JPH034979Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a reading device that reads magnetic recording on a magnetic recording medium using magneto-optical effect.

<Prior Art> As a magnetic recording readout device for reading magnetic records on a magnetic recording medium, a magnetic recording readout method has been proposed that uses magneto-optical effects to read out data in place of a conventional readout device using a magnetic head. This magnetic recording readout method that utilizes the magneto-optical effect places a soft magnetic film in contact with the magnetic recording medium, and transfers the perpendicular component of the magnetic recording signal on the magnetic recording medium to the soft magnetic film. It is an optical readout method that utilizes Faraday optical rotation depending on the magnetization direction of the domains of the soft magnetic film.

FIG. 1 is a diagram showing the configuration of a conventional magnetic recording/reading device. In the figure, it is assumed that 1 is a magnetic recording medium such as a magnetic tape, and its magnetic layer 1a is provided with magnetic recording by a modulation method such as pulse code modulation, frequency modulation, or pulse width modulation.

A read head 2 that utilizes the magneto-optical effect of a soft magnetic film is provided in contact with the magnetic layer 1a of the magnetic recording medium 1. The read head 2 includes, for example, as shown in FIG. 2, the soft magnetic film 2b is formed on the side facing the magnetic recording medium 1 of an optically transparent GdGa garnet substrate 2a having a thickness of 0.2 to 0.5 mm. It has a structure in which a reflective film 2c is deposited on top of the soft magnetic film 2b. The soft magnetic film 2b is optically transparent and has soft magnetic properties, for example, YSmCaFeGe garnet such as Y _1.92 Sm _0.1 Ca _0.98 Fe _4.02 Ge _0.98 O ₁₂ is used, and the axis of easy magnetization is perpendicular to the film surface. It is formed as a film with a thickness of approximately 6 μm. A protective film 2d made of, for example, silicon dioxide is provided on the surface of the reflective film 2c.

When the read head 2 is brought into contact with the magnetic recording medium 1, the domains of the soft magnetic film 2b are moved in a direction perpendicular to the film surface by the perpendicular component of the leakage magnetic flux generated from the magnetic recording signal of the magnetic recording medium 1. Become magnetized. To read out this domain signal, a laser beam or the like generated from the light source generator 3 is linearly polarized through a polarizer 4 and supplied to the beam splitter 5.
The light passing through the beam splitter 5 is passed through the objective lens 6.
The light is focused onto the soft magnetic film 2b. This focused light is reflected by the reflective film 2c, passes through the objective lens 6 again, is bent at a right angle by the beam splitter 5, and is supplied to the analyzer 7. During this time, the light undergoes Faraday rotation to the right or left depending on the magnetization direction of the domains of the soft magnetic film 2b. The light that has undergone Faraday optical rotation is guided through an analyzer 7 to a light receiving system 8, where it is converted into an electrical signal. The signal converted into an electric signal by the light receiving system 8 is reproduced by a reproducing device (not shown).

<Problem to be solved by the invention> However, in the conventional device, the soft magnetic film 2b is located between the beam splitter 5 and the read head 2.
The objective lens 6 is arranged at a position facing the upper signal image, and after the light from the light source device 3 is focused on the soft magnetic film 2b through the objective lens 6, the reflected light is directed back to the objective. Since the configuration is such that the signal is guided through the lens 6 to the beam splitter 5 and the light receiving system 8, the optical path length between the signal image on the soft magnetic film 2b and the beam splitter 5 becomes long, and as the optical system becomes larger. At the same time, there were drawbacks such as being susceptible to optical disturbances, lowering the S/N ratio and deteriorating sensitivity.

Therefore, the goal of this invention was to shorten the optical path length as much as possible to make the device more compact, prevent optical disturbances, improve the S/N ratio, and increase sensitivity. An object of the present invention is to provide a magnetic recording/reading device.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention utilizes the magneto-optical effect of a soft magnetic film having an axis of easy magnetization perpendicular to the surface to read magnetic records in a magnetic recording medium. In the output device, a light splitting means is provided on the optical path from the light source to the soft magnetic film and the light receiving system, and an objective is placed on the opposite side of the light splitting means to the signal image on the soft magnetic film. A lens is disposed, and an optical rotator having an optical rotation angle substantially equal to the optical rotation angle of the soft magnetic film is provided on the other side of the substrate on which the soft magnetic film is formed on one side.

<Operation> A light splitting means is provided on the optical path from the light source to the soft magnetic film and the light receiving system, and an objective lens is placed on the opposite side of the light splitting means to the signal image on the soft magnetic film. Therefore, the light passing through the light splitting means enters the soft magnetic film without passing through the objective lens, and the optical path length between the soft magnetic film and the light splitting means is significantly shortened compared to the conventional method. This allows us to reduce the size of the entire device and at the same time prevent optical disturbances.
The S/N ratio and sensitivity can be improved.

In addition, since the other side of the substrate with the soft magnetic film formed on one side is provided with an optical rotator having an optical rotation angle approximately equal to the optical rotation angle of the soft magnetic film, light that is Faraday-rotated to the right or left by the soft magnetic film can be On the other hand, it is possible to further rotate the light using an optical rotator and increase the amount of change in optical rotation of the receiving target. Therefore, the amount of change in optical rotation corresponding to the magnetization direction of the light receiving object is increased compared to the conventional case, and the maximum contrast can be obtained. Furthermore, since the amount of change in optical rotation to be received is increased, the S/N ratio is improved.

<Example> The content of the present invention will be specifically explained below with reference to the attached drawings which are examples. FIG. 3 is a diagram showing the configuration of a magnetic recording/reading device according to the present invention. In the figure, the same reference numerals as in FIG. 1 indicate the same components. As shown in the figure, in the present invention, conventional beam splitter 5 and read head 2
The objective lens 6 placed between the beam splitter 5 and the light receiving system 3, that is, the soft magnetic film 2
It is placed at a position opposite to the signal image on b. The beam splitter 5 is placed directly on the readout head 2, and an objective lens 6 is placed above the beam splitter 5. The beam splitter 5 can also be constituted by other light splitting means, such as a semi-transparent mirror.

With the above configuration, the light passing through the beam splitter 5 enters the soft magnetic film 2b without passing through the objective lens 6, and the optical path length between the soft magnetic film 2b and the beam splitter 5 is reduced. Since the time is significantly shortened compared to the conventional method, it is possible to reduce the size of the entire device, prevent optical disturbances, and improve the S/N ratio and sensitivity.

As shown in an enlarged view in FIG. 4, the read head 2 has a soft magnetic film 2b for reading on one side.
The structure is such that another soft magnetic film 2e having the same composition as the soft magnetic film 2b is deposited on the other side of the GdGa garnet substrate 2a. 2c is a reflective film, 2d
is a protective film.

As already mentioned, the soft magnetic films 2b and 2e are
Although it is formed using optically transparent and soft magnetic YSmCaFeGe garnet, etc., when forming the soft magnetic films 2b and 2e on the substrate 2a, the liquid phase epitaxial growth method (hereinafter referred to as
(referred to as the LPE method) is commonly used.
For this reason, if the soft magnetic film 2b is provided only on one surface of the substrate 2a, it is necessary to remove the magnetic garnet single crystal film on the other surface formed by the LPE method by polishing or other means. However, in the case of this embodiment, this work is not necessary, and the advantage is that the number of steps is small.

Further, a magnet 9 such as a permanent magnet or an electromagnet is provided on the soft magnetic film 2e.
The domains of the soft magnetic film 2e are magnetized in a direction having an optical rotation angle substantially equal to the optical rotation angle of the soft magnetic film 2b. With such a configuration, it is possible to further rotate the light Faraday-rotated to the right or left by the soft magnetic film 2b, thereby increasing the amount of change in optical rotation of the light-receiving target. For example, when trying to receive light when the domain of the soft magnetic film 2b is magnetized in a direction with the lower surface side of the film as an N pole and the upper surface side as an S pole (hereinafter referred to as NS direction magnetization), the polarity of the magnet 9 are arranged so that the N pole side faces the soft magnetic film 2e.
Then, as shown in FIG. 5, the light rotated by an angle θ in the left direction on the soft magnetic film 2 b
e, the light is further rotated to the left by an angle θ, and the optical rotation corresponding to the SN direction magnetization, which is a reversed magnetization state, becomes an optical rotation angle of 0. Therefore, as is clear from Fig. 5, the optical rotation change corresponding to the magnetization in the NS direction, which is the target of light reception, increases from the conventional Ksinθ to Ksin2θ,
The maximum contrast can be obtained in relation to the SN direction magnetization. Furthermore, since the amount of change in optical rotation that is the subject of light reception increases, the S/N ratio improves. Soft magnetic film 2e
Similar effects can also be obtained by arranging an independent optical rotator between the read head 2 and the beam splitter 5 instead of the magnet 9.

In addition, in this embodiment, the beam splitter 5 is constituted by a polarizing beam splitter, and the polarizing plane is set to the polarizing plane of the polarizing beam splitter 5 on the light source device 3 side and the light receiving system 8 of the polarizing beam splitter 5. Combined polarizers 10 and 11 are arranged, respectively. 1
2 is a condensing lens.

With this configuration, the optical system, which conventionally consisted of a polarizer and an analyzer, can be configured with the polarizing beam splitter 5, which is a single component, and the optical path length can be made significantly shorter than that of the conventional optical system. Moreover, the light source device 3 side of the polarizing beam splitter 5 and the light receiving system 8
Polarizers 10 and 11 whose polarization planes match the polarization plane of the polarization beam splitter 5 are arranged on the side, so that the light entering the polarization beam splitter 5 from the light source device 3 and the light passing through the polarization beam splitter 5 are arranged on the side. The light entering the light receiving system 8 becomes only linearly polarized light that is polarized by the polarizers 10 and 11 in the direction that it should originally be received by the polarizing beam splitter 5. Therefore, optical disturbance to the optical system, halo phenomenon, etc. are prevented.
The S/N ratio is improved.

<Effects of the invention> As described above, according to the present invention, the following effects can be obtained.

(a) In a device that reads magnetic records of a magnetic recording medium by using the magneto-optical effect of a soft magnetic film having an axis of easy magnetization in a direction perpendicular to the surface, optical light is transmitted from a light source to the soft magnetic film and a light receiving system. Since a light splitting means is provided on the road and an objective lens is placed on the opposite side of the light splitting means to the signal image on the soft magnetic film, the optical path length can be maximized. By shortening the length, it is possible to provide a magnetic recording/reading device that can miniaturize the device, prevent optical disturbances, improve the S/N ratio, and increase sensitivity.

(b) Since the substrate with the soft magnetic film formed on one side is provided with an optical rotator having an optical rotation angle approximately equal to the optical rotation angle of the soft magnetic film on the other side, the maximum contrast can be achieved with respect to reversed magnetization information of the magnetic recording medium. obtained,
A highly sensitive magnetic recording/reading device with an excellent S/N ratio can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional magnetic recording/reading device, FIG. 2 is a sectional view of its reading head, FIG. 3 is a diagram showing the configuration of a magnetic recording/reading device according to the present invention, and FIG. FIG. 5, which is an enlarged cross-sectional view of the read head portion, is also a diagram showing its Faraday optical rotation. 1...Magnetic recording medium, 2...Reading head, 2a
... Substrate, 2b... Soft magnetic film, 2e... Soft magnetic film, 5... Beam splitter, 6... Objective lens.

Claims (1)

[Claims for Utility Model Registration] (1) In an apparatus for reading magnetic recording of a magnetic recording medium using the magneto-optical effect of a soft magnetic film having an axis of easy magnetization in a direction perpendicular to the surface, A light splitting means is provided on the optical path leading to the film and the light receiving system, an objective lens is disposed on the opposite side of the light splitting means to the signal image on the soft magnetic film, and the objective lens is disposed on one side of the light splitting means. A magnetic recording/reading device comprising: an optical rotator having an optical rotation angle substantially equal to the optical rotation angle of the soft magnetic film on the other side of the substrate on which a soft magnetic film is formed. (2) The magnetic recording/reading device according to claim 1, wherein the objective lens is disposed between the light splitting means and the light receiving system. (3) Claim 1 of the utility model registration, characterized in that the light splitting means is a beam splitter.
The magnetic recording/reading device according to item 1 or 2. (4) The magnetic recording/reading device according to claim 3, wherein the beam splitter is a polarizing beam splitter. (5) The magnetic recording readout device according to claim 1 or 2, wherein the light splitting means is a semi-transparent mirror. (6) The utility model registration claim 1 is characterized in that the optical rotator is constructed by forming a soft magnetic film on the other surface of the substrate and arranging a magnet on the soft magnetic film. The magnetic recording/reading device described above.