JPS6159633A - Eccentricity correcting method of disc - Google Patents

Abstract

PURPOSE:To correct the eccentricity of a disc with a high precision by correcting the eccentricity on a basis of the sum of the counted-up/down value in the traversing direction of the number of eccentricity detecting tracks, which traverse a fixed head, and a tracking error detected in real time. CONSTITUTION:Plural eccentricity detecting tracks having concentric circle shapes are preliminarily recorded on a disc 10 provided with no guide grooves, and a recording and reproducing head 14 is allowed to face these tracks and is fixed. The number of tracks which traverse the head 14 in accordance with the rotation of the disc 10 is counted up or down in accordance with the traversing direction, and this counted-up/down value is stored as a function of the disc rotation angle. When data is recorded and reproduced, tracking correction of the head 14 is performed on a basis of the sum of the counted-up/down value, which is read out in accordance with the disc rotation angle, and the tracking error which the head 14 detects in real time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method for correcting eccentricity of a disk, which is applied when recording and reproducing a disk having tracks without guide grooves.

(Technical Background of the Invention and Prior Art) A disk recording/playback device that records digital information on a disk along concentric or spiral tracks and plays back the recorded digital information is capable of recording data at high density. Because of this, the track spacing on the disc is very small. In the case of an optical disc, this track interval is usually set to about 2 μm. On the other hand, when attaching a disk to a rotary drive device, it is necessary to
It is normal for a center of gravity of m to occur. For this reason, when recording and reproducing data, a tracking servo system is required to enable the recording/reproducing head to accurately follow the track.

However, if the disk does not have a guide groove that indicates a track, there is no guide groove for the head to follow.

If the disk eccentricity is large, it will not be possible to track the track being formatted.

(Object of the Invention) The present invention has been made in view of the above circumstances, and is intended to improve the performance of the (2)
Our objective is to provide a method for correcting the heart that enables stable recording and reproduction of data by accurately correcting the heart.

(Structure of the Invention) The present invention records a concentric eccentricity detection track on a disk in advance, and detects the eccentricity using this state of mind detection track prior to data recording/reproduction. The above objective was achieved by storing the data and recording and reproducing data while correcting the eccentricity based on the stored eccentricity amount.

That is, an object of the present invention is to attach a recording/reproducing head to a plurality of concentric detection tracks recorded in advance on a disk without a guide groove. They are fixed facing each other, and as the disk rotates, the number of tracks crossing the head is added or subtracted correspondingly in the transverse direction, and the added and subtracted values are stored as a function of the disk rotation angle. During recording and playback, the values are read out in accordance with the disc orientation angle.
This is achieved by a method for correcting eccentricity of a disk device, which is characterized by performing head tracking correction based on the sum of a subtraction value and a tracking error detected by the head in real time.

(Embodiments) The present invention will be described in detail below based on the illustrated embodiments.

FIG. 1 is a conceptual diagram for explaining a practical example fNLQ of the method of the present invention, and this practical IMLtj registers and reproduces data on an optical disk. In this figure, reference numeral 10 is an optical disk, for example, a transparent disc made of glass, etc., on one side of which a vapor deposited film 2 is formed, and this vapor deposited MP is further covered with a protective layer.

The structure of the optical disc is not limited to this. During recording on an optical disk, when a strong laser beam is focused on a vapor deposited film, the vapor deposited film is deformed and pits are formed therein, and digital information is recorded by the arrangement of these pits. In the figure, the deposited film is a recording surface 10a on which data and the like are recorded.

12 is a motor that rotates the disk IO at a constant speed.

Reference numeral 14 denotes a recording/reproducing head, which includes a semiconductor laser 16 that outputs a linear laser beam. Polarizing beam splitter 1
8. λ/4 plate 20. Objective lens 22° Tracking error (hereinafter referred to as TER) detection two-split photodetector 24
etc. The laser light emitted by the semiconductor laser 16 is transmitted through @optical beam splitter 18. λ/4 plate 20. It passes through the objective lens 22 and focuses on the recording 110a of the disk 10. Data is recorded using high-energy laser light.

Pits are formed by removing or deforming the deposited film on the recording surface 10a. Low-energy laser light when playing data? The presence or absence of pits is determined based on changes in the intensity of reflected light. This reflected light during reproduction is reflected by the polarizing beam splitter 18 and guided to the photodetector 24.

For example, a push-pull method is used as a method for detecting TER. FIG. 2 shows the image formed on photodetector 24 in this case. In this figure, 26 is an image of a pit, and if the laser beam is correctly focused on the bit, only 26 of the pits will be located at the center of the photodetector 24, as shown in this figure. As the pit deviates from the laser beam focus position, that is, as the tracking error increases, the pit image 26 shifts upward or downward in FIG. 2. Therefore, when the pit shifts, the light amount of each of the two divided photodetecting elements 24a and 24b of the photodetector 24 changes. Tracking error? The TER signals shown are those of each photodetector element 24a obtained by the subtracter 28.

24b. Also disk 10
RF multiplied signal indicating digital information read from adder 3
Each photodetector element 24a was determined by 0.

It is obtained as the sum of the outputs of 24b.

FIG. 3 is a plan view of the disk 10. On the outer periphery of the data recording section A of the disk 10, a large number of sentiment detection tracks are pre-recorded concentrically with the data recording tracks at predetermined intervals. The number of tracks is determined so that one seat of this eccentricity detection truck #B is wider than the expected eccentricity during chucking. In this track, pits are arranged at convenient lengths and intervals in order to determine the amount of eccentricity as described later.

FIG. 4 is a waveform diagram of the RF multiplied signal TER signal.

This is a waveform when the disk 103 is rotated with the head 14 fixed at a position where the reproducing laser beam enters the eccentricity detection track group. In other words, the reflected light at a place without pits becomes brighter, so the R and F signals a are at a high position, but when disc 1
Due to the eccentricity of 0, when the sentiment detection track enters the reproduction laser beam, the light reflected by the pit becomes weak. As a result, each time one track crosses the laser beam P, the RF multiplied signal amplitude changes for each pit of that track, and the RF
(K number changes as shown in Figure 4 ■. In Figure 1, 32
is an AC connection capacitor connected to the output end of the adder 30, which blocks the DC component of the RF multiplied signal and passes only the AC component. The RF multiplied signal passing through capacitor No. 32 (CB) in FIG. 4 has the waveform shown by b.

4C) and 4) show the TER signal, (Q shows the waveform 2 when the track crosses the laser beam from the outer circumference to the inner circumference, and (D) conversely, shows the waveform 2 when the track crosses the laser beam from the inner circumference to the outer circumference. In this way, depending on the direction in which the track crosses the laser beam,
The phase of the TER signal is inverted.

In the present invention, the number of tracks to be traversed depends on the phase inversion of this TER signal. Since addition or subtraction is performed, the configuration thereof will be explained using FIG. 1 and the output waveform diagram of each part shown in FIG.

In FIG. 1, 34 is a detection circuit which detects the envelope segment of the RF multiplied signal waveform b) passed through the capacitor 323 and outputs the 51st waveform. The output of this detection circuit 34 (output waveform C
) is a Schmitt circuit (output waveform d), a differentiator circuit 38 (
Output waveform e), waveform shaping circuit 40. Passes through the rectifier circuit 42 (output waveform f) 2.

The waveform f, which is the output of the rectifier circuit 42, is a rectangular wave that rises every time the eccentricity detection track crosses the laser beam.

The TER signal is sent to the waveform shaping circuit 44. The rectifier circuit 46 transforms the signal into a waveform g. In FIG. 5, in the range E of the TER signal, the track crosses from the outer circumference to the inner circumference, and in the range F, the laser beam P crosses from the inner circumference to the outer circumference. waveform f
,! : The AND output of g is obtained by the AND circuit 48 (output waveform h).

Further, the inverted output waveform i of the waveform g is obtained by the NOT circuit 50, and the AND output of the waveform f and the waveform 100 is obtained by the AND circuit 52.
(output waveform i).

Reference numeral 54 denotes a reset/set flip-flop, into which a waveform is inputted to its set input terminal S, and a waveform i is inputted to its reset input terminal R. As a result, waveform j is output to the Q output terminal of flip-flop 54. This waveform j
is at H level while the laser beam crosses the track from the outer circumference to the inner circumference.

While crossing from the inner circumference to the outer circumference, the level changes to L level.

In FIG. 1, 56 is an adder/subtracter, which uses the waveform j as an addition/subtraction signal to add/subtract 2 rectangular wave numbers of the waveform d.

For example, addition is performed when waveform j is at H level, and subtraction 2 is performed when waveform j is at L level.

Reference numeral 58 is a memory, which stores the addition/subtraction values of the adder/subtractor 56 as the rotation angle θ of the disk 10 (or the motor 12).
Store it as a function of . Note that this rotation angle θ is determined with reference to a predetermined reference point G for the disk 10, as shown in FIG. The base point G is a signal recorded near the inner or outer circumference of the disk 10, for example.
It may be read and detected by other detection means.

As described above, the amount of eccentricity of the disk 10 is stored in the memory 58, but the amount of eccentricity of the disk 10 stored at this stage is a rough value expressed by the rotation angle of the disk and the number of tracks traversed.

Next, while moving the optical head to follow the eccentricity detection trunk, output this eccentricity from the memory 58 and switch 78? The D/A converter 62 inputs the signal as an analog signal to the adder 64, where it is added to the real-time TER signal obtained by following the eccentricity detection track 2. If this added value is manually applied to the drive circuit 66 and the head 14 is moved by the drive motor 68, the detection track is caused to follow. At this time, the rotation angle of the disk (every minute angle required for tracking servo) is T.
The ER signal is converted into a digital quantity through an A/D converter 70 and stored in a memory 72. Next, using the TER signal stored in this memory 72 and the arithmetic circuit 74, the contents 3 of which memory 58 should be corrected first. ie this modified value? If you use it to follow the track as described above, TE
The R signal will be smaller than last time. This correction value calculation circuit 7
D through the 4° digital filter 76 and switch 78
/A conversion? In S62, the signal is converted to an analog signal, added to the real-time TER signal as in the previous case, and inputted to the drive circuit to cause the head to follow the track.

Does the digital filter 76 have a delay in the operation of the tracking/surge system? In order to compensate, for example, the amount of eccentricity at an angle O that precedes the rotation angle corresponding to the movement delay? It is something to read out. In this way, the track is followed again and stored in the memory 72 in the same way as the TER signal at that time, and the contents of the memory 58 are further corrected by the arithmetic circuit 74. Thereafter, the input to the drive circuit is modified in the same manner, and the tracking of the lateral sentiment detection track is performed again. By repeating this loop several times, it becomes possible to track the concentricity detection track with high accuracy. The number of repetitions can be determined, for example, until the maximum value of the TER signal becomes less than a certain threshold value, but it is also possible to predetermine the number of repetitions as two. loop? Once completed, the final digital filter 76 output is stored in memory 80. FIG. 6 shows a flowchart for calculating the eccentricity correction amount explained above.

If the head is moved after reading from the center correction ff1K memory 80 obtained in this way, the head will draw a track movement 5 trace concentric with the rotation amount detection track anywhere on the data recording area A on the disk. I can do it. Is there any information on the track in the recording section? Record or already recorded information? Is there an optical head near the track you want to access when playing? The head is moved based on the contents of the memory 80 to perform eccentricity correction.

Tracks are formatted on the disk 10 before data is recorded, and each track has only a sector mark to indicate the beginning of data in the data recording area A (third
(see figure). Therefore, when recording data, the head 14 is moved based on the contents of the memory 80 to correct eccentricity, the head position is corrected based on the TER of the sector mark, and data is recorded after this sector mark.

When reproducing data, the head 14P is moved based on the contents of the memory 80 to correct eccentricity, and at the same time, the position of the head 14 is determined based on the sector mark and TER detected from the data. Fix it.

For this reason, during recording and reproduction, the ability to follow the track is improved, and stable recording and reproduction are possible.

In this embodiment, the contents of the memory 80 and the TER signal are added by the adder 64, and the entire head 14 is moved based on the sum. However, in the present invention, the head may be moved by 14 minutes based on the contents of the memory 80, and only the objective lens 22 may be moved based on the TER signal. Furthermore, it is clear that the eccentricity correction method of the present invention can be used regardless of whether the tracks of the recording section A are concentric or spiral.

Further, the present invention is applicable not only to optical recording/reproducing devices but also to electrostatic type, magneto-optical type, etc., as long as they do not have guide grooves.

(Effects of the Invention) As described above, the present invention records eccentricity detection tracks concentrically on a disk in advance, and, prior to data recording/reproduction, detects eccentricity that traverses the head while the head is fixed. The number of the detection track is added or subtracted in accordance with its transverse direction, and head tracking correction is performed based on the sum of this addition/subtraction value and the tracking error detected in real time. For this reason, even though it is a disc without a guide groove.

The rotation of the disk can be corrected with high precision, making stable recording and playback possible.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an image of a photodetector, FIG. 3 is a plan view of a disk, and FIG. 4 is a diagram showing an R
FIG. 3 is a waveform diagram of an F signal and a TER signal. FIG. 5 is an output waveform diagram of each part in FIG. 1, and FIG. 6 is a flowchart for calculating the amount of eccentricity correction. 10...Disk, 14...Head. 56...addition/subtractor, 58,72.80...
memory. 64...Adder. Figure 5 Figure 6

Claims (1)

[Claims] A recording/reproducing head is fixed facing a plurality of concentric eccentricity detection tracks recorded in advance on a disk without a guide groove, and the number of tracks crossing the head is determined in the transverse direction as the disk rotates. While adding or subtracting correspondingly, this addition/subtraction value is stored as a function of the disk rotation angle, and when recording/reproducing data, the head reads the addition/subtraction value corresponding to the disk rotation angle in real time. A disk eccentricity correction method characterized by performing head tracking correction based on the sum of a tracking error detected by.