JPH071562B2 - Recording method for magneto-optical disk - Google Patents

Description

TECHNICAL FIELD The present invention relates to a recording method for a magneto-optical disk during repetitive recording of a magneto-optical disk of a constant angular velocity method called CAV method.

[Prior Art] In a magneto-optical disk device, a semiconductor laser light output is changed according to a signal to be recorded to perform thermal recording. For example, digital signal NRZ (non-return to zero change a
t one) When recording, first "0" on the entire surface of the disc
Leave the state. Then, when recording the state of "1" of the recording signal, the semiconductor laser light is strongly emitted as in the state of the optical output Pm shown in FIG. Record the state of "1" by making a change. Further, when recording the state of “0” of the recording signal, the semiconductor laser light is weakly emitted like the state of the optical output Pb so as not to raise the temperature of the irradiated portion. Therefore, the original “0” state is maintained without causing a magnetic change in the irradiated portion, and this “0” state is recorded.

In a magneto-optical disk device of the constant angular velocity system, the linear velocity changes with each radial position of the disc, so for example 10
When an NRZ signal with a constant bit rate that repeats 10 ... Is recorded with a constant laser light output, the size of the recording bit differs depending on the disk radial position. That is, the recording bit length 1 when the laser light output is Pm changes depending on the disk radial position, and the bit length 1 of the outer track becomes longer than the bit length 1 of the inner track.

This is because the amount of energy received by the outer track from the laser beam per unit area is smaller than the amount of energy received by the outer track. Therefore, when recording is performed on a track outside the reference track with the output of laser light such that the duty ratio of the reproduction signal becomes 50% at the reference track at the radial middle position, among the reproduction signals, The period T1 corresponding to the bit length 1 is shorter than T1 of the reproduction signal of the reference track, and is longer on the inner side of the reference track. FIG. 8 shows this state, and when the output of the recording laser beam is constant in this way, the duty ratio, which is the ratio of the period T1 to the bit period T of the reproduction signal, is not always 50% on the outer or inner track, but is two percent. It has the drawback of secondary distortion. So in the past,
The control method of the laser light output at the time of recording on the magneto-optical disk includes a method of controlling the laser light output by dividing some recording areas according to the disk radial position, and a write pulse while keeping the laser light output constant. A method of changing the width has been proposed. As the latter conventional technique, for example, Japanese Patent Publication No. 59-24452 is known.

However, although the above-mentioned drawbacks are alleviated by such a conventional method, they cannot be sufficiently removed. More specifically, the characteristics of the semiconductor laser light vary widely, and for example, the threshold current is 60 mA to 80 mA and the differential efficiency is 0.5 to 1.1, which is a fairly large characteristic distribution. Therefore, even if each magneto-optical disk device is controlled with predetermined control data, sufficient control is impossible. On the other hand, the magneto-optical disk is used in a situation where the environmental temperature T0 is, for example, 0 ° C. to 50 ° C., and the magneto-optical disk device performs thermal recording by converging laser light. Therefore, the recording sensitivity of the recording medium changes even with a slight change in the environmental temperature T0. Further, the characteristics of the semiconductor laser light also largely change due to temperature changes, and for example, the threshold current is 50 mA at 0 ° C., but increases to 70 mA at 50 ° C. From the above, it is necessary to finely control the semiconductor laser light with respect to changes in the environmental temperature T0.

Therefore, the temperature cannot be ignored to create the optimum recording state. For example, it is possible to use the magneto-optical disk device in a thermostatic chamber or in a room where the room temperature is strictly controlled so that it will not be affected by the environmental temperature, but the size of the device becomes large and the place of use is limited. It is impossible to avoid the drawbacks such as being done and the cost being high. That is, in the magneto-optical disk device, recording is performed by converging the laser light on the recording bit by using a servo system such as auto-tracking and auto-focusing, and raising the temperature of the converging portion as described above. The state of the optical output Pb shown in FIG. 7 is the minimum optical output necessary for stable operation of the servo system, and recording is not performed in this state. on the other hand,
The optical output Pm has a high optical output and recording is performed. Therefore, the light output Pb may be maintained at a constant laser light output only when the environmental temperature changes.
Has a great influence on the shape of the recording bit, so it is necessary to perform fine control in response to changes in the disk radial position and environmental temperature.

[Object of the Invention] An object of the present invention is to solve the above-mentioned drawbacks, and in a magneto-optical disk capable of repetitive recording, when the linear velocity or the environmental temperature changes depending on the disk radial position at the time of recording, the disk radial position or environment. Provided is a recording method for a magneto-optical disk, which enables a stable recording bit without secondary distortion to be formed on a disk by driving a semiconductor laser so as to obtain an optimum laser light output according to temperature. Especially.

[Summary of the Invention] The gist of the present invention for achieving the above-described object is to provide a standard optical method in a recording method for a magneto-optical disk in which the laser light output during recording is adjusted according to the radial position of the magneto-optical disk. When the recording / reproducing of a signal with a predetermined duty ratio is repeated while adjusting the laser drive current at a plurality of measurement points at different radial positions on the magnetic disk, and the duty ratio of the reproduction signal substantially matches the duty ratio of the recording signal. Is stored as optimum value data at the environmental temperature, and the drive current vs. optical output characteristic of the measuring point and the environmental temperature at that time obtained from the stored data for the magneto-optical disk to be recorded. Based on the above, the appropriate laser drive current at the radial position to be recorded and the actual environmental temperature is calculated to adjust the laser light output. A recording method of a magneto-optical disk characterized by the above.

Embodiments of the Invention The method according to the present invention will be described in detail with reference to the embodiments shown in FIGS. 1 to 6.

In a magneto-optical disk device, for example, a disk having a diameter of 30 cm is used as a recording medium, the recording area is set to an area having a radius of 5 cm to 15 cm, and the operating environment temperature is 0 to 50 °
And 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 taken.

(1) The drive current vs. optical output characteristics of the semiconductor laser light is measured using the operating environment temperature as a parameter.

(2) Optimum laser light output Pm depending on the disk radial position
Is measured using the ambient temperature as a parameter.

(3) Measure the optimum laser light output Pb.

Then, from the measurement of (1), for example, a graph of characteristics as shown in FIG. 1 can be obtained. In addition, the graph shown in FIG. 2 is obtained by the measurement of (2). The first of these
Fig. 2 and Fig. 2 are the data that gives the optimum laser light output in the standard disk and the standard magneto-optical disk device. Since the characteristics of the semiconductor laser light are different in other disk devices, the optimum laser light is obtained even with the same semiconductor laser light drive current. No light output.

Therefore, when recording for the first time with another disk device, recording and reproduction are performed while changing the drive current so that the optimum laser light output is obtained at several positions at different radial positions on the disk, for example, two positions in a simple example. The optimum drive currents I1 and I2 are automatically and repeatedly obtained, and at the same time, the environmental temperature T0 and the disk radial positions r1 and r2 are stored in the computer. If only this operation is performed, the semiconductor laser light can be controlled using the computer after the next recording.

This will be described in more detail. It is assumed that I1 = 130 mA and I2 = 150 mA are obtained as the optimum current values when T0 = 25 ° C., r1 = 7 cm, and r2 = 14 cm in an optical disk device. Second
From the figure, the optimum laser light output is 12.2 mW at a radius of 7 cm and 17.4 mW at a radius of 14 cm, and this state is shown in FIG. 3 (a). Therefore, the driving current of the semiconductor laser light is 130mA 12.
The laser light output is 2mW, which means that the semiconductor laser light has a driving current of 150mA and a laser light output of 17.4mW.

On the other hand, since the driving current-optical output characteristic of the semiconductor laser light has linearity at a certain threshold current or more, the driving current-optical output characteristic can be obtained if the above two points are known. This state is shown in FIG. 3 (b), and the broken line shows the characteristics of the semiconductor laser light of the standard disk device. The laser light output control method at the disk radial position when the environmental temperature T0 is 25 ° C. is to obtain the optimum laser light output at each radial position from the data of FIG. 3 (a), and to output this laser light output The optical drive current is obtained from the data shown in FIG. By doing so, it is possible to control the semiconductor laser light so as to output the optimum laser light output at a predetermined disk radial position at T0 = 25 ° C.

Now, when the environmental temperature T0 changes from 25 ° C., the characteristics of the semiconductor laser light only increase the threshold current as shown in FIG. 1, and the slope which is the differential efficiency hardly changes. Therefore, the drive current vs. laser light output characteristic at each temperature of the semiconductor laser light is shown in FIG. 4 in which the straight line of FIG. 3 (b) obtained at 25 ° C. is shifted by the change in the threshold current with respect to each temperature. You can guess. If you do this,
Since the characteristics of the semiconductor laser light at the operating environment temperature are obtained, the semiconductor laser light is controlled so that the optimum laser light output will be obtained depending on the disk radial position for other temperatures in the same way as when the environment temperature T0 is 25 ° C. can do.

Next, a method of controlling the light output Pb in FIG. 7 will be described. The light output Pb has only to be a constant value, and the semiconductor laser light control is performed using the graph shown in FIG. For example, if Pb = 3mW, even if the ambient temperature T0 changes as shown in Fig. 5, the driving current is 96mA at 25 ℃,
If it is controlled at 110 mA at 50 ° C, the output of the laser light can always be kept at a constant value.

FIG. 6 shows a block diagram for realizing control of laser light according to the present invention. The data shown in FIGS. 1 and 2 for optimum laser light control by the standard disk and the standard magneto-optical disk device are stored in the standard data ROM 1. First, when the magneto-optical disk device is used, semiconductor laser light control data is obtained by the following procedure. First, the temperature sensor 2
The ambient temperature T0 is measured by and is input to the computer 4 via the A / D converter 3. Next, the optical head 5 is moved to the radial position r1, and the computer 4 takes out the drive current value at the environment temperature T0 at the radius r1 from the standard data ROM 1 and sets the value as the drive current. At this time, the optical outputs Pm and Pb are input from the computer 4 to the drive circuit 8 via the Pm D / A converter 6 and the Pb D / A converter 7. On the other hand, the test signal generator 9 generates a square wave having a carrier frequency duty ratio of 50% and inputs it to the drive circuit 8. As a result, the optical output of the semiconductor laser light source 10 becomes an optical pulse as shown in FIG. 7, and a recording bit is formed on the disk 12 rotated by the motor 11 via the optical head 5. When recording of one track is completed, reproduction is performed this time and the reproduction signal is input to the light receiving element 13 and the secondary distortion detection circuit 14 via the optical head 5. The secondary distortion detection circuit 14 is composed of, for example, an integration circuit, and its output is input to the computer 4 via the A / D converter 15. If the duty ratio is greater than 50% in the computer 4, for example, the output is output as a positive value and the D / A for Pm is used.
The converter 6 is controlled so as to reduce the drive current during recording. On the contrary, if the duty ratio is smaller than 50%, the output is output as a negative value and the drive current is controlled to increase. Thus, until the output of the secondary distortion detection circuit 14 becomes zero, that is, the duty ratio of the reproduced signal is 50%.
The recording / reproducing is repeated while controlling the drive current using the Pm D / A converter 6 until. In this way
The minimum drive current I1 at the disk radial position r1 when the environmental temperature is T0 can be obtained. Similarly, the drive current I2 at the disk radial position r2 can be measured.

Control data is created from these measurement data and standard data and stored in the control data NVR 16 composed of nonvolatile RAM. In the subsequent use of the device, the stored data is read out to the computer 4, and the operation for the ambient temperature during use is performed by the above-mentioned method, and then the semiconductor laser light source is used.
Just drive 10. How to find the actual optimum drive current is 2
It is preferable to determine at more points, not at points. Once the control data has been created, the control data can be used to estimate the required drive current from the optimum drive currents at the measurement points in the vicinity of the measurement point using a general method, and the radial position of the disk 12 can be estimated. Also, it becomes possible to control the laser light according to the ambient temperature.

For example, if the D / A converters 6 and 7 have 8 bits, fine control can be performed in 256 steps, and if a device having a larger number of bits is used, more accurate control can be performed.

When the device is used for the first time as in the present invention, data including the peculiar performance of the device as a whole is taken and the laser light output is controlled by using the data, whereby the variation in the characteristics of the semiconductor laser light is sufficiently corrected. It becomes possible to do. If there is a change in characteristics such as aging of semiconductor laser light,
Optimum control of the semiconductor laser light becomes possible by newly retrieving the data unique to the device by the above operation. Of course, the method of updating the data is not limited to these, and may be automatically performed when the power is turned on, for example.

[Effects of the Invention] As described above, according to the recording method of the magneto-optical disk of the present invention, the correction operation of the laser drive current is strictly performed with respect to the variation of the laser light output characteristic peculiar to the apparatus and the change of the environmental temperature. Since an optimum laser light output can be obtained, stable recording bits without secondary distortion can be formed on the magneto-optical disk.

[Brief description of drawings]

The drawings show an embodiment of a recording method for a magneto-optical disk according to the present invention, and FIG. 1 is a temperature characteristic diagram of a semiconductor laser light output,
FIG. 2 is a characteristic diagram of the optimum laser light output depending on the radial position of the disk with temperature as a parameter, FIG. 3 is an explanatory diagram of how to obtain the optimum laser light output, and FIG. 4 is a characteristic diagram of the semiconductor laser when the temperature changes. FIG. 5 is an explanatory diagram of a method of controlling the laser light output Pb when the temperature changes, FIG. 6 is a configuration diagram for realizing optimum laser light output control, and FIG. 7 is a waveform of a write light pulse. FIGS. 8A and 8B are waveform diagrams of the reproduced signal depending on the radial position of the disk. Reference numeral 1 is a ROM, 2 is a temperature sensor, 3 and 15 are A / D converters, 4 is a computer, 5 is an optical head, 6 and 7 are D / A converters, 8 is a drive circuit, 9 is a test signal generator, and 10 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, and 16 is an NVR.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuo Nomura 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory (72) Inventor Katsuya Yokoyama 1-10-11 Kinuta, Setagaya-ku, Tokyo No. 72 Broadcasting Technology Institute of Japan Broadcasting Corporation (72) Inventor Shunichi Onishi 3-228 Asahigaoka, Hino-shi, Tokyo Inside Asaka Hino Plant (72) Inventor Koichi Okabe 3-2 Asahigaoka, Hino-shi, Tokyo No. 28 In-house company Asaka Hino Plant (72) Inventor Teruyoshi Kimoto 1-3-6 Nishi-oi, Shinagawa-ku, Tokyo Inside Oi Plant, Nippon Kogaku Kogyo Co., Ltd. (56) Reference Japanese Patent Laid-Open No. 59-84354 (JP, 59-84354) A) Actual development Sho 56-131516 (JP, U)

Claims (2)

[Claims] 1. In a recording method of a magneto-optical disk for adjusting a laser beam output at the time of recording according to a radial position of the magneto-optical disk, a plurality of measurement points having different radial positions on a standard magneto-optical disk. , The recording / reproducing of the signal with the predetermined duty ratio is repeated while adjusting the laser driving current, and the laser driving current when the duty ratio of the reproduction signal substantially matches the duty ratio of the recording signal is stored as the optimum value data at the ambient temperature. For the magneto-optical disk to be recorded, the radial position to be recorded, the actual environment, based on the drive current vs. optical output characteristics of the measurement point and the environmental temperature at that time obtained from the stored data. A method for recording a magneto-optical disk, which comprises adjusting an appropriate laser driving current at a temperature to adjust the laser light output. 2. The laser driving current according to claim 1, wherein the laser driving current is determined based on the interpolated data at the measurement points in the vicinity of the measurement points where the optimum laser driving current is obtained. Recording method of magneto-optical disk.