JP2664463B2 - Magneto-optical recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing apparatus that performs magneto-optical recording and, if necessary, reproduction using a semiconductor laser.

[Related Art] In recent years, a magneto-optical recording / reproducing apparatus capable of recording and reproducing data at a high speed using a semiconductor laser has been developed. This magneto-optical recording / reproducing apparatus generally irradiates a rotating magneto-optical disk with a laser beam, and when the medium temperature reaches the Curie point due to the heat of the laser light, the medium is turned in a direction in which an external magnetic field is applied. The magnetic recording is performed by forming magnetic recording pits utilizing the fact that is magnetized.

In this magneto-optical recording / reproducing apparatus, previously, erasing →
The same track is scanned three times for recording → confirmation playback,
It is common to perform recording while checking, but recently there has been a strong demand for faster processing. Therefore, it has been desired to employ an overwrite method in which erasure and recording are performed collectively.
As one of the overwrite methods, there is a magnetic field modulation method in which recording is performed by changing the direction of a magnetic field according to data in a state where light is irradiated with a certain laser power.

[Problem to be Solved by the Invention] However, in the above-described conventional example, there is a problem that the edge of the reproduction signal is different from the edge of the recording signal.

This phenomenon will be described with reference to FIG. Some data (t
In the case of recording (from t = t0 to t = t1, 1 and others are 0) (FIG. 3 (a)), the direction of the magnetic field is changed to the plus direction at t = t0, and changed to the minus direction at t = t1 (No. 3 (b). At this time, the laser power is emitted at a constant power PmW. As the disk rotates, the laser spot moves on the track (FIG. 3 (c)) and is magnetized according to the direction of the applied magnetic field. When t = t0, the portion hit by the laser spot is magnetized in the plus direction. Therefore, when the recording is completed, the magnetization pattern takes the shape of an arrow blade, which is called a chevron type (FIG. 3 (e)). When this track is reproduced, a phenomenon occurs in which the data is shifted from the actual data by the time td as shown in FIG. 3 (f). The occurrence of this shift is called a bit shift.

If a bit shift occurs, a deviation from the read clock occurs, resulting in a bit error, and data cannot be reproduced.

To solve this problem, the applicant has already determined the bit shift amount td
Means for delaying the pulse applied to the magnetic field by the amount described above to eliminate the bit shift.

 This method will be described with reference to FIG.

As shown in FIG. 4, the magnetic field is set to the plus direction at t = t0 + td. Then, the laser spot diameter hits the recording medium, the temperature of the medium rises, the laser spot diameter reaches the Curie temperature, and a chevron-type recording pattern is formed (FIG. 4 (e)). In this recording pattern, since the timing of the magnetic field modulation is delayed by the shift amount generated earlier, the reproduced signal can be reproduced without the bit shift amount.

It is known that the shift amount of the edge is inversely proportional to the linear velocity. Therefore, the shift amount is always constant when the rotation system of the magneto-optical disk is the CLV system, but the shift amount is different between the inner and outer circumferences of the disc in the CAV system. This will be described with reference to FIG.

When data which becomes High at t = t0 and becomes Low at t = t1 is input (FIG. 5 (a)), a certain bit shift amount td according to the above method is provided, and the magnetic field modulation signal is at t = t0 + td in the positive direction (FIG. 5 (b)). As a result, the laser spot when the magnetic field is switched is focused on a certain diameter and hits the disk (FIG. 5 (d)).

However, in this case, the linear velocity is slow because the inner circumference of the disk is tracked. Therefore, the temperature rise of the disk due to the hit of the laser spot is higher than before the linear velocity of the previous example was reduced. Therefore, the isotherm for magnetizing is expanded (FIG. 5 (e)), and the recording pattern after magnetizing is also widened (FIG. 5 (f)), and the pattern is reproduced and the half of the reproduced signal is reproduced. When binarized by level, t
A bit shift of d 'occurs (FIG. 5 (g)).

[Means for Solving the Problems] An object of the present invention is to provide a magneto-optical recording / reproducing apparatus capable of preventing occurrence of a bit shift accompanying a change in a linear velocity of a medium.

The object as described above has a means for condensing light on a magneto-optical recording medium and a bias magnetic field applying means for applying a predetermined bias magnetic field corresponding to a recording signal to the light condensing portion, and the recording pits are magnetically recorded. A magneto-optical recording / reproducing apparatus for recording information by forming a parameter, detecting means for parameters related to the linear velocity of the recording medium, calculating means for calculating a shift amount in accordance with detection from these detecting means, Delay means for delaying the magnetic field modulation signal to the bias magnetic field applying means with a delay by the shift amount.

[Operation] According to the present invention, the bit shift amount can be eliminated by changing the shift amount of the magnetic field modulation pulse at the time of recording in accordance with the linear velocity of the recording medium detected by the parameter.

EXAMPLES Hereinafter, a magneto-optical recording / reproducing apparatus according to the present invention will be described in detail based on specific examples.

FIG. 1 is a schematic configuration diagram of one embodiment of the present invention. In the figure, 1 is a magneto-optical disk as a recording medium, 2 is a spindle motor for rotating the disk 1, 3 is a magnetic field generating coil, 4 is a drive of the magnetic field generating coil 3, and 5 is an object for condensing light on the disk 1. A lens, 6 is a collimator lens for collimating a light beam, 7 is a semiconductor laser, 8 is a laser drive, 9 is a magnetic field modulation pulse generator, 10 is an actuator unit, 11 is an actuator motor block for controlling the unit, and 12 is recording data. And 13 are control circuits for the spindle motor and the actuator motor.

 Next, each operation will be described in order.

The spindle motor 2 is controlled by the motor control circuit 13.
Rotates, and the disk 1 is rotating at a constant rotation speed.

Now, a signal is output from the upper controller (not shown) to the motor control circuit 13 in order to track to a certain target track number, and the actuator motor block 11 operates so that the actuator 10 is positioned directly below the target track according to an instruction from the circuit 13. I do. The actuator 10
Can move in the radial direction of the disc.

The semiconductor laser 7 is driven by the laser drive 8, the laser light is converted into parallel light through the collimator lens 6, condensed by the objective lens 5, and is focused on the disk 1 with a certain spot diameter. The track number focused at this time is the target track.

Now, data 12 to be recorded on this track is input to the magnetic field modulation pulse generation circuit 9. At this time, the circuit 9 outputs a magnetic field modulation signal to the coil drive 4 with a certain shift amount, and the shift amount is determined by the linear velocity of the disk which can be calculated using the radius distance of the target track as a parameter. , And generates a magnetic field generation pulse with a delay corresponding to the shift amount with respect to the target track. Therefore, the magnetic field modulation pulse generation circuit 9 includes an arithmetic circuit for calculating the shift amount according to the parameter signal,
At least a delay circuit for delaying the magnetic field modulation signal to the coil drive 4 by delaying the shift is provided.

In this example, for the sake of simplicity, the description is based on the assumption that the actuator 10 can be moved in the radial direction one track at a time, but when the number of target tracks is changed from the preceding section, Since a signal corresponding to the number of moving tracks is output from the motor control circuit 13, a new shift amount may be generated from the pulse generation circuit 9 in accordance with the parameter signal.

FIG. 2 is a time chart of the present embodiment having a modulation magnetic field (FIG. 2 (b)) based on the shift amount tp in consideration of the linear velocity of the recording medium. With this configuration, no bit shift occurs in the reproduced signal regardless of how the linear velocity changes. Note that the shift amount tp needs to always change according to the change in the linear velocity, and it is necessary to select such a parameter.

[Other Embodiments] In the above embodiment, the shift amount of the magnetic field signal is determined based on the position of the actuator 10 in the radial direction. However, the shift amount may be determined based on the track number or the track number range during actual tracking. .

That is, if a parameter changes with a certain correlation due to a change in the linear velocity of the recording medium, the linear velocity of the recording medium can be measured by providing means for measuring the parameter. Therefore, the present invention can be easily implemented by determining the shift amount according to the output.

In the above embodiment, a disk-shaped recording medium is taken as an example, but the essence of the present invention is to shift the magnetic field modulation signal according to the linear velocity of the recording medium. Obviously, the scope of application is not limited to the disk shape.

[Effects of the Invention] As described above, according to the present invention, the delay amount of the rise time of the magnetic field modulation signal is measured with a parameter that changes due to the linear velocity, and the linear velocity is detected based on the parameter. By changing the amount of delay, bit shift of the reproduced signal can be eliminated, and as a result, bit errors can be eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a magneto-optical recording / reproducing apparatus according to the present invention. FIG. 2 is a timing chart of the magneto-optical recording / reproducing apparatus of the present invention. FIG. 3 is a timing chart of the conventional magneto-optical recording / reproducing apparatus. FIG. 4 is a timing chart according to the magneto-optical recording / reproducing apparatus already proposed by the present applicant. FIG. 5 is a timing chart for explaining a bit shift accompanying a change in linear velocity. 1: magneto-optical disk, 11: magnetic field modulation pulse generation circuit. 13: Motor control circuit

Claims (2)

(57) [Claims] 1. A recording magnetic recording medium comprising: a light condensing means for condensing light on a magneto-optical recording medium; and a bias magnetic field applying means for applying a predetermined bias magnetic field corresponding to a recording signal to the light condensing part, thereby forming recording pits magnetically A magneto-optical recording / reproducing apparatus for recording information by detecting the parameter relating to the linear velocity of the recording medium; calculating means for determining a shift amount in accordance with the detection from the detecting means; A magneto-optical recording / reproducing apparatus having a delay means for delaying the magnetic field modulation signal to the bias magnetic field applying means. 2. The method according to claim 1, wherein the parameter relating to the linear velocity is a linear velocity of the target track itself, a radial distance of the target track for calculating the linear velocity, a target track number, or a target track number range. 2. The magneto-optical recording and reproducing apparatus according to 1.