JPS59140634A - Recording system of optical disk device - Google Patents

Abstract

PURPOSE:To obtain an optimum function of optical modulation transmission from the outer circumference part to the inner circumference part of an optical disk, by correcting properly the ON period duty of a laser modulated signal in response to the radius direction of the optical disk. CONSTITUTION:An optical disk 1 is driven by a spindle motor 3 and rotated at a fixed angular speed. At the same time, a head access controller 8 drives an optical head moving motor 6 so that both an optical recording head 4 and an auxiliary magnetic field generator 5 are set at the designated recording track address. The duty ratio between the ON and OFF periods of the laser light obtained at the designated track address is set to a pulse duty modulator 7 by the controller 8. Thus the disk 1 is set in a stand-by state, and the modulated signal supplied synchronously with the readout of the designated address is modulated by the modulator 7. Then the modulated signal controls the laser diode within the head 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a recording method for an optical disk device that records on a thermal mode material using a light beam, and particularly relates to a recording method for an optical disk device that records by rotating a disk at a constant angular velocity. Regarding the recording method.

BACKGROUND OF THE INVENTION Conventional lightning disk devices include, for example, those based on magneto-optical recording. That is, a disk made of glass or the like with a magnetic material spun onto it is used as a recording medium, and the recording medium is magnetized in one direction by applying a perpendicular magnetic field, for example, and then By irradiating a light beam (generally a laser beam) corresponding to an information signal, the temperature of the magnetic material at the irradiated area is adjusted to the magnetic transition temperature (
Recording is performed by reversing the magnetization of the area above the Currie point. This disk is rotated by a motor at a constant angular velocity (C, A, V), and the position of the light beam irradiated onto the disk is controlled to record information signals on the disk in a spiral or concentric pattern.

In the recording method using C, A, and V rotations of the disk,
The optical energy density per unit area is significantly different between the outer track and the inner track, and as a result, the recorded perpendicular magnetization pits are not faithfully formed by the laser recording ON/OFF signal. The following method has been proposed.

That is, this is a method in which recording is performed by gradually decreasing the recording laser power from the outer circumferential track toward the inner circumferential track, and recording pits from the outer circumferential part to the inner circumferential part are corrected.

However, according to this method, the recording laser power is changed at a location in the radial direction of the disk, which causes gain changes in the servo system of the recording device, such as focus servo, tracking servo, etc. There are problems that adversely affect the stability control of the system.

Furthermore, there are various technical problems with the control method itself for gradually changing the laser power, and solving the problems requires an expensive device.

On the other hand, when the laser power is constant, C, A,
When magneto-optical pits are recorded on a disk using V rotation, the following problems naturally occur.

That is, the recording linear velocity is significantly different between the outer track and the inner track of a magneto-optical disk. For example, the linear velocity at a radius of 20 cm and at a radius of 10c+a of the disk is 7. Therefore, even if the laser power is turned on for the same period of time, the light energy (light energy density) per irradiated unit surface it I will differ significantly. Comparing this optical energy density at a radius of 10 cm and at a radius of 20 ca, there is a double difference.
In Fe, the temperature increase due to the previous irradiation changes significantly depending on the track position, and the finally recorded perpendicular magnetization pits do not faithfully follow the on/off of the laser, and are smaller at the outer periphery and smaller at the inner periphery. It will be recorded more clearly.

Purpose The present invention obviates the above-mentioned conventional problems; its purpose is to:
A light beam that reduces the duty ratio of the on-period of the laser pulse without gradually decreasing the laser power from the outer circumference of the disk toward the inner circumference of the disk, thereby leveling out the optical energy density in the radial direction of the disk. The object of the present invention is to provide a recording method for a disk device.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings.11 FIG. 1 shows an example of the configuration of an optical disk device according to the present invention, where 1 is an optical disk.

It consists of an optical disk substrate IA and a magneto-optical thin film IB provided on the optical disk substrate IA, and is rotated by a spindle motor 3 at a constant angular velocity. -4 is an optical recording head, which is disposed facing the magneto-optical thin film IB and irradiates the magneto-optical thin film IH with a light beam. 5 is an auxiliary magnetic field generator;
Reference numeral 6 denotes a motor that moves the rad 4 and the auxiliary magnetic field generator 5 as a pair toward optical recording. Further, 7 is a pulse duty modulator, and 8 is a head access controller.

To explain the operation of the optical disk device having such a configuration, first, the optical disk 1 is driven by the spindle motor 3 and controlled to rotate at a constant angular velocity. At the same time, the head access controller 8 drives the optical head movement motor 8 so that the optical recording head 4 and the auxiliary magnetic field generator 5 are moved to the designated recording track address of the optical disk 1.The laser beam at the designated track address The duty ratio of the on and off periods is set in the pulse duty modulator 7 by the head access controller 8.

The optical disk device is now in a standby state, and the modulation signal input in synchronization with the reading of the designated address is modulated by the pulse duty modulator 7, and the modulation signal is transmitted to the laser diode (not shown) in the optical recording disk 4.
control.

This pulse duty ratio control will be explained using the timing chart of FIG. 2. Here, (A) is a recording digital data string, and (B) is an input signal obtained by converting the data string into an MFM modulation signal.

(C) shows the output signal of the pulse duty modulator 7 at the inner circumference of the track, and (D) shows the output waveform of the AND gate 11 described in the explanation of FIG.

For example, when there is a digitally recorded data string as shown in FIG. 2(A) and it is modulated by the MFM method, the modulated signal has a waveform as shown in FIG. 2(B). Assume that faithful recording pits are formed in the outer track by recording on the optical disc 1 with this duty unchanged. Then,
In the inner track, the recording pit spreads in the track running direction, and the on period becomes longer. Therefore, as shown in Figure (C), the laser on period is reduced to some extent and the laser By driving the diode, recorded pits will be formed faithfully.

FIG. 3 is a block diagram showing an example of the configuration of a pulse duty modulator, where 8 is a shift register, 10 is a data selector, and 11 is an AND gate.

Second, supply the modulation signal input as shown in Figure (B) to the shift register 9, shift it in series with a sampling clock that is sufficiently higher than the data rate, and output the input data as the output QA-QH of the shift register 9. For example, similar waveforms delayed by 1 to 8 clocks are obtained. By sending these outputs QA-QH to the terminals DO to D7 of the data selector 11, and supplying selection signals from the host access controller 8 to the selection terminals A, B, and C, The optimum output can be obtained depending on the position. Therefore, the output Y of the data selector IO is a signal delayed by 1 to 8 clocks from the modulated input signal.
By processing this signal and the modulated input signal through AND gate 11, the modulated signal waveform shown in FIG. 2(D), which is equivalent to the waveform shown in FIG. 2(C), is obtained.

Effects As explained above, according to the present invention, in an optical disk device that performs recording by rotating an optical disk at a constant angular velocity, the duty of the on period of a laser modulation signal is appropriately corrected according to the radial position of the optical disk. By controlling this, it is possible to obtain the effect of optimizing the optical modulation transfer function (MTF) from the outer circumferential portion to the inner circumferential portion of the optical disc. Therefore, since the optical (thermal) energy density in the radial direction of the optical disc can be leveled, it is possible to prevent signal degradation at the inner peripheral portion of the optical disc when reading data.

In the above embodiment, the optimum laser output can be obtained for the outer tracks of the optical disc by keeping the modulation signal input, and the on-period of the laser is gradually shortened toward the inner track to finely adjust the on-period. I decided to control it, but in practice.

Since it is necessary to correct the laser on period from the middle to the inner circumference of the optical disk, the laser on period is modulated with the modulation signal input in the middle or outer circumference, and the pulse duty modulator is used in the middle or inner circumference. The on-period of the laser may be controlled to be short by operating the laser.

[Brief explanation of drawings]

FIG. 1 shows the configurations (A) to f of an optical disk device according to the present invention.
FIG. 3 is a block diagram showing an example of the above, a timing chart of the second Bt*1 pulse duty modulator, and FIG. 3 is a block diagram showing an example of the circuit configuration of the pulse duty modulator. l... Optical disk, \IA... Optical disk substrate, 1B... Magneto-optical thin film, 3... Spindle motor, 4... Optical head, 5... Auxiliary magnetic field generator, 6... motor, ? ... Pulse duty modulator, 8... Head access controller, 3... Shift register, 10... Data selector, 11... AND gate.

Claims (1)

[Claims] In a recording method of an optical disk device in which information is recorded by rotating a disc-shaped recording medium carrying a thermal mode material at a constant angular velocity and irradiating the recording medium with a light beam, irradiation of the light beam corresponding to the information is performed. A recording method for an optical disk device, characterized in that a period is different between an outer circumferential portion and an inner circumferential portion of the recording medium.