CN207992043U - A kind of optoacoustic spectroscopy detecting system - Google Patents
A kind of optoacoustic spectroscopy detecting system Download PDFInfo
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- CN207992043U CN207992043U CN201820459413.XU CN201820459413U CN207992043U CN 207992043 U CN207992043 U CN 207992043U CN 201820459413 U CN201820459413 U CN 201820459413U CN 207992043 U CN207992043 U CN 207992043U
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Abstract
The utility model is related to a kind of optoacoustic spectroscopy detecting systems, system uses broad-spectrum light source, the high frequency modulated of beam intensity and wavelength is carried out in conjunction with spectral dispersion device and spatial light modulator, eliminate mechanical chopper, reduce system bulk and weight, stability is improved, ambient noise is significantly reduced.
Description
Technical field
The present invention relates to a kind of optoacoustic spectroscopy detecting systems to be realized using non-mechanical approach especially for broad-spectrum light source
The high-frequency intensity and wavelength for encouraging light source are modulated, and accurate technical field of spectral detection is belonged to.
Background technology
With economic rapid development, problem of environmental pollution says beneficial serious, air quality degradation, and haze phenomenon is frequent
Occur, is mainly derived from the discharge of various polluted gas.Wherein, atmosphere pollution mainly has a carbon monoxide, sulfur dioxide and
The pernicious gases such as nitrogen oxides.These gases are present in air, if finding and solving not in time, it will to the body of people
Body health and daily life cause prodigious influence, therefore monitoring to environment and improvement have become very important task.
The direct occasioner that the leakage with hazardous gas is also serious accident is harmful in industrial production simultaneously, economy and people can be brought
Body massive losses for security.
Currently, the high-precision detection technique of trace gas includes non-optical means, such as electrochemical sensor, air-sensitive method, heat
Catalytic reaction, gas chromatography etc., these method accuracy of detection can reach ppm magnitudes, but compared with optical detecting method, non-light
The sensor service life for learning detection method is short, narrow dynamic range, collects sampling and processing time is slow, is not suitable for online inspection in real time
It surveys.Optical detecting method have many advantages, such as sensitivity and reliability it is high and can on-line real-time measuremen, be the ideal side of gas detection
Method.The new technology of optical detecting method occurs in succession in recent years, such as wavelength modulation spectroscopy, cavity-type BPM absorption spectrum skill
Art, cavity reinforced absorption spectrum technology and optoacoustic spectroscopy etc..Photoacoustic spectroscopy technology is the inter-species based on optoacoustic effect
Absorption spectrometry is connect, principle is, when material molecule is irradiated by light, molecule is excited to upper state because absorbing luminous energy,
Then the luminous energy of absorption is made to be changed into the kinetic energy of molecule by the non-radiative excitation process that disappears.If illumination beam is by periodically adjusting
System, then generate periodic temperature change in substance and lead to the cyclically-varying of pressure, thus generates sound wave, that is, optoacoustic letter
Number.The frequency of photoacoustic signal is identical as light modulation frequency, intensity and phase then depend on the optics of substance, calorifics, elasticity and
The geometrical property etc. of peripheral space.Since photoacoustic signal is directly proportional to the luminous energy of material absorbing, and the substance of heterogeneity has
There is the absorption peak of different wave length, therefore when the light source irradiating sample with continuous wide spectrum, the object of heterogeneity in sample
Matter will generate stronger photoacoustic signal at the corresponding optical wavelength of absorption peak, by analyzing change of the photoacoustic signal with wavelength
Change, the optoacoustic spectroscopy of substance can be obtained.Optoacoustic spectroscopy has the characteristics that the interference of no ambient noise, not the reflection of light and
Scattering influences, and detection sensitivity highest can reach ppt magnitudes, and suitable for various samples such as gas, liquid, solid, powder
Detection.
One important composition component of optoacoustic spectroscopy device is excitation light source, it is desirable that high energy wide spectrum.Though tunable laser
It is optimal light source, has the advantages that monochromatic, direct modulation.But its spectral coverage is narrow, expensive, is unfavorable for answering
With popularization.Therefore mainstream still uses thermal light source, such as xenon lamp, halogen lamp, infrared lamp, arc lamp at present.For such wide spectrum
Light source, the selection generally use narrow band filter slice of wavelength.The transmission loss of filter plate is big, cannot continuously change, and expensive.
In order to improve detection sensitivity and reduce various noise jammings, it is generally desirable to use higher modulation frequency for photo acoustic spectrometry system.But
Since the thermal inertia of above-mentioned thermal light source is big, it cannot be directly modulated using driving source, therefore mostly use mechanical chopper.But copped wave
The volume of device is big, and modulating frequency is relatively low, and frequency stability is poor.Therefore there is an urgent need for novel excitation light source and modulation techniques.
Invention content
The purpose of the present invention is proposed aiming at the deficiency of the broad-spectrum light source employed in current optoacoustic spectroscopy detection technique
A kind of novel optoacoustic excitation source device.The device uses spectral dispersion device combination spatial light modulator, realizes to broad-spectrum light
The wavelength selection in source and regulation and control.Broad-spectrum light source is pressed wavelength in space development by spectral dispersion device, and projects spatial light regulation and control
On device.Spatial light modulator can carry out the light of arbitrary wavelength the modulation of reflection direction, by periodically by specific wavelength
Light energy project in photoacoustic cell and encourage photoacoustic signal, the spectral bandwidth of specific wavelength can arbitrarily intercept as needed.
The intensity modulated of light can be achieved at the same time in the device and wavelength is modulated, and the inhibition of accomplished in many ways background signal may be used.It should
Device is not required to use mechanical chopper and optical filter, therefore the stability of system greatly improves, and modulating frequency is high, volume weight
It is small, it is suitble to commercial Application.
Description of the drawings
Fig. 1 is the photo acoustic spectrometry system schematic diagram for using thermal light source excitation in the prior art, wherein：
（a）For the photo acoustic spectrometry system schematic diagram being modulated using chopper；
（b）For using the photo acoustic spectrometry system schematic diagram of direct modulation light source；
Fig. 2 is the schematic diagram of several spectral dispersion devices, wherein：
（a）For using the spectral dispersion device of grating；
（b）For using the spectral dispersion device of prism；
Fig. 3 is several spatial light modulator schematic diagrames, wherein：
（a）To deflect the spatial light modulator of pixel using reflection type array light；
（b）For using the spatial light modulator of transmission-type array light valve pixel；
Fig. 4 is the photoacoustic signal excitation light source schematic diagram with spatial light modulator using spectral dispersion device, wherein：
（a）To deflect the system schematic of pixel using reflection type array light；
（b）For using the system schematic of transmission-type array light valve pixel；
Fig. 5 is a kind of optoacoustic spectroscopy detection device schematic diagram of the present invention；
Fig. 6 is a kind of optoacoustic spectroscopy detection device schematic diagram with wavelength modulation of the present invention；
Fig. 7 is photoacoustic signal Differential Detection principle schematic, wherein：
（a）It is the absorption peak schematic diagram for including photo acoustic background signal；
（b）For the photoacoustic signal at corresponding absorption peak and two, non-absorbing peak wavelength；
（c）Schematic diagram is changed over time for double frequency differential sense signal；
Fig. 8 is wavelength modulation optoacoustic spectroscopy frequency multiplication testing principle schematic diagram, wherein：
（a）For spatial light modulator spatial distribution schematic diagram；
（b）Schematic diagram is modulated for wavelength in the time domain；
（c）The fundamental frequency background signal schematic diagram generated is absorbed by window and photoacoustic cell；
（d）The frequency-doubled signal schematic diagram generated is absorbed by gas；
Fig. 9 is a kind of differential modulation optoacoustic spectroscopy detection device schematic diagram using resonance photoacoustic cell of the invention.
Specific implementation mode
In order to make the principle of the present invention and feature be better understood, below with reference to specific embodiment and attached drawing to this
Invention is described further.
Fig. 1（a）Shown in be one typically existing photo acoustic spectrometry system principle schematic, the system use thermal light source,
There are commonly xenon lamp, halogen lamp, infrared lamp, arc lamps etc..Light source 10 carries out the selection of spectral line by optical filter 11, then through cutting
12 intensity modulated of wave device, then projected into photoacoustic cell 13 by window 14, the detected gas in photoacoustic cell 13 is absorbing light energy
After generate photoacoustic signal, detected by sonic transducer 15 and be sent to lock-in amplifier 16, while chopper driver 17 exports one and cuts
Frequency signal is to lock-in amplifier 16 as with reference to signal.Fig. 1（a）The photoacoustic cell 13 shown has former and later two windows 14, this
Sample can be to avoid light in photoacoustic cell internal reflection, and is absorbed on pool wall and generate background signal.But only there are one windows for some photoacoustic cells
Mouthful so that light multiple reflections in photoacoustic cell absorb distance to increase gas, while reducing pool wall using certain methods and absorbing institute
The influence of generation.The form of photoacoustic cell is a variety of, such as resonance and disresonance.
Fig. 1（b）Shown in be that another has photo acoustic spectrometry system principle schematic, used modulated broad-spectrum light
Source 19 is still thermal light source, but special thin-film device, has the characteristics that thermal inertia is small, therefore can directly be driven by light source
Device 18 is modulated, and need not be used chopper 12, be greatly reduced system dimension, improve stability.But the light source lacks
Point is that power is not high, and modulating frequency is limited, only tens Hz or so, and frequency be more than after 10Hz modulation depth be just remarkably decreased.
There are many more infrared sharp as the optoacoustic spectroscopy for encouraging light source, such as in tunable wavelength using laser
Light device, but the tunable wave length of this laser is limited in scope, and the price is very expensive, is only suitable for laboratory use.Also it adopts
Letter is improved by high frequency modulated using the acoustic detection element of the high quality factors such as tuning fork with the method for short-wave infrared laser device
It makes an uproar and compares, obtained preferable effect.But it is very faint in short-wave infrared zone gas absorption peak, therefore the detection spirit of final gas
Sensitivity can not be improved significantly.And laser wavelength is fixed, gas with various needs to use different lasers.
In order to solve deficiency of the above-mentioned traditional photo acoustic spectrometry system in terms of encouraging light source, the present invention uses spectral dispersion device
The method that part 21 combines spatial light modulator 30 may be implemented high frequency, the luminous intensity of non-mechanical and wavelength and modulate.
Fig. 2（a）Shown in be spectral dispersion device 21 using grating, for by the output light of broad-spectrum light source 20 in space
It comes by wavelength dispersion.The grating of diagram is concave surface, has focusing function, simple system.Plane grating can also be used to combine
The mode of lens or speculum.Spectral dispersion device 21 can also use prism 22, such as Fig. 2（b）It is shown.Prism cost is very low,
Performance is extremely stable, but its dispersive power is weaker than grating very much.
Fig. 3（a）Shown is a kind of reflective spatial light modulator 30, which there is large number of array light to deflect
Pixel 31, in horizontal equilibrium state when these light deflection pixel 31 does not load.It is loaded by electricity, light deflects pixel 31 can
Leftward or rightward deflection occurs, the speed of deflection is very fast, can reach tens kHz, therefore can realize high frequency modulated.
When there is extraneous light beam 34 to be incident on spatial light modulator 30, the deflection state of pixel 31 is deflected according to each light, emergent light
Corresponding change will occur for direction.The core devices of typical spatial light modulator 30 can be the micro mirror battle array that MEMS technology makes
Row contain millions of light deflection pixels above such as the DLP devices that Texas Instruments produce, and each light deflects picture
Member can be controlled individually to be deflected in both direction high speed.Fig. 3（b）Shown in be array light valve modulator 35, which has
A large amount of low-light valves, are arranged in array, and carry out switching manipulation to each low-light valve by loading electric field, switching speed is also very fast.Allusion quotation
This kind of device of type is to use liquid crystal configuration, is such as used for the LCD device of projection device.Another array light valve device is LCOS
Device, operation principle is similar with LCD, but using reflection mode.
Fig. 4（a）Shown in be optoacoustic spectroscopy driving source signal in conjunction with spectral dispersion device 21 and spatial light modulator 30
Figure.The emergent light of broad-spectrum light source 20 is by the color separation of spectral dispersion device 21 and focuses on the surface of spatial light modulator 30.
By control system, spatial light modulator 30 can be by the light reflection of different wave length to two different directions.Fig. 4（b）Shown in
It is the optoacoustic spectroscopy driving source schematic diagram in conjunction with spectral dispersion device 21 and array light valve modulator 35.The outgoing of broad-spectrum light source 20
Light is by the color separation of spectral dispersion device 21 and focuses on array light valve modulator 35.Pass through control system, array light valve tune
Device 35 processed can selectively allow the light transmission of specific wavelength to be gone over.
It is a kind of photo acoustic spectrometry system using the technology of the present invention, a deflection side of spatial light modulator 30 shown in Fig. 5
It projects light beams upon in photoacoustic cell 13 to being, and another deflection direction is then that light beam is invested black matrix 51 and is absorbed.Cause
This is under the control that spatial light regulates and controls driver 52, and spatial light modulator 30 is periodically by the luminous energy corresponding to gas absorption peak
Amount projects in photoacoustic cell 13, and resulting photoacoustic signal is sent to lock-in amplifier 16, locking phase after the pickup of sonic transducer 15
16 required reference signal of amplifier then comes from spatial light regulation and control driver 52.Space in Fig. 5 seems more crowded, real
The deflection of light can be in the direction of vertical paper in the system of border.
The photoacoustic cell 13 used in the system of Fig. 5 can be significantly increased for single window, light beam multiple reflections in photoacoustic cell
The operating distance of light and gas.But the absorption of photoacoustic cell 13 will produce very strong background signal, be impacted to detection sensitivity.For
Differential mode may be used to eliminate background signal in this, is illustrated with reference to Fig. 6 and Fig. 7.With reference to figure 6, needle is chosen first
To the light beam λ 3 of gas absorption peak, another light beam λ 5 for deviateing gas absorption peak is then chosen.Fig. 7（a）It indicates, by
Absorption peak is not present in a wavelength range near gas absorption peak in 13 pool wall of photoacoustic cell and window 14, and absorptivity is basic
It is identical, therefore background signal caused by the two wavelength is of substantially equal.If being periodically the luminous energy of λ 3 and λ 5 by wavelength
It measures in alternating projection to photoacoustic cell 13, obtained photoacoustic signal is spectrally such as Fig. 7（b）It is shown, and received acoustic pressure
Signal such as Fig. 7（c）It is shown, there is prodigious DC component.Since λ 3 and the background signals caused by pool wall and window of λ 5 are basic
It is identical, therefore rear backdrop signal is handled by lockin signal and will largely be eliminated.
It is generated since the incident direction of λ 3 and λ 5 and the position for being irradiated to 13 pool wall of photoacoustic cell have a little difference
Background signal intensities might have minute differences.It, can since there are many light deflection 31 quantity of pixel of spatial light modulator 30
Accurate balance is carried out to deflect the quantity of pixel 31 by dynamic regulation light.
In order to further decrease the interference of background signal, the method that frequency multiplication can be taken to detect is subject to specific reference to Fig. 8
Explanation.Fig. 8（a）It is 30 surface spectrum distribution schematic diagram of spatial light modulator, if the absorption peak of gas is in the position of λ 3,
Certain spectral range near it can be chosen, such as 4 from λ 2 to λ, usually 2-4 times of system spectral bandwidth, then according to Fig. 8
（b）Shown in sequentially press modulating frequency f and carry out continuous spectral line scanning, be not great-jump-forward.Due to photoacoustic cell 13 and window 14
Absorptivity be substantially dull, therefore the background signal frequency showed and modulating frequency f in minizone with spectrum change
It is identical, such as Fig. 8（c）In curve 80 shown in.But for absorption peak in the gas of λ 3, the uplink and downlink process of spectral line scanning is all
The 2 times of modulating frequencies of photoacoustic signal frequency that can occur once to absorb, therefore generate.By the frequency of the reference signal of lock-in amplifier
Rate is set as 2f, can effectively filter out the interference of the background signal in fundamental frequency f.Another advantage of this technology is, for
Resonance photoacoustic cell, modulating frequency are the half of resonant frequency, and the resonant frequency of photoacoustic cell can double in other words, this is right
Raising system anti-noise acoustic energy is helpful.
Also due to the energy of light can change in spectral range between λ 2 to λ 4, incident direction and it is irradiated to optoacoustic
The position of 13 pool wall of pond has a little difference, therefore generated background signal intensities might have minute differences, this can lead to
The quantity of dynamic regulation light deflection pixel 31 is crossed to carry out accurate balancing.
Shown in Fig. 9 is a kind of differential type photo acoustic spectrometry system using resonance photoacoustic cell 90.Resonance photoacoustic cell 90 has
Two symmetrical resonant cavities 91, the sound pressure signal amplitude in two resonant cavities is identical, but opposite in phase.Therefore spatial light tune is utilized
The characteristic that device 30 alternately deflects light beam in two spaces direction is controlled, the light beam in the two directions is directed respectively into resonance photoacoustic cell
In the symmetrical resonant cavity of two of 90 91, resonance excitation is formed, the energy of light beam is made full use of in this way, effectively improves photoacoustic signal
Signal-to-noise ratio.
In system shown in Fig. 9, Fig. 6 and bispectrum line differential technique shown in Fig. 7 can be superimposed use, i.e. wavelength is λ 3
With the light beam of λ 5 by two symmetrical resonant cavities 91 of 30 alternating projection of spatial light modulator to resonance photoacoustic cell 90, by dynamic
State adjusts the quantity of light deflection pixel 31 to balance the intensity of two-beam so that by pool wall and window institute in two resonant cavities 91
Reasons for its use signal is identical, can further increase system detectio performance in this way.
The above description of this invention is illustrative and not restrictive, such as Differential Detection is not limited to two waves
Long light alternately imports photoacoustic cell 13, but can the light energy of the multiple absorption peaks of correspondence alternately be imported photoacoustic cell 13, realizes
It is detected while multigroup part.In addition to convenient for telling, mainly with the spatial light modulator of Optical Beam Deflection in the above
It is introduced to implement example, but transmissive light valve device slightly adjusts in light path can also obtain same effect.Therefore
It modifies, change and equivalent to it in the range of the claims, will all fall within protection scope of the present invention.
Claims (6)
1. a kind of optoacoustic spectroscopy detecting system, which is characterized in that the system comprises：
Broad-spectrum light source（20）, the broad-spectrum light source（20）For encouraging photoacoustic signal；
Spectral dispersion device（21）, the spectral dispersion device（21）For by the broad-spectrum light source（20）Energy by frequency spectrum it is suitable
Sequence is in space development；
Spatial light modulator（30）, the spatial light modulator（30）Positioned at spectral dispersion device（21）Focal plane, for pair
The broad-spectrum light source（20）Different spectral component carry out periodic spatial orientation modulation；
Photoacoustic cell（13）, the photoacoustic cell（13）Including window（14）With sonic transducer（15）, described for containing under test gas
Sonic transducer（15）For detecting by the spatial light modulator（30）The under test gas of periodic projection can absorb spectrum component
Generated acoustic signals after being acted on under test gas.
2. a kind of optoacoustic spectroscopy detecting system according to claim 1, which is characterized in that the spatial light modulator（30）
By the broad-spectrum light source（20）In the spectrum component in absorption peak and spectrum component in non-absorbing peak periodically replace
Project the photoacoustic cell（13）In.
3. a kind of optoacoustic spectroscopy detecting system, which is characterized in that the system comprises：
Broad-spectrum light source（20）, the broad-spectrum light source（20）For encouraging photoacoustic signal；
Spectral dispersion device（21）, the spectral dispersion device（21）For by the broad-spectrum light source（20）Light energy press frequency spectrum
Sequence is in space development；
Spatial light modulator（30）, the spatial light modulator（30）Positioned at spectral dispersion device（21）Focal plane, for pair
The broad-spectrum light source（20）Different spectral component carry out the modulation in periodic spatial orientation；
Resonance photoacoustic cell（90）, the resonance photoacoustic cell（90）Including sonic transducer（15）With two resonant cavities（91）, for containing
Carry detected gas, the sonic transducer（15）Detection is by the spatial light modulator（30）The under test gas of periodic projection can
Absorption spectrum component and generated acoustic signals after under test gas effect.
4. a kind of optoacoustic spectroscopy detecting system according to claim 3, which is characterized in that the spatial light modulator（30）
By the broad-spectrum light source（20）In under test gas can absorb spectrum component periodically alternating projection to described two resonant cavities
（91）In.
5. a kind of optoacoustic spectroscopy detecting system according to claim 3, which is characterized in that the spatial light modulator（30）
By the broad-spectrum light source（20）In the spectrum component in absorption peak and spectrum component in non-absorbing peak periodically replace
Project described two resonant cavities（91）In.
6. a kind of optoacoustic spectroscopy detecting system, which is characterized in that the system comprises：
Broad-spectrum light source（20）, the broad-spectrum light source（20）For encouraging photoacoustic signal；
Spectral dispersion device（21）, the spectral dispersion device（21）For by the broad-spectrum light source（20）Light energy press frequency spectrum
Sequence is in space development；
Array light valve modulator（35）, the array light valve modulator（35）Positioned at spectral dispersion device（21）Focal plane, use
In to the broad-spectrum light source（20）Different spectral component carry out periodic spatial intensity modulation；
Photoacoustic cell（13）, the photoacoustic cell（13）Including window（14）With sonic transducer（15）, described for containing under test gas
Sonic transducer（15）For detecting by the array light valve modulator（35）The under test gas periodically transmitted can absorb frequency spectrum point
Amount and generated acoustic signals after under test gas effect.
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| CN201820459413.XU CN207992043U (en) | 2018-04-02 | 2018-04-02 | A kind of optoacoustic spectroscopy detecting system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111435111A (en) * | 2019-01-11 | 2020-07-21 | 英飞凌科技股份有限公司 | Photoacoustic gas sensor with optimal reference path length |
| CN115615928A (en) * | 2022-11-17 | 2023-01-17 | 之江实验室 | Photoacoustic spectrum phase locking method, device and system |
-
2018
- 2018-04-02 CN CN201820459413.XU patent/CN207992043U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111435111A (en) * | 2019-01-11 | 2020-07-21 | 英飞凌科技股份有限公司 | Photoacoustic gas sensor with optimal reference path length |
| CN111435111B (en) * | 2019-01-11 | 2023-10-27 | 英飞凌科技股份有限公司 | Photoacoustic gas sensor with optimal reference path length |
| CN115615928A (en) * | 2022-11-17 | 2023-01-17 | 之江实验室 | Photoacoustic spectrum phase locking method, device and system |
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