JP2001014693A - Method and device for supplementing tracking error signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and a device for supplementing tracking error signal in which supplementing of TE signal of an optical disk is more strictly conducted without being adversely affected by the amount of eccentricity. SOLUTION: The following operations are conducted, i.e., TE signal 2 of the disk which is eccentrically rotated, is detected by a time series tn, a derivation ΔX(tn) in computed by the series tn based on the signals 2, an abnormality of the signals 2 is detected and while the signal 2 is abnormal in a certain interval, successively and cumulatively adding the derivation ΔX(tn) to the signal 2 located immediately before the interval to reproduce the signal 2 during the period. The differential value of a disk being eccentrically rotated is generally not zero. TE signal which is a sine curve approximate function that fluctuates one period for every revolution, reproduce extremely strict and correct TE signal in a minute rotational angle range such as a scratch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for complementing a tracking error signal, and more particularly, to complementing a tracking error signal for reproducing a normal TE signal when a surface of an eccentrically rotating optical disk has a scratch. Method and its equipment.

[0002]

2. Description of the Related Art A disk such as an optical disk is a recording medium. A tracking device is used for reading data recorded therein. In order to correctly read data from a disk for which eccentric rotation cannot be avoided, TE
(Tracking error) A signal complement circuit is provided. If the disk surface is damaged and the disk is eccentrically rotated, an incorrect value is output as a TE signal. When the TE signal outputs an illegal value, the TE signal complementing circuit complements the TE signal by using the value immediately before the illegal value is output while the illegal value is outputted.
When the disk has eccentricity, the error increases by the amount of the eccentricity, and the greater the amount of eccentricity, the greater the possibility that the tracking is deviated.

The T of the disk is not affected by the magnitude of the eccentricity.
It is desired that the complementation of the E signal be stricter.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for complementing a tracking error signal in which the complementation of a TE signal of an optical disk is stricter regardless of the amount of eccentricity. .

[0005]

Means for solving the problem are described as follows. The technical matters corresponding to the claims in the expression are appended with numbers, symbols, etc. in parentheses (). The number, the symbol, etc. are at least one of the technical items corresponding to the claims and the plurality / forms of implementation.
Although the agreement and correspondence with the technical matters of the two forms are clarified, it is not intended to show that the technical matters corresponding to the claims are limited to the technical matters of the embodiment.

A method of complementing a tracking error signal according to the present invention includes detecting a TE signal (2) of a disk (31) that rotates eccentrically in a time series (tn), and detecting a TE signal (2) based on the TE signal (2). ) (ΔX (t
n)) in time series (tn), detecting that the TE signal (2) is abnormal, and during the period in which the TE signal (2) is abnormal, the TE signal (2) immediately before the period. ) Is successively cumulatively added to the differential value (ΔX (tn)) to reproduce the TE signal (2) during that period. For an eccentrically rotating disk, its derivative is generally not zero (it may be zero near extremes).

[0007] A TE (tracking error) signal obtained from the tracking function of the disk is represented by an approximate sine curve in one cycle corresponding to one rotation of the disk, and there is no sharp change. Since the angle area where dust and flaws are present on one circle is minute compared to 2π, signal complementation by interpolation of differential value addition in the minute area is extremely strict. Therefore, the present invention is particularly useful for signal complementation of optical discs where high precision complementation is required, due to the presence of (small) scratches (34) on the surface of such discs. It is particularly useful when (2) is abnormal.

The TE signal immediately before the period is the TE signal immediately before the period (particularly, the period when the defect period is entered near zero degree where the differential value of the sine curve is maximum) as long as the differential calculation is possible. Preferably, it is a signal.

A tracking error signal complementing device according to the present invention comprises a discriminator (1) for discriminating whether a TE signal (2) of an eccentrically rotating disk (31) is normal or abnormal, and a TE signal (1). The magnitude of (2) is expressed in time series (t
n) a detector (9) for detection in time series (tn)
From the TE signal (2) before and after (X (tn) 2
A calculator (21) for calculating 5) and an adder (13) for cumulatively adding the differential value (ΔX25) to the TE signal (2) every unit time when the TE signal (2) is abnormal. ).

A circuit for outputting a normal TE signal (2) and a circuit for outputting a cumulatively added TE signal (2)
It is preferable to provide a changeover switch (4, 12, 16) for switching between 7) based on whether it is normal or abnormal in terms of simplifying the circuit configuration.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Corresponding to the drawings, an embodiment of a tracking error signal complementing device according to the present invention is provided with a TE signal supplementing circuit together with a defect discriminating circuit. As shown in FIG. 1, the TE signal 2 is input to the defect determination circuit 1. When the defect determination circuit 1 determines that the TE signal 2 is not an illegal value (hereinafter, referred to as normal or normal), the TE signal 2
Is output as a normal value 3 as it is, and the normal value 3 is output as a tracking drive signal via the A terminal of the switch 4.

The TE signal 2 is input to a TE signal complement circuit 5. When the defect discriminating circuit 1 discriminates that the TE signal 2 is an illegal value (a period from that point onward until the signal returns to a normal value is called a defect), the defect discriminating circuit 1 causes the switch 4 to select the terminal B and simultaneously outputs the operation signal 6 is output.
The operation signal 6 is input to the TE signal complement circuit 5. The TE signal complementing circuit 5 to which the operation signal 6 has been input starts its complementing operation. The complementary signal 7 output from the TE signal complementary circuit 5 is output as a tracking signal via the B terminal. The TE signal complement circuit 5 includes a TE signal interpolation circuit 8.

FIG. 2 shows details of the TE signal interpolation circuit 8. The TE signal interpolation circuit 8 includes an LPF (low-pass filter) 9 and a gradient (differential) detection filter 11. The LPF 9 includes a first switch 12 in the filter, a second switch 14 in the filter, and an amplifier 15, and removes noise from the TE signal 2. The LPF 9 further includes a hold filter circuit 13. The hold filter circuit 13 has a function of sequentially recording the TE signal 2 from which noise has been removed.

The TE signal 2 is the first switch 1 in the filter.
2 is input to the hold filter circuit 13, and is sequentially recorded by the hold filter circuit 13. The first switch 12 in the filter and the second switch 14 in the filter are:
The switch terminal A is selected in a normal state, and the switch terminal B is selected in a defect state.

The LPF 9 is connected to the inclination detecting filter 11 via a connection switch 16. The connection switch 16
Open at the time of defect (OFF), close at normal time (O
N). The gradient detection filter 11 is a differential circuit 2 formed by a delay circuit 17, a first amplifier 18, and a second amplifier 19.
1 is provided. The differentiating circuit 21 successively takes in the two TE signals 2 which are recorded in the hold filter circuit 13 and which are successive in time through the connection switch 16 which is normally closed, and obtains the unit time of the fluctuating TE signal 2. Calculate the amount of change (differential value) and output the differential value.

The inclination detecting filter 11 further includes an averaging L
PF22 is provided. The averaging LPF 22 to which the differential value output from the differentiating circuit 21 is input includes an amplifier 23 and a delay circuit 24, removes noise from the differential value, and averages the differential value. The differential value is an increase / decrease amount (also referred to as a slope value) per unit time. This inclination value is hereinafter represented by ΔX25.

The inclination value ΔX25 is determined by the plurality of amplifiers 26 and 2
It is adjusted and optimized at 6 '. The slope value ΔX25 is
The signal is transmitted to the output line 27 via the first switch 12 in the filter whose B terminal is selected at the time of the defect. The hold filter circuit 13 is connected to the amplifier 27.

Normally, the connection switch 16 is ON,
The tilt detection filter 11 sequentially differentiates the TE signal 2 and sequentially holds ΔX25 at that time. However, since the first switch 12 in the filter is not connected to the hold filter circuit 13, ΔX25 is Nothing is output from the filter 11. When a defect occurs, the connection switch 16 is turned off at that moment, and the first
The switch 12 and the second switch 14 in the filter select their B terminals.

The hold filter circuit 13 holds the value of the TE signal 2 at that moment (the time sequence is represented by tn-1). Its value is represented by a function Y (tn-1).
At that moment, the inclination value held by the inclination detection filter 11 is output from the inclination detection filter 11 as ΔX25,
The signal is input to the hold filter circuit 13 via the first switch 12 in the filter. At the time of the defect, the hold filter circuit 13 performs the following calculation. Y (tn) = Y (tn−1) + ΔX. ... (1)

FIGS. 3 and 4 analyze the swing of the optical disk 31. FIG. When the rotation center O is slightly eccentric and deviated to the point O ′, each point on the center line of the track 32 swings in the radial direction within the range of the swing width W as shown in FIG. When such a swing occurs, the TE signal 2 appears as a sine curve approximation curve that increases and decreases once during one rotation cycle with respect to the normal signal 33 when there is no swing, as shown in FIG.

It is assumed that the optical disk 31 has a scratch 34 as shown in FIG. Considering a 12 cm optical disk, the signal surface is standardized in the range of 50 mm to 116 mm in diameter, the rotation speed is constant at a linear velocity, and
/ S to 1.4 m / s. Assuming that the disk surface has a flaw of 2 mm in the outermost peripheral area, one cycle is about 303.7 m / s.
The wound portion is approximately 1.67 m / s, and the defect period is 1.67 msec.

When such a scratch is present, 1.67 msec.
6, the signal of the TE signal 2 is interrupted, or an illegal / abnormal value is output from a detection mechanism (not shown) as shown by a circle in FIG. In the first period of this period, the calculation of Expression (1) is performed. Equation (1) is represented by the following equation. Y (t1) = Y (t0) + ΔX (t0). ... (2)

Here, t0 is, as shown in FIG.
The order of the time sequence immediately before entering the defect period is shown. Y (t0) is the magnitude of the TE signal 2 at the time sequence time point t0 immediately before entering the defect period, and ΔX (t
0) is a differential value (slope value) of the time sequence time point t0.
The time sequence t0 is represented by a point C in FIG. The defect period ends at time point D.

There are some unit times between the line segments CD. The calculation of the equation (1) is executed as a sequential cumulative addition for each unit time at a minute time interval such as a calculation delay and a circuit operation delay. In this case, as shown in FIG. 8, five repetitive calculations are performed, and Y (t1), Y (t
2), Y (t3), Y (t4), and Y (t5) are obtained.

The TE complemented by such interpolation calculation
The signal 2 'has been reproduced very accurately. This value sequence Y
(T1) to Y (t5) are the first switch 12 in the filter.
, The signal is optimized by the amplifier 36 in the first switch 12 in the filter, is transmitted to the complementary signal 7 in FIG. 1, and is transmitted to the control system (shown in FIG. ).

[0026]

According to the method and apparatus for compensating for a tracking error signal according to the present invention, when an erroneous TE signal is extracted from an eccentric rotating disk, it is possible to reproduce and extract a very accurate correct signal.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an embodiment of a tracking error signal complementing device according to the present invention.

FIG. 2 is a circuit diagram showing a part of FIG. 1 in detail;

FIG. 3 is a plan view for analyzing the eccentric rotation of the optical disc.

FIG. 4 is a graph showing a TE signal of an optical disk that rotates eccentrically.

FIG. 5 is a plan view showing an example of a scratch on an optical disc.

FIG. 6 is a graph showing a TE signal of the embodiment of the optical disc.

FIG. 7 is a graph showing a TE signal during a defect period.

FIG. 8 is a graph showing reproduction of a TE signal during a defect period.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Discriminator 2 ... TE signal 4, 12, 16 ... Changeover switch 9 ... Detector 13 ... Adder 21 ... Calculator 25, DELTA X (tn) ... Derivative value 27 ... Circuit (output line) 31 ... Disk 34 ... Scratches tn …Time series

Claims (6)

[Claims] 1. detecting a TE signal of an eccentric rotating disk in a time series; calculating a differential value of the TE signal in a time series based on the TE signal; detecting that the TE signal is abnormal During the period in which the TE signal is abnormal, the differential value is successively cumulatively added to the TE signal immediately before the period to reproduce the TE signal during the period. Is a non-zero tracking error signal interpolation method. 2. The disk according to claim 1, wherein the disk is damaged due to a scratch on the surface of the disk.
A method for complementing a tracking error signal in which the E signal is abnormal. 3. The method according to claim 2, wherein the normal value of the TE signal is a tracking error signal represented by an approximate sine curve with one cycle of the disk as one cycle. 4. The method according to claim 1, wherein the TE signal immediately before the period is a tracking error signal that is the TE signal immediately before the period. 5. A discriminator for discriminating whether a TE signal of an eccentrically rotating disk is normal or abnormal, a detector for detecting the magnitude of the TE signal in time series, A calculator for calculating a differential value from the TE signal before and after the series; and an adder for cumulatively adding the differential value to the TE signal for each unit time when the TE signal is abnormal. Compensation method for tracking error signal. 6. A tracking error signal comprising a changeover switch for switching between a circuit for outputting the normal TE signal and a circuit for outputting the cumulatively added TE signal based on whether the circuit is normal or abnormal. Completion method.