JPS62157003A - Composite filter - Google Patents

Abstract

PURPOSE:To operate a composite filter optically and effectively against the interference of radio waves by providing a metallic plate with an aperture part or providing the composite filter having an optical characteristic with metallic narrow wire meshes. CONSTITUTION:A copper thin plate meshes having 0.25mm pitch, 0.03mm wire width, and about 0.15mm thickness are placed between a glass filter 71 which cuts a long wavelength area and an organic resin filter 73 which cuts long and short wavelength areas of visible rays, and they are stuck by an epoxy resin or the like. If a display device, an illuminating device, or the like in a dark visual field monitor system is covered with the composite filter obtained in this manner, near infrared rays of artificial light from them are cut completely not to have an inverse influence upon a dark field device. Since this filter is used effectively as a filter against the interference of radio waves, it is useful for safe operating of the whole of the system.

Description

[Detailed Description of the Invention] Image forming technology using starlight as a light source under almost dark conditions when the moon is not out has been developed due to the advent of multi-channel plates and the development of photocathode suitable for the Yagiri optical spectrum. Great advances have been made with the advent of image pickup tubes, for example electron multiplier tubes. When the Earth passes through about 100,000 stars, the UV light emitted from the newly born stars is scattered and absorbed by the atmosphere and does not reach the relatively grown 5X1 stars.
Near-infrared and long-wavelength light emitted from stars around 2006 has reached the earth. (Figure 1) In the military and police fields, dark field surveillance systems that utilize starlight have been developed for night security purposes.

That is, the photocathode used in this dark-field system is not sensitive to visible light but sensitive to near-infrared light. However, there are a large number of artificial lights that emit light in the near-infrared wavelength range, including lighting bulbs, readouts, and displays. In general, these artificial lights are several hundred to tens of millions of times stronger than the intervening light, so if the light emitted from these light sources enters a dark field monitoring system, it will not only cause noise but also cause burn-in on the photocathode. Or, it had a serious flaw that could burn the retinas of the observer's eyes.

It is generally difficult to achieve desired characteristics of an optical filter using a single material. Therefore, the patent application No. 58-12657 disclosed that the desired characteristics of an optical filter could be obtained by combining a filter made of an organic resin with dye added and a colored glass filter, which allows the absorption wavelength to be photographed relatively easily.
I mentioned it in issue 6.

Figure 2 shows the transmission wavelength characteristics of an organic resin filter, Figure 3 shows the characteristics of a glass filter that does not transmit near-infrared light, and Figure 4 shows the characteristics of these composite filters.

Optically, the composite filter described above perfectly achieves its purpose, but when considering shielding against electromagnetic interference, it has the drawback of being completely defenseless against this. Ta.

In order to compensate for such drawbacks, the present invention provides optical protection against electromagnetic wave interference by providing an opening in a metal plate or by providing a thin metal wire mesh in a composite filter having the optical characteristics. This is also an effective composite filter.

Next, one embodiment of the present invention will be described.

Generally, shielding effectiveness is expressed in dB (decibels). dB is a comparison value, and the measurement method is λ[LL-5T
D-285,416.

60-90dB is average shielding, 90-120dB
However, it is considered to be an excellent shield.

It is necessary to measure the magnetic field and electric field in a wide frequency band to determine the shielding effect.

In the case of a magnetic field, the thickness and magnetic permeability of the metal are significantly related to the shielding effect, and in the case of an electric field, the contact area and conductivity are significantly related to the shielding effect. On the other hand, in the present invention, which was originally intended to be an optical filter, the balance between the electrical shielding effect described above and the physical shielding effect that makes it difficult to visually see the optical filter becomes a serious problem.

As a result of various studies, a thin metal plate mesh (pitch 0.25, line width 0.01-0
, 05, thickness 013~o, ia), it does not cause any optical obstruction and fully exhibits its original function as an optical filter, while at the same time maintaining the electric field shielding effect and magnetic field shielding effect as shown in Figure 6. The shielding effect is about 30 to 50 dB,
Admitted.

In this way, the aperture ratio is 85 for a rope around 100 meshes.
If this is placed within clear viewing distance,
It is difficult to confirm this with the normal human eye. Therefore, it has been found that even if the optical filter is provided with the metal mesh, it does not cause any optical hindrance.

FIG. 7 shows an embodiment of the optical composite filter according to the present invention.

As shown in FIG. 5(b), there is a pitch of 0.5 mm between the glass filter 71 that cants the long wavelength range and the organic resin filter 73 that cuts the long and short wavelength bands of visible light.
25. A copper R-plate mesh with a line width of 003 and a thickness of about 0415 is placed and bonded with, for example, epoxy resin.

Furthermore, an optically transparent glass plate 74 may be bonded as a holding glass if necessary.

If the metal mesh is exposed on at least one side surface of the optical filter, it becomes possible to electrically connect the metal mesh to the casing, which is convenient for electromagnetic shielding. Of course, on all four sides of this composite filter,
For the purpose of complete electromagnetic shielding, it is desirable to have terminals that can be electrically connected exposed.

The example shown in FIG. 8 shows an embodiment of the present invention in which a side surface of a composite filter is covered with a conductive organic resin 85 and a metal mesh 82 is connected to an external casing or the like. When the composite filter according to the present invention obtained in this manner is covered with a display, lighting device, etc. in the above-mentioned dark field monitoring system, it completely cuts near infrared rays from these artificial lights, so it can be used for night vision. It will not have any negative effect on the equipment. Furthermore, since it works effectively as a filter against electromagnetic interference, it is not only useful for the safe operation of the entire system, but also has the advantage that this composite filter can be mass-produced at low cost, making it easier to use as a cheap simple set. has.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the radiant energy distribution from the night sky. FIG. 2 shows an example of an organic resin filter, and FIG. 6 shows an example of a glass filter that cants the near-infrared region. FIG. 4 shows the wavelength transmission characteristics of a composite filter that combines the organic filter and glass filter shown in FIGS. 2 and 6. FIG. 5 is a diagram for explaining the metal mesh used in the composite filter of the present invention. FIG. 6 is a diagram showing the electromagnetic shielding effect of the metal mesh shown in FIG. 5 on frequency. FIG. 7 (al is a perspective view for explaining how to make the composite filter of the present invention. (bl is a cross-sectional view, and (C) is a cross-sectional view of the filter provided with a transparent holding glass plate 74. Fig. 8 is a cross-sectional view for explaining that an electrode 85 is formed of a conductive organic resin on the side surface of the composite filter of the present invention.Glass filter; 71, 81 Organic resin filter; 73, 85 For electromagnetic shielding. Metal mesh; 74, 84 Transparent holding glass plate; 74, 84 Conductive organic resin electrode; 85

Claims (4)

[Claims] (1) In a composite filter that combines at least one kind of organic film, a glass filter, and a mesh using a thin metal plate or thin metal wire having openings, the organic film filter is prepared by adding a dye and a plasticizer to the composite filter. In addition, it has optical properties that cut long and short wavelength bands of visible light, and in combination with a colored glass filter that mainly cuts this wavelength band, it blocks radiation spectrum in the 600 to 900 nm region, and the metal mesh prevents electromagnetic interference. A composite filter characterized by shielding. (2) A composite filter that includes the scope of claim (1) and is characterized in that an organic resin filter, a glass filter, and a metal mesh are bonded together with an adhesive. (3) A composite filter which includes the scope of claims (1) and (2) and is characterized in that an optically transparent holding glass plate is added in the filter region. (4) Including claims (1), (2), and (3), an electrical connection portion with the metal mesh is provided on the side surface of at least one end surface of the composite filter. A composite filter characterized by: