JPH04325948A - Magneto-optical recording and reproducing method - Google Patents

Abstract

PURPOSE:To reproduce data recorded with high density by surely transferring desired pits to be reproduced to a reproductions layer by executing the pulse- shaped radiation of beams for reproduction synchronously with a channel clock in the case of reproducing information. CONSTITUTION:For a disk, SiN as a protecting film, NdDyFeCo as the reproducing layer, TbFeCo as a recording layer and the protecting layer again are successively laminated on a poly-carbonate disk preformatted by the reference of a discrete block format, and such a disk is used. First of all, one-byte data are recorded up to 16 bytes at the data recording byte part of respective blocks over all the areas of this disk. Afterwards, the center of a channel bit is irradiated with the beams for reproduction for each clock channel in the shape of a pulse, and differential detection is executed. The error rate for each byte is almost fixed, and the data recorded with high density can be reproduced to a disk position without controlling power.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording and reproducing method for a magneto-optical recording device in which the operation of some or all of the components of the device is synchronized with a single clock.

0002

2. Description of the Related Art Generally, a magneto-optical recording device continuously irradiates data recorded on a disk with a coherent laser beam of a certain amount of light and receives the reflected or transmitted light with an optical detector. The Kerr rotation angle, or in the latter case the Faraday rotation angle, was detected and reproduced.

0003

[Problems to be Solved by the Invention] However, the above-mentioned conventional technology uses a laser beam that is focused to the optical limit by an optical system within an optical head, so the spatial resolution is limited by the optical system. It is impossible to detect anything below the cutoff frequency due to the characteristics of the optical transfer function. In other words, two or more pits are included in the beam spot, making it impossible to distinguish between the pits. Therefore, it becomes impossible to reproduce information in which pits are recorded at high density. Most of the magneto-optical recording devices currently on the market are semiconductor lasers with wavelengths ranging from 770 nm to 84 nm.
0 nm range, and due to its optical limit, the shortest pit length is specified by the ISO standard as 0.76 μm, and the capacitance is also set accordingly. Furthermore, in the discrete block format method proposed as a standard candidate for 3.5-inch magneto-optical recording devices, the shortest pit length was specified as 0.76 μm for the same reason, and the total capacity was extremely limited to 120 MB. Ta.

[0004] As one way to solve this problem, shortening the wavelength of laser light is being considered. Specifically, the oscillation wavelength of the semiconductor laser itself is shortened, or the wavelength of the laser light is halved by using a second harmonic generation element. However, in the former case, it is difficult to dramatically shorten the wavelength using current laser structures or materials, and in the latter case, there are problems in terms of efficiency and it is difficult to increase the density.

[0005] As another means, Japanese Patent Application Laid-Open No. 01-143
As seen in 041, relatively high power continuous light is irradiated during reproduction, the pits to be reproduced in the recording layer are transferred to the reproduction layer, and pits unrelated to reproduction are masked by the reproduction layer to reproduce minute pits. There is a method to do this, but since it uses the delicate temperature distribution within the beam spot, it is affected by fluctuations in the linear speed of the disk rotation and fluctuations in the power of the reproduction light, resulting in insufficient transfer and the carrier-to-noise ratio (C/N). ) The problem is that the error rate is high and jitter occurs due to insufficient reproduction, making it impossible to obtain a high-quality reproduced signal.

[0006]The present invention is intended to solve these problems, and its purpose is to reliably transfer the pits to be reproduced to the reproduction layer by irradiating the reproduction light in a pulsed manner during information reproduction. However, it is an object of the present invention to provide a magneto-optical recording and reproducing method capable of reproducing data recorded at high density and obtaining a good reproduced signal with few errors.

[0007]

[Means for Solving the Problem] In a magneto-optical recording and reproducing method for a magneto-optical recording device in which the operation of some or all of the device components is synchronized with a single clock extracted from a disk, a channel is provided when reproducing information. It is characterized by irradiating the reproduction beam in a pulsed manner in synchronization with the clock.

[0008]

【Example】

(Example 1) The present invention will be explained in detail below based on an example.

In order to realize the reproducing method of the present invention, a magneto-optical recording and reproducing device capable of recording and reproducing the 3.5-inch discrete block format (hereinafter referred to as DBF) proposed as an ISO standard was partially modified. It was used as The original device detects the clock pits on the disk, performs PLL control on the signals, and 5.
A 5176 MHz channel clock was generated, and data management (recording, playback, modulation, demodulation) and optical head control were performed based on the channel clock. In this embodiment, this signal is frequency-divided twice and used as a channel clock (11.0352 MHz). Furthermore, the signal processing system was changed to support a data format of 16 bytes per block with the same preformat.

The magneto-optical disk used in this example is a DB
On a polycarbonate disk preformatted according to the F standards, SiN 80 nm was used as a protective film, NdDyFeCo 100 nm was used as a reproduction layer, and TbF was used as a recording layer.
A disk was used in which 100 nm of eCo and 80 nm of eCo were sequentially laminated as a protective layer by sputtering. The magnetic properties of the recording layer are a large coercive force at room temperature (compensation composition) and a Curie temperature of approximately 195°C, and the magnetic properties of the reproducing layer are a room temperature coercive force of 1.2 kO.
e, Curie temperature was approximately 190°C. First, 1
16 bytes of byte data (00100100110) were recorded. The recording power was 5 mW, and the applied magnetic field was 30 mW.
It was set to 0 Oe. Thereafter, the center of the channel bit was irradiated in a pulsed manner with a pulse width of 40 nsec and a power of 3 mW for each clock channel, and the difference in 4-11 modulation was detected, and the error rate for each byte was measured. The initialization magnetic field was set to 1.5 kOe in the recording direction of the recording layer. Figure 1 shows the measurement data at each radial position. As a result, the error rate was approximately 1*10-4 regardless of the radius.

On the other hand, as a comparative example, after recording a signal in the same manner as before, normal reproduction was performed using continuous light at 0.8 mW without using an initializing magnetic field (this laminated film exhibits an integral inversion type loop at high temperatures). However, the differential detection method could not detect data at any radius.

Furthermore, as a comparative example, a similar experiment was conducted using continuous light of 4 mW for reproduction. The data is shown in Figure 2. The error rate fluctuates in the radial direction. In this experiment, when the power of the reproduction light was varied according to the radius, a nearly constant error rate was obtained, but it is necessary to control the power in the radial direction.

As described above, according to the reproducing method of the present invention, data recorded at high density can be reproduced without controlling the power to the disk position, and the large capacity and high data transfer rate of the magneto-optical recording/reproducing device can be achieved. It becomes possible to rate.

[0014]

[Effects of the Invention] As described above, according to the present invention,
By irradiating reproduction light in a pulsed manner for each channel clock, data recorded at high density can be reproduced, and a magneto-optical recording/reproducing device with a large capacity and a high data transfer rate can be provided. The magneto-optical recording and reproducing device of the present invention can be applied to optical information recording and reproducing devices such as computer memories and optical disk files, and has great effects such as improving the performance of the device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the radius dependence of the error rate according to the magneto-optical recording and reproducing method of the present invention.

FIG. 2 is a diagram showing the radius dependence of the error rate according to one of the conventional magneto-optical recording and reproducing methods.

Claims (1)

[Claims] Claim 1: In a magneto-optical recording and reproducing method for a magneto-optical recording device in which the operation of some or all of the device components is synchronized with a single clock extracted from a disk, the operation is synchronized with a channel clock when information is reproduced. A magneto-optical recording and reproducing method characterized by irradiating a reproducing beam in a pulsed manner.