JPH0713261A - Picture projection screen for electronic instrument - Google Patents

Abstract

PURPOSE:To make the visibility of a picture excellent and to eliminate the need of using a special expensive material by obtaining an electromagnetic shielding function and simultaneously making the transparency of a screen high. CONSTITUTION:At least, one conductive pattern is provided and can be grounded on the outer periphery of the screen. Then, the conductive pattern can be formed by the photoetching of a metallic film such as an ITO film or coating with a transparent or opaque conductive coating material. One or plural conductive patterns are provided in either of the vertical and horizontal directions of the screen 30 or in both of them respectively. Moreover, as the conductive pattern, one obtained in such a manner that a ruled line formed on the screen 30 is coated with the conductive coating material or a metallic wire is stuck to one surface of the screen 30 or arranged so as to face the screen 30 can be used as well. Then, it is desirable that the interval of the conductive pattern is etalambda/10 when the wavelength of an electromagnetic wave as the main factor of the obstruction of the radio wave of an electronic instrument is defined as lambda.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projection screen used in electronic equipment such as a microfilm reader and having an electromagnetic shield function.

[0002]

2. Description of the Related Art Weak electromagnetic waves generated by electronic devices such as computers may interfere with radio waves of various wireless communications, televisions, radios and the like. In addition, there is a problem that electronic devices such as various computers are damaged.

Therefore, organizations such as the Voluntary Control Council for Radio Interference (VCCI), such as information processing devices, recommend that they voluntarily restrict the electromagnetic waves generated by electronic devices.

Under such circumstances, in a normal electronic device such as a computer, the housing itself is provided with conductivity to be electromagnetically shielded. For example, using a conductive material for the housing,
The housing made of synthetic resin was metal-plated.

On the other hand, since the microfilm reader usually has a built-in electronic device such as a computer, its housing is electromagnetically shielded like other electronic devices. Also, because the screen that optically magnifies and projects the image has a large area,
Electromagnetic waves emitted to the outside through this are also very important.

Therefore, the applicant of the present application has proposed to coat the entire screen with a transparent coating containing an electromagnetic shield material (Japanese Patent Laid-Open No. 3-48837). It is also conceivable that the screen itself is made of a conductive resin and has an electromagnetic shield function.

[0007]

2. Description of the Related Art In a method of coating a transparent coating of an electromagnetic shield material on the entire surface of a screen, an opaque electromagnetic shield material is mixed with a transparent binder and a liquid dispersed in a solvent is applied. The transparency decreases. Therefore, there is a problem in that the visibility of the projected image on the screen is deteriorated.

Further, when the screen is made of a material having an electromagnetic shielding property, there are problems that this material is special and difficult to obtain, and that the visibility of the projected image is deteriorated due to the limited transparency. It was

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an electromagnetic shield function, improves transparency of a screen to improve image visibility, and uses a special and expensive material. A first object is to provide a screen for projecting an image of an electronic device that does not need to be provided.

[0010]

According to the present invention, this object has at least one conductive pattern, and the conductive pattern can be grounded at the outer peripheral edge of the conductive pattern. Achieved by

Here, the conductive pattern is formed by photoetching a metal film such as an ITO film,
It may be drawn using a transparent or opaque conductive paint. In the case of an opaque conductive pattern, it is desirable to make the line width as small as possible.

One or a plurality of conductive patterns may be provided in the vertical or horizontal direction of the screen,
One or more may be provided in both the vertical and horizontal directions.
Also, draw the ruled lines drawn on the screen with conductive paint,
A metal wire may be attached to one surface of the screen or arranged so as to face the screen.

The distance between the conductive patterns is preferably set to λ / 10 or less, where λ is the wavelength of the electromagnetic wave that is the main cause of radio interference in electronic equipment.

[0014]

1 is a perspective view of an embodiment of the present invention, and FIG. 2 is a front view of the screen. The detailed structure of the microfilm reader used in this embodiment is described in JP-A-4-3.
No. 254, the main configuration will be briefly described here.

In FIG. 1, reference numeral 10 is a light source, and the light from this light source 10 is a condenser lens 12 and a heat insulating glass 1.
4, cold mirror 16, microfilm 18, projection lens 20, image inverting prism 22, mirrors 24, 2
It is guided to the transmissive screen 28 via 6 and an enlarged image of the microfilm 18 is formed on this screen 28.

A CCD line sensor 30 is arranged on the back surface of the screen 28 so as to be movable left and right. That is, the line sensor 30 is arranged long in the direction that crosses the screen 28 longitudinally, and the line sensor 30 reads out an image in the length direction (main scanning direction) and sequentially outputs the image signals as time-series signals to perform main scanning. Sub-scanning is performed by moving the line sensor 28 in the left-right direction by the motor 32.

The microfilm 18 is supplied from the supply-side reel 34 contained in the cassette, and the winding-side reel 3
Take up to 6. Between the reels 34 and 36, the microfilm 18 is guided by guide rollers 38 and 40 so as to horizontally traverse below the projection lens 20. The device is housed in an electrically conductive enclosure 44 and has a screen 3
0 appears in front of it.

The screen 30 is made of transparent synthetic resin or glass in the shape of a plate, and a conductive pattern 46 in the vertical direction is formed near the center thereof. This conductive pattern 46 can be drawn with a transparent or opaque conductive paint, or a metal film such as an ITO film can be formed by photoetching or the like.

When forming the opaque conductive pattern 46, the pattern 46 can be used as a ruled line drawn on the screen 30. Further, a metal wire may be attached to the screen 30 or may be arranged so as to face the back surface. This conductive pattern 46 has 1 in both vertical and horizontal directions or both.
A book, a plurality of books, or a curved line may be provided.

Further, it has been found that, when a plurality of conductive patterns 46 are provided, the magnetic shield effect can be sufficiently obtained by setting the interval to λ / 10 or less. Here, λ is the wavelength of an electromagnetic wave that causes radio interference. In this embodiment, a CCD line sensor 32 is arranged behind the screen 30, and the line sensor 32 is driven by a clock pulse of a predetermined frequency, so this clock pulse can be a major cause of radio interference.

Since the frequency ν of the clock pulse of the line sensor 32 is usually about 10 ² MH _Z , if the speed of light C is 3 × 10 ⁸ m, the wavelength λ is λ = 3 × 10 ⁸ / (1
0 ² · 10 ⁶ ) = 3 m. Therefore, the conductive pattern 4
The interval of 6 is about λ / 10 = 0.30 m. On the other hand, the size of the screen 30 is vertical 3 as shown in FIG.
Since the length is 0 cm and the width is about 42 cm, in this case, it is sufficient to provide one conductive pattern 46 vertically or horizontally near the center. The conductive pattern 46 is
It is attached to the housing 44 and is grounded to the housing 44 via the outer peripheral edge of the screen 30.

[0022]

As described above, according to the present invention, since at least one conductive pattern is provided on the screen, it is possible to block the electromagnetic wave passing therethrough by grounding the conductive pattern. Therefore, radio wave interference can be prevented. Further, since the transparency of the screen is not lowered, the visibility of the projected image becomes good. Furthermore, there is no need to use special materials or expensive materials.

[Brief description of drawings]

FIG. 1 is a perspective view of a microfilm reader that is an embodiment of the present invention.

[Figure 2] Front view of the screen

[Explanation of symbols]

 30 screen 32 CCD line sensor 44 housing 46 conductive pattern

Claims (1)

[Claims] 1. A screen for projecting an image of an electronic device, comprising at least one conductive pattern, and the conductive pattern can be grounded at an outer peripheral edge thereof.