JPS62285258A - Recording method for magneto-optical disk - Google Patents

Abstract

PURPOSE:To form a recording pit without secondary distortion on a disk by calculating a laser drive current at an optional radial position and ambient temperature based on a data of a laser drive current at the optimum recording obtained at plural measured positions on the magneto-optical disk. CONSTITUTION:The data for the optimum laser light control by the standard disk and the standard magneto-optical disk device is stored in a standard data ROM1. When a disk is recorded by the disk device at first, the optimum drive current is obtained by repeating the recording/reproduction while the drive current is being changed to obtain an output of optimum laser light at several position with different radio on the disk 12, and the ambient temperature and the disk radius position are stored in a computer 4. The control data is generated from the measurement data and the standard data and stored in a control data NVR16. The control data is used to estimate a required drive current at positions other than the measuring positions and the laser light control is attained depending on the radius position of the disk 12 and the ambient temperature.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a recording method for a magneto-optical disk during repeated recording on a magneto-optical disk of a constant angular velocity force type called CAM method. It is.

[Prior Art] In a magneto-optical disk device, thermal recording is performed by changing the optical output of a semiconductor laser depending on the signal to be recorded6.For example, NRZ (non-return
o zero change at one) When performing recording, the entire surface of the disk is first set to the "0" state, and when recording the "1" state of the recording signal, the optical output Pa+ shown in FIG. In this state, a semiconductor laser beam is emitted strongly to raise the temperature of the irradiated area on the disk, causing a magnetic change and recording the "1" state. Also, when recording the "0" state of the recording signal,
Semiconductor laser light is emitted weakly as in the state of optical output pb, and the temperature of the irradiated area is not raised. Therefore, no magnetic change occurs in the irradiated portion, and the 1-element rOJ state is maintained, and this "0" state is recorded.

Angular velocity - In a magneto-optical disk drive of the Takarato type, the linear velocity changes depending on the radial position of the disk.
When recording an NRZ signal with a constant bit rate that repeats green as 010... with a constant laser light output, the size of the recorded bits differs depending on the radial position of the disk. #Chi,
The recording bit length when the laser light output is P is changed depending on the disk radius l, and the bit ff1N of the outer track is longer than the bit length g of the inner track.

This is the unit surface Jj that the inner track receives from the laser beam.
! This is because the amount of energy received by the outer track is smaller than the amount of energy received by m. Therefore, the duty ratio of the reproduced signal is 5 at the reference track at the intermediate position in the radial direction.
When recording is performed on a track outside the reference track with a laser beam output of 0%, the period T! of the reproduced signal corresponding to the bit length is 0%. is shorter than 〒1 of the reproduction signal of the reference track, and conversely becomes longer for tracks inside the reference track. FIG. 8 shows this situation. In this state, when the output of the recording laser beam is constant, the duty ratio, which is the ratio of the period T1 to the throat period flJIT of the reproduction signal, is always 50% on the outer or inner track. It has the disadvantage of having a rather secondary type. Conventionally, methods for controlling laser light output during recording on optical discs include methods in which the laser light output is controlled by dividing several recording areas according to the radial position of the disc, and methods in which the laser light output is controlled at a constant level. A method has been proposed in which the interpolated pulse radiation is varied while maintaining the same value. As for the latter conventional technology, for example,
-24452 publication is known.

However, although the above-mentioned drawbacks can be alleviated by such conventional methods, they cannot be completely eliminated.

To explain this in more detail, there are many variations in the characteristics of semiconductor laser light.
The differential efficiency has a considerably large characteristic distribution of 0.5 to 1.1. Therefore, even if M control is performed using predetermined rtil W data for each optical LA disk, it is impossible to perform upward control. On the other hand, magneto-optical disks are used in situations where, for example, the environmental temperature is between 0°C and 50°C, and magneto-optical disk devices perform thermal recording by converging laser light. Therefore, even slight changes in the environmental temperature TO The deployment sensitivity of recording media varies. In addition, semiconductor laser light
Its characteristics change greatly with a change in S1 degree.1 For example, the threshold current is 50 mA at 0°C and increases to 70 mA at 50°C. Therefore, temperature cannot be ignored to create optimal recording conditions.For example, a magneto-optical disk! It is also possible to use the device at a constant temperature #e or in a room with strictly controlled room temperature so that it is not affected by the environmental temperature.
In other words, magneto-optical disk drives cannot avoid drawbacks such as increased device size, limited usage locations, and increased costs. The optical output p shown in FIG.
State b is the minimum optical output necessary to operate the servo system stably, and no recording is performed in this state.
On the other hand, in the state of optical output P■, there is a high optical output and recording is performed. Therefore, the optical output pb can be maintained at a constant laser output only in response to changes in the environmental temperature, but the optical output Pa has a large influence on the shape of the recording bits, so It is necessary to perform fine control in response to changes in environmental temperature.

[Object of Development 1] The object of the present invention is to solve the above-mentioned drawbacks and to provide a magneto-optical disk capable of one-time recording, in which the disk radius changes when the linear velocity or CJ temperature changes depending on the disk radial position during recording. Magneto-optical disks enable stable recording bits without secondary formation to be formed on the disk by driving a semiconductor laser to obtain an appropriate laser light output depending on the position or environmental temperature. The goal is to provide a recording method.

[Summary of the Invention] The gist of the present invention to achieve the above-mentioned object is to provide a magneto-optical disk that can be repeatedly recorded by preliminary recording and reproduction at a certain environmental temperature. The data of the optimum laser drive current during recording obtained at a plurality of measurement points at different radial positions is stored, and based on the data, the laser drive current at each radial position and at the arbitrary environmental temperature is determined when recording an arbitrary environmental temperature. Calculate the laser drive current,
A recording method for a magneto-optical disk is characterized in that laser output is controlled based on the result of the calculation.

[Embodiments of the Invention] The method according to the present invention will be explained in detail based on the embodiments illustrated in FIGS. 1 to 6.

In a magneto-optical disk device, for example, a disk with a diameter of 30 cm is used as a recording medium, the recording area is an area with a radius of 5 cm to 15 cm, and the operating environment temperature is 0°C.
~50°C. In such a magneto-optical disk device, a standard disk and a standard magneto-optical disk device are determined, and the following three measurement data are collected.

(1) Semiconductor laser light drive ``¥f'', wave-to-front wave power-to-output characteristics, and environmental temperature are measured as parameters.

(2) Optimum laser light output P depending on disk radial position
m is measured using the operating environment temperature as a parameter.

(3) Measure the optimum laser light output pb.

Then, from the measurement in (1), a graph of characteristics as shown in FIG. 1, for example, can be obtained. Furthermore, a graph as shown in FIG. 2 is obtained by the Jll determination in (2). These figures 1 and 2 are data that allows you to enjoy the optimum laser light output for standard disks and standard magneto-optical disk devices.Since the characteristics of semiconductor laser light differ in other disk devices, the same semiconductor laser light cannot be used. Even the drive current does not result in optimal laser light output.

Therefore, when recording for the first time on another disk device, recording and playback are performed while changing the drive current so that the optimum laser light output is achieved at several different radial positions on the disk, for example, two points in a simple example. Iteratively and automatically determines the optimum drive current 11, (2), and at the same time determines the environmental temperature TO and disk radial position r1. By simply storing r2 in the computer, the semiconductor laser beam can be controlled using a combination or a computer from the next recording onward.

To explain this in more detail, in a certain optical disk device, TO=25°C, rl=7 cm, r2=1
In the case of 4 cm, the optimal current value is Il = 130 mA,
Suppose that I2=150 mA is obtained. From Figure 2, it is 12.2 mW at a radius of 7 cm and 17.0 mW at a radius of 14 cm.
4mW is the optimum laser light output, and this situation is shown in the third section.
As shown in FIG.
This means that a laser light output of mW is output.

On the other hand, the drive current vs. light output characteristic of semiconductor laser light has linearity above a certain threshold radio wave.

If the above two points are known, the drive current vs. optical output characteristic can be determined. This situation is shown in FIG. 3(b), where the broken line indicates the characteristics of the semiconductor laser light of the standard disk device.

The method for controlling the laser light output at each radial position of the disk when the temperature TO is 25°C is to find the optimal laser light output at each radial position from the data in Figure 3(a), and then select the semiconductor that outputs this laser light output. Laser light drive 71
1i flow is determined from the data in FIG. 3(b). In this way, the semiconductor laser light can be controlled so that the optimum laser light output is output at a predetermined disk radial position at TO=25°C.

Now, when the environmental temperature To changes from 25°C, the characteristics of the semiconductor laser light are as shown in Figure 1, only the threshold current increases and the slope, which is the differential efficiency, hardly changes. From FIG. 4, which is obtained by shifting the straight line in FIG. 3(b) obtained in FIG. Can be done. In this way, the characteristics of the semiconductor laser light at the usage environment temperature can be determined, so the optimum laser light output can be determined for other temperatures depending on the disk radius position using the same method as when the environment temperature TO is 25°C. Semiconductor laser light can be controlled in this manner.

Next, we will discuss the method of controlling the optical output pb in FIG. 7. The optical output pb should always be a constant value, and the semiconductor laser light control method is performed using the graph diagram in FIG. 5, which is the same as in FIG. 4. For example, if Pb = 3 mW, even if the environmental temperature TO changes as shown in Figure 5, the drive current will be reduced to 25 mW.
By controlling the output to 96 mA at 0.degree. C. and 110 mA at 50.degree. C., the output of the laser light can always be maintained at a constant value.

FIG. 6 shows a block diagram for realizing laser light control according to the present invention. The data shown in FIGS. 1 and 2 for optimal laser light control using a standard disk and a standard magneto-optical disk device is as follows. It is stored in the standard data ROMI.

First, when using a magneto-optical disk device, semiconductor laser light control data is obtained by the following procedure. First, the temperature sensor 2 measures the environmental temperature zero, and the A/D converter 3
The 0th order is input to the computer 4 via the optical herad 5
is moved to the radial position r1, and the computer 4 extracts the drive current value at the radius "l" and the environmental temperature TO from the standard data ROMI, and uses that value as the drive current.At this time,
The optical outputs Pa and Pb are output from the computer 4 as D/
The signal is input to the drive circuit 8 via the A converter s and the D/A converter 7 for pb. On the other hand, the test signal generator 9 generates a square wave with a carrier frequency duty ratio of 50% and inputs it to the drive circuit 8. As a result, the semiconductor laser light source 1
The optical output of 0 becomes an optical pulse as shown in FIG.
2 to form recording bits. When the recording of one track is completed, reproduction is performed this time, and the reproduced signal is inputted to the light receiving element 13 and the secondary distortion detection circuit 14 via the optical radar 5. The secondary distortion detection circuit 14 is composed of, for example, a distribution circuit, and its output is input to the computer 4 via an A/D converter 15. In computer 4, if the duty ratio is greater than 50%, the output of 1, for example 7, is output as a positive value,
The drive current during recording is controlled to be lowered via the Pa D/A converter 6. Also, conversely, the duty ratio is 50
%, the output is output as a negative value and the drive current is controlled to increase. In this way, recording and reproduction are repeated while controlling the drive current using the Prs D/reconverter 6 until the output of the secondary distortion detection circuit 14 becomes zero.In this way, when the environmental temperature is TO, The optimum drive current If at the disk radial position "1" is determined. Similarly, the drive current I2 at the disk radial position r2 can be measured.

Control data is created from these measured data and standard data, and stored in a certain control data NVR 16 from non-volatile RAM.The actual optimal drive current is determined not at two locations but at more locations. Preferably, once the control data has been created, it is possible to use this control data to estimate the required drive current at a location other than the measurement location using a general method from the optimum drive current at the measurement location in the vicinity. Laser light control becomes possible according to the radial position of 12 and the environmental temperature.

For example, if the D/A converter 6.7 is 8 bits, 2
Fine control is possible in 56 steps, and if a device with a larger number of bits is used, even more precise control is possible.

When the device is used for the first time, as in the present invention, data including the inherent performance of the entire device is collected, and that data is used to control the laser light output.

It becomes possible to sufficiently correct variations in the characteristics of semiconductor laser light. If the characteristics of the semiconductor laser light change due to aging, etc., the semiconductor laser light can be optimally controlled by re-gathering new device-specific data using the above-described operation. Of course, the method of updating data is not limited to these methods, and may be performed automatically, for example, when the power is turned on.

[Effects of the Invention] As explained above, according to the magneto-optical disk recording method according to the present invention, when measuring device-specific data, it is only necessary to measure data at multiple locations at different radial positions.
Moreover, control data can be created in a short time, and it is possible to obtain an optimal drive current including temperature conditions during repeated recording.

[Brief explanation of the drawing]

The drawings show an embodiment of the magneto-optical disk recording method according to the present invention, and FIG. 1 is a temperature characteristic diagram of semiconductor laser light output;
Figure 2 is a diagram of the optimum laser light output characteristics depending on the disk radial position with temperature as a parameter, Figure 3 is an explanatory diagram of how to determine the optimum laser light output, and Figure 4 is a diagram of semiconductor laser characteristics when the temperature changes. , FIG. 5 is an explanatory diagram of a method of controlling the laser light output pb when the temperature changes, and FIG. 6 is a configuration diagram for realizing optimal laser light output control.
FIG. 7 is a waveform diagram of the write light pulse, and FIG. 8 is a waveform diagram of the reproduction signal depending on the disk radial position. 1 is a ROM, 2 is a temperature sensor, 3.15 is an A/D converter, 4 is a computer, 5 is an optical head, 6.7 is a D/A converter, 8 is a drive circuit, 9 is a test signal generator, 10 11 is a semiconductor laser light source, 11 is a motor, 12 is a disk, 13 is a light receiving element, 14 is a secondary distortion detection circuit, 16
is an NVR. Patent applicant: Japan Broadcasting Association Asaiki Co., Ltd. Nippon Kogaku Kogyo Co., Ltd. Figure 1, Drive current (mA) Teeth 4 stroke radius (am) Figure 3 CG) (b) Cantering t: Circle (mA) ) Figure 4 Figure 5 8096+10, drive chamber - tip (mA)

Claims (1)

[Scope of Claims] 1. In a magneto-optical disk that can be repeatedly recorded, it is determined at a plurality of measurement points at different radial positions on the magneto-optical disk by preliminary recording and reproduction at a certain environmental temperature. Store the laser drive current data during optimal recording,
A magneto-optical disk characterized in that, based on the data, a laser drive current is calculated at each radial position and at the arbitrary environmental temperature when recording an arbitrary environmental temperature, and the laser output is controlled based on the result of the calculation. How to record. 2. The magneto-optical device according to claim 1, wherein the laser drive current is determined based on interpolated data from neighboring measurement locations at locations other than the measurement location where the optimum laser drive current was determined. How to record a disc.