JPH1153775A - Method for evaluating optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluating method for an optical recording medium which can precisely estimate a skew characteristic without measuring crosstalk. SOLUTION: A signal is recorded in a prescribed track, jitter J1 in a state where the signal is not recorded in an adjacent track and jitter J2 in a state where the signal is recorded in the adjacent track are respectively measured and the skew characteristic is estimated from difference between these jitters. Deterioration quantity of jitter ΔJ calculated by formula: ΔJ<2> =J2 <2> -J1 <2> from the jitter J1 in the state where the signal is not recorded in the adjacent track and the jitter J2 in the state where the signal is recorded in the adjacent track may be a simple and convenient estimation parameter for evaluating the skew characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating an optical recording medium, and more particularly to a novel method for evaluating a skew characteristic without measuring crosstalk. It is.

[0002]

2. Description of the Related Art In recent years, in the field of high-density recording disks and the like, with the rise of multimedia, it is necessary to accumulate a large amount of information such as digital moving pictures and to reproduce the information by random access as necessary. Is growing.

An optical recording disk is a memory having features of random access, large capacity, and removable, and is widely used in various fields. However, the linear density and the track density are improved to further increase the density. There is a need for technology for this.

In general, increasing the recording density increases the degree of signal deterioration due to skew of the substrate, and it is important how to properly evaluate the skew as a system margin.

Therefore, a simple evaluation method for evaluating the skew characteristic is demanded.

[0006] Under such circumstances, conventionally, jitter and error rate are mainly used as parameters for evaluating system performance, and crosstalk is used as a parameter for evaluating skew, particularly radial skew.

[0007]

However, it is very difficult to measure the skew, particularly the amount of crosstalk that affects the radial skew, and the parameter corresponding to the amount of crosstalk that can be easily measured as a drive system is: The fact is that it does not substantially exist.

Accordingly, the present invention has been proposed in view of such conventional circumstances, and provides an optical recording medium evaluation method capable of accurately estimating skew characteristics without measuring crosstalk. With the goal.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, without measuring crosstalk itself, it is possible to measure the deterioration of jitter due to crosstalk. It has been found that the skew characteristics can be estimated, and the present invention has been completed.

[0010] Namely, the present invention records a signal on a predetermined track, for the signal, the jitter J ₁ in a state where the signal on the adjacent track is not recorded, the jitter J in a state where the signal on the adjacent track is recorded ₂ is measured, and the skew characteristic is evaluated based on the difference between these jitters.

[0011] There is a correlation between the above-mentioned difference in jitter (or the amount of jitter deterioration calculated from this difference in jitter) and the radial skew margin. By measuring or calculating these, the crosstalk itself is measured. Without this, the radial skew margin can be accurately estimated.

[0012]

DETAILED DESCRIPTION OF THE INVENTION and jitter J ₁ in a state where the signal on the adjacent track is not recorded, the jitter deterioration amount calculated from the jitter J ₂ Metropolitan in a state where the signal on the adjacent track is recorded (hereinafter, delta jitter ) Can be a simple evaluation parameter for evaluating the skew characteristic.

According to the present invention, the skew characteristic can be measured by measuring the delta jitter in an optical disk drive system, for example, and the measurement result is used as a feedback amount for improving the skew characteristic to thereby reduce the skew of the system. The characteristics can be improved.

FIG. 1 shows how the jitter changes when there is no signal on the adjacent track when the radial skew is changed (shown by a line a in the figure), and when the signal is on the adjacent track. FIG. 6 shows how the jitter changes (indicated by line b in the figure).

As is apparent from FIG. 1, the jitter in a state where there is no signal in the adjacent track does not show any significant deterioration even if the disk is tilted (even if the radial skew changes).

On the other hand, the jitter when there is a signal in the adjacent track rapidly deteriorates when the disk is tilted (when the radial skew changes).

Therefore, a value calculated by the following equation from the difference in jitter due to the presence or absence of the adjacent track signal is defined as a delta jitter (jitter deterioration amount) ΔJ, and the relationship between the value of the delta jitter ΔJ and the radial skew margin is defined. Upon examination, it was found that there was a correlation as shown in FIG.

ΔJ ² = J ₂ ² −J ₁ ² J ₁ : Jitter when there is no adjacent track signal J ₂ : Jitter when there is an adjacent track signal Therefore, from FIG. 2, for example, delta jitter ΔJ
Is 5.4% or less, a radial skew margin of ± 0.7 degrees or more can be secured.

By defining the value of the delta jitter ΔJ, the radial skew margin can be specified.

In order to measure the delta jitter ΔJ as described above, for example, a circuit for measuring the jitter when only the main track signal is present, a circuit for measuring the jitter when the adjacent track signal exists, and A drive system including an arithmetic circuit that calculates the amount of jitter deterioration (delta jitter ΔJ) from two values is used.

FIG. 3 shows an example of a delta jitter calculating circuit in such a drive system.

In this delta jitter calculating circuit, first,
The reproduction signal passes through an equalizer circuit 1 and is converted into a binary signal by a binarization circuit 2.
Valued.

The binarized data is supplied to a PLL circuit 3
The phase difference / voltage conversion circuit 4 converts the phase difference into a voltage,
A / D conversion is performed in the / D conversion circuit 5.

Further, based on the clock signal from the PLL circuit 3, the period / voltage conversion circuit 6 converts the voltage for one clock cycle, and similarly the A / D conversion circuit 7 performs A / D conversion.

Then, the output of the A / D conversion circuits 5 and 7 is subjected to arithmetic processing by the arithmetic circuit 8 to calculate the jitter in the reproduced signal.

At this time, it is possible to measure the delta jitter ΔJ by recording and reproducing signals as shown in FIG. 4 on the optical disk.

That is, at the time of recording, for example, signals are continuously recorded on even-numbered tracks in the same manner as usual (in the figure, the area where signals are recorded is shown as hatched areas), and on odd-numbered tracks, recording is performed for each sector. -Repeat unrecorded.

At this time, when the even-numbered track is reproduced, two states of a state A without crosstalk (a state without an adjacent track signal) A and a state B with a crosstalk (a state with an adjacent track signal) B are provided for each sector. Will be repeated.

The delta jitter ΔJ can be measured by measuring and calculating each jitter at this time by the delta jitter calculation circuit shown in FIG.

Since the state of the reproduction signal is intermittent, the timing circuit 11 uses the sector sync generated from the address signal in the synchronization detection circuit 9 as a reference signal, based on the track / sector discrimination signal from the address recorder 10, for example. The jitter value in each state is sampled by each sample signal generated in step (1), and each processing is performed.
Here, the sampling gate is set to be narrower than the actual sector width in consideration of the rotation fluctuation and the stabilization time of the clock pull-in operation.

Since the reproduction signal itself is intermittent in the odd-numbered tracks, the reproduction signal and the clock reproduction in the PLL circuit 3 are also processed by the sample and hold signal (S / H signal) generated by the timing circuit 11. .

In this system, a state C having no meaning as a state is input / output instead of the state A without crosstalk in an odd track, and this state is converted into a digital signal. Then, it is sent to the system control unit and fed back to, for example, a skew servo circuit.

In the above measurement, in order to minimize the fluctuation due to noise or the like of the reproduced signal, it is possible to perform an averaging process based on a plurality of data to improve the measurement accuracy.

Also, as shown in FIG. 5, the delta jitter can be measured similarly by recording a signal with two sectors / staggered lattice and shifted one sector position on the optical disk. .

In this case, the state C, which has no meaning as a state,
Therefore, selection and sampling are performed by the timing signal.

In the present system, two states A and B can be obtained for both odd and even tracks, and the delta jitter can be calculated more accurately.

In the above description, a block for signal processing is described as a sector, but it is needless to say that the interval is not a sector interval. Further, the number of continuous sectors does not need to be two, but may be two or more. When the number of sectors is three or more, the position shift does not need to be one sector.

If a similar signal is recorded in advance on a so-called ROM disk, the delta jitter can be measured similarly.

[0039]

As is apparent from the above description, according to the present invention, it is possible to accurately estimate the skew characteristic without measuring the crosstalk itself, and to provide a simple skew characteristic evaluation method. It is possible.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing how jitter changes due to radial skew when there is an adjacent track signal and when there is no adjacent track signal.

FIG. 2 is a characteristic diagram showing a relationship between a delta jitter ΔJ and a radial skew margin.

FIG. 3 is a circuit diagram illustrating a configuration example of a delta jitter calculation circuit.

FIG. 4 is a schematic diagram showing an example of a recording state for measuring digital jitter.

FIG. 5 is a schematic diagram showing another example of a recording state for measuring digital jitter.

Claims (2)

[Claims] 1. A signal is recorded on a predetermined track, and a jitter J ₁ in a state where no signal is recorded in an adjacent track and a jitter J ₂ in a state where a signal is recorded on an adjacent track are recorded. A method for evaluating an optical recording medium, comprising measuring and evaluating a skew characteristic based on a difference between these jitters. 2. A jitter deterioration amount Δ from the jitter difference.
The J is calculated by the following equation ^{_{ΔJ 2 = J 2 2 -J 1}} 2, evaluation method of claim 1, wherein the optical recording medium and evaluating the skew characteristics by the jitter amount of reduction .DELTA.J.