CN1890554A - Gas sensor - Google Patents
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- CN1890554A CN1890554A CNA200480036879XA CN200480036879A CN1890554A CN 1890554 A CN1890554 A CN 1890554A CN A200480036879X A CNA200480036879X A CN A200480036879XA CN 200480036879 A CN200480036879 A CN 200480036879A CN 1890554 A CN1890554 A CN 1890554A
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- G01—MEASURING; TESTING
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Abstract
A unique optical cavity for NDIR gas sensor module and test results for the C02 concentration from 100 ppm to 2,000 ppm are disclosed. The proposed sensor module shows the maximum peak voltage at 500 ms pulse duration, however, it has a maximum fractional voltage changes at 200 ms pulse duration with 18,000 times amplification gain. From 100 ppm to 2,000 ppm, the voltage difference of sensor module (V) is 200 mV at 200 ms pulse duration and 3 sec. turn-off time.
Description
Technical field
The present invention relates to a kind of optical gas sensor and relate in particular to a kind of non-dispersive infrared gas sensor.
Background technology
The principle of work of traditional optical gas sensor is as follows.
Common, light intensity is owing to diffraction, reflection, refraction and the absorption of light path glazed thread strengthen or weaken.When incident ray passed through light path, gas absorption light on this light path and initial light intensity reduced.
When gas concentration J is an isotropy and when evenly distributing on light path, infrared ray is by light path L, final light intensity I can explain that this law is absorption coefficient k, path L and initial light intensity I by the Beer-Lambert law
oFunction.
That is I=I,
oE
-KJL (x)------formula (1)
The Beer-Lambert law is expressed as top formula (1).If initial light intensity I
oConstant with the absorption coefficient of gas to be measured, then final light intensity I is expressed as gas concentration J on the light path and the function of path L.
If do not have gas in above-mentioned formula (1), if i.e. J=0, then final light intensity equals initial light intensity.
Be I=I
o----------formula (2)
Therefore, the difference of optical strength obtains by formula (3) when not having gas and gas concentration to be J:
Δ I=I
o(1-e
-KJL (x))------formula (3)
Yet, because the voltage that the output of traditional infrared sensor is directly proportional with light intensity, according to existence or the output of the sensor when not having gas be expressed as formula (4):
Δ V=α Δ I=α I
o(1-e
-KJL (x))------formula (4)
In order to obtain having the optical gas sensor of measurement range very wide from the low concentration to the high concentration, at first, should provide the optical cavity with very long light path L (perhaps gas compartment); Secondly, should use the minimum light intensity I that detects
ThEnough low infrared ray sensor; Perhaps the 3rd, have higher relatively and a little less than initial light intensity I from the infrared radiation source emission
OThe saturated light intensity I
SatInfrared ray sensor.
Yet,, therefore need provide the method for optimizing of optical cavity with long enough path because commercial infrared detection sensor (for example thermopile (Thermopile) infrared sensor or passive infrared sensor) is not enough to satisfy above-mentioned all conditions.
Therefore proposed to extend in limited optical cavity the whole bag of tricks of light path, wherein the names for Jacob Y.Wong invention are called the U.S. Patent No. 5,341,214 of " NDIR GAS ANALYSIS USING SPECTRALRATIONING TECHNIQUE ".As shown in Figure 1, this invention aims to provide the light path tubular structure, and this structure causes repeatedly reflection, thereby average path length is greater than the physical length of optical waveguide.And it attempts to increase light path by any direction that will lead from the infrared ray of light emitted.Yet the infrared gas sensor has the visual field of limited reception incident ray usually.Because the visual field is limited, it is very little to arrive the light amount that infrared ray sensor measures fully.Therefore, optical cavity efficient is very low, and lacks practicality.
The another kind of method of using White ' s Cell principle is called in the U.S. Patent No. 5,009,493 of " MIRRORARRANGEMENT FOR A BEAM PATH IN A MULTIPLE-REFLECTIONMEASURING CELL. " open in name.As shown in Figure 2, a plurality of focuses are positioned on the reflecting surface of minute surface, thereby incident light can reflect pre-determined number by three mirror surfaces that are provided with, and the length that can extend light path is to analyze very a spot of gas on the light path.
Yet,, therefore be not suitable for measure CO because this system uses laser as light source
2Deng gas.And, because therefore the long distance between the reflecting surface is difficult in the less detector and uses.
Another kind method is that Christopher R.Sweet is called in name in the U.S. Patent No. 5,488,227 of " GAS ANALYZER " and proposes, wherein the gas sensor that is combined to form by convex reflecting mirror and concave mirror.In order to ensure long effective optical path footpath, the characteristics of this method are to install the convex reflecting mirror that moves in the gas closed chamber, as shown in Figure 3.Gas tester according to this method comprises: structure 12 is used to guarantee the certain space in the gas sensor and prevent internal contamination, lid 13, cylinder optical mirror 15, stepper motor 16 is used to rotate described catoptron, infrared ray sensor 24, the stepper motor 23 that has the rotating circular disk 21 of a plurality of filtrators and rotate described disk.
Yet, need stepper motor owing to be difficult to obtain the rotation of such system and catoptron, therefore small portable, use and be not easy in the simple gas tester to use.
Be called in name that Martin has proposed another method among the PCT/SE97/01366 (WO 98/09152) of " GAS SENSOR ".For long relatively light path is provided in having the optical cavity of finite size, described method is provided with 3 concave mirrors as shown in Figure 4.In other words, the gas sensor that Martin proposes comprises three oval concave surfaces, and have optical gas sensor closed chamber structure (cell structure), adopt White ' sCell notion with the focal point settings of the reflection ray of each concave surface on opposite reflecting surface or near it.
Yet described gas sensor closed chamber with three reflectings surface is very complicated.And,, therefore be difficult to determine the appropriate location of optical sensor owing to the incident light that passes optical cavity from the lip-deep light emitted that is positioned at primary mirror (minute surface of main body) can have subtle change on its incident angle.
The present invention relates to a kind of optical gas sensor, and relate in particular to a kind of NDIR (Non-Dispersive Infrared) NDIR gas sensor.
Measure CO
2Concentration has dual mode.A kind of is the NDIR system, another kind is a disclosed solid state electrolysis system, " A carbon dioxide gas sensor based on solidelectrolyte for air quality control " (Sensors and Actuators B.vol.66 of people such as K.Kaneyasu for example, pp.55-66,2000).
Although the solid state electrolysis sensor is more cheap than NDIR sensor, the NDIR sensor is better than the solid state electrolysis sensor at aspects such as long-time stability, high precision and low-power consumption.And the NDIR sensor has good selectivity and sensitivity, because it has adopted object gas can absorb the ultrared physical sensing principle of certain wavelength.
The optical characteristics of NDIR sensor is as follows.
Common, diffraction, reflection, refraction and the absorption of light intensity by the light path glazed thread reduces or increases.For the NDIR sensor, along with incident light passes light path, gas absorption light and initial light intensity on the light path reduce.
When gas concentration J is an isotropy and when evenly distributing on light path, infrared ray is by light path L, final light intensity I can explain by the Beer-Lambert law, promptly be absorption coefficient k, path L and initial light intensity I
oFunction.
That is I=I,
oE
-KJL (x)------formula (5)
The Beer-Lambert law is expressed as top formula (5).If initial light intensity I
oConstant with the absorption coefficient of gas to be measured, then final light intensity I is expressed as gas concentration J on the light path and the function of path L.
If do not have gas in above-mentioned formula (5), if i.e. J=0, final light intensity equals initial light intensity.
Be I=I
o---------formula (6)
Therefore, the difference of optical strength obtains by formula (7) when not having gas and gas concentration to be J:
Δ I=I
o(1-e
-KJL (x))------formula (7)
Yet, because the voltage that the output of traditional infrared sensor is directly proportional with light intensity, according to existence or the output of the sensor when not having gas be expressed as formula (8):
Δ V=α Δ I=α I
o(1-e
-KJL (x))------formula (8)
Wherein α is a proportionality constant.
In order to obtain having the optical gas sensor of measurement range very wide from the low concentration to the high concentration, at first, should provide the optical cavity with very long light path L (perhaps gas compartment); Secondly, should use the minimum light intensity I that detects
ThEnough low infrared ray sensor; And the 3rd, have higher relatively and a little less than initial light intensity I from infrared radiation source emission
OThe saturated light intensity I
SatInfrared ray sensor.
Yet,, therefore need provide the method for optimizing of optical cavity with long enough path because commercial infrared detection sensor (for example thermopile (Thermopile) infrared sensor or passive infrared sensor) is not enough to satisfy above-mentioned all conditions.
Four kinds of optical cavities have been used in the existing NDIR gas sensor system.
The first, disclosed in the U.S. Patent No. 5,444,249 as the Jacob Y.Wong that issues in August 22 nineteen ninety-five, a kind of square optical cavity or cylinder cast optical cavity with an infrared IR source and a photodetector is provided.
The second, the name of issuing on May 30th, 2000 is called " An implementation of NDIR typeCO
2Gas sample chamber and measuring hardware for capnograph system inconsideration of time response characteristics " U.S. Patent No. 6 of disclosed MahesanChelvayohan invention in the article of (Journal of Korean Sensor Society; vol.5; no.5; pp.279-285; 2001 by I.Y.Park; et al.), 067, in 840, an a kind of photodetector and two optical cavities that are used for the IR light source of heat ageing compensation of comprising have been proposed.
The 3rd, be called " CO in name
2/ H
2O Gas Sensor Using Tunable Fabry-Perot Filterwith Wide Wavelength Range " disclose in the article of (IEEE International Conference on MEMS; pp.319-322; 2003 by Makoto Noro, et al.) and a kind ofly used the cylindrical tube optical cavity and use the air chamber of Fabry-Perot filtrator with select target gas wavelength.
The 4th, in the name in people such as Martins Hans on March 5th, 1998 is called the PCT/SE97/01366 (WO 98/09152) of " Gas Sensor ", disclose and a kind ofly comprised that three concave mirrors are to increase the air chamber of optical path length in the low capacity air chamber.
Especially, the method that proposes of Martin relate to a kind of comprise three recessed reflectings surface and adopt White ' sCell notion with the focal point settings of reflection ray on opposite reflecting surface or near the optical gas sensor it.
Yet,, therefore be difficult to determine the appropriate location of optical sensor owing to the incident light that passes optical cavity from the lip-deep light emitted that is positioned at primary mirror (minute surface of main body) can have subtle change on its incident angle.
Summary of the invention
The present invention is conceived to address the above problem.Target of the present invention is the maximization optical path length and the optical gas sensor that has very wide measurement range and have optical cavity (perhaps air chamber) structure that is easy to design is provided.
And, the invention provides a kind of new optical cavity structure that is used for new optical gas sensor closed chamber, and based on the CO of the sensor that adopts described optical cavity
2The measurement of concetration experimental result has proposed a kind of new gas sensor.
For aforementioned target, comprise according to the optical gas sensor of one aspect of the invention: air chamber is used to hold sample gas; Gas openings is used for being injected into sample gas in the described air chamber or is used for discharging sample gas from described air chamber; Light source is used for to described sample gas projection infrared ray; And infrared ray sensor, being used for the ultrared intensity that sensing passes described sample gas, the wall of wherein said air chamber comprises that but two relative have different focal have the concave mirror of public focus.
For aforementioned target, comprise according to the optical gas sensor of one aspect of the invention: air chamber is used to hold sample gas; Gas openings is used for being injected into sample gas in the described air chamber or is used for discharging sample gas from described air chamber; Light source is used for to described sample gas projection infrared ray; And infrared ray sensor, be used for the ultrared intensity that sensing passes described sample gas, the wall of wherein said air chamber comprises that but two relative have different focal have the concave mirror of public focus, and described concave mirror has following curvature, promptly make the incident light be parallel to described concave mirror optical axis on the surface of described concave mirror, reflect and the focus by described concave mirror, and feasible incident light by described concave mirror focus reflect and is parallel to the optical axis propagation of described concave mirror on the surface of concave mirror.
Described gas openings is included in the gas vent that is provided with on certain wall of described air chamber and is arranged on the bottom of described air chamber or a plurality of gas diffusion paths on the upper support board.
Described a plurality of gas diffusion paths is covered by gas filter.
Described a plurality of gas diffusion paths preferably is arranged on the optical axis of incident ray of infrared ray sensor.
Described gas openings preferably is bent downwardly or can be equipped with removable cap.
The surface of described concave mirror forms by gold-plated or deposition of gold.
Described air chamber comprise with described back up pad on the contiguous integrally formed parabolic reflector of the back up pad with described air chamber of the infrared light sources that forms.
Described air chamber has light exit and is used at least a portion is projected described back up pad from the infrared ray of described infrared light sources.
Described infrared light sources can be arranged on the focus of described parabolic reflector.
The back up pad of described air chamber can comprise the altimetric compensation structure, is used to compensate because the inclination of the described back up pad that the height of described infrared light sources causes.
Description of drawings
Fig. 1-Fig. 4 is an optical gas sensor of the prior art;
Fig. 5 has shown the optical characteristics of parabolic shape catoptron;
Fig. 6 has shown the optical characteristics of the optical cavity system that comprises two parabolic reflectors with public focus;
Fig. 7 has shown the light path according to the focus difference of two parabolic reflectors with public focus;
Fig. 8 is the top plan view of optical gas sensor according to an embodiment of the invention;
Fig. 9 is the A-A ' sectional view of optical gas sensor shown in Figure 8;
Figure 10 is the B-B ' sectional view of optical gas sensor shown in Figure 8;
Figure 11 is the C-C ' sectional view of optical gas sensor shown in Figure 8;
Figure 12 is the skeleton view of optical gas sensor according to an embodiment of the invention;
Figure 13 is the top plan view of optical gas sensor in accordance with another embodiment of the present invention;
Figure 14 is the A-A ' sectional view of optical gas sensor shown in Figure 13;
Figure 15 a has shown the left side of optical cavity according to an embodiment of the invention;
Figure 15 b has shown the right-hand part of optical cavity according to an embodiment of the invention;
Figure 15 c has shown the optical cavity that fits together according to the foregoing description;
Figure 16 is the light path that optical cavity structure produces that passes through according to the foregoing description;
Figure 17 has shown the focusing effect of the light that produces by the optical cavity structure according to the foregoing description;
Figure 18 has shown according to the received power on the photodetector of the above embodiment of the present invention in optical cavity structure;
Figure 19 a has shown the left side of optical cavity in accordance with another embodiment of the present invention;
Figure 19 b has shown the right-hand part of optical cavity in accordance with another embodiment of the present invention;
Figure 19 c has shown the optical cavity that fits together according to the foregoing description;
Figure 20 is the light path that optical cavity structure produces that passes through according to the foregoing description;
Figure 21 has shown the focusing effect of the light that produces by the optical cavity structure according to the foregoing description;
Figure 22 has shown according to the received power on the photodetector of the above embodiment of the present invention in optical cavity structure;
Figure 23 has shown NDIR gas sensor module according to an embodiment of the invention;
Figure 24 shown NDIR gas module according to the above embodiment of the present invention according to CO under the room temperature
2The output voltage characteristic of gas concentration;
Figure 25 has shown that the output voltage of the pulsed modulation time of NDIR gas sensor module according to the above embodiment of the present invention changes; And
Figure 26 has shown the CO of NDIR gas sensor module according to the above embodiment of the present invention
2The output voltage of gas concentration changes.
Accompanying drawing critical piece title
10,15: air chamber lower support plate
20: the first catoptrons
25: the first parabolic reflectors
30: the second catoptrons
35: the second parabolic reflectors
40,45: gas vent
50,55: parabolic reflector
60,65: infrared ray sensor
70,75: the air chamber upper board
80,85: light exit
90,95: infrared lamp
100: lid
110,115: the altimetric compensation structure
120,125: gas diffusion hole
130,135: gas filter
Embodiment
Describe embodiments of the invention in detail below with reference to accompanying drawing.
Fig. 5 has shown the optical characteristics of parabolic reflector.
As shown in Figure 5, for parabolic reflector, be parallel to the focus that the reflection ray of the incident ray that optical axis enters passes catoptron all the time, the reflection of incident light light by reflector focal point is parallel to optical axis all the time and propagates.
The present invention uses these optical characteristics of parabolic reflector.
Fig. 6 has shown the optical characteristics of the optical cavity system that comprises two parabolic reflectors with public focus.
Optical cavity system shown in Figure 6 is arranged so that two parabolic reflectors relative to each other having public focus, and two focal length (O of two parabolic reflectors
A-F, O
B-F) unequal.
According to light source position, described optical cavity system is divided into the diverging system (divergence system) that incident light disperses in optical cavity (Fig. 6 a) and the paradigmatic system (convergencesystem) (Fig. 6 b) of incident light polymerization in optical cavity.
Shown in Fig. 6 b, O wherein satisfies condition
A-F＜O
B-F, if light is launched from the focal point F of concave surface B on optical axis, then light reflects to be parallel to optical axis by described focus and from concave surface A.Reflected light repeat from concave surface B again the process of secondary reflection be aggregated to optical axis and finally arrive concave surface A or B up to it.And the light that is aggregated to optical axis is reflected and gets back to the direction that it enters.
The same experience of the diverging system process identical with above-mentioned paradigmatic system is positioned at concave surface A or B from the emission light that optical axis is dispersed then.
Fig. 7 has shown the light path according to the different focal of two parabolic reflectors with public focus.
Shown in Fig. 7 b, satisfy O
AF-O
BF＞O
A' F-O
B' the optical cavity system of F has following feature, promptly the light path of optical cavity C ' is longer than the light path of optical cavity C, because the optical reflection number of times among the optical cavity C ' is more than the order of reflection in the optical cavity C shown in Fig. 7 a.
As mentioned above, in the optical cavity system, wherein two parabolic reflectors are oppositely arranged to have two focal length (O of public focus and two parabolic reflectors
A-F, O
B-F) unequal, control the length of light path by changing focal length, and can control light path by the angle and the incident angle that change optical axis.
And because two parabolic reflectors have public focus and different focal lengths, and incident light is aggregated to optical axis, therefore is easy to infrared ray sensor is established the position.
Optical gas sensor according to the present invention makes the light that produces on the light path between light source and the infrared ray sensor as far as possible repeatedly reflect by the aforementioned optical characteristics of using the optical cavity system, thereby has increased the optical path length of the optical cavity of intended size.Embodiment according to optical gas sensor of the present invention is described below.
Fig. 8 is the top plan view of optical gas sensor according to an embodiment of the invention.
Optical gas sensor comprises air chamber, gas vent 40, parabolic reflector 50, infrared ray sensor 60, light exit 80, infrared lamp 90, altimetric compensation structure 110, gas diffusion hole 120 and gas filter 130 according to an embodiment of the invention, and wherein said air chamber comprises air chamber lower support plate 10, first catoptron 20, second catoptron 30 and air chamber upper board 70.
Shown in the top plan view of the optical gas sensor among Fig. 8, described optical gas sensor comprises the air chamber that seals optical cavity, and it comprises lower support plate 10, air chamber upper board 70 and air chamber wall.
Described air chamber wall comprises first catoptron 20 and second catoptron 30, and wherein said first catoptron 20 and second catoptron 30 have public focus F
1, and they are configured to have the local circular arc of different curvature radius.
Use the reason of two circular-arc catoptrons to be under the situation of circular arc, its focus is positioned at 1/2 of diameter to be located, and acts on similar to para-curve.If light is parallel to the optical axis emission, determine that then catoptrical path is near focus place or focus.Therefore, the definite part of circular-arc catoptron has shown the optical characteristics closely similar or identical with parabolic reflector.
In first catoptron 20, be formed for launching the ultrared opening that sends from the infrared lamp (not shown), and on air chamber lower support plate 10, form parabolic reflector 50.Parabolic reflector 50 is guaranteed the straight line emission from the light of infrared lamp.
And, on air chamber lower support plate 10, form the ultrared light exit 80 that radiating portion only sends from infrared lamp.
The infrared ray sensor 60 that is used to detect the light that sends from infrared lamp is arranged on second catoptron 30.Be used to inject reference gas and be arranged on the position that first catoptron 20 and second catoptron 30 intersect with the optical characteristics of identification optical gas sensor and the gas vent 40 that carries out initial calibration.
Shown in the light path of the optical gas sensor among Fig. 8, propagate to second catoptron 30 by the infrared ray that is parallel to optical axis that parabolic reflector 50 is introduced with aforementioned structure.Then, passed the public focus F of first catoptron 20 and second catoptron 30 by the infrared ray of second catoptron, 30 reflections
1Perhaps public focus F
1Neighbouring and by the reflection of first catoptron 20.Finally, the infrared ray of polymerization arrives the infrared ray sensor 60 that is arranged on second catoptron 30.
Simultaneously, in order to minimize loss and the diffuse reflection of light from the air chamber wall reflex time, air chamber can be made of metal.In the case, can reduce diffuse reflection by the generation minute surface such as the metal inner surface being polished.
Under the situation of producing the air chamber make by nonmetallic materials, can by on locular wall, cover have high reflectance material layer for example the double layers of gold, nickel, silver and copper or gold/chromium minimize light losing.
Following table 1 has shown the reflectivity according to the various metals of optical wavelength.Gold and silver have at least 98% reflectivity under 800nm or bigger wavelength, aluminium and copper have about at least 94% reflectivity under 1 μ m or bigger wavelength.Yet, common, if silver, aluminium and copper etc. humidity is very high at normal temperatures can autoxidation and change color.Therefore, in order to prevent aging and to guarantee long-time reflecting surface reliably, preferably with the described plenum surface of metalworking.
Table 1 is according to the reflectivity of the various materials of optical wavelength
| Wavelength | Light reflectivity (%) according to wavelength | |||
| Au | Ag | Al | Cu | |
| 200nm | 23 | 23 | 91 | 40 |
| 400nm | 39 | 96 | 92 | 47 |
| 600nm | 92 | 98 | 91 | 93 |
| 800nm | 98 | 99 | 87 | 98 |
| 1μm | 99 | 99 | 94 | 98 |
| 2μm | 99 | 99 | 98 | 98 |
| 4μm | 99 | 99 | 98 | 99 |
| 5μm | 99 | 99 | 98 | 99 |
Therefore, preferred for infrared ray is carried out usable reflection, reflecting surface covering or the deposited gold or the gold/chromium of first catoptron 20 and second catoptron 30.
Fig. 9 is the A-A ' sectional view of optical gas sensor shown in Figure 8.As shown in Figure 9, on air chamber lower support plate 10, be formed for will send from infrared lamp 90 infrared ray introduce the light exit 80 of optical cavity, and the linear parabolic reflector 50 that is used to guarantee the incident light that sends from infrared lamp forms and is connected to first catoptron 20 and air chamber lower support plate 10.
Figure 10 is the B-B ' sectional view of optical gas sensor shown in Figure 8.As shown in figure 10, wherein shown and be connected to gas vent 40 to prevent that air chamber is by the lid 100 of contamination by dust.Lid 100 can separate with gas vent 40.
On air chamber lower support plate 10, be formed for a plurality of diffusion holes 120 of snap-out release gas.Gas diffusion hole 120 is covered with selectivity infiltration gas and avoid dust and the diffusion of steam only by gas filter 130.Simultaneously, below air chamber lower support plate 10, be formed for compensating because the altimetric compensation structure 110 of the difference in height that infrared lamp 90 causes.
Figure 11 is the C-C ' sectional view of optical gas sensor shown in Figure 8.As shown in figure 11, be understandable that at a plurality of diffusion holes 120 that form on the air chamber lower support plate 10 and preferably be formed on the optical axis identical with infrared ray sensor 60.
Figure 12 is the skeleton view of optical gas sensor according to an embodiment of the invention.
Figure 13 is the top plan view of optical gas sensor in accordance with another embodiment of the present invention.Figure 14 is the A-A ' sectional view of optical gas sensor shown in Figure 13.
Optical gas sensor among the structure of optical gas sensor shown in Figure 13 and above-mentioned Fig. 8-Figure 12 much at one, except two mirror arrangement that wherein form air chamber wall are para-curve rather than circular arc.
In other words, but the air chamber wall of optical gas sensor shown in Figure 13 uses two relative parabolic reflectors with same focal point different focal.And gas vent 45 is crooked to prevent the internal contamination of air chamber on gravity direction.
Shown in the principle of work of the optical gas sensor among Figure 13 and Figure 14, the infrared ray that sends from infrared lamp 95 passes through light exit 85 and parabolic reflector 55, and enters air chamber.
Incident light is penetrated the public focus of biography to first parabolic reflector 25 and second parabolic reflector 35, by first parabolic reflector 25 and 35 reflection and the polymerizations of second parabolic reflector.In infrared ray sensor 65 place's measured light intensity.
Although described the present invention with reference to specific embodiment, these descriptions only are examples of the present invention.The various changes of the feature of these embodiment disclosed herein and being combined within the scope of the present invention of appended claims definition.
Target of the present invention is the optical cavity of the non-infrared gas sensor of dispersing of design, comprise two concave mirrors that are provided with relative to each other, its cross section is a circular arc, its central point is positioned on the identical optical axis, and except be used to that the inlet of light source is set and photodetector is set and the outlet of gas inlet/outlet for optics sealing.
And target of the present invention can realize that comprise: light source is used to launch infrared ray by a kind of non-infrared gas sensor of dispersing; Light detector is used for the final light that detects from described light source; Optical cavity, form by two relative concave mirrors, the cross section of described concave mirror is that circular arc, central point are positioned on the identical optical axis, and described optical cavity except be used to that the inlet of light source is set and photodetector is set and the outlet of gas inlet/outlet for optics sealing; The optical modulation parts have the pulsed modulation time of 200-600ms and 2,2.5,3 seconds turn-off time, are used to control the light that sends from light source; And amplifier unit, be used to amplify electric signal from light detector.
Further describe the present invention below with reference to the accompanying drawing shown in the embodiment of the invention.
Basic, optical cavity of the present invention is made by circular arc.The central point of two circular arcs is on same axis.
And embodiments of the invention are designed to the central point of each circular arc and mid point identical (two centers of two circular arcs are on same straight line) from a circular arc to the straight line of another circular arc.Its reason is to make that the light of emission under certain condition can be by certain a bit (if the circular arc feature is identical with para-curve, circular arc be designed to pass through same focal point) on the same straight line.The reason that adds this condition is for example, have parabolic characteristic in order to ensure circular arc, thereby the light that is parallel to optical axis incidence reflection mirror to be aggregated to focus.In other words, if the present invention is designed to said structure, the light that then is parallel to optical axis emission reflects on each catoptron, focuses on a bit towards opposite surfaces and at certain.Shown in experimental result below, this is because the characteristic that directional light focuses on light path.
Simultaneously, the above embodiment of the present invention is designed to two circular arcs and has different radii, have the central point of the circular arc of major radius more and be positioned at outside the circular arc with short radius more, and have more the central point of the circular arc of short radius and be positioned at and have the more inboard of the circular arc of major radius.In the case, the light path that is determined by experiment from the light source to the light detector carries out the circulation of suitable number of times.
Under the situations that above-mentioned condition all satisfies, for the optical cavity design of accomplished light polymerization effect with effectively increase the optical cavity design of light path, followingly carry out optical analogy.
In simulation, the infrared light sources with 4.2 mum wavelengths and 0.66 watt of power input (power consumption under the steady-working state) is set.And the golden Au of the inboard covering of optical cavity has the minute surface of about 97% reflectivity with simulation.This is to have at least 97% reflectivity because have certain thickness gold thin film in infra-red range, particularly under 1 μ m or bigger wavelength.And the incident light that vertically enters the ingate is a parallel rays.Simultaneously, the size of the shape of light detector, effective coverage is set to identical with commercial infrared ray sensor with configuration or the like.And, use the analysis tool of the TracePro program of Lambda research company as simulation.
In simulation for the first time, use the optical texture shown in Figure 15 a, 15b and 15c.Optical cavity among Figure 15 c is the combination of the right-hand part of the left side of Figure 15 a and Figure 15 b.This is the design example of the deposition of the manufacturing cost of reduction initial testing and the gold thin film that promotes catoptron.This combination only is an example, and other optical cavities that therefore have various combination also are possible.In other words, can make whole optical cavity by mold, and deposited gold or cover gold from the teeth outwards.
In simulation for the first time, optical cavity is designed to make can be checked light path and realize that the light focusing effect to increase the detected light amount of light detector, keeps the small-sized of optical cavity simultaneously.In other words, as shown in Equation (8),, at first, should increase the length of the light path in the optical cavity, secondly, should use to have the very little minimum light intensity I that detects in order to measure very micro-gas
ThInfrared ray sensor, perhaps the 3rd, can use to have higher relatively but a little less than the initial light intensity I of sending from infrared radiation source
OThe saturated light intensity I
SatInfrared ray sensor.Except these methods, also has a kind of method that arrives the light intensity of infrared ray sensor by focused ray with increase.Below with reference to accompanying drawing the present invention is described.
The light path of Figure 16 for producing by the optical cavity structure shown in Figure 15 c.
Figure 16 has shown the light path of incident light, and the useful information that can calculate the optical path length in the optical cavity is provided.
Figure 17 has shown the focusing effect of the light that produces by the optical cavity structure shown in Figure 15 c.
Figure 17 has shown the characteristics that focus on certain point from the parallel rays of light emitted.In other words, if being parallel to the optical axis that passes center of arc's point from the light source in precalculated position, sends light, and reflect twice, then it focuses near the infrared ray sensor that is positioned on the catoptron relative with light source, thereby increases the output voltage of infrared ray sensor.
Figure 18 has shown the received power on the photodetector in the optical cavity structure shown in Figure 15 c.
In Figure 18, with the received power colour-coded of position He each position of light acceptance point.
Board design for the second time is for increasing light path, and this is that the detection minimum gas is necessary.Optical cavity structure shown in application drawing 19a, 19b and the 19c.Optical cavity among Figure 19 c combines the left side of Figure 19 a and the right-hand part of Figure 19 b.This combination only is an example, and other optical cavities that therefore have various combination also are possible.The optical cavity of integral type also is possible.
In simulation for the second time, the circular arc that optical cavity condition of the present invention is satisfied in use forms optical cavity, use following structure simultaneously, if promptly directional light is near emission (perhaps the being transmitted into central point) central point of two circular arcs, then two circular arcs cause reflected light to arrive near certain point of central shaft of two circular arcs.Yet when order of reflection increased, because light intensity can reduce in practical embodiments, the light receiving intensity between simulation and the embodiment may have very big-difference.Therefore, on analog sense, reduce in order to prevent the light receiving intensity, order of reflection is limited to 5 times before light arrives infrared ray sensor.And, in said structure,, optical transmitting set (perhaps infrared light sources) and optical receiver (infrared ray sensor) are set on identical circular arc in order to make light arrive near the center of arc.Yet the present invention is not limited to above-mentioned feature.
The light path of Figure 20 for producing by the optical cavity structure shown in Figure 19 c.
Figure 20 has shown that from the light of optical transmitting set emission be the center of infrared ray sensor from the light arrival optical receiver of transmitter center emission particularly.
Figure 21 has shown the focusing effect of the light that produces by the optical cavity structure shown in Figure 19 c.
Figure 21 has shown that the light beam of the size (for example radius 2mm) that has greater than the light emitting members of light source arrives optical receiver.Optical cavity structure with this configuration is of great use when being applied to many gas sensors (for example radius sensor of 5mm), and this many gas sensors are the optical receivers with radius bigger than light source.
Figure 22 has shown the received power on the photodetector in the optical cavity structure shown in Figure 19 c.
Figure 22 has shown that the energy that arrives the light-receiving member (circular configuration) of infrared ray sensor in the unit interval is approximately per hour 0.523 watt.With its with 5 secondary reflections after arrive infrared ray sensor when not losing ideal capacity per hour compare for 0.567 watt and lacked about 0.044 watt as can be known.Its reason is because of the zone outside the light-receiving member of part divergence of beam of launching from optical transmitting set and arrival infrared ray sensor.
When using TracePro to check the received power of the focusing effect of light path in the above-mentioned simulation, light and each optical cavity, can obtain following result.
Can confirm in the whole optical path electrical path length from the light path that the central shaft of optical transmitting set is launched.The light path longer can be realized according to optical cavity of the present invention, and the focusing effect of light can also be obtained in addition than prior art.And,, can determine because the light intensity that the reflection of catoptron reduces arrives photodetector if light source (output voltage: 0.66 watt) is worked under steady state (SS).Although the received power on the photodetector, is considered not all light-ray condensing slightly less than calculated value to photodetector, it only is considered to approximation.
According to above-mentioned analog result, particularly the optical cavity of simulating for the first time can obtain the following examples.
Embodiments of the invention adopt two known assemblies, i.e. infrared light sources and photodetector.For infrared light sources, for example can use to have the infrared light sources that paraboloidal reflector is used to focus on parallel rays and the ultrared Gilway special lamp of emission 1-5 μ m.And, can adopt the ZTP-315 GS thermal coupling infrared detector of GEThermometrics Technologies, its traditional heating, heating ventilation and air-conditioning HVAC that is applied to automobile uses, but because therefore the gas sensing target of this research uses the alternative CO with 4.26 μ m centre wavelengths and 20nm FWHM (half peaked full duration) of long wavelength's bandpass filter
2Wave filter.
Figure 23 has shown NDIR gas sensor module according to the above embodiment of the present invention, comprises three critical pieces.First parts are the modulation of infrared rays parts, and wherein the duration of pulse is 200-600ms, and the turn-off time changed into 3 seconds from 2 seconds, have 0.5 second interval.The new optical cavity structure that second parts propose for the present invention.The 3rd parts are amplifying circuit.In this embodiment, used secondary amplifying circuit with reference voltage driver LM385.
Figure 24 shown NDIR gas module according to the above embodiment of the present invention and with reference to transmitter at room temperature output voltage with respect to CO
2Gas concentration.As shown in figure 24, the maximum output voltage of new sensor assembly is at the CO of 100ppm
2Be approximately 4.75V under the gas concentration.Along with CO
2Gas concentration increases between 100-2000ppm, and the maximum peak voltage of sensor assembly is reduced to 4.45V.CO between above-mentioned 100-2000ppm
2Gas concentration changes down, and the maximum peak voltage difference is 300mV.
Figure 25 has shown worked as CO in the above embodiment of the present invention
2When gas concentration is constant according to the output voltage difference of pulsed modulation time.The output voltage difference table is shown in output voltage under the light source opening and the difference between the output voltage under the light source off state.Along with the pulsed modulation time increases, the output voltage difference also increases.Yet if the pulsed modulation time surpasses 500ms, the output voltage difference begins saturated.Therefore, output voltage also becomes does not have any difference.And because the infra-red intensity that absorbs is very big, the heat of absorption does not discharge fully, and the lost of life of light source.
Figure 26 has shown in the above embodiment of the present invention according to CO
2The output voltage that gas concentration changes changes.Wherein shown and worked as CO
2The normalized output signal of NDIR sensor assembly when gas concentration increases between 100-2000ppm.Described normalization output signal demonstrates maximum the change during for 200ms at the infrared pulse modulating time.Along with modulating time increases between 300-500ms, described standard output signals reduces significantly.
Simultaneously, when the duration of pulse of 500ms, demonstrate maximum voltage difference, but reference voltage increases slightly simultaneously.It is maximum that the change of output voltage became when the duration of pulse of 200ms, and demonstrate 18000 times gain amplifier.At this moment, the turn-off time of infrared light sources is 3 seconds.
Although the specific embodiment with reference to NDIR gas sensor and optical cavity has been described the present invention, these are described only is that the example used of the present invention and should not thinking limits the scope of the invention.The various changes of simulation disclosed herein and embodiment and combination are all in the scope of the present invention of appended claims definition.
For example, in order to obtain directional light of the present invention, can adopt the additive method of in optical cavity, making para-curve type catoptron not use the product of Gilway special lamp to make cost-efficient optical cavity.
Industrial usability
As mentioned above, according to optical gas sensor of the present invention, increase considerably from the length of the light path of infrared light sources projection, and can measure the gas of low concentration to high concentration.And can measure all gases.
And, used two concave mirrors as air chamber wall, thereby realized simplified design and made gas sensor and the effect of reduction manufacturing cost.
The present invention has proposed a kind of new gas sensor configuration by the optical cavity design that improves traditional NDIR gas sensor.Optical cavity structure of the present invention is very simple, be made up of two concave mirrors, and light beam focuses on the photodetector.
According to the present invention, can obtain to have the new optical cavity structure of the NDIR gas sensor of the light path of prolongation and light focusing feature.By using described new optical cavity structure, can obtain the new sensor assembly of the HVAC system or the like of air quality measuring system, automobile.
Claims (25)
1. optical gas sensor, comprising: air chamber is used to hold sample gas; Gas openings is used for being injected into sample gas in the described air chamber or is used for discharging sample gas from described air chamber; Light source is used for to described sample gas projection infrared ray; And infrared ray sensor, be used for the ultrared intensity that sensing passes described sample gas, it is characterized in that:
The wall of described air chamber comprises that but two relative have different focal have the concave mirror of public focus, and described concave mirror has following curvature, promptly make the incident light of the optical axis be parallel to described concave mirror on the surface of described concave mirror, reflect and the focus by described concave mirror, and the incident light of feasible focus by described concave mirror reflect and is parallel to the optical axis propagation of described concave mirror on the surface of concave mirror.
2. optical gas sensor according to claim 1, wherein said gas openings are included in the gas vent that is provided with on certain wall of described air chamber and are arranged on the bottom of described air chamber or a plurality of gas diffusion paths on the upper support board.
3. optical gas sensor according to claim 1 and 2, wherein said a plurality of gas diffusion paths are covered by gas filter.
4. optical gas sensor according to claim 3, wherein said a plurality of gas diffusion paths are arranged on the optical axis of incident ray of described infrared ray sensor.
5. optical gas sensor according to claim 2, wherein said gas openings is bent downwardly or is equipped with removable cap.
6. optical gas sensor according to claim 1, the surface of wherein said concave mirror is by gold-plated or deposited gold.
7. optical gas sensor according to claim 2, wherein said air chamber comprise with described back up pad on the contiguous integrally formed parabolic reflector of the back up pad with described air chamber of the infrared light sources that forms.
8. optical gas sensor according to claim 7 wherein forms light exit with the infrared ray of projection at least a portion from described infrared light sources on the back up pad of described air chamber.
9. according to claim 7 or 8 described optical gas sensors, wherein said infrared ray is arranged on the focus of described parabolic reflector.
10. optical gas sensor according to claim 2, the back up pad of wherein said air chamber comprises the altimetric compensation structure, is used to compensate because the inclination of the described back up pad that the height of described infrared light sources causes.
11. an optical gas sensor comprises: air chamber is used to hold sample gas; Gas openings is used for being injected into sample gas in the described air chamber or is used for discharging sample gas from described air chamber; Light source is used for to described sample gas projection infrared ray; And infrared ray sensor, be used for the ultrared intensity that sensing passes described sample gas, it is characterized in that:
The wall of described air chamber comprises that but two relative have different focal have the concave mirror of public focus.
12. optical gas sensor according to claim 11, wherein said gas openings are included in the gas vent that is provided with on certain wall of described air chamber and are arranged on the bottom of described air chamber or a plurality of gas diffusion paths on the upper support board.
13. according to claim 11 or 12 described optical gas sensors, wherein said a plurality of gas diffusion paths are covered by gas filter.
14. optical gas sensor according to claim 11, the surface of wherein said concave mirror is by gold-plated or deposited gold.
15. optical gas sensor according to claim 12, wherein said air chamber comprises parabolic reflector, thereby described parabolic reflector makes the incident light from described infrared light sources be parallel to the horizontal supporting plate propagation of described air chamber.
16. the optical cavity of a non-infrared ray sensor of dispersing is characterized in that:
Described optical cavity is formed by two relative concave mirrors, and the cross section of described concave mirror is a circular arc, and the central point of two circular arcs is on same axis, and except being used for light source, photodetector, gas vent and gas diffusion hole, described optical cavity is that optics seals.
17. optical cavity according to claim 16, the central point of wherein said each circular arc overlaps with mid point from a circular arc to the straight line of another circular arc.
18. according to claim 16 or 17 described optical cavities, wherein said circular arc has mutually different radius.
19. optical cavity according to claim 18, wherein said have the central point of the circular arc of major radius more and be positioned at outside the described circular arc with short radius more, and describedly have more that the central point of the circular arc of short radius is positioned at the described more inboard of the circular arc of major radius that has.
20. optical cavity according to claim 19, wherein said light source is positioned on the different circular arcs with photodetector, and be parallel to the axle emission at the central point place of described two circular arcs from the incident light of described light source, on described each circular arc, reflect and once and by described photodetector detect.
21. optical cavity according to claim 20, the wherein said circular arc of directional light at described photodetector place from light emitted focuses on.
22. optical cavity according to claim 17, wherein said light source is positioned on the identical circular arc with photodetector, and reflects odd number time and detected by described photodetector on described each circular arc from the incident light of described light source.
23. optical cavity according to claim 22, wherein said incident light from light source is transmitted near the center of described optical cavity or its, repeated polymerization and disperse and arrive photodetector in reflection repeatedly, and the area of section of light beam of circular arc that wherein arrives described photodetector place is greater than the area of section from the light beam of described light emitted.
24. the optical cavity of a non-infrared ray sensor of dispersing comprises:
Light source is used to launch infrared ray;
Photodetector is used for the final infrared ray that detects from described light source;
Optical cavity forms by two relative concave mirrors, and the cross section of wherein said concave mirror is a circular arc, and the central point of two circular arcs is on same axis, and except being used for light source, photodetector, gas vent and gas diffusion hole, described optical cavity is that optics seals;
Optic modulating device is used to control the infrared ray from described light emitted, and wherein said light modulation device has the pulsed modulation time and 2 seconds, 2.5 seconds of 200-600ms and 3 seconds turn-off time; And
Multiplying arrangement is used to amplify the electric signal from described photodetector.
25. it is the pulsed modulation time of 200ms and 3 seconds turn-off time that optical cavity according to claim 24, wherein said optic modulating device are provided with described light source.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020030090539A KR100494103B1 (en) | 2003-12-12 | 2003-12-12 | Optical gas sensor |
| KR1020030090539 | 2003-12-12 | ||
| KR1020040091776 | 2004-11-11 |
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| Publication Number | Publication Date |
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| CN1890554A true CN1890554A (en) | 2007-01-03 |
| CN100592075C CN100592075C (en) | 2010-02-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN200480036879A Active CN100592075C (en) | 2003-12-12 | 2004-12-10 | Gas sensor |
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| KR (1) | KR100494103B1 (en) |
| CN (1) | CN100592075C (en) |
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| CN102338737A (en) * | 2010-07-21 | 2012-02-01 | 友丽系统制造股份有限公司 | Photoelectric gas sensing device and its manufacturing method |
| CN101587068B (en) * | 2009-05-27 | 2012-03-28 | 陈小英 | Multi-sensor gas analyzer |
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Also Published As
| Publication number | Publication date |
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| CN100592075C (en) | 2010-02-24 |
| KR100494103B1 (en) | 2005-06-10 |
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