JPS62177738A - Transfer type photomagnetic head - Google Patents

Abstract

PURPOSE:To perform the tracking control easily and smoothly by taking laser light for reproducing and reflected light from a main magnetic pole out of a cantilever, which performs the tracking servo of a vertical magnetic head part, through a polarization plane maintaining fiber to supply said laser light and detect said reflected light. CONSTITUTION:A main magnetic pole excitation type vertical magnetic head 20 where a yoke body 21 around which an exciting coil 22 is wound and a thin film main magnetic pole 25 protected by a transparent base body 26 are formed into one body is supported in one end of a cantilever 10. The laser light led from the other end of the cantilever 10 through a polarization plane maintaining fiber 28 is allowed to pass an optical system consisting of glass base bodies 23 and 24 including a distributed index lens 27 provided in one side part of the vertical magnetic head 20, and is multireflected in the transparent body 26 protecting the main magnetic pole 25 and reaches the main magnetic pole, and this reflected laser light is taken out of the cantilever 10 through the transparent base body 26, the optical system, and the polarization plane maintaining fiber 28 and is led to photodetectors 37 and 38.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a transfer method in which recording on a medium is performed using a perpendicular magnetic head, and the recorded information signal is reproduced by reflecting or transmitting a laser beam onto a main magnetic pole. This invention relates to the structure of a reproducing means using a magneto-optical head.

2. Description of the Related Art As methods for writing and reading information into a recording medium having perpendicular anisotropy, there are two methods: a magnetic perpendicular magnetization method and an optical method. This perpendicular magnetic recording method is
The linear density and areal density can be increased compared to the horizontal in-plane magnetic recording method that utilizes in-plane anisotropy.

In this Kawamuka magnetic recording, the magnetic thin film is made with 1 mm magnetic domain, so the linear density can be increased compared to an optical recording method using optical modulation by irradiation with a light beam spot. In this direct magnetic recording system, the density can be increased by narrowing the width of the recording trunk, but the reproduction output, that is, the CN ratio, deteriorates accordingly when performing magnetic reproduction. Therefore, when the irG signal is generated while maintaining a high CN ratio, the optical method can achieve a higher density than the perpendicular magnetic recording method. This is because the width of the recording track depends on the width of the main pole film, and there is a limit to how narrow this width can be.

Therefore, it has been considered to narrow the track width and increase the CN ratio.As a method for achieving this, in order to increase the recording density, information is written magnetically, and information is read by magnetization during reproduction. A method has been considered in which the change in direction is extracted as a change in light and carried out optically. In that case,
A high permeability magnetic thin film is used as the main pole film, and the main pole is magnetized by the leakage magnetic field according to the magnetization distribution recorded on the perpendicular magnetic recording medium, and the tip of the main pole is irradiated with laser light. This is done by concentrating light, guiding the reflected or transmitted light to a photodetector via an optical system, and converting it into an air signal. At the tip of the main pole, a slanted distribution appears that corresponds to the magnetization information, ie, the polarity of the recording bit, on the magnetic recording medium in contact with it. In this way, the Kerr effect or Faraday effect, which is a magneto-optical effect, occurs in the laser light reflected or transmitted through the main pole, whose magnetization direction changes depending on the magnetization distribution of the medium. Detecting the rotation of the polarization plane due to this,
A reproduced signal is obtained. Therefore, by recording with the perpendicular magnetization method, a thin film main pole is used for linear density, which is higher than laser light recording (1 μm/bit) (0.1 μm/bit).
m/bit), and in order to increase the CN ratio during reproduction, the track density, that is, the track width, was set to a value similar to Genferi recording (1.6 μm), which was the limit of magnetic recording and reproduction up until now. 4 μm).

Problems to be Solved by the Invention However, this type of transfer-type magneto-optical head that has been conventionally considered has a structure in which optical reproducing means is integrally provided on the main magnetic pole side, so the head section where the main magnetic pole is provided is particularly difficult to solve. Not only is it heavy and large, but it also has poor movement, making it impossible for a tracking servo system to achieve 70% tracking servo, and there are various problems in putting it into practical use.

In addition, if a main pole excitation type perpendicular magnetic head is applied to a transfer type magneto-optical head, the mechanism for feeding the head body in the tracking direction can be simplified, but since the excitation coil is provided integrally, the tip of the main pole There were various problems that needed to be solved in the configuration of the optical system for irradiating and focusing laser light.

This invention uses a main pole excitation type perpendicular magnetic head, which allows easy tracking servo and high C.
It is an object of the present invention to provide a transfer type magneto-optical head that can reliably perform optical reproduction at an N ratio.

Means for Solving the Problems This invention writes information on a perpendicular magnetic recording medium using a perpendicular magnetic head, and upon reproduction, a laser beam is irradiated onto the main pole of the perpendicular magnetic head whose magnetization is transferred from the medium. This is a transfer-type magneto-optical head that reads information by detecting changes caused by the magneto-optic effect that appear in reflected or transmitted laser light from a magnetic pole using a photodetector. A main pole excitation type perpendicular magnetic head integrally formed with a protected thin film main pole is supported at one end of the cantilever, and a laser beam guided from the other end of the cantilever via a polarization maintaining fiber is directed to the perpendicular magnetic head. The reflected laser beam passes through an optical system consisting of a glass substrate including a gradient index lens provided on one side, and is subjected to multiple reflections in a transparent substrate that protects the main magnetic pole to reach the main magnetic pole. It is characterized by being taken out of the cantilever and guided to a photodetector via an optical system and a polarization maintaining fiber.

According to the transfer type magneto-optical head of the present invention, a main pole excitation type perpendicular magnetic head is supported at one end of the cantilever, and a light source of a laser beam irradiating the main pole and a laser beam reflected from the main pole are connected. A photodetector for detection is provided at a separate location outside that does not affect the operation of the cantilever, and the laser beam is directed to the main magnetic pole via a polarization maintaining fiber. The laser beam guided to the head part via the fiber passes through the glass base and the transparent base that protects the main pole, reaches the tip of the main pole, and returns, bypassing the excitation coil of the main pole excitation type. It forms an optical path. Therefore, the weight of the dome in contact with the medium is reduced, the movement of the cantilever that supports the head becomes smoother, and tracking servo operation becomes easier. The CN ratio makes it definitely possible.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 3 show an embodiment of the transfer type magneto-optical head according to the present invention, and FIGS. 1 and 2 show the main pole excitation type head structure, and FIG. FIG. 2 is a diagram showing a reproduction optical system. In the figure, 1 is a disk medium, 10 is a cantilever, 2
0 indicates a main pole excitation type head section.

A disk medium 1 applied to a transfer type magneto-optical converter has a substrate 2 made of, for example, a polyester film and a substrate 2 made of Fe-Ni.
A layer 3 is formed by vapor deposition or sputtering, and a Co--Cr layer 4 having perpendicular magnetic anisotropy is further formed thereon by vapor deposition or sputtering. A cantilever 1 is attached to the Co-Cr layer 4 of this medium 1.
The head unit 20 supported by the medium 1 is brought into contact with one end of the medium 1.
Information is written to and read from the medium 1.

The cantilever 10 supporting the head portion 20 at one end is
The rear end near the other end is neutrally supported on the head (pink amplifier) device main body (not shown) side by a damper member 11.11. A permanent magnet 12 is attached to the other end of the cantilever 10. Tracking control excitation coils 13.13 are arranged on both sides of the permanent magnet 12.

On the other hand, the head portion 2 supported by one end of the cantilever 10
0 indicates a U-shaped yoke body 21 with both ends bent downward, an excitation coil 22 wound around one bent piece of the yoke body 21, and one side of the yoke body 21 on the side of the excitation coil 22. A rectangular glass base 23 is attached to the glass base 23, a right triangular prism-shaped glass base 24 is attached to the glass base 23, and a permeable glass base 24 is installed vertically at the bottom of the center of the excitation coil 22. It is formed by integrally combining a main magnetic pole 25 made of a highly magnetic garnet thin film or the like, and a transparent substrate 26, 26 that sandwiches and protects the main magnetic pole 25 in a sandwich-like manner. A transparent substrate 26.26 that protects the main magnetic pole 25 is provided so as to extend from one lower end of the yoke body 21 to the other lower end of the rectangular glass substrate 23, and is placed on the side so that the tip of the main magnetic pole 25 comes into contact with the medium. It is formed into a substantially right triangular shape that slopes upward.

A gradient index lens 27 is attached in contact with the inclined surface of the triangular prism-shaped glass substrate 24 on the cantilever 10 side provided on the upper part of the head section 20, and a laser beam is attached to the other of the gradient index lens 27. One end of a polarization-maintaining fiber 28 that transmits light while maintaining its polarization plane is connected thereto. The polarization maintaining fiber 28 is disposed through the cantilever 10 to a position in the head device main body at the rear of the cantilever 10 to reach an optical system disposed at a position away from the cantilever. The polarization maintaining fiber 28 is located in the middle from the lens 27 to the tip of the cantilever 10.
In order to prevent shaking when the cantilever moves, it is fixed and held at the tip side of the cantilever by a holding member 29. Further, the fiber 28 enters through a hole at one end of the cantilever at its intermediate portion, and exits from a hole at the other end.

A reproducing optical system is provided in the head device main body behind the cantilever 10 to which light is guided via the polarization maintaining fiber 28. This optical system includes a diode laser 30, a collimator lens 31, a half mirror 32, and a fiber coupling lens 33 arranged in the optical axis direction reaching the other end of the polarization maintaining fiber 28.
A 1/2 length plate 34, a convex lens 35,
A polarizing beam splitter 36 is provided. moreover,
Photodetectors 37 and 38 are respectively arranged in two orthogonal directions in which the light is separated through the polarizing beam splitter 36. In this way, the optical system detects changes in the so-called Kerr rotation angle, and
It consists of a magneto-optical detection system that performs signal reproduction. The half mirror 32 and the polarization maintaining fiber 28 are connected by a coupling lens 33.

As described above, in the transfer type magneto-optical head device, which is composed of a main body section provided with an optical system, a cantilever 10, and a head section 20, the main magnetic pole 25 can reciprocate in the radial direction of the disk medium 1, that is, in the tracking direction. It is supported by a known feeding mechanism.

Next, the disk medium 1 by the above-mentioned transfer type magneto-optical head is
Describe writing and reading information to.

First, when writing information to the disk medium 1,
A current is applied to the excitation coil 22 based on the information signal to excite it. Then, the Co--Cr layer (recording layer) 4 of the disk medium 1, which has been previously magnetized to one polarity, has its magnetization polarity reversed in accordance with the information signal. In this case, a signal of a different frequency that switches between each revolution of the disk medium 1 is mixed as a tracking signal together with the information signal into the low frequency range of the information signal "i" pre-component. A recording trunk containing alternating frequency components is magnetized and formed in the recording layer 4, and information is written to the disk medium 1.Since the principle of perpendicular magnetic recording is well known, detailed explanation will be omitted. do.

Next, when reading information from the disk medium 1 on which information has been written as described above, a laser beam is guided from the semiconductor laser 30 to the tip of the main pole and irradiated thereon.

The laser beam irradiated from the semiconductor laser 30 passes through the collimator lens 31 and the half mirror 32 and reaches the fiber coupling lens 33, and then the polarization maintaining fiber 2
The light is focused on the other end of the fiber 8 and guided to the head section 20 via the fiber 28. The laser beam guided to the head section 20 is
The glass substrate 24 is irradiated in an oblique direction as a condensed beam through the gradient index lens 27, and the rectangular glass substrate 2
It reaches one side of 3 and is totally reflected. The laser beam that is totally reflected on one side of the glass substrate 23 reaches one transparent substrate 26 that protects the main magnetic pole 25 located below, is multiple reflected on the upper and lower surfaces of the transparent substrate 26, and is reflected between the pair of transparent substrates. 2B, 2B
The light reaches the main magnetic pole 25 sandwiched between them and is reflected. At this time, magnetization is transferred to the main magnetic pole 25 according to the magnetization direction of the recorded information by the magnetic field that is magnetized in the recording layer 4 of the medium 1 . Therefore, when the laser beam is focused on the tip,
The reflected laser beam or transmitted light reflected by the main magnetic pole 25 is given rotation of the plane of polarization in different directions by magneto-optical effects such as Kerr effect and Faraday effect depending on the magnetization direction. This reflected or transmitted laser light is reflected within the transparent substrate 26 and the glass substrates 23 and 24, reaches the gradient index lens 27, and is returned to the optical system via the polarization maintaining fiber 28. The laser beam returned to the optical system is passed through a half mirror.
32, a 1/2 wavelength plate 34, and a convex lens 3.
5, the light beam reaches the polarizing beam splinter 36, where the light is split into two directions, and the light is sent to the photodetector 37.
I am led to 38. The light received and detected by the photodetectors 37 and 38 is converted into an electric signal according to its intensity, and a reproduced RF signal is generated by extracting the differential output of each electric signal. In this way, information is read from the medium 1. On the other hand, the RF multiplied signal -f'A< is applied to a bandpass filter, and components of different frequencies mixed during recording are extracted, converted into DC components by a rectifier circuit, and differentially output. As a result, a tracking error signal that excites the excitation coil 13.13 is obtained, and this error signal excites the excitation coil 13.13 for tracking control to perform tracking servo.

As described in detail, according to the transfer type magneto-optical head of the present invention, the supply of laser light for reproduction and the detection of reflected light from the main magnetic pole are carried out via a polarizing fiber to the perpendicular magnetic head section. Since the tracking servo is carried out by taking it out to the outside away from the cantilever, the weight of the head section provided with the main magnetic pole is reduced, and tracking control can be performed easily and smoothly. In addition, an optical path that bypasses the excitation filter is formed in the head section so that the laser beam reaches the main pole located in the F section of the excitation coil of the main pole excitation type vertical magnetic head. It is easy to put a magneto-optical head into practical use.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a head portion of a transfer type magneto-optical head according to the present invention, FIG. 2 is an exploded perspective view of the same, and FIG. 3 is a configuration diagram showing the head portion and optical system. DESCRIPTION OF SYMBOLS 1... Disk medium, 10... O cantilever, 20... Head part, 22... Excitation coil, 23.24... Glass substrate, 25... Main magnetic pole, 26... Transparent substrate, 27...Gradient index lens, 28...-Polarization maintaining fiber, 3011-Fist semiconductor laser, 37.38-Fist photodetector.

Claims (1)

[Claims] (1) Information is written on a perpendicular magnetic recording medium by a perpendicular magnetic head, and during reproduction, a laser beam is irradiated onto the main magnetic pole of the perpendicular magnetic head whose magnetization is transferred from the medium, and the reflected or transmitted laser beam from this main magnetic pole is In a transfer-type magneto-optical head that reads information by detecting changes caused by the magneto-optic effect that appear in light using a photodetector, a yoke body around which an excitation coil is wound and a thin-film main pole protected by a transparent base are integrated. The formed main pole excitation type perpendicular magnetic head is supported at one end of a cantilever, and a laser beam guided from the other end of the cantilever via a polarization maintaining fiber is provided on one side of the perpendicular magnetic head. The reflected laser beam passes through an optical system made of a glass substrate including a molded lens and is multiple-reflected in a transparent substrate that protects the main magnetic pole to reach the main magnetic pole, and this reflected laser light is transmitted through the transparent substrate, optical system, and polarization maintaining. A transfer type magneto-optical head, characterized in that it is taken out of the cantilever via a fiber and guided to the photodetector.