with a constant linear velocity
The optical disk 1 is rotationally driven by a V (Constant Linear Velocity) recording method, and desired data is recorded on the optical disk 1 by forming pits 6 in the guide groove 2 by laser light.

FIG. 7 shows a wobble signal extraction circuit in a conventional optical disk recording / reproducing apparatus. The photodetector 4 (see FIG. 6) that receives the reflected light of the light beam 5 is provided in the radial direction of the optical disc 1 and in the direction along the guide groove 2 as described above.
It has four light receiving surfaces of A, B, C and D which are divided, and outputs signals AIN, BIN, CIN and DIN, respectively. These signals AIN, BIN, CIN and D
IN is input to the first stage gain control amplifier (hereinafter referred to as GCA (Gain Control Amplifier)) 10A, 10B, 10C and 10D of the wobble signal extraction circuit to roughly adjust the reflected light intensity level.

Next-stage limit circuit (Limit) 11A
11D clamp the light reflected from the light beam 5 at a level equal to or higher than a read level described later.
The eccentricity component of the optical disc 1 is reduced by the following high pass filters (HPF) 12A to 12D. Amplifier 13
Calculates β {(A + D)-(B + C)} (β: constant) to extract a signal containing a wobble component.

In an ideal case where the detection signal has no eccentricity component, noise, etc., the calculation of β {(A + D)-(B + C)} removes the RF frequency component of the in-phase carrier. The wobble signal is extracted by sampling the read level signal in the sample hold circuit (S / H) 14.

Hereinafter, the output signal of the sample and hold circuit 14 is converted into a high-frequency removing filter (LPF) for removing high-frequency noise.
15. High-pass filter (HPF) for removing low frequency noise
16. Only a wobble component is taken out through a band pass filter (BPF) 17 that passes the wobble frequency band, and an AGC (Automatic Gain Control) circuit 18 makes the wobble signal have a constant amplitude.

2A and 2B show in principle the waveforms of the four detection signals AIN to DIN of the photodetector 4. The waviness component of the amplitude is caused by the eccentricity of the optical disc or the like. The detection signal has a waveform as shown in FIG. 2C when the time axis is enlarged. This waveform basically has a form in which a write level WL having a high laser power for writing the pits 6 in the guide groove 2 of the optical disc 1 and a read level RL having a low laser power for reading the pits 6 alternately appear. Has become.

In the sample hold circuit 14 described above, only the read level RL is sampled and processed. Therefore, the limit circuits 11A to 11D in the preceding stage allow the read level signal below the one-dot chain line in FIGS. 2 (c) and 2 (d). Pass only through and clamp any more.

[0012]

Here, in order to sample a more accurate read level signal in the sample and hold circuit 14, GCA 10A to 10A, which are the first-stage circuits, are used.
The circuits from D to the sample hold circuit 14 have an operating band equal to or higher than the RF frequency component. Therefore, the sample and hold circuit 14 also receives a noise component higher than the RF frequency component.

Therefore, in the case of a noise band apart from the wobble signal frequency band, only the wobble band can be extracted by the band pass filter. However, if the noise component exists up to the maximum frequency band of RF, noise near the wobble band is sampled. Can occur. This is,
After the sampling, the LPF 15 for removing the high frequency band and the HPF for removing the low frequency band noise such as the eccentricity component cause deterioration of the extraction accuracy of the wobble signal and deterioration of the writing quality.
16. Even if the wobble signal frequency band is extracted through the BPF 17 that extracts the wobble signal frequency, FIG.
Noise remains as in (b).

Further, since the signal frequency becomes higher as the writing speed becomes higher, the sampling interval T becomes longer with respect to the signal period of the maximum signal frequency due to the influence of the signal slew rate, etc., and the vicinity of the wobble band described above. The phenomenon that the noise is generated becomes remarkable.

The present invention is intended to solve such a problem, and in an optical disk recording / reproducing apparatus using an optical disk having a wobbled guide groove, such as a CD-R and a CD-RW, a wobble signal is used. It is an object of the present invention to provide a wobble signal extraction circuit and an optical disc recording / reproducing apparatus which can reduce noise components contained in components and can cope with high speed writing.

[0016]

In order to solve the above-mentioned problems, the present invention detects a reflected light from an optical disc having a wobble for reading absolute time information formed in a guide groove in the radial direction of the optical disc. A first sample-hold circuit for sampling a read level signal from the difference signal between the first and second output signals detected by the two light-receiving surfaces of the light detecting means having at least two light-receiving surfaces; In the wobble signal extraction circuit for extracting the wobble signal component corresponding to the wobble formed in the guide groove based on the output of the first sample and hold circuit, in parallel with the sampling of the read level signal by the first sample and hold circuit. A second sample and hold circuit for sampling a write level signal, and the first sample and hold circuit An adding means for adding the output signals of the second sample-hold circuit is provided, and the wobble signal component corresponding to the wobble formed in the guide groove is extracted based on the output of the adding means. .

With this configuration, when the wobble signal is extracted, both the read level signal and the write level signal are sampled and the signals detected by the photodetector are added. As a result, in-phase wobble signal components included in both signals are simply added, and noise components that are not in-phase are averaged. As a result, the ratio of the noise component to the wobble signal component is reduced.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a block diagram showing the configuration of a wobble signal extraction circuit according to an embodiment of the present invention. In this embodiment, the gain control amplifier (GCA) 10A is used as in the conventional circuit shown in FIG.
-10D and limit circuits (Limit) 11A-11
D and high-pass filters (HPF) 12A to 12D,
Amplifier 13 and sample hold circuit (S / H) 14
, A high pass filter (LPF) 15, a high pass filter (HPF) 16 and a band pass filter (BPF) 1
7 and an AGC circuit 18, a high-pass filter (HPF) 20A to 20D, and a limit circuit (L).
(imit) 21A to 21D, an amplifier 22, a sample hold circuit (S / H) 23, and an adder 24.

The present embodiment will be described in detail below. The photodetector 4 (see FIG. 6) has four light receiving surfaces A, B, C and D which are divided into four in the radial direction of the optical disc 1 and in the direction along the guide groove 2, and the signals AIN and BIN are respectively provided. ，
Output CIN and DIN. These signals AIN ~
As shown in FIG. 2, the DIN has a waviness of amplitude due to the eccentricity of the optical disk. This waviness is shown in FIG.
And (b), signals AIN and DIN are in phase, signals BIN and CIN are in phase, and signals AIN and B are in phase.
IN has a reverse phase. When the time axes of the signals AIN to DIN are expanded, a carrier signal including a wobble signal appears as shown in FIGS. 2 (c) and 2 (d).

Signals AIN, BIN, CIN and DIN
Is the GCA 10A, 10 at the first stage of the wobble signal extraction circuit.
B, 10C and 10D are input to roughly adjust the reflected light intensity level.

The Limits 11A to 11D in the next stage pass only the component corresponding to the read level RL of the reflected light of the light beam 5, and clamp the higher level. Next HPF
With 12A to 12D, only the high frequency band of the detection signal is passed, and the eccentricity component of the optical disk 1 having a low frequency is reduced. The amplifier 13 is β {(A + D)-(B + C)}.
(Β: constant) is calculated, and a signal including a wobble component is extracted. Then, by sampling the read level signal with the S / H 14, the RF caused by the eccentric component is detected.
A frequency component is reduced and a wobble signal is extracted.

On the other hand, the following signal processing is performed in parallel with the same signal processing as the above-mentioned conventional circuit.

The output signals of the GCAs 10A to 10D are HP
Only the wobble signal component passes through F20A to 20D,
The low frequency waviness component due to the eccentricity of the optical disk is removed. Next, by Limits 21A to 21D, only the component corresponding to the light level WL of the reflected light is passed through, and the higher level is clamped. The amplifier 22 uses α {(A +
D)-(B + C)} (α: constant) is calculated, and a signal including a wobble component is extracted. And with S / H23,
By sampling the light level signal, the RF component caused by the eccentricity component is reduced and the wobble signal is extracted. Here, the constants α and β of the amplifiers 12 and 13 are set so that the read level signal and the write level signal have the same level.

3A shows the signal waveforms of the input signals AIN to DIN, FIG. 3B shows the waveform and timing of the sample pulse for write level sampling, and FIG. 3C shows the waveform and timing of the sample pulse for read level sampling. There is.

Further, (d) shows the waveform of the output signal of the S / H 14 obtained by sampling the read level RL, and (e) shows the waveform of the output signal of the S / H 23 obtained by sampling the write level WL. (F) shows a waveform in which a noise component is superimposed on the wobble signal component.

Considering the noise component,
The noise generated in the signal obtained by sampling the read level RL by the S / H 14 and the noise generated in the signal obtained by sampling the write level WL by the S / H 23 are different in the sampled signal, and can be considered to be uncorrelated.

Therefore, when these signals are added by the adder 24, the wobble signal component becomes a simple addition as represented by the following equation. Sw = Swr + Sww Here, Sw is a wobble signal component after addition, Swr is a wobble signal component included in the signal obtained by sampling the read level RL, and Sww is a wobble signal component included in the signal obtained by sampling the write level WL.

On the other hand, read level RL by S / H14
Is not correlated with the noise component included in the signal obtained by sampling the write level WL by the S / H 23, the noise component of the output of the adder 24 is
It is considered to be expressed by the following formula. Nw = √ {(Nwr) ² + (Nww) ² } where Nw is the noise component after addition, Nwr is the noise component included in the signal obtained by sampling the read level RL, and Nww is the signal obtained by sampling the write level WL. It is the included noise component.

In this way, since the wobble signal component is simply added and the noise component is averaged with the square root of the sum of squares, the ratio of the noise component to the wobble signal component in the output of the adder 24 is reduced. . FIG. 3F shows the waveform of the output signal of the adder 24 together with the noise component. Here, the noise component is exaggerated for the sake of explanation.

The signal whose noise is suppressed by the adder 24 is L
High-frequency noise components are removed by the PF15, and the next-stage H
The PF 16 removes low frequency noise components.

Then, the BPF 17 extracts the wobble frequency band to extract only the wobble component. further,
The wobble signal has a constant amplitude by the AGC circuit 18.

FIG. 4 shows an output signal waveform of the AGC circuit 18. (A) is an embodiment of the present invention, and (b) is a conventional example. Comparing these waveform diagrams, in the conventional example, there are many noise components with respect to the wobble signal waveform and the waveform is distorted, whereas in the embodiment of the present invention, the noise component is suppressed and the distortion of the wobble signal component is reduced. You can see that

In the above embodiment, the photodetector has a light-receiving surface divided into four parts. However, if only the structure for reproducing the wobble signal is taken into consideration, the light-receiving part is divided into at least two parts in the radial direction of the optical disc 1. The present invention can be applied to a structure having a surface.

The wobble signal extraction circuit having the above configuration is
D-R, CD-RW, DVD-R, DVD-RW, DV
The present invention is applied to a disc drive device for driving an optical disc, which is a data-writable optical disc such as a D-RAM, and an optical disc recording / reproducing device provided with a light beam irradiation means for irradiating a light beam to the optical disc. Therefore, a high-performance device capable of high-speed writing can be realized.

[0035]

According to the first aspect of the present invention, a second sample and hold circuit for sampling the write level signal is provided in parallel with the first sample and hold circuit for sampling the read level signal. By adding the output signals of the hold circuit, the in-phase wobble signal components are simply added and the uncorrelated noise components are averaged. As a result, the ratio of the noise component to the wobble signal component is reduced, and it is possible to obtain a wobble signal extraction circuit that can handle high-speed writing even at a slew rate equivalent to that of the conventional circuit.

According to the third aspect of the present invention, there is provided a high performance optical disc recording / reproducing apparatus which is equipped with the wobble signal extracting circuit according to the first aspect and is capable of high speed writing.

According to the invention described in claims 2 and 4,
A component corresponding to the read level signal to be sampled by the first sample and hold circuit and a component other than the component corresponding to the write level signal to be sampled by the second sample and hold circuit are reduced in advance to achieve high accuracy. Sampling can be done.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wobble signal extraction circuit according to an embodiment of the present invention.

FIG. 2 is an enlarged view of four detection signal waveforms of the photodetector and their time axes.

3A is a signal waveform diagram of input signals AIN to DIN, FIG. 3B is a waveform diagram of a write level sampling sample pulse, FIG. 3C is a waveform diagram of a read level sampling sample pulse, and FIG. Waveform diagram of the output signal of the sample and hold circuit that samples the read level,
(E) is a waveform diagram of the output signal of the sample hold circuit that samples the write level, and (f) is a waveform diagram of the output signal of the adder.

FIG. 4A is a wobble signal output waveform diagram in the embodiment of the present invention, and FIG. 4B is a conventional example.

FIG. 5 is an explanatory diagram showing a configuration of a guide groove and a wobble of the CD-R.

FIG. 6 is an explanatory diagram showing a configuration of a photodetector and a guide groove of the optical disc in the optical disc recording / reproducing apparatus.

FIG. 7 is a block diagram showing a wobble signal extraction circuit in a conventional optical disc recording / reproducing apparatus.

[Explanation of symbols]

1 Optical Disc 2 Guide Groove 3 Wobble 4 Photo Detector 5 Light Beam 6 Pit 10A to 10D Gain Control Amplifier (GCA) 11A to 11D Limit Circuit (Limit) 12A to 12D High Pass Filter (HPF) 13 Amplifier 14 Sample Hold Circuit (S / H) (first sample-hold circuit) 15 high-pass removal filter (LPF) 16 high-pass filter (HPF) 17 band-pass filter (BPF) 18 AGC circuit 20A to 20D high-pass filter (HPF) 21A to 21D limit circuit (Limit) 22 amplifier 23 sample hold circuit (S / H) (second sample hold circuit) 24 adder

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5D044 BC04 CC04 EF03 FG10 FG16                       FG18                 5D090 AA01 BB04 CC01 CC05 CC14                       CC16 EE01 EE18 FF21 FF30                       FF36 GG03 HH01 LL08

Claims (4)

[Claims] 1. A light detecting means for detecting reflected light from an optical disk having wobbles for reading absolute time information formed in a guide groove, the light detecting means having a light receiving surface divided into at least two in a radial direction of the optical disk. A first sample hold circuit for sampling a read level signal from a difference signal between the first and second output signals detected on the light receiving surface is provided, and the first sample hold circuit is formed in the guide groove based on an output of the first sample hold circuit. A wobble signal extraction circuit for extracting a wobble signal component corresponding to the generated wobble; a second sample hold circuit for sampling a write level signal in parallel with the sampling of the read level signal by the first sample hold circuit; Adds the output signals of the first sample hold circuit and the second sample hold circuit That the adding means is provided, the wobble signal extraction circuit, characterized in that so as to extract a wobble signal component corresponding to the wobble formed on the guide groove on the basis of an output of said adding means. 2. A first high-pass filter reduces the eccentricity component of the optical disc to limit output that passes only the component corresponding to the read level signal of the reflected light detected by the light detection means, and the first sample. The eccentric component of the optical disc, which is supplied to the hold circuit and is included in the difference signal of the output of the photodetector, is reduced by the second high-pass filter, and the limit output is passed through only the component corresponding to the light level signal of the reflected light. The wobble signal extraction circuit according to claim 1, wherein the wobble signal extraction circuit is supplied to the second sample hold circuit. 3. A disk drive means for driving an optical disk having wobbles formed in a guide groove for reading absolute time information, a light beam irradiation means for irradiating the optical disk with a light beam, and reflection from the optical disk. A light detecting means for detecting light, which has a light receiving surface divided into at least two in the radial direction of the optical disc, and a level difference between the first and second output signals detected by the two light receiving surfaces of the light detecting means. An amplifying means for outputting and a first sample-hold circuit for sampling a read level signal from the output signal of the amplifying means are provided, and the wobble formed in the guide groove is formed on the basis of the output of the first sample-hold circuit. In an optical disc recording / reproducing apparatus having a wobble signal extraction circuit for extracting a corresponding wobble signal component, And a second sample-hold circuit for sampling a write-level signal in parallel with the sampling of the read-level signal by the first sample-hold circuit, the first sample-hold circuit and the second sample. An optical disc recording / reproducing device, comprising: an adder unit for adding output signals of the hold circuit, and a wobble signal component corresponding to a wobble formed in the guide groove is extracted based on an output of the adder unit. apparatus. 4. A first limit circuit for passing only a component corresponding to the read level signal of the reflected light detected by the light detecting means, and an eccentric component of the optical disk included in the output of the first limit circuit. A first high-pass filter that reduces and supplies the first sample-and-hold circuit to the first sample-hold circuit; a second high-pass filter that reduces an eccentric component of an optical disc included in a difference signal of the output of the photodetector; The optical disc recording / reproducing apparatus according to claim 3, further comprising a second limit circuit which supplies only the component corresponding to the write level signal of the reflected light, which is included in the output of the high-pass filter, to the second sample-hold circuit.