JPH03189680A - Magneto-optical projecting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a magneto-optical display element, the present invention aims to reduce the size of a circular pixel to the order of μm and to greatly improve the sensitivity of thermomagnetic writing, and to provide a recording element, an electromagnet, It has a writing means, a reading means, and a screen, the recording element is one in which an optical image is written and read, and the electromagnet has a hollow cylindrical shape without a magnetic center, The recording element is held in a hollow space, and the writing means includes:
The device includes a light source that emits a laser beam, a deflector that scans the laser beam in the XY force direction, and a writing optical system that focuses the laser beam on a recording element, and the readout device is a projection device that emits a projection beam. A light source, a readout optical system that irradiates the projection light onto a recording element via a polarizer, and a projection optical system that enlarges and projects the projection light reflected from the recording element onto a screen via an analyzer. The screen is such that projection light is projected from the back side and viewed from the front side, and the recording element is provided with a heat-resistant transparent substrate and the substrate by sputtering,
A thin film recording medium having perpendicular magnetic anisotropy that reaches the Curie temperature when irradiated with a laser beam and whose direction of magnetization is reversed by a magnetic field applied from an electromagnet, and a metal layer provided on the recording medium. In writing, the laser beam is imaged on the reflective film of the recording element, and in reading, the projection light is irradiated from the substrate of the recording element.

[Industrial application field]

The present invention relates to a magneto-optical projection device having a recording element using a garnet film formed by sputtering.

Recently, with the development of large-capacity storage means such as optical disks, it has become possible to easily store vast amounts of information such as not only text information but also images. Along with this, it has become commonplace to display this information on, for example, a CRT display.

However, although there are exaggerated and expensive displays that can be projected on a large screen, called projection displays, there is still no simple projection display that has satisfactory performance.

[Conventional technology]

Projection displays have been developed using highly directional and powerful light sources such as laser beams, developments in semiconductor technology, and LCD (Liq.
With the availability of display elements with high resolution and flat display surfaces, such as the UID Crystal D.1spray (liquid crystal display), they are once again attracting attention.

2. Description of the Related Art Displays in which a CRT screen is enlarged and projected onto a screen have been known for a long time, and as high-intensity phosphors have been developed, methods for enlarging and projecting commercial TV (television) moving images onto a screen have become popular.

However, there are only 525 horizontal scanning lines (particularly when displaying in color, the three-color images projected from the three electron guns of the BGH are enlarged and projected onto the screen through an optical system. Since the images are synthesized using high-definition TV, the equipment becomes exaggerated and the screen lacks brightness and clarity.HDTV (high-definition T
V), etc., are expected to be put into practical use.

On the other hand, since LCDs apply the principle of moving large molecules in a viscous liquid, they have a slow response and are said to be unsuitable for fast-moving displays such as moving images.

However, with the realization of so-called active matrix drive in which TPT (thin film transistors) are arranged for each pixel, and with advances in color filter manufacturing technology, for example, portable or wall-mounted color TVs are beginning to appear.

FIG. 3 is an explanatory diagram of an example of a conventional transmission type projection device.

In the figure, 1 is a recording element, 4 is a reading means, 5 is a screen, and 7 is a projection light.

The recording element 1 is, for example, an LCD, and basically has a so-called matrix electrode structure in which a liquid crystal material is sealed between a substrate on which striped X electrodes and Y electrodes are provided.

Recently, active matrix driving in which TPTs are arranged for each pixel has been widely used because it can display moving images. Color display is also performed by arranging blue, cyan, and magenta color filters for each pixel.

When a transmissive LCD is used as the recording element 1, for example, E L (Electro-luminescence)
, an electroluminescent element) is disposed on the back of the recording element 1, which is the so-called backlight type LCD. All you have to do is project it onto the screen 5.

In this readout means 4, projection light 7 emitted from a high-brightness projection light source 4a such as a halogen lamp is transmitted through the recording element 1 and projected onto a screen 5 via a projection optical system 4e. It is configured.

This screen 5 is a so-called rear projection type screen on which the projection light 7 is projected from the back, and when viewed with the naked eye, it is viewed from the front of the screen 5.

The recording element 1, such as an LCD, has the possibility of high resolution because the gap between the upper and lower electrodes, that is, the thickness of the liquid crystal layer is, for example, about 10 μm. However, since it is difficult to produce a large number of TPTs without defects, the resolution in each of the vertical and horizontal directions is, for example, about 100 lines per inch.

Therefore, the size of each pixel is, for example, a rectangle with a negative side of about 200 am. Furthermore, since there are gaps of, for example, about 20 μm between pixels, 10% of the area of the display surface is full of tiny gaps. A method of blocking light from this gap has also been adopted, but when projected in a large size, the light-blocking portion stands out in a grid pattern, and the contrast is generally low, for example, about 4:1, and does not look good.

Furthermore, when displaying characters, dot display characters are generally designed with circular dots, but LCD pixels have to be square, so when enlarged, the font becomes ungainly, especially with jagged diagonal lines. Put it away.

For writing on an LCD, for example, there is a thermal writing method that utilizes phase transition due to heat, and writing is performed using, for example, a laser beam.

This thermally writable recording element has the advantage of being less constrained by the resolution determined by the electrode spacing as in the matrix electrode method, and has certain advantages for displaying and projecting still images. However, performance depends largely on the liquid crystal material, including memory stability and lifespan, and future development progress is awaited.

FIG. 4 is an explanatory diagram of an example of a conventional reflection type projection device.

In the figure, ■ is a recording element, 4 is a reading means, and 5 is a screen.

The reflective recording element 1 uses, for example, a so-called LPE garnet film formed by liquid phase epitaxy (LPE).

For writing, although not shown, a conductive pattern of several tens of micrometers is formed on the LPE garnet film, and a specific current corresponding to the information is passed through this conductive pattern. The LPE garnet film is magnetized in an arbitrary direction by the magnetic field generated in this way, which is so-called current writing.

On the other hand, reading is performed using the magnetic optical rotation of the magnetic garnet film, that is, the Faraday effect.

That is, the readout means 4 is arranged in front of the recording element 1 and includes a projection light source 4a that emits the projection light 7, a readout optical system 4c that irradiates the recording element 1 with the projection light 7, and a readout optical system 4c that emits the projection light 7.
a polarizer 4b that converts the light into linearly polarized light, and an analyzer 4d that transmits the projection light 7 whose plane of polarization has been rotated by being reflected from the recording element 1.
and a projection optical system 4e for enlarging and projecting onto the screen 5.
It is composed of etc.

The LPE garnet film that constitutes this recording element 1 is
Since the coercive force is small, it is necessary to place the electromagnet 2 on the recording element 1 and always apply a bias magnetic field when operating the recording element 1.

Additionally, the resolution is limited by the conductor pattern, and contrast is poor because garnet thin films are transparent to light from visible to near-infrared light.

(Problems to be Solved by the Invention) As mentioned above, projection displays originated from enlarged projection of TVs using CRTs, but active matrix type LCs in which TPTs are arranged pixel by pixel are used.
D was developed, and projection-type displays that could also display moving images began to appear.

Among these, transmissive projection devices using active matrix LCDs have problems in increasing the number of pixels, as it is difficult to make tens to tens of thousands of TPTs without defects. .

Furthermore, since it is difficult to make the pixels small and close the gaps between the pixels, there is a problem in that when the image is enlarged and projected, the contrast deteriorates and the image looks unsightly.

Furthermore, since the pixel shape is rectangular, there is a problem that it is not particularly suitable for dotted characters.

In addition, for example, a projection device that uses a thermally written LCD using a laser beam has a problem in that its performance is largely dependent on the liquid crystal material, and its stability and lifespan are still insufficient.

On the other hand, in the case of a projection device using LPE garnet that allows current writing to the recording element, a bias magnetic field is always required, and there is a problem in that it is difficult to improve resolution and contrast.

Therefore, an object of the present invention is to provide an element in which the pixel shape is circular, the pixel size can be reduced to the micrometer level, and the sensitivity of thermomagnetic writing can be greatly improved.

[Means for Solving the Problems] The above-mentioned problems include a recording element, an electromagnet, a writing means, a reading means, and a screen, and the recording element has a recording element on which an optical image is written and read. The electromagnet has a hollow cylindrical shape without a magnetic core and holds a recording element in the hollow, and the writing means includes a light source that emits a laser beam and a recording element that emits a laser beam. It has a deflector that scans the laser beam in the XY force directions, and a writing optical system that focuses the laser beam on a recording element, and the reading means includes a projection light source that emits projection light, and a polarizer that directs the projection light. and a projection optical system that enlarges and projects the projection light reflected from the recording element onto a screen via an analyzer, and the screen has a readout optical system that illuminates the recording element through an analyzer. The recording element is projected from the back and visually viewed from the front, and the recording element is made of a heat-resistant transparent substrate, is provided on the substrate by sputtering, reaches the Curie temperature by irradiation with laser light, and is equipped with an electromagnet. It has a thin film recording medium with perpendicular magnetic anisotropy whose direction of magnetization is reversed by a magnetic field applied from the magnetic field, and a metal reflective film provided on the recording medium. is imaged on the reflective film of the recording element, and during reading, the projection light is resolved by a magneto-optical projection device configured to irradiate from the substrate of the recording element.

[For production]

The recording element of the present invention applies the principle of magneto-optical recording using an optical modulation method, which is well known in rewritable optical disks and the like.

In other words, in magneto-optical recording, first, writing is done by
A magnetic thin film having perpendicular magnetic anisotropy, such as magnetic garnet, is uniformly magnetized and then locally heated using, for example, a laser beam while applying external magnetization in the opposite direction. This applies the principle that the direction of magnetization reverses when the temperature exceeds the Curie temperature.

Next, reading is performed using the magneto-optical effect caused by the direction of magnetization of the magnetic thin film being reversed, ie, the Kerr effect or the Faraday effect. In optical discs, reading is generally performed using the Kerr effect.

By the way, the writing method in the present invention involves applying a magnetic field in the opposite direction to a recording medium made of a magnetic thin film that is uniformly magnetized in the perpendicular direction, that is, in the film thickness direction, while applying a laser beam to the recording medium in the form of a spot. This writing method is very similar to the writing method for optical discs, and uses the principle that the magnetization is reversed in a spot shape when the magnetization reaches the Curie temperature.

However, the structure of the recording element is different, and a reflective film made of a thin metal film is provided on the recording medium.

When writing, the reflective film itself is first heated by a spot-shaped laser beam, and the heat is used to heat the recording medium to the Curie temperature.

Further, during reading, the reflective film has a function of reflecting the projection light irradiated through the substrate.

In other words, by controlling the thickness of the reflective film to an optimum thickness, the reflective film has the dual functions of a heating medium and a reflecting mirror.

On the other hand, for readout, magnetic optical rotation called the Faraday effect or Faraday rotation is used.

In other words, when linearly polarized light passes through a polarizer through a recording medium made of a magnetic thin film, for example, when the polarized light travels parallel to the direction of the magnetic field in the area where information is recorded, the plane of polarization rotates. For the polarized light that is reflected back from the reflective film, the analyzer is rotated to match the plane of polarization, and only the light that passes through that area is extracted.

In this way, whether or not information is recorded is selectively read out and enlarged and projected onto the screen through the projection optical system.

According to the present invention, when writing, the spot system of the laser beam corresponding to a pixel can be narrowed down to a micrometer unit, so the resolution of the recording element can be increased.
Compared to D, etc., it is possible to obtain images with an order of magnitude higher resolution.

(Example) FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 is an enlarged perspective view of the main parts of a recording element.

In the figure, 1 is a recording element, 2 is an electromagnet, 3 is a writing means,
4 is a reading means, 5 is a screen, 6 is a laser beam, 7
is the projected light.

The recording element 1 is a GG with a thickness of 0.5 mm and a diameter of 3 inches.
A film with a thickness of 1
μm, Bi-substituted magnetic garnet film, completely Bi
A sputtered film of 2D )'Ga 6.6Fe a, aoIt is provided. This garnet film is 50
The recording medium 1b is crystallized by heat treatment at 0° C. and has perpendicular magnetic anisotropy.

On the recording medium 1b, a vacuum-deposited film of A having a thickness of 70 nm is deposited.
A thin film 2 is provided to serve as a reflective film 1c.

In this way, the recording element 1 is completed.

The electromagnet 2 is a hollow cylindrical coil without a magnetic core in which the recording element 1 having a diameter of 3 inches φ is accommodated, and is adapted to apply a magnetic field of 1000 e to the recording element 1 in the perpendicular direction.

The writing means 3 includes a semiconductor laser that emits a laser beam 6 of 50 mW and a wavelength of 830 nm, a hyperdeflector 3b made of a galvanometer, and a writing optical system 3c. The laser beam 6 is designed to form a 1 μm spot on the surface of the reflective film 1c of the recording element 1.

The readout means 4 includes a projection light source 4a made of a 150W halogen lamp that emits projection light 7, a readout optical system 4c arranged so that the projection light 7 is irradiated from the side of the substrate 1a of the recording element 1, and a polarizer 4b. The recording element 1 is irradiated with polarized projection light 7 .

Furthermore, the reading means 4 reads the recording medium 1b of the recording element 1.
The analyzer 4d is composed of an analyzer 4d through which only the projection light 7 that has been optically rotated and returned by the analyzer 4d is transmitted, and a projection optical system 4e that is arranged so that the transmitted projection light 7 is projected onto the back surface of the screen 5.

The screen 5 has a negative side of 2 m and is a rear projection type screen in which an image projected from the rear is viewed from the front.

With the magneto-optical projection device configured in this way, first,
Try writing.

The laser beam 6 modulates the light source 3a directly at 50 kHz, focuses the laser beam to a half-width of 1 μm, and focuses it on the reflective film 1c.

However, due to the diffraction limit in the deflector 3b and the writing optical system 3c, in this embodiment, the half width of the spot is 25μ.
It was about mφ.

Therefore, one pixel corresponding to one spot of the laser beam 6 is
The deflectors 3b were controlled so that they were arranged vertically and horizontally at a pitch of 20 μm.

The image once written on the recording medium 1b is stable and will not disappear unless exposed to an atmosphere of high temperature and high magnetic field.

Next, when reading was performed, the maximum Faraday rotation angle of the recording medium 1b was 24 degrees for visible light with a wavelength of 514 nm due to the synergistic effect with the reflective film 1c.

Furthermore, between the recording medium 1b and the reflective film 1c, a film thickness of 1100 nm, which is also effective as an enhanced layer in an optical disc, is provided.
SiO! It was confirmed that the Faraday effect was increased by 8% when .

When the image was enlarged and projected onto the screen 5 at a magnification of 25, a good projected image was obtained with no gaps between pixels and a contrast of 50:1.

In this case, GGG is used for the substrate of the recording element, and Bi-substituted garnet, which is said to have a large Faraday effect, is used for the recording medium, but these materials can be modified in various ways.

In addition, although the recording medium was formed into a film by sputtering and then crystallized by heat treatment, there are also differences in film thickness and processing conditions.
Various modifications are possible.

Furthermore, various modifications can be made to the dielectric material interposed between the recording medium and the reflective film.

Furthermore, the specifications of the writing means, reading means, etc. are not uniquely determined, and various modifications are possible.

[Effects of the Invention] As described above, conventional projection devices using, for example, an LCD or a magneto-optical recording element have low resolution, poor contrast, and problems with stability and longevity.

In contrast, the magneto-optical projection device of the present invention uses a unique recording element made of crystallized garnet with a reflective film, thereby achieving writing performance with unprecedentedly high resolution and unprecedented contrast. An enlarged projected image can be obtained.

Therefore, the present invention greatly contributes not only to the development of magnifying projection devices, which are expected to increase even more in the future, but also to the development of magneto-optical recording.

[Brief explanation of drawings]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is an enlarged perspective view of the main parts of a recording element, Fig. 3 is an explanatory diagram of an example of a conventional transmission type projection device, and Fig. 4 is a conventional reflection type FIG. 2 is an explanatory diagram of an example of a projection device. In the figure, ■ is a recording element, la is a substrate, 1b is a recording medium, 2 is an electromagnet, 3 is a writing means, 3b is a deflector, 4 is a reading means, 4b is a polarizer, 4d is an analyzer, 5 is a screen, 7 is the projection light. lc is a reflective film, 3a is a light source, 3c is a writing optical system, 4a is a projection light source, 4c is a reading optical system, 4e is a projection optical system, 6 is a laser beam, Fig.

Claims (1)

[Claims] 1) A recording element (1), an electromagnet (2), a writing means (3), a reading means (4), and a screen (5), the recording element (1) The electromagnet (2) has a hollow cylindrical shape without a magnetic center, and holds the recording element (1) in the hollow. The writing means (3) includes a light source (3a) that emits a laser beam (6), a deflector (3b) that scans the laser beam (6) in the X and Y directions, and a light source (3a) that emits a laser beam (6). a writing optical system (3c) for forming an image on the recording element (1), and the reading means (4) includes a projection light source (4a) that emits projection light (7); a readout optical system (7) that irradiates the recording element (1) through a polarizer (4b);
4c) and the projection light (
7) on the screen (5) via an analyzer (4d), and the screen (5) is configured to project the projection light (7) from the back side. The recording element (1) includes a heat-resistant transparent substrate (1a), is provided on the substrate (1a) by sputtering, and is exposed to the laser beam (6). ) A thin film recording medium (1b) having perpendicular magnetic anisotropy that reaches the Curie temperature by irradiation with the electromagnet (1b) and whose direction of magnetization is reversed by the magnetic field applied from the electromagnet (2), and the recording medium (1b) The laser beam (6) is imaged on the reflective film (1c) of the recording element (1) during writing, and during reading, the laser beam (6) is imaged on the reflective film (1c) of the recording element (1). , the projection light (7) is transmitted to the substrate (
A magneto-optical projection device characterized in that it is irradiated from 1a). 2) The recording medium (1b) has the general formula: Bi_XR_3_-_XM_YFe_S_-_YO_1
2. The magneto-optical projection device according to claim 1, wherein the magnetic garnet is a magnetic garnet represented by _2 (R: rare earth element, etc.; M: Ni, Co, etc.). 3) The reflective film (1c) is a multilayer film in which a dielectric film made of SiO_2 or the like is interposed between the reflective film (1c) and the recording medium (1b). The magneto-optical projection device described.