JP2001028131A - Optical disk drive - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To cancel the influence of a circuit offset generated in a track error signal at the time of a recording operation, and to improve the track positioning accuracy of a light spot at the time of a recording operation. A deviation amount detecting means for detecting a deviation amount between an amplitude of a reproduction signal when the light spot passes through the pit A and an amplitude of a reproduction signal when the light spot passes through the pit B,
Track offset applying means for adding an offset to the track error signal during the recording operation is provided so that the deviation amount at the end of the recording operation is equal to the deviation amount at the end of the reproducing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device capable of recording and reproducing information, and more particularly to an optical disk device capable of improving the accuracy of track positioning of a light spot during a recording operation.

[0002]

2. Description of the Related Art Conventionally, in an optical disk apparatus, an optical disk is irradiated with a light spot so that the light spot follows a track defined by a guide groove provided on the optical disk, and a sinusoidal light detected from the reflected light is applied to the optical disk. Feedback control using a wavy track error signal, so-called track positioning control, is performed. Generally, since an offset exists in this track error signal, an offset is applied to the track error signal in the optical disk device in order to improve the track positioning accuracy of the light spot. The most well-known first method is to add an offset to the track error signal so that the amplitude center of the sinusoidal track error signal becomes zero.

Next, a second well-known method will be described with reference to FIG. A guide groove 12 for detecting a track error signal is provided intermittently on the optical disk 10. A pit A16 and a pit B18 are provided at the position where the guide groove 12 is cut, at a fixed distance from the center of the track. The optical head 22 irradiates the optical disk 10 with the light spot 20 and detects a track error signal 24 and a reproduction signal 26 from the reflected light.

The deviation amount detecting means 34 detects the amplitude of the reproduction signal 26 when the light spot 20 passes through the pit A16 and the reproduction signal 26 when the light spot 20 passes through the pit B18.
Is detected as the deviation amount 44 from the amplitude. A low frequency component signal 66 is extracted by the LPF circuit 64 from the deviation amount 44. The adding circuit 68 adds the low frequency component signal 66 to the track error signal 24 and outputs a composite track error signal 70. By performing feedback control using the composite track error signal 70, the deviation amount 44
The track positioning of the light spot 20 is performed such that is zero.

[0005]

In the first prior art described above, if a circuit offset occurs in the track error signal during the recording operation, the track positioning accuracy of the light spot during the recording operation cannot be improved. According to the above-described second conventional technique, it is known that the amplitude of the reproduction signal when the light spot passes through the pit A and the amplitude of the reproduction signal when the light spot passes through the pit B change depending on the inclination of the optical disk. ing. For example, as shown in FIG. 8, when the optical disc 10 is bent at a certain diameter and the axis of the spindle motor 72 is inclined with respect to the optical axis of the optical head 22, the track deviation of the light spot occurs. In spite of the absence, as shown in FIG. 9, the deviation amount 44 is a secondary sine wave signal having an offset. Therefore, the deviation amount 4
In the prior art in which 4 is set to zero, the track positioning accuracy of the originally intended light spot cannot be improved, and there is no example applied to products to date. When a circuit offset occurs in the track error signal during the recording operation, the responsiveness of the LPF circuit is slow, so that the track positioning accuracy of the light spot particularly at the start of the recording operation cannot be increased.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical disc apparatus capable of improving the track positioning accuracy of a light spot during a recording operation.

[0007]

In order to achieve the above object, a track is defined by intermittently provided guide grooves, and a fixed distance is provided at a position where the guide grooves are cut and at the center of the track. Use an optical disk provided with pits A and B on the left and right.

In a seek operation or a reproducing operation, an offset is added to the track error signal so that the amplitude center of the track error signal obtained by the reflected light from the guide groove becomes zero so that the track error signal is not erroneously corrected. Add. First, at the end of the seek operation or the reproduction operation, the deviation amount between the amplitude of the reproduction signal when the light spot passes through the pit A and the amplitude of the reproduction signal when the light spot passes through the pit B is detected. Means, and the deviation amount is stored in the deviation amount storage means.

Next, at the end of the recording operation, the deviation between the amplitude of the reproduction signal when the light spot passes through the pit A and the amplitude of the reproduction signal when the light spot passes through the pit B is determined by a deviation amount detecting means. And the deviation amount is stored in the recording deviation amount storage means. Here, the difference between the deviation amount detected at the end of the seek operation or the reproduction operation and the deviation amount detected at the end of the recording operation means the track deviation of the light spot caused by the circuit offset of the track error signal generated at the time of the recording operation. I do.

The circuit offset of the track error signal generated during the recording operation can be canceled by adding an offset to the track error signal by the track offset applying means so that the difference between the deviation amounts becomes zero during the recording operation. It is possible to improve the track positioning accuracy of the light spot during the recording operation.

Since the deviation amount detected at the end of the seek operation or the reproduction operation is affected by the disk tilt, it tends to be a sine wave having the same period as the disk rotation period or a sine wave having a period half the rotation period. In order to reduce the detection error due to the fluctuation component, the deviation amount is detected at least 4 points, preferably 8 points or more in one round, and an average value thereof is used. As a result, it is possible to further increase the track positioning accuracy of the light spot during the recording operation.

Further, by measuring the deviation amount at the end of the recording operation and the deviation amount at the end of the seek operation or the reproduction operation in the same pit, it is possible to reduce errors due to characteristic variations in the disk.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

First, an optical disk and signals obtained therefrom will be described. A track 14 defined by intermittently provided guide grooves 12 and a pit A16 and a pit B18 at a position where the guide grooves 12 are cut and at a fixed distance from the track center are located on the optical disc 10 at right and left. Is provided. The optical head 22 irradiates the optical disk 10 with the light spot 20 and detects a track error signal 24 and a reproduction signal 26 from the reflected light.

The track error signal 24 is detected by, for example, a well-known push-pull method, and if it corresponds to the guide groove 12 shown in FIG. 3A, it is a sinusoidal signal shown in FIG. 3B. The track error signal 24 generally has an offset due to a circuit offset or the like. In order to cancel the offset, a reproduction offset 28 is added to the track error signal 24 by the addition circuit 30, and a track error signal R32 to be offset-corrected is output during the reproduction operation. FIG. 3C shows the track error signal R32.

On the other hand, the reproduction signal 26 is a total light amount signal reflected from the optical disk 10, and if it corresponds to the guide groove 12, pit A16 and pit B18 shown in FIG. Signal. When the light spot 20 passes through the center of the track and the optical disk 10 is not tilted, the amplitude Sa corresponding to the pit A16
And the amplitude Sb corresponding to the pit B18 have the same value.
When the light spot 20 does not pass through the center of the track, or when the optical disk 10 is inclined, FIG.
As shown in (1), Sa and Sb do not have the same value.

The deviation amount detecting means 34 detects the amplitude Sa of the reproduced signal 26 when the light spot 20 passes through the pit A16.
And a deviation 44 from the amplitude Sb of the reproduction signal 26 when the light spot 20 passes through the pit B18. The deviation amount detection means 34 includes, for example, an amplitude detection circuit 36, a sample and hold circuit A38, a sample and hold circuit B40, and a subtraction circuit 42. Sample hold circuit A38
The timing of holding by the sample hold circuit B40 is when the light spot 20 passes through the pits A16 and B18, respectively.

Next, a method of improving the track positioning accuracy of the light spot during the recording operation, which is the object of the present invention, will be described. According to the present invention, before information is recorded, a recording offset, which is an offset correction value of a track error signal during a recording operation, is obtained in a test area provided on an optical disk in advance. After the recording offset is determined, information is recorded in the data area using the value. Hereinafter, the method will be described in detail.

First, the light spot is moved to a test area on the optical disk. Generally, the test area is provided on the innermost circumference of the optical disc. The deviation amount storage means 46 stores the deviation amount 44 at the end of the seek operation or the reproduction operation, and then the recording deviation amount storage means 48 stores the deviation amount 44 after the end of the recording operation. The reason will be described with reference to FIGS. FIG. 5 shows the waveform of the track error signal R32 during the recording operation. At this time, the switch 58 is open. The track error signal R32 is observed at the start of recording as if a track shift has occurred due to a circuit offset of the track error signal generated during the recording operation. Thereafter, the light spot 20 moves so that the added circuit offset becomes zero. As a result, the track error signal R3
2 becomes zero, but a track shift actually occurs.

FIG. 6A shows the light spot 20 after the reproducing operation.
Shows a state passing through the pits A16 and B18. In this case, the deviation amount 44 described above is
This signal is proportional to the slope of 0. FIG. 6B shows the light spot 20 passing through the pits A16 and B18 after the recording operation. As described with reference to FIG. 5, the light spot 20 passes through a position deviated from the track center due to the circuit offset of the track error signal generated during the recording operation. In this case, the above-described deviation amount 44 is the sum of a signal proportional to the inclination of the optical disk 10 and a signal proportional to the track deviation amount of the light spot 20. Therefore, by subtracting the deviation amount 44 after the end of the recording operation and the deviation amount 44 after the end of the reproducing operation, it is possible to detect the track deviation amount due to the circuit offset of the track error signal generated during the recording operation.

The deviation amount 44 stored by the deviation amount storage means 46
A subtraction circuit 50 subtracts the difference between the deviation amount 44 stored in the recording deviation amount storage means 48 and a track deviation signal 52 proportional to the track deviation amount. If the track shift signal 52 can be made zero, the amount of track shift newly generated during the recording operation becomes zero as compared with the reproduction operation. In order to make the track deviation signal 52 zero, the track offset applying means 54 outputs a recording offset 56 given an appropriate value.

By closing the switch 58 during the recording operation, the adding circuit 60 adds the recording offset 56 to the track error signal R32 and outputs the track error signal W62. By the feedback control using the track error signal W62, the track positioning of the light spot 20 is performed so that the track shift signal 52 becomes zero. In general, it is difficult to determine the recording offset 56 for the track deviation signal 52 to be zero. Therefore, by changing the value of the recording offset 56 and repeating the above operation, the recording for setting the track deviation signal 52 to zero is performed. The offset 54 is obtained.

Since the deviation amount detected at the end of the seek operation or the reproduction operation is affected by the disk tilt as described with reference to FIGS. 8 and 9, the deviation amount is a sine wave having the same period as the disk rotation period or half the rotation period. It tends to have a sine wave shape with a period. In order to reduce the detection error due to the fluctuation component, the deviation amount is detected at least 4 points, preferably 8 points or more in one round, and an average value thereof is used. As a result, it is possible to further increase the track positioning accuracy of the light spot during the recording operation.

Further, by measuring the deviation amount at the end of the recording operation and the deviation amount at the end of the seek operation or the reproduction operation in the same pit, it is possible to reduce errors due to characteristic variations in the disk.

Finally, the information recording operation will be described. The track offset applying means 54 outputs the recording offset 54 obtained in the test area. Switch 52 during recording operation
By closing, it is possible to make the track shift signal 52 zero, and it is possible to record information while making the amount of track shift newly generated during the recording operation zero compared with the reproduction operation.

[0026]

As described above, according to the present invention, it is possible to cancel the circuit offset generated in the track error signal at the time of the recording operation, so that the track positioning accuracy of the light spot can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical disk device showing a configuration of an embodiment.

FIG. 2 is a diagram showing an optical disk of the present invention.

FIG. 3 is a characteristic diagram showing a track error signal.

FIG. 4 is a characteristic diagram showing a reproduced signal.

FIG. 5 is a characteristic diagram showing a track error signal during a recording operation.

FIG. 6 is a diagram showing a track shift.

FIG. 7 is a block diagram showing a configuration of a conventional optical disk device.

FIG. 8 is a diagram showing an inclination of an optical disk.

FIG. 9 is a characteristic diagram showing a deviation amount.

[Explanation of symbols]

10 optical disk, 12 guide groove, 14 track, 1
6 pit A, 18 pit B, 20 light spot, 2
2 optical head, 24 track error signal, 26 reproduction signal, 28 reproduction offset, 30 addition circuit, 32
... Track error signal R, 34 ... deviation amount detecting means, 36
... Amplitude detection circuit, 38 ... Sample hold circuit A, 40
... Sampling and holding circuit B, 42 ... Subtraction circuit, 44 ...
Deviation amount, 46: deviation amount storage means, 48: recording deviation amount storage means, 50: subtraction circuit, 52: track deviation signal, 54
... Track offset applying means, 56 ... Recording offset, 58 ... Switch, 60 ... Addition circuit, 62 ... Track error signal W, 64 ... LPF circuit, 66 ... Low frequency component signal, 68 ... Addition circuit, 70 ... Composite track error signal .

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D118 AA13 AA18 BA01 BF02 BF03 CA13 CB03 CD03 CD11

Claims (3)

[Claims] 1. A track is defined by intermittently provided guide grooves, and pits A and B are provided at the position where the guide grooves are cut and at a fixed distance from the track center on the left and right. An optical disk device for recording information on an optical disk, the optical head irradiating the optical disk with a light spot and detecting a reproduction signal and a track error signal from reflected light thereof, and And the amplitude of the reproduced signal of the pit B
Deviation amount detection means for detecting a deviation amount from the amplitude of the reproduction signal when the signal passes through, a deviation amount storage means for storing the deviation amount at the end of a seek operation or a reproduction operation, and the deviation at the end of a recording operation. Recording deviation amount storage means for storing an amount, and a track offset for adding an offset to the track error signal during the recording operation such that the deviation amount at the end of the recording operation is equal to the deviation amount at the end of the seek operation or the reproducing operation. An optical disk device comprising an application unit. 2. The optical disk device according to claim 1, wherein
The deviation amount detecting means detects at least four deviation amounts in one round of the track, and the track offset applying means calculates an average value of the deviation amounts at the end of the recording operation when the seek operation or the reproduction operation ends. An optical disk device characterized in that an offset is added to the track error signal so as to be equal to the average value of the track error signal. 3. The optical disc device according to claim 1, wherein the deviation amount at the end of the recording operation and the deviation amount at the end of the seek operation or the reproduction operation are measured at the same pit A and pit B. Optical disk device.