JP2817688B2 - Optical disk recording power control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording power control apparatus, and more particularly to an optical disk apparatus for recording information on a disk-shaped recording medium using optical means such as a magneto-optical disk, a phase change disk, and a write-once optical disk.
The present invention relates to a light beam recording power control method.

[0002]

2. Description of the Related Art A standardized first-generation optical disk uses a recording method called a pit position recording method (inter-mark recording method) as shown in FIG. This is a method of recording RZ as a code of a sequence Y generated by a modulation code, and a method of reproducing a signal by detecting a mark position by differential detection of a recording pit position (differentiation of a reproduction signal R) during reproduction. Therefore, it has a wide margin for offset fluctuation. That is, the recording power margin is wide.

On the other hand, in the mark edge recording method (mark length recording method), as shown in FIG. 10, a magnetization reversal is performed from a code string of a series Y generated by a certain modulation code to NRZI (data “1”). A waveform train Z is generated and recorded by a method in which magnetization reversal does not occur with data "0"), and at the time of reproduction, both ends (edges) of the recording pit are detected by, for example, a level detection method to reproduce a signal. It is a method to do. Therefore, the mark edge recording method can be expected to improve the recording density as compared with the pit position recording method, but has a problem that the margin for the offset fluctuation or the recording power is narrow.

When recording on an optical disk with a laser beam, the recording power often deviates from the optimum value due to the temperature of the recording medium, the temperature of the laser diode, the focus deviation, the spot diameter variation due to optical components, and the aging. I do.

[0005] For this reason, the recording mark shape deviates from the regular shape. As a result, the symmetry of the reproduced signal eye pattern is lost, and if the level detection is simply performed at the intermediate level of the envelope, the probability of misreading the data increases.

FIG. 7 shows an optimum recording power (see FIG. 7 (A)) when the recording power is too low (see FIG. 7 (A)), in order to show the deviation of the pit shape and the reproduction eye pattern symmetry due to the recording power deviation. B) and the case where the recording power is excessive (see FIG. 7C).

[0007] As shown in FIG.
In the reproduced eye pattern, it appears as if it is superimposed as an offset on the portion having the smallest amplitude. Therefore, higher-precision recording power control is required than in the pit position method in which a differential signal of a reproduced signal is detected.

Conventionally, in order to obtain an optimum recording power at which an eye pattern of a reproduced signal is symmetrical, a recording pattern having a duty ratio of 50% included in a recording code is actually recorded, and the reproduced signal is measured by a measuring instrument such as a spectrum analyzer. The recording power at which the level of the second harmonic was minimized was determined as the optimum recording power.

At this time, if the second harmonic level is plotted on the vertical axis and the recording power is plotted on the horizontal axis, a graph having one minimum value can be drawn.

[0010] Conventionally, in order to widen the margin of the recording power, measures have been taken by devising a detection method at the time of reproduction.

There is a method of coping with a change in symmetry at the time of recording by changing a threshold level at the time of reproduction. For example, FIG.
As shown in FIG. 1, the reproduced signal is passed through a low-pass filter (LP
F) A DC component is extracted by 19, and this level is given to a comparator 20 as a threshold, and the comparator 20 compares the reproduced signal with this threshold to detect a level, or as shown in FIG. A method has been proposed in which a maximum value and a minimum value are detected by a hold circuit, and an average value thereof is given to a comparator (Comp) as a threshold level to form a pulse.

In addition to these methods, the detection system having a reproduction envelope having a temporal amplitude fluctuation also has the effect of absorbing information deterioration.

[0013]

In order to reproduce information without error, it is desirable to perform recording with an optimum recording power at the time of recording.

For this reason, in a conventional system using a magneto-optical disk, after recording data, it is checked whether or not the recorded data has been correctly recorded. At this time, there is no error in the recorded data, or a predetermined error correction code (Erro
r Correction Code) to determine whether the data was recorded correctly.

However, it is impossible to optimize the recording power only from this information.

Although there are several types of recording patterns with a duty ratio of 50% included in the modulation code, the optimum recording power for each is not the same, and the second
Due to the fact that the next harmonic level has a characteristic having one minimum value, the experience of a technician is required to determine the optimum recording power.

Further, in consideration of the realization of a device, an FFT (Fast Fourier Traversal) for expanding a time-series reproduced signal on a frequency axis.
It is difficult to incorporate an nsform (fast Fourier transform) circuit.

For this reason, there has been proposed a method in which a result of measurement under conditions such as environmental temperature is previously stored in a memory such as a ROM (read only memory) and an optimum recording power is set based on information from a sensor. , Conventionally.

However, it is necessary to measure and store the optimum recording power for many parameters such as the type of medium, the number of rotations of the disk, and the environmental temperature, which requires complicated work and processing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and a first object of the present invention is to provide an optical disk recording apparatus which has a simple configuration and detects a deviation of recording power from a reproduction signal. A power control device is provided.

It is a second object of the present invention to provide an optical disk recording power control device having a characteristic that a detection signal monotonically increases or decreases monotonically with respect to recording power on the premise of feedback control. is there.

[0022]

In order to achieve the above object, the present invention relates to an optical disc apparatus for performing mark edge recording / reproducing, wherein an independent recording beam and reproducing beam positioned on the same information track are used. A first detecting means for detecting an intermediate level of a reproduction signal envelope from a reproduction signal from the reproduction beam; and a sampler for reproducing the reproduction signal from the reproduction beam.
Edge time point is detected from the sampled signal level change point
Only the sample values of the reproduced signal before and after the edge
Second detection means for detecting a reproduction signal level near the edge by averaging
Signal envelope intermediate level detected by the detection means
Contact to detected edge near Le and said second detecting means
An optical disc recording power, comprising: a subtraction means for generating a difference between reproduction signal levels to be read out, and means for controlling the LD drive circuit so that an output of the subtraction means becomes zero. A control device is provided.

[0023]

The principle and operation of the present invention will be described in detail below.
In optical discs, recording pits are reproduced by a condensed spot whose size is determined by the wavelength of the laser and the numerical aperture of the lens. Even information is read as an interference component. For this reason, the amplitude before and after the sign change point decreases, and the amplitude margin decreases.

If the resolution is reduced by the increase in density, a large number of errors occur during data reproduction corresponding to a reproduction signal having a small amplitude level in a normal level detection method.

Therefore, if an optimum threshold value can be detected from the reproduced signal of the pattern in which the most errors occur, the total errors can be reduced.

The sample point having the smallest amplitude margin is the point where the intersymbol interference occurs most, so it can be seen that it is before or after the code change point.

Therefore, only this sample point is extracted, the value obtained by averaging is Lm, and the intermediate level of the envelope is Lm.
When e, the difference L m -L e represents the amount of deviation from the optimum recording power.

[0028] In other words, when the L m -L e> 0, when the excessive power, L m -L e <0, the under-power. Therefore,
By controlling the recording power so as to L m -L e = 0, it is possible to maintain an optimal recording condition.

FIG. 8 is a graph showing the characteristics of the recording power control signal with respect to the recording power in the present invention. FIG.
, The horizontal axis represents the recording power, and the vertical axis represents the difference Le−L.
m. That is, in the present invention, the recording power control signal is supplied to the LD drive circuit so that the difference between Le and Lm becomes zero, and control is performed to obtain the optimum recording power.

[0030]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an entire configuration of an embodiment of the present invention.

Referring to FIG. 1, when information is recorded on the disk medium 1 by the mark edge recording method, the information immediately after recording is reproduced by the reproduction beam 3 which is accurately positioned on the same track slightly away from the recording beam 2. To play. However, at the start of recording, an initial recording power corresponding to a certain reference voltage is applied.

From the detected reproduced signal, the intermediate level Le of the reproduced envelope amplitude is detected by the envelope intermediate level detecting means 4. At the same time, the amplitude level Lm at the edge position is detected by the edge near level detection means 5.

The difference between Lm and Le is generated by the subtractor 6, and the difference signal Le-Lm output from the subtractor 6 is generated by an integrating circuit such as a CR circuit including a resistor and a capacitor.
(The integrating circuit may be another averaging circuit), the averaged output is added to a predetermined reference potential by an adder 7, and the added output is used as a recording power control signal.
This is fed back to the D drive circuit 8.

The LD drive circuit 8 supplies a recording current corresponding to the given recording power to an LD (Laser Diode, semiconductor laser) to control the laser light power and reduce the temperature of a minute area on the recording medium. Change.

As a result, it is possible to control the recording power to an optimum value at which the difference signal between Lm and Le becomes zero. That is, it is possible to adaptively compensate for power fluctuations during recording, environmental temperature changes, and the like, and it is possible to perform good recording.

FIG. 2 is a diagram showing the configuration of the second embodiment of the present invention. In the case where recording and reproduction are performed using the same light beam, the recording power cannot be corrected while detecting a reproduction signal.

Therefore, test recording is performed on the test track by changing the recording power based on the disc reference position signal by the recording power controller 9. Then, the track information is reproduced to detect a difference (output of the subtractor 6) between detection signals by the envelope intermediate level detecting means 4 and the edge near level detecting means 5.

At this time, by using the disc reference position signal as a reference, it is possible to make a correspondence between the recording power and the detected difference signal. By using this, the recording power level P having the smallest absolute value of the difference signal between Lm and Le is determined, and the subsequent recording is performed, whereby pseudo recording power control can be performed.

FIG. 3 shows a third embodiment of the present invention.
FIG. 3 is a diagram illustrating a configuration of an envelope intermediate level detection unit 4. In the present embodiment, the envelope intermediate level detecting means 4 includes a minimum value detector 10 and a maximum value detector 11 of the reproduced signal, and outputs the average level of the detected maximum value and minimum value as the envelope intermediate level. It is characterized by.

FIG. 4 shows a fourth embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of an edge vicinity level detection unit 5.

Referring to FIG. 4, in the present embodiment,
After the reproduction signal is sampled by the sampling means 12, the reproduction signal is digitized by the level detector 13.

Further, the time sequence pattern detector 14 detects the edge point when the digital signal changes from "0" to "1" or from "1" to "0". As shown in FIG. 4, the time-series pattern detector 14 has an exclusive-OR circuit (EX-O) that receives an input signal and a signal obtained by delaying the input signal by a unit time (synchronous clock cycle).
R), an exclusive OR circuit (EX) which receives the unit time delay signal and a signal obtained by further delaying the unit time signal by the unit time.
-OR) and the logical sum (O) of these exclusive OR circuits
R) output.

At the same time, in the sampled signal, only the sample values before and after the edge time are averaged by the averaging means 15, and the level near the edge is output. The delay circuit 16 is inserted for correcting timing.

FIG. 5 shows a fifth embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of an edge vicinity level detection unit 5. If the intersymbol interference is large and the noise is large, digitization by level detection increases the possibility of erroneous detection, and reduces the S / N ratio of the recording power control signal. The part corresponding to the level detection is a Viterbi detector 17
By replacing with, improvement in the reliability of the detection signal can be expected.

FIG. 6 shows a sixth embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of an edge vicinity level detection unit 5.

When the intersymbol interference is large, the level detector 1
If the threshold level of 8 is fixed, there is a high possibility that the change point detector will erroneously output, so it is necessary to adaptively change the threshold level. Therefore, in the present embodiment, it is possible to output a stable recording power control signal by feeding back the output of the averaging means 15 to the level detector 18 having a variable threshold value.

[0048]

As described above, according to the present invention,
This has the effect that the optimum recording power can be determined with a simple configuration. Further, by adopting the two-beam configuration, it is possible to adaptively compensate for power fluctuations and environmental changes during recording, and thus it is possible to perform good recording. That is, the reliability at the time of reproducing the optical disk can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical disk recording power control device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an optical disk recording power control device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an optical disc recording power control device according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of an optical disk recording power control device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of an optical disk recording power control device according to a fifth embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an optical disk recording power control device according to a sixth embodiment of the present invention.

FIG. 7 is a diagram illustrating a deviation in symmetry between a pit shape and a reproduction eye pattern due to a recording power deviation.

FIG. 8 is a graph showing recording power control signal characteristics of the present invention with respect to recording power.

FIG. 9 is a diagram for explaining signal reproduction by a conventional pit position recording method.

FIG. 10 is a diagram illustrating signal reproduction by a conventional mark edge recording method.

FIG. 11 is a diagram showing an example of a configuration of a DC fluctuation tracking system according to the related art.

FIG. 12 is a diagram illustrating an example of a configuration of a DC fluctuation tracking system according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc medium 2 Recording beam 3 Reproduction beam 4 Envelope intermediate level detecting means 5 Edge near level detecting means 6 Subtractor 7 Adder 8 LD drive circuit 9 Recording power controller 10 Minimum value detector 11 Maximum value detector 12 Sampling means 13 Level Detector 14 time-series pattern detector 15 averaging means 16 delay circuit 17 Viterbi detector 18 threshold-changeable level detector 19 low-pass filter 20 comparator

Claims (11)

(57) [Claims] 1. An optical disk device for performing mark edge recording / reproduction, comprising a recording beam and a reproduction beam which are independent of each other and positioned on the same information track, and further comprising a reproduction signal from the reproduction beam. First detecting means for detecting an intermediate level of a reproduction signal envelope , sampling a reproduction signal from the reproduction beam , and
Edge point is detected from the change point of the
Average only the sample values of the reproduced signal before and after the edge
Second detection means for detecting a reproduction signal level near the edge by converting the signal into an edge; an LD drive circuit; and a reproduction signal envelope detected by the first detection means.
Intermediate level and edge detected by the second detection means
Optical disc recording, comprising: a subtraction unit for generating a difference between reproduction signal levels in the vicinity; and a unit for controlling the LD drive circuit so that the output of the subtraction unit becomes zero. Power control device. 2. An optical disk apparatus for performing mark edge recording / reproduction, wherein: first detection means for detecting a reproduction signal envelope intermediate level from a reproduction signal; and sampling the reproduction signal to obtain a signal level of the sampled signal.
Detect the edge time from the change point, and before and after the edge time
A second detection means for detecting a reproduction signal level near an edge by averaging only the sample values of the reproduction signal, an LD drive circuit, and a reproduction signal envelope detected by the first detection means
Intermediate level and edge detected by the second detection means
A subtraction unit that generates a difference in a reproduction signal level at a position; and a recording power control unit that maintains and manages an output level of the subtraction unit. During recording, a recording power is set based on information of the recording power control unit. An optical disk recording power control device, comprising: 3. The recording power control means performs test recording by changing recording power on a track of a test optical disk recording medium based on a disk reference position signal, and performs the first and second detections on a reproduction signal. 3. The recording method according to claim 2, wherein a difference signal of the detection signal of the means is detected, a recording power is associated with the difference signal, and a recording power level having the smallest absolute value of the difference signal is determined to perform recording. Optical disk recording power control device. 4. The optical disk recording power control device according to claim 1, wherein said first detection means comprises a maximum value detection circuit and a minimum value detection circuit. 5. The digital signal output from the level detecting means, wherein the second detecting means includes a sampling means for sampling a reproduced signal, a level detecting means for detecting a level of a signal sampled by the sampling means, Time-series pattern detection means for detecting a change time point of the signal for each synchronous clock; and averaging for adding and averaging sample values in the sampling means corresponding to the change time point of the digital signal detected by the time-series pattern detection means. 3. The optical disk recording power control device according to claim 1, further comprising: means. 6. The optical disk recording power control device according to claim 5, wherein said level detecting means comprises a Viterbi detector. 7. An optical disk recording power control apparatus according to claim 5, wherein a threshold level of said level detecting means is controlled by an output of said averaging means. 8. A means for controlling the LD drive circuit, comprising: means for smoothing a difference signal from the subtracting means; and means for adding an output of the smoothing means and a predetermined reference voltage. 2. The optical disk recording power control device according to claim 1, wherein: 9. An optical disk device for performing mark edge recording and reproduction.
An edge vicinity level detection circuit used in a sampling device, wherein a sampling means for sampling a reproduced signal; and a level of a signal sampled by the sampling means.
Level detecting means for detecting the digital signal and the digital signal output from the level detecting means.
Time series pattern to detect the point of change for each synchronous clock
And emission detection means, said digital signal detected by the time series pattern detecting means
In the sampling means corresponding to the change point of the signal
Averaging the sample values and reproducing signal level near the edge
And an averaging means for outputting an edge vicinity level detection circuit. 10. The level detecting means is a Viterbi detector.
10. The vicinity of the edge according to claim 9, wherein:
Level detection circuit. 11. The apparatus according to claim 11, wherein a threshold level of said level detecting means is set to a previous level.
Characterized by being controlled by the output of the averaging means
The edge near level detection circuit according to claim 9 .