JPS6064376A - Recording method of magnetic hologram - Google Patents

Abstract

PURPOSE:To obtain stably an image which has high resolving power and superior reproducibility of continuous gradations by recording hologram information on a specific magnetic thin film with thermomagnetic effect in a two-dimensional pattern of magnetism. CONSTITUTION:A thin film 2 of resin, a thin film 3 of amorphous TbFe, and a thin film 4 of SiOx (X: 1-2) are laminated on the surface of a glass substrate 1 successively. An essential body as a recording medium is the magnetic thin film 3 of amorphous TbFe. A light beam from a Q switched ruby laser 2 is transmitted through an object 29 to reach the surface of a recording medium 10. Its object light interferes with reference light to form an optical pattern containing image information on the object 29, and this pattern is recorded on the TbFe thin film 3 of the recording medium 10 by photo-electro-magnetic effect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to holography technology, and particularly to a magnetic hologram recording method for magnetically recording hologram information using thermomagnetic effects.

As is well-known, magnetic holograms write an optical pattern containing image information created by interference of an object beam and a reference beam created by coherent light onto a magnetic thin film, which is a recording medium, by the photothermal magnetic effect. It is recorded as a dimensional pattern.

To reproduce a recorded image, the magneto-optic effect of a magnetic thin film is used, and by irradiating it with coherent light, the recorded information is read out in the form of light, and an optical image is obtained using the Faraday effect or Kerr effect.

Compared to holograms using photosensitive materials as recording media, magnetic holograms have the essential advantages of not requiring troublesome development processing, and that old recorded information can be easily erased and rewritten. For example, it is attracting a lot of attention for its application as a hologram memory that records not only digital data but also documents and photographs.

However, in the past, the reality is that recording and reproducing images using magnetic holograms has not achieved sufficient characteristics in terms of resolution and reproducibility of intermediate gradations.

A typical conventional magnetic hologram recording medium is MnB1 (
Manganese/Bismuth) iJII! ! However, the following problems have been pointed out.

The single Curie point of 1vln3i is as high as about 360° C., and high-output light is required when writing information, thus requiring a large-scale light source.

Furthermore, the material structure of 1yln3i is polycrystalline, which is a major constraint in increasing the recording density.

Furthermore, MnB1 has poor magnetic domain stability when the coercive force is low, and its structure becomes unstable due to crystal transformation.

Due to these characteristics of recording media, conventionally only black and white binary images can be recorded and reproduced well, and even in that case the resolution was not very high (and unstable).

Furthermore, since a high-output light source is required for writing, it is extremely disadvantageous that small, easy-to-handle, and inexpensive semiconductor lasers cannot be used.

Another problem is that in order to increase the stability of the 11th section, the peripheral magnetic circuit in the recording device becomes large-scale.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to stably obtain high resolution, have excellent continuous gradation reproducibility, and use relatively low-power coherent light emitted from semiconductor lasers etc. An object of the present invention is to provide a magnetic hologram recording method that allows writing.

To achieve this objective, the present inventors conducted hologram recording experiments using various magnetic materials, and found that a magnetic hologram recording method using an amorphous TbFe (terbium iron) thin film yielded good results. I learned how to show.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows the cross-sectional structure of a recording medium used in the magnetic hologram recording method according to the present invention. This is a thin resin film 2 on the surface of a glass substrate 1. Amorphous TbFe thin film 3.
SiOx (x is approximately 1 film 2) thin films 4 are laminated in order, and the main body of the recording medium is amorphous TbFe.
The thin film 3 is a magnetic thin film.

The resin thin film 2 is formed by spin coating a resin such as PMMA, vinyl acetate chloride, or PVA to a thickness of about 1 to 10 μI11. Although this resin thin film 2 is not necessarily necessary, it has the effect of improving the photosensitivity of the TbFe1l film 3 by about 2 to 10 times.

The amorphous Tb Fe thin film 3 is formed to a thickness of 100 to 100 nm by vapor deposition using a two-electron gun time evaporation method or by sputtering.
It is made up of about 00 people. According to experimental data, T
The thickness of the bFe1 film 3 greatly affects the ease of recording images and the contrast of reproduced images, and particularly when reproducing using the Faraday effect, a good thickness is in the range of 100 to 350, more preferably 250. The number ranges from ~330 people.

5- Also, the SiOx thin film 4 is a coating layer of the TbFe'Jlj film 3.

Since the recording density of the amorphous TbFe thin film 3 is not limited by its crystal structure, high resolution can be stably obtained.

Furthermore, since the single Curie point is as low as about 120° C., writing can be performed at relatively low temperatures, and the light source used for writing can be of relatively low output. Therefore, a small semiconductor laser can be used as a light source to perform sufficiently good writing.

Furthermore, since the magnetic domain of the amorphous Tb Fe thin film 3 is very stable even in a region of low coercive force, the configuration of the peripheral magnetic circuit required for writing can be simple. These facts were confirmed by the information writing and reproduction experiments described below.

FIG. 2 shows an information recording apparatus system for the recording medium 1o shown in FIG.

In the figure, a Q-switched ruby laser 21 outputs a pulsed coherent light beam with a peak power of o and emw and a pulse width of 30 nS and a beam width of 0.1 to several sn+.

The beam width of this light beam is widened to some extent by a lens system 22, and is split into two systems by a beam splitter 23.

One of the branched light beams passes through a mirror system 271.25 and is irradiated onto the surface of the recording medium 10 as a reference light.

The other branched light beam is sent to the lens/mirror system 26
, 27 and 28, the object 29 is irradiated with the light.

In this example, the object 29 has a two-dimensional pattern such as characters to be recorded on a plane measuring 35 mm x 35,111 m.

The light beam that has passed through the object 29 passes through the lens system 30, becomes object light, and reaches the surface of the recording medium 1o.

A light pattern containing image information of the object 29 generated by the interference between the reference light and the object light is recorded on the Tb Fe thin film 3 of the recording medium 10 by the photothermal magnetic effect.

In other words, as is known, the TbFe thin film 3 is initially magnetized in one direction perpendicular to the film surface by a strong magnetic field applied from the outside, and when recording information, it is magnetized in the opposite direction to the initial magnetization direction. A weak bias magnetic field is applied in the direction.However, this bias magnetic field does not need to be applied when the light intensity is sufficiently large.It is effective when the light intensity is small.

When light hits the surface in this state, the heat from the light reverses the magnetization direction of that part.

Due to this thermomagnetic effect, the light pattern irradiated onto the TbFe thin film 3 is recorded as a two-dimensional pattern of perpendicular magnetization on this surface.

To reproduce the image information recorded as described above, the third
A method using the Faraday effect shown in Figure (A) and a method using the Kerr effect shown in Figure (B) are well known.

In the reproduction method shown in FIG.
2, the reference beam is irradiated onto the recording medium 10 at approximately the same angle as the incident angle of the reference beam during recording.

At this time, the light transmitted through the recording medium 10 is transmitted through the TbFe thin film 3.
The plane of polarization rotates depending on the magnetization state.

This transmitted light is received by the lens system 3/I via the analyzer 33, and is imaged on the imaging surface of a two-dimensional imaging device 35 such as a COD.

As a result, a light pattern corresponding to the two-dimensional pattern of the magnetization state of the TbFe thin film 3, that is, an optical image, is reproduced on the imaging surface of the image sensor 35, and this image information is transferred to the image sensor 35.
is converted into an electrical signal by Although the analyzer 33 is not necessarily required, it is preferable to include it in order to improve image quality such as removing ghost images during reproduction.

The reproduction method shown in FIG. 3(B) is similar to the reproduction method shown in FIG. , the reflected light generated from this is received by the analyzer 33 and the lens system 34, and an optical image is formed on the imaging surface of the m-image element 35.

By the way, according to the magnetic hologram recording method 9- of the present invention, there are the following differences in optimal conditions during information recording compared to conventional hologram recording.

In other words, in the case of conventional hologram recording, the intensity of the reference beam is made stronger than that of the object beam, and better results can be obtained in terms of resolution and the like.

However, in the recording method of the present invention, it has been experimentally confirmed that, on the contrary, better recording and reproduction results can be obtained by making the intensity of the object light stronger than that of the reference light.

In the case of the recording method of the present invention, if the intensity of the reference light is 1, when recording a black and white binary image, good recording/reproduction characteristics can be obtained when the intensity of the object light is 1.2. ~1
5, preferably 2 to 10, more preferably 4 to 7.

In addition, images with continuous tone (Qray Tone p
In order to record and reproduce data well (attern), the intensity of the object light during recording should be in the range of 1.1 to 10.
It is preferably in the range of 1.2 to 3.

By adjusting the intensities of the reference light and the object light in this way (10-), it is possible to record and reproduce good images with good contrast and high resolution. The resolution obtained by the embodiment of the present invention is 0.35 μm, which is an extremely high value close to the half wavelength of a ruby laser.

As described above in detail, according to the magnetic hologram recording method according to the present invention, information can be easily recorded and stable high resolution can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the structure of a recording medium used in the magnetic hologram recording method of the present invention, FIG. 2 is a system diagram showing an example of an information writing system for the same recording medium, and FIG.
) and (B) are system diagrams of apparatus systems that reproduce image information from the same recording medium. 1...Glass substrate 2...Resin thin film 3...Amorphous Tt+Fe@ film 4...3iQx thin film 10...Recording medium patent applicant Nippon Gakki Manufacturing Co., Ltd. Procedural formalities (Method) February 2, 1980 1. Case indication patent application No. 173732 @ 2. Name of the invention Magnetic hologram recording method 3. Relationship with the case of the person making the amendment Patent applicant address 10 Nakazawa-cho, Hamamatsu City, Shizuoka Prefecture Number 1 Name (40
7) Nippon Gakki Illzou Co., Ltd. Representative Hiroshi Kawakami 4, Agent 101 Address 1-15-16-6 Uchikanda, Chiyoda-ku, Tokyo
Target of amendment In column 7 of the brief description of the drawings, "Fig. 2" on page 11, line 14 of the description of the contents of the amendment is corrected to "Fig. 3." 2-

Claims (4)

[Claims] (1) A magnetic hologram characterized in that a magnetic thin film having a thermomagnetic effect made of an amorphous Tb Fe thin film is formed on the surface of an appropriate substrate, and hologram information is recorded as a two-dimensional pattern of the magnetization state of this magnetic thin film. Recording method. (2) The thickness of the amorphous Tb Fe thin film is 100 to 35
2. The magnetic hologram recording method according to claim 1, wherein the number of recording persons is 0. (3) The substrate is glass, and the amorphous Tb
2. The magnetic hologram recording method according to claim 1, wherein a synthetic resin thin film layer is formed between the Fe1I film and the Fe1I film. (4) The magnetic hologram recording method according to claim 1, wherein the surface of the amorphous lower bl''e thin film is coated with Si 02.