JPH03189944A - Magneto-optical recorder - Google Patents

Abstract

PURPOSE:To form a pit without drifting the duty of a regenerative signal by giving an offset magnetic field in a quantity to be decided by the size and direction of a magnetic field of an AC magnetic field. CONSTITUTION:In the magneto-optical recorder for recording information on a magneto-optical recording medium 1 by irradiating the medium 1 with a light beam corresponding to a recording signal S1 after modulating the beam in synchronization with the AC magnetic field, a means 18 for detecting a magnetic field of the AC magnetic field and means 19-21 for giving the offset magnetic field in a quantity to be decided by the size and direction of the above magnetic field are provided. That is, a large magnetic field is impressed in the direction of shortening a recording pit pattern, and a small magnetic field is impressed in the direction of prolonging the recording pit pattern, and hence synthetic energy of magnetic intensity and laser power on the magneto- optical recording medium 1 is enlarged in the direction of shortening the recording pit pattern, and is diminished in the direction of prolonging the pit pattern. By this method, the length of the recording pit pattern and the length of the recording signal pattern are equalized to each other, and a drift of the duty of the regenerative signal S2 against the recording signal can be corrected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording device, and in particular to a magneto-optical recording medium, which applies an alternating magnetic field as a recording bias magnetic field and which corresponds to a recording signal. The present invention relates to a magneto-optical recording device that records information on a magneto-optical recording medium by modulating and irradiating a light beam in synchronization with an alternating current magnetic field.

[Conventional technology]

Conventionally, an alternating magnetic field is applied to a magneto-optical recording medium as a recording bias magnetic field, and a light beam corresponding to a recording signal is modulated and irradiated in synchronization with the alternating magnetic field. The one shown in FIG. 3 has been proposed as a magneto-optical recording device in which information can be rewritten by writing.

In FIG. 3, l indicates a magneto-optical disk, and 2 indicates a magnetic film. This magneto-optical disk 1 is rotatably driven by a motor 3.

The magneto-optical disk 1 is irradiated with light by the optical pickup 4, and information is recorded or reproduced (2). The optical pickup 4 has a built-in semiconductor laser 5 as a light source. The light emitted from this semiconductor laser 5 is
The light passes through the collimator lens 6 and the beam slit 7a, and is focused onto the magneto-optical disk 1 by the objective lens 8. On the other hand, the light reflected by the magneto-optical disk 1 passes through the objective lens 8 again and is separated from the incident light by the beam splitter 7a.
Furthermore, after the light is split into two parts by the beam derrick 7b, one part is received by the optical sensor 10m via the sensor lens 9a. Then, based on the output of this optical sensor 10a, %
The AT-AF circuit 11 detects a focus error signal and a tracking error signal.

These error signals are input to the actuator 12,
Auto tracking and auto focusing are performed by driving the objective lens 8.

The other light is further split into two by a beam splitter 7c, and each light is sent to a sensor lens 9b.

The light is received by the optical sensors 10b and 10c via the light beam 9c.

A reproduced signal is obtained by summing the signals from the optical sensor 10b and the optical sensor 10c. optical pickup 4
In this method, the magnetic film 2 of the magneto-optical disk 1 is locally irradiated with laser light of a constant intensity emitted in a pulsed manner by the semiconductor laser 5, and the temperature of the magnetic film 2 in this irradiated area is raised to above the Curie point. is configured to be

Reference numeral 13 denotes an electromagnet for applying a magnetic field to the magnetic film 2 of the magneto-optical disk 1. In this example, this electromagnet 13 is interlocked with the optical pickup 4 across the magneto-optical disk 1 to apply a magnetic field in the radial direction of the magneto-optical disk. It is configured so that it can be moved.

Further, 14 indicates a reference oscillator, and the laser light emitted from the semiconductor laser 5 is modulated by the recording signal produced by the recording signal modulator 15 in synchronization with the reference signal of a constant frequency produced by the reference oscillator 14. be done. The laser light emitted from the semiconductor laser 5 passes through a collimator lens 6 and a beam splitter 7a, and is focused onto the magneto-optical disk 1 by an objective lens 8. At the same time, the electromagnet 13 is driven by the drive circuit 16 at a constant frequency generated by the reference oscillator 14, and an alternating current magnetic field synchronized with (the modulation signal of) the laser beam is applied onto the magneto-optical disk 1 to perform recording. It is done. Note that 17 is a capacitor for matching the resonance frequency of the electromagnet 13 with the reference frequency.

In a magneto-optical recording device configured in this way, for example, a recording signal as shown in FIG.
When input to
When the laser beam is irradiated onto the magneto-optical disk 1 in a pulsed manner as shown in FIG.
4 a e 4 b t4c, . . . are formed.

In reality, when recording on a magneto-optical disk with groups, the pits are corrected in groups, resulting in pits 411'+4 b'+4 c'H... as shown in FIG.
is formed.

According to such a magneto-optical recording device, it is possible to record new information by overwriting the information irrespective of the information previously written on the magneto-optical disk 1.

(5) [Problem to be solved by the invention] However, the above-mentioned magneto-optical recording device is
(When attempting to record a 3T pattern recording signal with high level ``'1'' as 3T and low level 10'' as shown in the original, 3T pattern, as shown in Figure 4 CB), The laser beam is turned on as shown in Figure 4 0. In this case, the signal level of the recording signal is high level "1".
During the period, the laser beam is turned on when the alternating current magnetic field reaches its maximum positive value, and the signal level of the recording signal is at the low level "'0".
”, the laser beam is turned on when the AC magnetic field reaches the negative minimum value. Then, as shown in Figure 4 (0), the recording signal changes from high level “1” to low repeat A/”.
When changing to "0", the time interval (T1) at which the laser lights up is long, and the recording signal is low L/Hell "0".
When the level changes to "1", the time interval (T2) between laser lighting becomes shorter, so the lengths of the 1 and O pits are different.Therefore, the playback signal and the recording signal are 3T/ Even though it was an f-turn, the high level was ``1'' at 3.5 T and the low level was ``0'' as shown in Figure 4 (6).
is 2.5T, relative to the duty of the recording signal.

There was an inconvenience that the duty of the reproduced signal was shifted.

In view of the above-mentioned problems of the prior art, the present invention provides a magneto-optical recording device that forms bits such that the duty of a reproduced signal does not shift with respect to a recorded signal and can perform good overwriting. The purpose is to

[Means to solve the problem]

The magneto-optical recording device of the present invention has the following features for the magneto-optical recording medium:
In a magneto-optical recording device that records information on a magneto-optical recording medium by applying an alternating magnetic field as a recording bias magnetic field and modulating and irradiating a light beam corresponding to a recording signal in synchronization with the alternating magnetic field, the alternating magnetic field and means for applying an offset magnetic field in an amount determined by the magnitude and direction of the magnetic field.

[Effect]

The present invention generates an offset magnetic field in an alternating current magnetic field in a direction in which the recording bit pattern is shorter than the signal pattern of an actual recording signal, and this offset amount is determined by adjusting the magnitude of the generated alternating magnetic field by using a Hall element, etc. By applying a large magnetic field in the direction in which the recording bit pattern becomes shorter and applying a smaller magnetic field in the direction in which the recording bit pattern becomes longer, the magnetic field on the magneto-optical recording medium is determined. In this case, the total energy of the magnetic field strength and laser power is made to increase as the recorded bit pattern becomes shorter, and decrease as the recorded bit pattern becomes longer.

This is an attempt to make the length of the recording bit pattern equal to the length of the recording signal pattern and to correct the shift in duty of the reproduced signal with respect to the recorded signal.

〔Example〕

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail using the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the magneto-optical recording device of the present invention.

FIG. 2 (Al-) is an explanatory diagram of the recording operation of the magneto-optical recording device.

Note that in FIGS. 1 and 2, parts corresponding to those in FIGS. 3 and 4 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, as shown in FIG. 1, a magnetic field sensor 18 (such as a Hall element) is placed near the objective lens 8 of the optical pickup 4, and the magnetic field generated by the electromagnet 13 is measured, and its output is By inputting the current into the magnetic field measurement circuit 19 and comparing it with the magnitude of a certain reference magnetic field, the direction and magnitude of the current input to the offset magnetic field drive circuit 20 are determined, and the offset magnetic field drive circuit 20 generates an offset magnetic field. drive the coil 21.

To make it possible to add an offset to an alternating current magnetic field generated by an electromagnet 13.

In the magneto-optical recording device of this embodiment configured in this manner, a recording signal of a 3T pattern (9) in which the high level "1" is 3T and the low level 10" is 3T as shown in FIG. 2 is supplied. In this case, as shown in FIG. 2(B), by applying an offset () to the alternating current magnetic field in a direction that shortens the length of the recording bit to the offset magnetic field generating coil 21, By reducing the strength of the magnetic field during the high level "1" period of the recording signal and increasing the strength of the magnetic field 1 degree during the low level "0" period, the magneto-optical disk can be created as shown in Figure 2.0. ]The size of the recording bit formed above is increased during the period of low level "0" when the length of the recording bit is short, and during the period of high level "1" when the length of the recording bit is long. Note that when recording bits are recorded on a magneto-optical disk 1 with groups, both sides of the recording bits as shown in Fig. 2 (arrows) are corrected by the groups, and Becomes a good quality recording bit.

Therefore, the length of the recording bits recorded on the magneto-optical disk does not correspond to the length of the recorded signal, and the reproduced signal also has a length shown in Fig. 2 (
As shown at F+, the duty does not deviate from the recording signal.

(10) [Effects of the Invention] As explained above, according to the present invention, an alternating magnetic field is applied as a recording bias magnetic field, and a light beam corresponding to a recording signal is modulated and irradiated in synchronization with the alternating magnetic field. In a magneto-optical recording device that records information on a magneto-optical recording medium by.

An offset is applied in a predetermined direction of an alternating magnetic field for a bias magnetic field by means for applying an offset magnetic field determined by the magnitude and direction of the magnetic field of the alternating magnetic field, and the length of the recording bit is shortened in the direction in which this offset is applied. Naru 1
1″ by matching the “O” pattern
Since the length of the recording bit corresponding to 10" and the length of the recording pit corresponding to 10" can be adjusted, the duty of the reproduction signal can be made equal to the recording signal.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the magneto-optical recording device of the present invention. Figure 2 (■) is an explanatory diagram of the recording operation of the magneto-optical recording device. Figure 3 is a schematic configuration diagram showing a conventional magneto-optical recording device. ) is an explanatory diagram of the recording operation of the conventional magneto-optical recording device. 1... magneto-optical disk, 2... magnetic film, 3... motor, 4... optical pickup, 5... Semiconductor laser, 6... Collimator lens, 7at7tz7c, beam splitter, 8... Objective lens, 9 a + 9
b*9 e...sensor lens, 10a, 10b,
10c... optical sensor. 11...AT-AF circuit, 12...actuator. 13... Electromagnet, 13B... Coil, 14... Reference oscillation circuit, 15... Recording signal modulator, 16... Drive circuit, 17... Capacitor, 18... Magnetic field sensor, 19 . . . AC magnetic field measurement circuit, 20 . . . Offset magnetic field drive circuit, 21 . . . Coil for offset magnetic field.

Claims (1)

[Claims] (1) Information is recorded on the magneto-optical recording medium by applying an alternating magnetic field as a recording bias magnetic field to the magneto-optical recording medium and modulating and irradiating a light beam corresponding to the recording signal in synchronization with the alternating magnetic field. A magneto-optical recording device that performs the following: means for detecting the magnitude and direction of the magnetic field of the alternating magnetic field;
1. A magneto-optical recording device comprising means for applying an offset magnetic field of an amount determined by the magnitude and direction of the magnetic field.