JPS6353619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical storage element that can record, reproduce, and erase information using light.

In recent years, information has been optically recorded, reproduced, and recorded using light such as HeNe lasers, Ar lasers, and semiconductor lasers.
The erasing method, that is, the magneto-optical recording method, has attracted attention, and research and development has been intensively promoted in industry.

When this method is used in devices such as magnetic disks, magnetic drums, and magnetic tapes, it is possible to create a gap of about 0.5 to 1 mm between the recording medium and the tip of the condenser lens, which is the recording head or reproduction head. Therefore, by providing a transparent protective plate between the recording medium and the condensing lens, it is possible to reliably prevent dust from directly adhering to the recording medium, and compared to the conventional recording method using a magnetic head. This has the advantage that the influence of dust can be reduced.

Further, by appropriately changing the thickness of the transparent protective plate, it is possible to reliably prevent contact between the condensing lens and the memory element, and there is an advantage that head crushing, which could not be removed with conventional methods, can be completely prevented.

Furthermore, according to this method, for example, since the reproduction signal is proportional to the amount of read light, the diameter of the recording bit can be minimized to about the wavelength of light (approximately 1 μm or less), so the reproduction signal is proportional to the size of the recording bit. It also has the advantage of being able to achieve much higher density than conventional methods.

Conventionally, when implementing the magneto-optical recording method which has many advantages as described above, an apparatus as shown in FIG. 1 has been used.

FIG. 1 shows an example of reproducing information recorded on a magnetic thin film. After a laser beam 6' emitted from a laser light source 8 passes through a polarizer 1', a condensing lens 4',
The light passes through a magnetic thin film 2', a collimator lens 5', and an analyzer 3' in this order, enters a photodetector 7', and reproduces information using the incident light.

However, this method has the disadvantage that the S/N ratio cannot be made very high because the condensing lens 4' and the collimator lens 5' cause depolarization.

The present invention solves the above-mentioned drawbacks and simplifies the optical system by integrating a polarizer, a magnetic thin film, and an analyzer and placing them between a condenser lens and a collimator lens. Embodiments will be described in detail below with reference to the accompanying drawings showing examples.

FIG. 3 is a side view of a magneto-optical memory element formed in the shape of a disc, in which a magnetic thin film 2 is deposited on the lower surface of a polarizing disc as a polarizer 1 using a vacuum evaporation method, sputtering method, ion plating method, etc. Further, a polarizing disk as an analyzer 3 is attached to the lower surface of the magnetic thin film 2 with an adhesive 9 such as an ultraviolet curing agent.

The polarizing disk is composed of a polymer plate such as dichrome, Polaroid H, K, L, etc., and the magnetic thin film 2 is composed of heavy rare earths such as Gd, Tb, Dy, Ho, Sm, Er, Eu, iron, Amorphous ferrimagnetic materials formed by mixing transition metals such as cobalt and nickel in various composition ratios, and crystalline magnetic materials such as MuBi, EuO, and MuBiCu, are thin films with an axis of easy magnetization perpendicular to the film surface. Further, as the adhesive 9, photobond, Loctite, etc. are used.

Further, the transmission axes of the polarizing disks are 90±ΘF, assuming that the Faraday angle of the magnetic thin film 2 is ΘF.
It is positioned so that it is at either of the following angles.

FIG. 2 shows a device for reproducing information recorded on the magnetic thin film 2 of the magneto-optical storage element having the configuration shown in FIG. , passes through a magneto-optical memory element that integrates a polarizer 1, a magnetic thin film 2, and an analyzer 3, further passes through a collimator lens 5, and enters a photodetector 7.

Therefore, the condenser lens 4 and the collimator lens 5
It is possible to reliably eliminate the depolarization caused by this, and it is possible to obtain a high S/N ratio.

Furthermore, since the polarizer 1 and analyzer 3 are integrated with the magnetic thin film 2, it is also possible to simplify the optical system.

FIG. 4 shows an embodiment applied to a bit-by-bit reproducing device having no mechanically movable parts, in which a laser beam 6 emitted from a laser light source 8 is positioned by a two-dimensional polarizer 11, and a condensing lens 4, the light passes through a magneto-optical storage element, and further passes through a focusing lens 12 and enters a photodetector 7.

The magneto-optical memory element shown in FIG. 4 has a different structure from that shown in FIG. 3, in that a magnetic thin film 2 is formed on one side of a transparent substrate 10 made of glass, plastic, etc. Polarizer 1 with adhesive 9 on the side
At the same time, the analyzer 3 is attached to the other side with an adhesive 9.

Therefore, the transparent substrate 10 plays a reinforcing role,
The strength is improved compared to that shown in Figure 3.

The configuration of the magneto-optical memory element is not limited to that shown in FIGS. 3 and 4, and includes, for example, a polarizer 1 and an analyzer 3.
A transparent plate may be attached to the outer surface of the magnetic thin film 2, or a dielectric thin film may be formed on the surface of the magnetic thin film 2.

Also, the transmission axes of polarizer 1 and analyzer 3 are 90°±ΘF.
It is not limited to positioning so that the angle becomes the maximum, but it is also possible to set the angle at which the S/N ratio is maximized.

Furthermore, the S/N ratio can be improved by interposing a phase plate between the magnetic thin film 2 and the polarizer 1 or the analyzer 3 to change the polarization state entering the analyzer 3.

As described above, the present invention includes a polarizer 1, a magnetic thin film 2,
By integrating the analyzer 3 and the analyzer 3, unique effects such as significantly improving the S/N ratio and simplifying the optical system can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a simplified side view of a conventional magneto-optical reproducing device, FIG. 2 is a simplified side view of a reproducing device using a magneto-optic storage element showing an embodiment of the present invention, and FIG. FIG. 4 is a side view of a disk-shaped magneto-optical memory element showing an embodiment of the present invention, and FIG. Simplified side view. 1...Polarizer, 2...Magnetic thin film, 3...Analyzer, 9...Adhesive.

Claims (1)

[Claims] 1. A magneto-optical memory element characterized in that a magnetic thin film is sandwiched between two polarizing plates, and a polarizer, a magnetic thin film, and an analyzer are integrated.