JPH034980Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magneto-optical recording device that records signals by applying a laser beam and a magnetic field to a perpendicularly magnetized thin film.

A conventional magnetic field modulation type magneto-optical recording head device of this type is shown in FIG. In the drawings, A is a disk having a perpendicularly magnetized thin film formed on its surface, and is rotated in the circumferential direction by a driver. B is a focus actuator for always focusing the laser beam Ba on the perpendicularly magnetized thin film, and the actuator C includes a lens system D for focusing the laser beam Ba;
It consists of a non-magnetic lens barrel E that houses the lens system D, a focus coil F wound around the lens barrel E, and a magnetic circuit G that drives the focus coil F. Reference numeral H denotes a signal magnetic field generating coil, and the coil H is arranged by a connector I to face the focus actuator C via the disk A.
The oscillator B, the focus actuator C, and the signal magnetic field generating coil H move together in the direction of the disk A during signal recording and reproduction.

Next, to explain the above operation, oscillator B
The laser beam Ba emitted from the lens system D is focused onto the perpendicularly magnetized thin film of the disk A to form a minute spot. At this time, if there is surface wobbling of the disk A, the control signal flowing to the focus coil F and the magnetic flux of the magnetic circuit G move the lens system D in the vertical direction (in the direction of the optical axis of the laser beam Ba), and the disk Control is performed so that the spot is always connected on A. The temperature of the focused point where the spots are connected increases due to the optical energy of the laser beam Ba, and the coercive force H _C decreases depending on the properties of the magnetic film. At this time, when a magnetic field H _B exceeding a coercive force H _C is applied to the focal point from an external signal magnetic field generating coil H, the direction of the spontaneous magnetization M _S in the perpendicularly magnetized thin film becomes the direction of the magnetic field H _B. Then, as the perpendicularly magnetized thin film cools after passing through the spot, the coercive force H _C of the part passing through the spot increases again, and the direction of the spontaneous magnetization M _S changes according to the magnetic field H _B
Since it is fixed in the direction of the magnetic field H _B , a signal (pit) is recorded in the direction of the magnetic field H B. Therefore, since the direction of the magnetic field H _B is determined by the direction of the signal current applied to the signal magnetic field generating coil H, the direction of the spontaneous magnetization M _S of the spot passing portion is determined by the direction of the above signal current. That will happen. The signals (pits) recorded in the perpendicularly magnetized thin film in this manner can be read by the difference in rotation angle of the reflected light deflection plane (Kerr effect).

However, in the conventional magneto-optical recording device, as described above, the focus actuator C that focuses the laser beam Ba and the signal magnetic field generating coil H that applies the recording signal are arranged oppositely on both sides with the disk A interposed between them. Therefore, both must be fixed to each other. In addition, the signal magnetic field generation coil H is connected to the disk A.
Since it is arranged so that it cannot move vertically relative to the disk A, it is unable to follow the surface wobbling (vertical movement) of disk A, and the magnetic field strength on the perpendicularly magnetized thin film surface fluctuates greatly, causing recording. The size of the bit may change. In order to avoid such a situation, if the signal magnetic field generating coil H is brought too close to the disk A, there is a risk that the disk A will collide due to surface runout. Furthermore, since the focus actuator C and the signal magnetic field generating coil H are arranged on both sides of the disk A, there is a drawback that the entire head becomes large and heavy.

Therefore, in order to solve this problem, conventionally, the coil for generating the signal magnetic field is placed on the same side near the lens system of the focus actuator. There was one in which the coil was made to follow the magnetic field at the same time, thereby reducing fluctuations in the magnetic field strength on the perpendicularly magnetized thin film surface.

However, according to the above-mentioned conventional technology, since the signal magnetic field generation coil and the focus actuator for driving the lens system are provided in close proximity, there is a problem that there is an adverse magnetic effect. was. Therefore, there was a problem in that the magnetic flux generated by the signal magnetic field generating coil could not be effectively concentrated at the focal point of the laser beam.

Therefore, the present invention was devised to eliminate the above-mentioned drawbacks, and consists of a lens system that focuses laser light on a perpendicularly magnetized thin film, a non-magnetic lens barrel that houses the lens system, and a lens barrel made of a non-magnetic material that houses the lens system. An actuator consisting of a movable part consisting of a focus coil wound around the upper end of the tube, a magnetic circuit as a fixed part that provides a magnetic field to drive the coil in the vertical direction, and the lower end of the lens barrel. a signal magnetic field generating coil wound around the perpendicularly magnetized thin film, applying a laser beam and a magnetic field to the perpendicularly magnetized thin film so that either the laser beam or the magnetic field changes in accordance with the recording signal,
A focus error signal is extracted from the laser beam reflected by the thin film, and the position of a lens that focuses the laser beam on the thin film is controlled in accordance with the focus error signal. In a magneto-optical recording device that also controls the position of a magnetic field generating means that generates a magnetic field, a core formed of a high magnetic permeability material is provided at the outer lower end of the lens barrel, and a signal magnetic field generating coil is attached to the core. In addition to wrapping the
By arranging the tip of the core so as to concentrate the laser beam on the focal point of the laser beam, the signal magnetic field generating coil and the actuator for driving the lens system can be placed on the same side without affecting each other. It is an object of the present invention to provide a magneto-optical recording device that can increase the effectiveness of the magnetic flux by concentrating the magnetic flux generated by a signal magnetic field generating coil on the focal point of a laser beam.

Hereinafter, the present invention will be explained based on the embodiments shown in the drawings. Fig. 2 is a schematic diagram of a magneto-optical recording device according to the present invention, in which 1 is a perpendicularly magnetized thin film magnetized in the thickness direction, that is, in the perpendicular direction. is formed on the surface, and is rotated in the circumferential direction by a driving body (not shown). 2 is an oscillator that emits a laser beam 2a; 3 is a focus actuator that focuses the laser beam 2a onto a perpendicularly magnetized thin film;
A lens system 4 that condenses the laser beam 2a, a lens barrel 5 made of a non-magnetic material that houses the lens system 4, and a lens barrel 5 that is made of a non-magnetic material.
It is composed of a movable part consisting of a focus coil 6 wound around the upper end, and a magnetic circuit 7 as a fixed part that provides a magnetic field to drive the coil 6 in the vertical direction. 8 is a signal magnetic field generation coil for applying a recording signal, and 9 is a hollow core made of a high magnetic permeability material, and has a structure in which a conducting wire is wound several times to several tens of times around the outer periphery of the core 9. And it's lighter. The signal magnetic field generating coil 8 is fixed by fitting a hollow core 9 into the lower end of the lens barrel 5. In this case, the lens barrel 5 has a focus coil 6 and a signal magnetic field generating coil 8. They are formed to have a sufficient length so that they do not influence each other magnetically. Further, the tip of the hollow core 9 fixed to the lower end of the lens barrel 5 is formed to be tapered toward the direction of the perpendicular magnetization thin film. The magnetic flux is concentrated at the focal point of the laser beam 2a.

Next, to explain the above operation, the oscillator 2
The laser beam 2a emitted from the perpendicularly magnetized thin film 1 is focused by a lens system 4 to form a spot on the focused point of the perpendicularly magnetized thin film 1. The laser beam 2a reflected by the perpendicularly magnetized thin film is guided to a focus error signal detection device (not shown), and the focus error signal extracted there is supplied to the focus coil 6. Therefore, the movable part of the focus actuator 3 moves in the optical axis direction of the laser beam 2a, and the focus servo device operates so that the distance between the perpendicularly magnetized thin film and the lens system 4 is always constant. The temperature of the condensing point where the spots are connected rises due to the optical energy of the laser beam 2a, and the coercive force of the condensing point decreases. on the other hand,
A current that changes in accordance with the recording signal is applied to the signal magnetic field generating coil 8, and a magnetic field exceeding the coercive force is applied to the above-mentioned focal point to change the direction of the spontaneous magnetization of the focal point to the direction of the magnetic field, as described above. Signals (bits) are recorded according to the direction of this magnetic field. At this time, the signal magnetic field generation coil 8 is connected to the focus actuator 3.
Since it is integrated with the movable part of the disk 1, the distance between the signal magnetic field generating coil 8 and the perpendicular magnetization thin film is always kept constant even if the surface of the disk 1 is shaken.
The magnitude of the magnetic field generated by the coil 8 is constant on the perpendicularly magnetized thin film. Therefore, even if there is surface wobbling of the perpendicularly magnetized thin film, the size of the recorded pits remains constant. In addition, since the tip of the hollow core 9 is tapered toward the direction of the perpendicularly magnetized thin film, the magnetic flux generated by the signal magnetic field generating coil 8 is focused into the laser beam 2a. Since it can be concentrated at a point, convergence of the magnetic field is effective.

FIG. 3 shows another embodiment of the present invention. In the above embodiment, the signal magnetic field generating coil 8 is coaxially fixed to the lens barrel 5 of the focus actuator 3, but in this embodiment, The signal magnetic field generating coil 8 is fixed to the lower side end of the lens barrel 5 at a predetermined angle, and has a structure in which a conducting wire is wound around a rod-shaped core 9. The other points are the same as those of the previous embodiment.

In the above embodiment, the laser beam 2a remains irradiated and the magnetic field modulation method is used in which the current flowing through the signal magnetic field generating coil 8 is changed according to the recording signal. The present invention can also be applied to an optical modulation method that changes the irradiation of the laser beam 2a in accordance with the recording signal without changing the flowing current. In this case, instead of the coil 8, a permanent magnet may be used as the magnetic field generating means. Further, an actuator for driving the magnetic field generating means is connected to the lens system 4.
The focus actuator 3 may be independent from the focus actuator 3 that drives the focus actuator 3.

As mentioned above, the present invention consists of a lens system that focuses laser light onto a perpendicularly magnetized thin film, a non-magnetic lens barrel that houses the lens system, and a focus coil that is wound around the upper end of the lens barrel. an actuator consisting of a movable part, a magnetic circuit as a fixed part that applies a magnetic field to drive the coil in the vertical direction; and a signal magnetic field generating coil wound around the lower end of the lens barrel. A laser beam and a magnetic field are applied to the perpendicularly magnetized thin film, and either the laser beam or the magnetic field is changed in accordance with the recording signal,
A focus error signal is extracted from the laser beam reflected by the thin film, and the position of a lens that focuses the laser beam on the thin film is controlled in accordance with the focus error signal. In a magneto-optical recording device that also controls the position of a magnetic field generating means that generates a magnetic field, a core formed of a high magnetic permeability material is provided at the outer lower end of the lens barrel, and a signal magnetic field generating coil is attached to the core. In addition to wrapping the
The tip of the core is provided so as to concentrate the laser beam at the focal point.

Therefore, the signal magnetic field generating coil 8 and the lens system 4
By placing the actuator 3 for driving on the same side, the entire device is made smaller and lighter.
Coil 8 for generating magnetic field without affecting each other
Since the magnetic flux generated can be concentrated at the focal point of the laser beam 2a, the convergence of the magnetic field becomes effective. Furthermore, even if the disk surface is shaken, the strength of the applied magnetic field remains constant, improving the S/N ratio of the recorded signal.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional magneto-optical recording device, and FIGS. 2 and 3 are schematic diagrams showing different embodiments of the magneto-optical recording device according to the present invention. DESCRIPTION OF SYMBOLS 1... Disk, 2a... Laser light, 3... Focus actuator, 8... Signal magnetic field generation coil, 9... Core.

Claims (1)

[Scope of utility model registration request] A movable part consisting of a lens system that focuses laser light on a perpendicularly magnetized thin film, a non-magnetic lens barrel that houses the lens system, a focus coil wound around the upper end of the lens barrel, and the coil. The actuator consists of a magnetic circuit as a fixed part that provides a magnetic field to drive the lens vertically, and a signal magnetic field generating coil wound around the lower end of the lens barrel. Applying light and a magnetic field, causing either the laser light or the magnetic field to change in accordance with the recording signal, extracting a focus error signal from the laser light reflected on the thin film, and detecting the focus error signal. In a magneto-optical recording device, the position of a lens that focuses the laser beam on the thin film is controlled in response to an error signal, and the position of a magnetic field generating means that generates the magnetic field is also controlled. , a core made of a high magnetic permeability material is provided at the outer lower end of the lens barrel, a signal magnetic field generating coil is wound around the core, and the tip of the core is configured to focus the laser beam at a focal point. A magneto-optical recording device characterized by being provided with.