JPH0429398Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The present invention relates to an improved technology for interference filters used in dual-wavelength infrared gas analyzers. When measuring from the amount of infrared radiation, the wavelength to be measured includes not only the radiation component from the sample gas but also the radiation component from the cell, cell window, etc. Therefore, in order to perform precise concentration measurements, it is necessary to remove the latter radiation component (hereinafter referred to as background infrared radiation). By the way, background infrared rays have a similar amount of radiation not only in the measurement wavelength range but also in other wavelength ranges. Therefore, by measuring the amount of background infrared radiation in a nearby wavelength range other than the measurement wavelength range and subtracting it from the total radiation amount in the measurement wavelength range, it is possible to determine the concentration of a specific component in the sample gas without being affected by the background infrared radiation. Can be measured precisely. A measuring instrument that performs such a measurement method is called an infrared radiation gas analyzer (a type of dual-wavelength infrared gas analyzer), and was previously disclosed by the applicant in Utility Model Application No. 57-33703. There is.

By the way, in the above analyzer, it is necessary to perform measurements in two different wavelength ranges: a wavelength range for measuring a specific component and a wavelength range for measuring background infrared rays. There must be a relationship between the amount of energy measured in both wavelength ranges, such that the amount of energy of the background infrared rays is equal. This is because otherwise, the influence of background infrared rays cannot be canceled out.

[The problem that the idea aims to solve]

Interference filters are mainly used for the purpose of, at present, detecting each wavelength with a detector and then amplifying it with amplifiers with different amplification factors, without relying on electrical methods. It's something you can't get. For this reason, there are problems such as the need for an extra electric circuit, which complicates the circuit.

In view of these points, the present invention has been developed to achieve not only the above-mentioned objectives but also the following objectives using an interference filter. The purpose of the present invention is to provide an interference filter that can contribute to the simplification of the system.

[Means to solve the problem]

The interference filter of the dual-wavelength infrared gas analyzer according to the present invention, which has achieved the above object, has two types of multilayer filters with different infrared transmission wavelength ranges formed on the same substrate, and each filter transmits infrared rays. It is characterized in that a part of the side surface is opened and the rest is covered with a material that does not transmit light, and the diameter of the opening is set to be inversely proportional to the transmitted energy of the infrared rays that pass through each filter. .

[Effect]

According to the characteristic configuration described above, the diameter of the opening is made inversely proportional to the transmitted energy of infrared rays, so that the ratio of transmitted energy of infrared rays to each filter becomes constant.

〔Example〕

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

An embodiment of the present invention will be described below based on the drawings. In FIG. 1, 1 is a substrate, and 2 and 3 are multilayer filters formed by laminating a large number of thin films on the front and back surfaces of the substrate 1. In FIG. The transmission wavelength ranges of both filters 2 and 3 are different, for example, 4.3μ and 3.9μ.

Reference numeral 4 denotes a substance that does not transmit light, and is a substance that does not transmit light.
It covers all the other surfaces except for parts 5 and 6 above 3. Therefore, the portions 5 and 6 that are not covered by the substance 4 become openings that allow light to enter the filters 2 and 3. The shape of the openings 5, 6 may be circular as shown in FIG. Alternatively, although not shown, it may be a rectangle or a polygon. However, both openings 5,
It is necessary to set the diameter of 6 so that it is inversely proportional to the transmitted energy. That is, if the amount of energy that passes through each filter 2, 3 when it is not covered with the substance 4 that does not transmit light is I ₂ and I ₃ , then the aperture 5 is α・1/I ₂ and the aperture 6 is β・1/I ₃ , the diameter is set so that it is inversely proportional to the transmitted energies I ₂ and I ₃ of the filter. Here α and β are proportionality constants. With this setting, the filters 2 and 3 with openings 5 and 6
The transmitted energy of each filter is as follows: I ₂ ×α・1/I ₂ =α I ₃ ×β・1/I ₃ =β, and the ratio of the transmitted energy of both filters 2 and 3 is constant (α/β) becomes. As a result, by appropriately determining α/β, the purpose stated at the beginning can be achieved by the interference filter.

Also, in this case, the light entering the interference filter is
As shown in the figure, when cutting is performed by the chopper 7, the arrangement relationship of each opening 5, 6 with respect to the chopper 7, and both openings 5, 6 are cut at the same ratio by the chopper 7. It is necessary to set the distance of 6 as appropriate.

Note that the substance 4 that does not transmit light can be an opaque metal film. In this case, the metal film may be made of the same material as one of the layers in the multilayer filters 2 and 3 and formed into a thick film. By using such a thick film, the entire interference filter including the material 4 that does not transmit light can be manufactured by a semiconductor manufacturing process, which is highly advantageous in terms of production efficiency, mass productivity, etc.

[Effect of idea]

As explained above, the interference filter according to the present invention used in a dual-wavelength infrared gas analyzer has two types of multilayer filters with different transmission wavelength ranges of infrared rays formed on the same substrate, and the infrared rays of each filter. A part of the transmitting side surface is opened and the rest is covered with a substance that does not transmit light, and the diameter of the opening is set to be inversely proportional to the transmitted energy of the infrared rays that pass through each filter. The ratio of the transmitted energy of infrared rays to This has the effect of reducing the cost of dual-wavelength infrared gas analyzers.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is an overall sectional view, Fig. 2 is an overall plan view, and Fig. 3 is a diagram showing the arrangement of each aperture when applied to a configuration in which light is interrupted by a chopper. It is. 1...Substrate, 2, 3...Multilayer film filter, 4...
...Substance that does not allow light to pass through, 5,6...Aperture.

Claims (1)

[Scope of utility model registration request] An interference filter used in a dual-wavelength infrared gas analyzer, with two different infrared transmission wavelength ranges.
Various multilayer film filters are formed on the same substrate, a part of the infrared transmitting side of each filter is opened, and the rest is covered with a material that does not transmit light, and the diameter of the opening is set to the diameter of each filter. An interference filter for a dual-wavelength infrared gas analyzer, characterized in that it is set to be inversely proportional to the transmitted energy of transmitted infrared rays.