JP2001126260A - Optical information recording device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize a recording strategy under a high recording density condition. SOLUTION: An optical information recorder 10 irradiating an optical disk 12 with a laser beam b and recording/reproducing information is provided with an optical head 14 irradiating with the laser beam b, an LD driver 16 changing the intensity of the laser beam b and a CPU 18. Then, the CPU 18 is provided with a function recording the known recording data c onto the optical disk 12, the function reproducing the recording data (a) from the optical disk 12 and leading out a pulse response from a reproducing waveform c obtained by that and the function adjusting a recording pulse waveform so that deviation between the waveform obtained with the convolution of the pulse response with the recording data (a) and the reproducing waveform c becomes the smallest.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical information recording apparatus and method for recording and reproducing information by irradiating an optical recording medium with a laser beam.

[0002]

2. Description of the Related Art As optical recording media, there are rewritable optical disks such as magneto-optical disks and phase-change optical disks. Typical recording methods for recording on these optical recording media include mark position recording, in which information is provided at the position of a recording mark, and mark edge recording, in which information is provided at each of a front end and a rear end of the recording mark. is there.

[0003] Mark edge recording is a recording method suitable for high density recording, but the length of recording marks must be controlled with high precision. The length of a recording mark in a magneto-optical disk or a phase-change optical disk is determined by a rise in the temperature of a recording film caused by laser light irradiation. The temperature rise when irradiating an optical disk with laser light greatly changes depending on the configuration and linear velocity of the disk.

Therefore, in order to control the mark length with high accuracy by controlling the amount of temperature rise, the intensity and width (called "recording strategy") of the pulse light applied to the optical disk are determined by changing the linear velocity and the linear velocity. It needs to be optimized according to the disk configuration. As an example of how to optimize the recording strategy,
There is a method described in “Technical Report MR93-55, CPM93-107, p.13-p.18”. In this method, the length (time) from the reference mark to the front end and the rear end of the measured mark is measured, and the irradiation start position and the width of the pulse light are determined.

[0005]

However, as the recording density increases and the mark length recorded on the disk becomes shorter, the signal amplitude of the reproduced waveform decreases as shown in FIG. As a result, the positions of the front end and the rear end of the measured mark cannot be measured with high accuracy, and it becomes difficult to optimize the recording strategy.

[0006]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical information recording apparatus and method capable of optimizing a recording strategy even when a recording density is high.

[0007]

SUMMARY OF THE INVENTION An optical information recording apparatus according to the present invention is an optical information recording apparatus for recording and reproducing information by irradiating an optical recording medium with laser light. A head, a drive unit for changing the intensity of the laser beam, and a control unit are provided. The control unit has a function of recording known recording data on the optical recording medium via the optical head and the driving unit, and reproduces recording data from the optical recording medium via the optical head. It has a function of deriving a pulse response from the reproduced waveform, and a function of adjusting the recording pulse waveform such that the difference between the reproduced waveform and the waveform obtained by convolution of the pulse response and the recording data is minimized.

An optical information recording method according to the present invention is used in the optical information recording apparatus according to the present invention, and records known recording data on an optical recording medium, and records the recording data from the optical recording medium. A pulse response is derived from the reproduced waveform obtained by reproducing the waveform, and the recording pulse waveform is adjusted so that the difference between the reproduced waveform and the waveform obtained by convolution of the pulse response and the recording data is minimized. .

Optical information recording apparatus and method according to the present invention
Can take the following form. . As recording data, 12
Random data having a length of 8 to 4096 bits is used. .
Recording pulse wave with first pulse and subsequent multi-pulse
Shape, and as a method of adjusting the recording pulse waveform,
Loose irradiation position and pulse width and multi-pulse pulse
The recording width is changed according to the length of the recording mark. . Pa
As a method for deriving the pulse response, when the reproduced waveform is recorded data
Data obtained by sampling at intervals_k, Record
Data_kWhere ε = 式_k(Y_k−Σ_ia_ki* H_i)²  The pulse response h that minimizes ε represented by_iAsk for. What
Note that the subscripts k and i at the lower right of Σ are strictly added below Σ.
Things.

The operation of the optical information recording apparatus and method according to the present invention will be described. In the prior art, the length of each recording mark from the reference position must be individually and accurately measured in order to optimize the recording strategy. Therefore, if the length of the recording mark is short, measurement cannot be performed with high accuracy, and it is difficult to optimize the recording strategy under high-density recording conditions. On the other hand, in the present invention, for random data in which recording marks of various lengths are mixed, the recording strategy is determined not by the length of the recording mark itself but by the linearity of the entire reproduced waveform. The recording strategy can be optimized even under the density recording condition.

[0011]

FIG. 1 is a block diagram showing one embodiment of an optical information recording apparatus and method according to the present invention.
Hereinafter, description will be made based on this drawing.

The optical information recording apparatus 10 of the present embodiment is for irradiating an optical disk 12 as an optical recording medium with a laser beam b to record and reproduce information. It includes a head 14, an LD driver 16 as a drive unit for changing the intensity of the laser beam b, and a CPU 18 as a control unit. And CPU1
A function 8 of recording known recording data a on the optical disk 12 via the optical head 14 and the LD driver 16;
A function of reproducing recorded data a from the optical disk 12 via the optical head 14 and deriving a pulse response from a reproduced waveform c obtained thereby;
And the function of adjusting the recording pulse waveform so that the difference between the waveform obtained by convolution of the waveform and the reproduced waveform c is minimized. These functions are realized by software stored in the CPU 18.

In other words, the CPU 18 has the following role. (1) Generate recording data to be used for determining a recording strategy. (2) Change the recording strategy.
(3) Retrieve the reproduced waveform and derive the pulse response.
(4) Calculate the difference between the waveform obtained by convolution of the pulse response and the recording data and the reproduced waveform.

As the recording data used for determining the recording strategy, general random data such as an M sequence may be used. The length of the recording data is from 128 bits to 409
Desirably, it is about 6 bits. This is because if the recording data is too short, the accuracy of deriving the pulse response is reduced, and if it is too long, the calculation of deriving the pulse response takes time.

The pulse response is derived by the following method. Playback signal
At fixed time intervals (time interval T of recorded data)
Pulled and loaded into the CPU 18. This time series data
To y _kAnd Time series data of pulse response_iTo be
And the pulse response to be determined is the error ε expressed by the following equation:
H to be minimized_iIt is. ε = Σ_k(Y_k−Σ_ia_ki* H_i)²  In the above equation, a_kIndicates recording data. Record day
Ε in the above equation based on the time series data of the
H_iIs the pulse response to be determined.

When the recording strategy is changed, the error ε also changes. A recording strategy that minimizes the error ε is the most desirable recording strategy. A small ε means that the reproduced waveform has high linearity, which means that it is closer to the waveform assumed in mark edge recording. Ideally, it is desirable to set ε to 0. However, it is difficult to actually set ε to 0 due to the influence of noise and the like when capturing the reproduced waveform.

[0017]

Embodiment 1 Next, a more specific embodiment will be described.
The phase change optical disk shown in FIG. 2A was used as an optical recording medium. The optical disc 20 is such that a protective film 24, a recording film 26, a protective film 28, and a reflective film 30 are laminated on a substrate 22 in this order. As the substrate 22, polycarbonate having a guide groove pitch of 1.0 [μm] was used.

Subsequently, the disk is rotated at a linear velocity of 5 [m / s], and the length of the shortest mark recorded on the disk is set to 0 using an optical head having a wavelength of 650 [nm] and NA = 0.6. .25 [μm] clock frequency 40 [MHz]
Was recorded. As a recording modulation method, (1-7)
Recording was performed by mark edge recording using modulation.
(1-7) When modulation is used, there are seven types of recording marks 2T to 8T (T = 25 [ns] in this embodiment). The recording signals 2T and 5T among them are shown in FIGS. 2 [2] and [3].

Subsequently, recording was performed while changing the recording compensation parameters shown in FIGS. 2 [2] and [3], and the parameter that minimized ε was determined. The parameters changed are the head pulse irradiation position T1 of each recording signal and the pulse width T2 of the multi-pulse portion. The recording power is 8 [m
W], and the erasing power was 4.5 [mW]. FIG. 3 shows parameters that minimize ε. When an error was measured by performing recording using the recording strategy shown in FIG. 3, a good bit error rate of 1E-6 or less was obtained.

[0020]

Embodiment 2 Using the same phase change optical disk as in Embodiment 1, rotating the disk at a linear velocity of 5 [m / s],
Using an optical head with 0 [nm] and NA = 0.6, recording was performed under the condition that the length of the shortest mark recorded on the disk was 0.3 [μm]. As the modulation method of recording,
(8-16) Recording was performed by mark edge recording using modulation. The recording power and the erasing power were the same as in Example 1. Then, recording was performed by changing the same recording compensation parameter as in Example 1, and a parameter that minimized ε was obtained. In this case as well, it was possible to determine the optimum recording strategy as in the first embodiment.

In the above embodiments, a phase change optical disk is used as an optical recording medium. However, the present invention can be applied to other optical disks such as a magneto-optical disk.

[0022]

As described above, according to the optical information recording apparatus and method according to the present invention, a pulse response is derived from a reproduced waveform obtained by recording known random data on an optical recording medium, By adjusting the recording pulse waveform so as to minimize the deviation of the waveform obtained by convolution of the pulse response and the recording data from the reproduction waveform, the recording mark can be adjusted for random data in which recording marks of various lengths are mixed. Since the recording strategy is determined noting the length itself but the linearity of the entire reproduced waveform, the optimum recording strategy can be determined even under high-density recording conditions.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical information recording apparatus and method according to the present invention.

FIG. 2 is a view for explaining an embodiment of the present invention. FIG. 2A is a cross-sectional view showing a configuration of a phase-change optical disc.
[2] is a waveform diagram of the recording signal 2T, and FIG. 2 [3] is a waveform diagram of the recording signal 5T.

FIG. 3 is a table showing optimal recording compensation parameters obtained in an embodiment of the present invention.

FIG. 4 is a waveform diagram in a conventional example, in which FIG. 4 [1] shows recorded data, and FIG. 4 [2] shows a reproduced waveform.

[Explanation of symbols]

 Reference Signs List 10 optical information recording device 12 optical disk (optical recording medium) 14 optical head 16 LD driver (drive unit) 18 CPU (control unit) a recording data b laser light c reproduction waveform

Claims (8)

[Claims] 1. An optical information recording apparatus for recording and reproducing information by irradiating an optical recording medium with a laser beam, comprising: an optical head for irradiating the laser beam; and a driving unit for changing the intensity of the laser beam. And a control unit. The control unit has a function of recording known recording data on the optical recording medium via the optical head and the driving unit. The control unit transmits the recording data from the optical recording medium to the light. A function of reproducing through a head and deriving a pulse response from a reproduced waveform obtained by the method; and a method of minimizing a deviation between the pulse waveform and a waveform obtained by convolution of the recording data and the reproduced waveform. An optical information recording device, having a function of adjusting a recording pulse waveform. 2. The optical information recording apparatus according to claim 1, wherein the recording data is random data having a length of 128 to 4096 bits. 3. The recording pulse waveform is composed of a leading pulse and a subsequent multi-pulse, and the irradiation position and pulse width of the leading pulse and the pulse width of the multi-pulse are changed according to the length of a recording mark. The optical information recording apparatus according to claim 1, wherein the recording pulse waveform is adjusted by: 4. The method according to claim 1, wherein the reproducing waveform is performed for a time period of the recording data.
Data obtained by sampling at intervals_k, The record
Data_kWhere ε = 式_k(Y_k−Σ_ia_ki* H_i)²  The pulse response h that minimizes ε represented by_iSeeking
The optical information recording device according to claim 1, wherein the pulse response is derived by: 5. A method for recording known recording data on an optical recording medium, deriving a pulse response from a reproduction waveform obtained by reproducing the recording data from the optical recording medium, An optical information recording method, comprising: adjusting a recording pulse waveform so as to minimize a difference between a waveform obtained by convolution and the reproduction waveform. 6. The recording data includes 128 to 4096.
The optical information recording method according to claim 5, wherein random data having a bit length is used. 7. The recording pulse waveform is composed of a leading pulse and a subsequent multi-pulse, and as an adjustment method of the recording pulse waveform, an irradiation position and a pulse width of the leading pulse and a pulse width of the multi-pulse are recorded. 6. The method according to claim 5, wherein the value is changed according to the length of the image.
The optical information recording method described in the above. 8. A method of deriving the pulse response, wherein the reproduction waveform is sampled at a time interval of the recording data.
The data obtained by_kAnd the recorded data is a_kWhen
Then, the following equation ε = Σ_k(Y_k−Σ_ia_ki* H_i)²  The pulse response h that minimizes ε represented by_iAsk for
The optical information recording method according to claim 5.