JPH0590352U - Optical filter for gas analyzer - Google Patents

Abstract

(57) [Summary] [Object] To obtain an optical filter for a gas analyzer capable of preventing H ₂ O from penetrating into the BP surface of the optical filter and preventing a zero-point rising drift occurring in the gas analyzer. [Structure] The first light source 7a is provided on one side of the first cell 1a and the second cell 1b.
And the second light source 7b, the optical filter 8, the main detector 15 and the sub-detector 16 are arranged on the other side, and the sample gas 5 and the reference gas 6 are supplied to the first cell by the switching operation of the four-way switching valve 4. 1a and the second cell 1b are alternately introduced. Then, the substrate of the optical filter 8 is made of SiO ₂ , and a pair of mask plates provided with a plurality of vapor deposition holes are superposed on both sides of the substrate 9, and the positions of the vapor deposition holes are aligned and fixed. A BP surface is formed on one surface and an SLC surface is formed on the other surface by vapor deposition. In this way, the substrate provided with the BP surface and the SLC surface is cut at the exposed portion to form the optical filter 8.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

The present invention relates to an optical filter used in a gas analyzer for measuring a measurement component such as hydrocarbon (HC) or CO ₂ in various exhaust gases.

[0002]

[Prior Art]

 Known gas analyzers for analyzing HC and other measurement components are shown in FIGS. 6 to 8, for example. In FIGS. 6 to 8, 21a and 21b are a first cell and a second cell, which are provided with gas inlets 22a and 22b and gas outlets 23a and 23b. 24 is a sample gas supplied to the gas inlet 22a, 25 is a reference gas supplied to the gas inlet 22b, and 26a and 26b are the first and second infrared light sources, and the infrared rays emitted from these are choppers. At 27, the light enters the first and second cells 21a and 21b as intermittent light.

Reference numeral 28 is an optical filter on which infrared rays transmitted through the first and second cells 21a and 21b are incident, 29 is a main detector on which infrared rays transmitted through the optical filter 28 are incident, and 30 is a main detector 29 transmitted through Sub-detectors on which infrared rays are incident, 31a and 31b are preamplifiers to which the detection signals of main detector 29 and sub-detector 30 are input, and 32 is a preamplifier 31b from the output signal of preamplifier 31a. Is a subtracter that subtracts the output signal of and outputs the measurement signal.

As shown in FIG. 7, the optical filter 28 has a band-pass surface 28b (a band-pass surface 28b for transmitting an absorption wavelength region of a measurement component such as HC) on one surface of a substrate 28a made of an infrared transmitting optical material such as Ge. (Hereinafter referred to as the BP surface), and the other surface is provided with a short long cut surface 28c (hereinafter referred to as the SLC surface) that cuts a shorter wavelength region and a longer wavelength region than the absorption wavelength region of the measurement component. is there. The BP surface 28b and the SLC surface 28c are, for example, laminated by combining vapor-deposited thin films of germanium (Ge) which is a high refractive index material and silicon monoxide (SiO) which is a low refractive index material. It is necessary to considerably increase the number of thin film layers constituting the SLC plane 28c as compared with the number of thin film layers constituting the BP plane 28b. The SLC surface 28c is considerably thicker than the surface 28b.

The optical filter 28 is provided with a BP surface on one surface and an SLC surface on the other surface of a substrate (not shown) made of Ge or the like having an appropriate size for forming the optical filter 28. It is formed by cutting a substrate into a predetermined size. In this cutting, the BP plane has a relatively small number of thin film layers constituting it, and even if it is cut at the same time as the substrate, it is hardly affected. However, since the number of thin film layers that make up the SLC surface is considerably large, the SLC surface is very likely to be chipped at the edges of the SLC surface when it is cut together with the substrate, and this chipping is the source of light leakage. May be a cause.

Therefore, conventionally, as shown in FIG. 8, for example, a mask plate 35 made of stainless steel or the like having a plurality of holes 34 of a required size provided at intervals is placed on one surface of the substrate 28 before being overlaid. By forming the SLC surface by vapor deposition or the like, an undeposited cut portion with a mask is formed on the SLC surface. On the other hand, a BP surface is formed on almost the other surface of the substrate 28. Then, by cutting the substrate 28 at the cutting portion, the BP plane is cut together with the substrate 28, but it is not necessary to cut the SLC plane, and chipping of the SLC plane is prevented. Therefore, in the optical filter 28, as shown in FIG. 7, the BP surface 28 is formed on the entire surface of the substrate 28a, and the SLC surface 28c is formed in the range excluding the peripheral edge of the substrate 28a.

In the gas analyzer, the infrared rays of the first and second light sources 26a and 26b are incident on the first cell and the second cells 21a and 21b as intermittent light by the chopper 27, and the sample gas 24 is supplied to the first cell 21a. The reference gas 25 is introduced into each of the second cells 21b. In this way, when the infrared rays are transmitted through the first and second cells 21a and 21b and the optical filter 28 and enter the main detector 29 and the sub-detector 30, the main detector 29 and the sub-detector 29 are detected. Since each of the detectors 30 inputs each detection signal to the subtractor 32, the subtractor 32 subtracts each detection signal and outputs a signal corresponding to the concentration of the measurement component in which the influence of the interference component is compensated. .. The concentration of the measurement component is measured based on the output of the subtractor 32.

[0008]

[Problems to be solved by the device]

There is almost no obstacle to the measurement of the measurement components such as HC by the gas analyzer, but there is a problem that the zero-point rising drift sometimes occurs. As a result of various investigations on the cause of the zero-point rising drift, it was found that the optical filter 28 was caused by H ₂ O. Since the BP surface 28b of the optical filter 28 is cut together with the substrate 28a and the entire peripheral surface of the BP surface 28b is a fractured surface, from this fractured surface to the BP surface 28b. ₂ O is there cause this product to penetration, the thus H ₂ O from entering, considered the zero point rising drift occurs. Therefore, when the optical filter 28 was dried, the zero-point rising drift did not occur. Further, when the BP surface 28b is cut, fine peeling may occur in the film at the end portion thereof, and H ₂ O may enter from the peeled portion.

The present invention solves the above problems, and prevents H ₂ O from penetrating into the BP surface of an optical filter and can prevent a zero-point rising drift that occurs in a gas analyzer. The purpose is to obtain an optical filter for a gas analyzer.

[0010]

[Means for Solving the Problems]

In the optical filter for gas analyzer of the present invention, a light source for injecting infrared rays into the cell is arranged on one side of the cell through which the sample gas flows, and a detector for detecting infrared rays transmitted through the cell is arranged on the other side. In a gas analyzer optical filter in which the infrared ray is permeable between a light source and a detector, the substrate constituting the optical filter is made of SiO ₂ or sapphire, and A pair of mask plates in which a band-pass surface provided on one surface and a short long cut surface provided on the other surface are provided with a plurality of vapor deposition holes at intervals so that their size and position match each other. The deposition holes are formed by aligning the positions of the vapor deposition holes on the both sides of the substrate of appropriate size for forming the optical filter, and depositing a film material on the substrate through the vapor deposition holes. Also of the is characterized in that the substrate is cut in the non-deposition portion by chromatography and.

The gas analyzer according to the present invention may be of any type, and the introduction of the cell and the sample gas or the like into the cell is performed by using a pair of cells and alternately supplying the sample gas and the reference gas. Sample gas and zero gas are alternately introduced into one cell. Furthermore, as in the conventional example, a pair of cells are used to compare the sample gas to one of the cells with the other. It is possible to have an arbitrary configuration, such as introducing gas and making infrared rays incident on them into intermittent light with a chopper. In addition, the detector is composed of, for example, two main detectors of a pneumatic type using a condenser microphone and a sub-detector on which infrared rays transmitted through the main detector are incident, or It is also possible to configure the detector with a nimatic type using one condenser microphone for detecting the measurement component. Further, the detector can be composed of a non-selective detector such as a pyro.

[0012]

[Action]

The gas analyzer optical filter of the present invention comprises a plurality of vapor deposition holes formed on both sides of a substrate for optical filter formation, which is made of SiO ₂ or sapphire that transmits visible light, so that the size and the position are matched. This is a pair of mask plates that are placed with a gap between them when the optical filter is formed, and the positions of the vapor deposition holes of each mask plate on both sides of the substrate can be directly checked visually through the substrate and matched. is there. In this manner, a film material such as Ge and SiO is vapor-deposited on the substrate having the mask plates fixed on both sides to form the bandpass surface and the short long cut surface on top of each other. Then, each mask plate is separated, and the substrate is cut at the non-evaporated portion generated in each mask plate, and cutting of the bandpass surface and the short long cut surface is not necessary. Therefore, it is possible to prevent H ₂ O from penetrating into the cut surfaces of the bandpass surface and the short long cut surface, prevent the peeling of a part of the bandpass surface and the short long cut surface from occurring, and It also prevents the infiltration of H ₂ O. Therefore, it is possible to eliminate the zero-point rising drift of the gas analyzer due to the penetration of H ₂ O into the optical filter.

[0013]

【Example】

 An embodiment of the optical filter for a gas analyzer of the present invention will be described with reference to FIGS. In FIGS. 1 and 2, 1a and 1b are first cells and second cells arranged in parallel, which are configured to be capable of transmitting infrared rays, and have gas inlets 2a and 2b and gas outlets 3a, 3b and are provided. Numeral 4 is a four-way switching valve connected to each of the gas inlets 2a and 2b. The sample gas 5 and the reference gas 6 supplied to this are switched by the operation of the four-way switching valve 4, and the first and second cells are connected. It is configured to be introduced alternately into each of 1a and 1b.

Reference numerals 7a and 7b are arranged on one side of the first and second cells 1a and 1b, and a first light source and a second light source for injecting infrared rays into them, and 8 is the other side of the first and second cells 1a and 1b. The optical filter is arranged on one side of the substrate 9 made of SiO ₂ , and the BP surface 10 made of each thin film of Ge and SiO that transmits the absorption component of HC, which is a measurement component, is The SLC surface 11 is formed on each surface of the thin film of Ge and SiO, which reflects and cuts the wavelength range longer and shorter than the absorption wavelength range of the measurement component, and the SLC surface 11 is provided on the BP surface 10. In comparison, the SLC surface 11 is formed in a considerably large number of layers.

As shown in FIGS. 3 to 4, the optical filter 8 includes a pair of mask plates 12a and 12b made of stainless steel, and a substrate 9 of a suitable size for forming the optical filter 8. A plurality of vapor deposition holes 13a and 13b, which are stacked on both sides and have the same size, shape and position on the mask plates 12a and 12b, are aligned with each other and fixed to the substrate 9 (see FIG. 4). ). Although not shown, for example, the mask plates 12a and 12b are fixed to the substrate 9 by attaching a polyimide adhesive tape or the like over both the substrate 9 and the mask plates 12a and 12b. Since the substrate 9 transmits visible light, the vapor deposition holes 13a and 13b can be aligned with each other by directly observing the vapor deposition holes 13a and 13b through the substrate 9, which is a special case. No jig or the like is required, and the vapor deposition holes 13a and 13b can be easily aligned. Further, as shown in FIG. 4, each of the vapor deposition holes 13a and 13b formed in the mask plates 12a and 12b is provided with a step 14 at the periphery thereof, thereby thinning that portion, thereby reducing the Ge and SiO 2 contents. The respective film materials are vapor-deposited uniformly over the vapor deposition holes 13a and 13b.

As described above, the vapor-deposited thin films of Ge and SiO are combined and laminated on each surface of the substrate 9 on which the mask plates 12a and 12b are superposed and fixed on both surfaces, and shown by a chain line in FIG. As described above, the BP surface 10 and the SLC surface 11 are provided so as to overlap each other, but the BP surface 10 and the SLC surface 11 are formed only on the substrate 9 in the portions of the vapor deposition holes 13a and 13b. When the deposition of Ge and SiO on both surfaces of the base plate 9 is completed, the mask plates 12a and 12b are separated from the substrate 9. At this time, on both surfaces of the substrate 9, the BP surface 10 and the SLC surface 11 are respectively formed in a block shape so as to correspond to the vapor deposition holes 13a and 13b, and the mask plates 12a and 12b are overlapped with each other. Since the substrate 9 is exposed, the substrate 9 is cut at this exposed portion to obtain the optical filter 8 shown in FIG. 2, and the BP surface 10 and the SLC surface 11 are completely cut. Absent.

Reference numeral 15 denotes a pneumatic main detector using a condenser microphone into which infrared rays transmitted through the multilayer interference filter 8 are incident, which is configured to detect a measurement component, for example, HC. Has been done. Reference numeral 16 is a pneumatic sub-detector on which the above-mentioned red rays that have passed through the main detector 15 are incident, and is configured to detect noise components other than HC. Reference numerals 17a and 17b denote preamplifiers to which the detection signals of the main detector 15 and the subdetector 16 are input, and 18 subtracts the output signal of the preamplifier 17b from the output signal of the preamplifier 17a to obtain the measurement signal. It is a subtractor that outputs.

In the gas analyzer configured as described above, the sample gas 5 such as exhaust gas and the comparative gas 6 are switched to the first and second cells 1a and 1b by the switching operation of the four-way switching valve 4. The first and second light sources 7a and 7b are alternately introduced, and infrared rays are incident on the first and second cells 1a and 1b, respectively. Then, since each infrared ray that has passed through the gas introduced into each of the first and second cells 1a and 1b passes through the optical filter 8 and enters the main detector 15, the infrared ray that the main detector 15 enters A detection signal corresponding to is output, and the signal is input to the subtractor 18 via the preamplifier 17a. Further, since the infrared light incident on the main detector 15 passes through it and is incident on the sub-detector 16, the sub-detector 16 inputs the detection signal to the subtractor 18 via the preamplifier 17b. Therefore, the detection signal of the sub-detector 16 is subtracted from the detection signal of the main detector 15, and the subtractor 18 outputs the measurement signal corresponding to the concentration of the measurement component such as HC that compensates the influence of the interference component. The concentration of HC or the like is measured based on the output signal of the subtractor 18.

As described above, in the optical filter 8, only the substrate 9 is cut, and the BP surface 10 and the SLC surface 11 are not cut, so that the peripheral surfaces thereof are not broken at all. Also, there is no risk of peeling between the BP surface 10 and a part of the SLC surface 11. Therefore, there is no risk of H ₂ O penetrating into the BP surface 10 and the SLC surface 11, and it is possible to prevent the zero-point rising drift from occurring in the gas analyzer.

The substrate 9 of the optical filter 8 is made of SiO ₂ , and since this SiO ₂ is easier to cut than sapphire, the optical filter 8 can be manufactured efficiently. Is possible. Further, as is clear from the spectroscopic characteristics of SiO ₂ and sapphire shown in FIG. 5, the spectral characteristic of SiO ₂ has a falling wavelength on the shorter wavelength side than the falling wavelength of sapphire. Therefore, the substrate 9 made of SiO ₂ can reduce the number of thin film layers forming the SLC surface 11 as compared with the substrate made of sapphire, so that the manufacturing efficiency of the SLC surface 11 can be improved and the cost thereof can be improved. It is also possible to lower the temperature. FIG. 5 also shows the spectral characteristics of the optical filter 8 and the spectral characteristics of the absorption wavelength region of the measured component HC.

[0021]

[Effect of the device]

As described above, the optical filter for a gas analyzer of the present invention has a pair of mask plates having a plurality of vapor deposition holes preliminarily stacked on both surfaces of a substrate made of SiO ₂ or sapphire that transmits visible light. However, since it is possible to visually confirm the matching of the vapor deposition holes of this pair of mask plates through the substrate, it is easy to set the position of each mask plate with respect to the substrate. In addition, it can be performed with high accuracy. In this way, the exposed surfaces of the substrate, which are formed by the mask plate and overlap each other, are formed on both surfaces of the substrate on which the bandpass surface is formed on one surface and the short cut surface is formed on the other surface by vapor deposition. The board is cut at the exposed part. Therefore, this optical filter is formed by cutting only the substrate, and no breaks or peeling parts are formed on either the bandpass surface or the short long cut surface. For this reason, it is possible to reliably prevent the infiltration of H ₂ O into the bandpass surface and the short long cut surface, and thus to prevent the zero-point rising drift of the gas analyzer due to the infiltration of H ₂ O. Is possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an enlarged front view of a main part of the embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of an optical filter according to an embodiment of the present invention.

FIG. 4 is an enlarged view of an essential part of an optical filter manufacturing process according to an embodiment of the present invention.

FIG. 5 is an optical filter according to an embodiment of the present invention, its substrate, and H.
It is a model spectral-characteristic figure of C.

FIG. 6 is a configuration diagram of a conventional example.

FIG. 7 is an enlarged front view of a main part of a conventional example.

FIG. 8 is a manufacturing process diagram of a conventional optical filter.

[Explanation of symbols]

1a, 1b ... 1st, 2nd cell, 7a, 7b ... 1st, 2nd light source, 8
… Optical filter, 9… Substrate, 10… BP surface, 11… SLC
Surface, 12a, 12b ... Mask plate, 13a, 13b ... Deposition hole, 15
… Main detector, 16… Sub detector.

Claims (1)

[Scope of utility model registration request] 1. A light source for injecting infrared rays into the cell is arranged on one side of a cell through which a sample gas flows, and a detector for detecting infrared rays transmitted through the cell is arranged on the other side.
In the optical filter for a gas analyzer, wherein the infrared ray is permeable between the light source and the detector, the substrate constituting the optical filter is made of SiO ₂ or sapphire, and provided on one side of the substrate. The band pass surface and the short long cut surface provided on the other surface,
A pair of mask plates in which a plurality of vapor deposition holes are provided at intervals so that the size and the position coincide with each other, and a substrate having an appropriate size for forming the optical filter by aligning the positions of the vapor deposition holes with each other. An optical filter for a gas analyzer, wherein the optical filter is formed by depositing a film material on a substrate by depositing it on both sides and fixing it on each side, and cutting the substrate at an undeposited portion by each mask plate.