JPH0485740A - magneto-optical disk device - Google Patents

Abstract

PURPOSE:To keep a constant distance between a bias magnetic field generating coil and a disk by using an objective lens to control the distance from the disk with the focusing control. CONSTITUTION:The distance between a disk 2 and a lens 3 is gradually increased by the warp, etc., of the disk 2, and the focus of the laser beam condensed by the lens 3 is shifted from the recording surface of the dish 2. Thus a focusing error sensor 5 outputs a focusing error signal proportional to the shifted variable of the focus. The focusing error signal is inputted to a focus control circuit and this circuit drives a focus actuator 4 in the direction where the shifted variable is reduced. Then the lens 3 moves close to the disk 2. The laser beam condensed by the lens 3 is controlled so as to always form a focal point on the recording surface of the disk 2. Thus the distance between the lens 3 and the disk 2 is kept constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to data recording and
The present invention relates to a magneto-optical disk device that is capable of reproducing and erasing data.

[Prior art] Optical disk devices are characterized by their large storage capacity.
However, optical pickups are generally orders of magnitude larger in weight and volume than the magnetic heads of hard disk drives.The track access time and equipment required to move the optical pickup and the optical spot from one track to another are Figure 4 is an explanatory diagram of the recording principle of the magneto-optical recording method, which has been considered disadvantageous in terms of miniaturization compared to hard disk drives.First, as shown in Figure (a), the magnetic field coil 1 is excited and the downward A bias magnetic field 12 is generated, and the objective lens 3 focuses the laser beam into a spot of about 1 μm, and the temperature of this spot is raised to near the Curie point of the magnetic material constituting the recording layer of the magneto-optical disk 2. Since the coercive force of the magnetic material is almost zero near the Curie point, the recording layer is easily magnetized downward by the bias magnetic field 12, and when heating with laser light is stopped, it remains magnetized downward by the coercive force of the magnetic material. On the other hand, if the polarity of the current in the magnetic field coil 1 is reversed and an upward magnetic field is generated, the upwardly magnetized state can be maintained using the same procedure.In other words, the magnetic field of the recording layer is as shown in the same figure (b). As shown in , only the portion irradiated with the laser beam is selectively magnetized in the direction of the bias magnetic field. Digital data can be recorded by making the upper or lower magnetization direction of this recording layer correspond to data 1 or O. Recording can be done using a method called intensity modulation. First, as shown in Figure 1 (a), magnetic field coil 1
Excite the disk to generate a steady downward bias magnetic field 12, irradiate the disk with laser light, rotate the disk once, magnetize everything downward, and initialize the recorded data to 0. Next, in the same figure (b) ), the polarity of the current in the magnetic field coil 1 is reversed to steadily generate an upward bias magnetic field 13, and while the disk is rotated one more time, the data 1 and 0 of the data to be recorded are temporarily generated. When the temperature of the spot is modulated according to the high output and low output states, the temperature of the spot rises to near the Curie point of the magnetic material only at high output.
It is magnetized upward by the bias magnetic field 13, and at low output the temperature of that spot does not rise to near the Curie point.
) As shown in the final state, this method is the most common recording method at present.In addition to this optical intensity modulation, there is also a recording method called magnetic field modulation.4 Figure 6 shows a recording method using magnetic field modulation. This is a diagram explaining the principle of recording. First, Figure (a)
As shown in Figure 2, while the disk is being irradiated with laser light, the polarity of the current in the magnetic field coil 1 is reversed according to 1 or O of the data to be recorded, and the direction of the bias magnetic field 11 is switched upward or downward. After modulation, regardless of the old data, the recording layer will be magnetized in the direction of the bias magnetic field j1 when the mirror laser beam is irradiated, that is, when the temperature rises to near the Curie point. Even though the data is recorded as shown in JP-A No. 62-175948 and JP-A No. 62-15
Although a recording method such as that shown in 4347 in which recorded data is recorded by light intensity modulation without initialization has been proposed, the optical disk device L in either method is as shown in Figures 4 and 5. The magnetic field coil 1 is configured to face an optical pickup equipped with optical components such as an objective lens 3, a laser light source, a prism, an optical sensor, etc. with the magnetic field coil 1 in between. In the conventional configuration, an optical pickup and a bias magnetic field generating coil are required on both sides of the GEL magneto-optical disk, and the structure is complicated, which not only hinders miniaturization of the device but also reduces the size of the magneto-optical disk. The configuration of the mechanism for loading and unloading the device becomes complicated. Also, due to surface runout that occurs during disk rotation due to disk warpage, etc., the distance between the recording layer of the disk and the bias magnetic field generating coil changes, causing the magnitude of the bias magnetic field in the recording layer to change. [Means for Solving the Problem] In order to solve the above problems, the laser beam is always focused on the recording surface of the magneto-optical disk. [Function] The present invention has a bias magnetic field generating coil which is fixed to an objective lens whose focus is controlled so as to connect the disc and which is provided between the disk disk and the objective lens. is located on the same side of the disk as the optical pickup and is fixed to the objective lens, and the distance between the objective lens and the disk is controlled to be constant by focus control.
Although the distance between the bias magnetic field generating coil and the disk disk can be kept constant [Embodiment] FIG. In the figure,
1 is a magnetic field coil/k that generates a bias magnetic field when erasing and writing data 2 is a magneto-optical disk a 3 is an objective lens The focus error sensor 5 is a focus error sensor that detects the amount of deviation between the focus of the laser beam and the recording surface of the disk 2, and is configured using a method called the astigmatism method, which is found in, for example, the 53-39123. Ru. Reference numeral 6 denotes a focus control circuit, which generally consists of a stability compensator and an actuator driver, and uses a focus error signal output from the focus error sensor 5 to ensure that the laser beam focused by the lens 3 is always focused on the recording surface. 7). Reference numeral 7 denotes a mounting member, which fixes the magnetic field coil 1 to the objective lens 3.
FIG. 2 is a top view of the magnetic field coil 1. As shown in the figure, the magnetic field coil l has a hole or a window 11 made of a material that transmits laser light in the center, and the light is focused by the objective lens 3. The laser beam passes through the window 11 and reaches the top of the disk 2.The reflected light from the disk 2 also passes through the window 11 and reaches the objective lens 3.The fourth operation will be explained as the disk 2 rotates and the disk If the distance between the disc 2 and the objective lens 3 increases slightly due to warpage of the disc 2, etc., and the focus of the laser beam focused by the i-lens shifts slightly from the recording surface of the disc, Focus error sensor 5
outputs a focus error signal proportional to the amount of deviation. The error signal is input to a focus control circuit, and the control circuit drives the focus actuator 4 in a direction that reduces the amount of deviation, so that the objective lens 3 is placed on the disk disk 2 side. move in the direction of approaching. Further, when the distance between the disk disk 2 and the objective lens 3 is slightly reduced, the focus actuator 4 is driven in exactly the same way, and the objective lens 3 moves in the direction away from the disk disk 2 side. Therefore, if the gain of the focus control circuit 6 is set to a sufficiently large value, the laser beam focused by the lens 3 can be controlled so that it is always focused on the recording surface of the disk 2. Therefore, the objective lens 3
The distance between and the disk 2 is kept constant, and the deviation is the allowable deviation of the focus error (typically about ±0.5 μm)
The magnetic field coil 1 is maintained within & -X by the mounting member 7.
Since it is fixed to the objective lens 3 by Coil diameter: 5 ma; distance between magnetic field coil 1 and recording layer of disk 2: 1.5 ma; number of coil turns: 10
0@ When the coil current is 2A, the magnetic flux density in the recording layer is 0.032T, and it is possible to obtain the magnetic flux density of 0.03T, which is generally required for alignment and erasing of a magneto-optical disk. 3 is a configuration diagram of an optical pickup section of a magneto-optical disk device in another embodiment of the present invention, in which FIG. 3(a) is a top view and FIG.
In the figure, 1 is a magnetic field Koinok, 2 is a magneto-optical disk IIL3, and objective lens X7 is a mounting member.
414 is a yoke that operates in the same way as the one in figure s1,
It is composed of a magnetic material such as ferrite or iron, and is used to pass the magnetic flux generated by the magnetic field coil 1. In this case, by adding the yoke 14, the magnetic field coil 1 is made of a magnetic material such as ferrite or iron. The inductance increases, most of the magnetic flux passes through the yoke 14, and the magnetic flux density in the recording layer of the disk 2 increases. Therefore, the number of coil turns and current to obtain the necessary magnetic flux density need to be smaller than when the core is air-core. [Effect of the Invention] As described above, according to the present invention, the bias magnetic field generating coil, which was conventionally provided on the opposite side to the magneto-optical disk, is arranged on the optical pickup section side. This simplifies the structure of the magneto-optical disk drive, simplifies the mechanism for loading and unloading the magneto-optical disk into the device, and facilitates miniaturization of the device. By fixing the bias magnetic field generating coil to the disk and making it follow the surface runout caused by warpage of the disk, the bias magnetic field generating coil can be accurately maintained near the disk without coming into contact with the disk. ＼ It is possible to use a small magnet, that is, one with small inductance. Therefore, it is possible to reverse the bias magnetic field at high speed, and it is possible to use not only optical modulation type disk devices but also magnetic field modulation type optical devices that can perform high-speed recording. The life of being able to realize a disk device and the ability to obtain many excellent effects.

[Brief explanation of the drawing]

Fig. 1 shows the components of the optical pickup section of a magneto-optical disk device in one embodiment of the present invention. Fig. 2 shows a top view of the magnetic field coil. Fig. 3 shows an optical pickup of a magneto-optical disk device in another embodiment of the present invention. Figure 4 is an explanation of the recording principle of magneto-optical recording method Figure 5 is an explanation of the principle of optical intensity modulation recording 1 Figure 6 is a diagram explaining the principle of magnetic field modulation recording
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Claims (1)

[Scope of Claims] An objective lens that focuses laser light on the recording surface of a magneto-optical disk to be mounted, a holding member that holds the objective lens, and a detection means that detects the distance between the objective lens and the magneto-optical disk. a focus actuator that moves the holding member so that the distance detected by the detection means becomes a predetermined distance; and a focus actuator that is placed on the holding member that holds the objective lens driven by the focus actuator, and that A magneto-optical disk device comprising: a bias magnetic field coil that determines the direction of magnetization of the disk.