CN209372684U - A kind of tunable laser light acousto-optic spectrum trace gas detection experiment device for teaching - Google Patents
A kind of tunable laser light acousto-optic spectrum trace gas detection experiment device for teaching Download PDFInfo
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- CN209372684U CN209372684U CN201920024251.1U CN201920024251U CN209372684U CN 209372684 U CN209372684 U CN 209372684U CN 201920024251 U CN201920024251 U CN 201920024251U CN 209372684 U CN209372684 U CN 209372684U
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Abstract
A kind of tunable laser light acousto-optic spectrum trace gas detection experiment device for teaching, belongs to photoelectric measurement class teaching and experiment equipment technical field.The device includes tunable laser source, optics collimator, photoacoustic cell, photothermal conversion element, microphone, air inlet, gas outlet, light source driving, Signal acquiring and processing circuit and computer.Increase a photothermal conversion element in traditional photoacoustic cell, for modulation laser by after under test gas, generating gas photoacoustic signal, remaining light energy is converted to heat after being absorbed by photothermal conversion element, and generates solid photoacoustic signal.In the lower situation of gas concentration, the concentration of minimum gas to be measured can be finally inversed by by measuring the size of 2f/1f signal.Increase a photothermal conversion element in traditional photoacoustic cell, a background photo acoustic signal is introduced as reference, 2f/1f ratio mensuration is used again, that is, realizes and the calibration-free of Laser Photoacoustic Spectroscopy experiment device for teaching is measured, considerably reduce the maintenance workload of device.
Description
Technical field
The utility model belongs to photoelectric measurement class teaching and experiment equipment technical field, is related to a kind of tunable laser light acousto-optic
Compose trace gas detection experiment device for teaching.
Background technique
The principle of Laser Photoacoustic Spectroscopy is laser irradiation into gas absorption cell, and gas molecules sorb laser jumps from low-lying level
High level is adjourned, then release heat makes the gas expansion in photoacoustic cell during radiationless transition is to low-lying level, in turn
The acoustic signals of generation can be detected by microphone, and the amplitude of signal is directly proportional to the concentration of under test gas molecule.Swash
The advantages that highly sensitive, highly selective and small sampling volume that light optoacoustic spectroscopy trace gas detection technology has with it, exist
The analysis of electric device fault characteristic gases, industrial production minimum discharge monitoring, the monitoring of coal mine flammable explosive gas and medicine breathing
Important function has been played in the application such as gas diagnosis.
Currently, the trace gas detection experiment device for teaching based on Laser Photoacoustic Spectroscopy has very in practical work process
More situations can make the power of light source change, such as aging, loss of optical fiber connection procedure of optical fiber or laser etc., and gas
Second harmonic (2f) the photoacoustic signal amplitude that body absorbs laser generation is also directly proportional to tunable laser source power, surveys concentration
Amount generates biggish error, reduces the reliability of experimental provision.In order to reduce error, one of common method is regular
Experimental provision is calibrated, but this has increased considerably the maintenance workload of experimental provision.But traditional optoacoustic spectroscopy
It is a kind of no background detection method, the amplitude of first harmonic (1f) component at absorption spectrum center is almost nil, therefore cannot adopt
Calibration-free measurement is realized with 2f/1f method.Thus, design the laser light of a kind of pair of tunable laser source changed power calibration-free
Acousto-optic, which composes trace gas detection experiment device for teaching, has important value.
Utility model content
The purpose of this utility model is that proposing a kind of tunable laser light acousto-optic spectrum trace gas detection teaching experiment dress
It sets, it is intended to solve tunable laser source power present in current Laser Photoacoustic Spectroscopy trace gas detection experiment device for teaching
Variation cause gas concentration measurement error increase the problem of, be Laser Photoacoustic Spectroscopy experiment device for teaching in Experiment of College Physics
In popularization expand bigger space.
To achieve the above object, the utility model uses following technical scheme:
A kind of tunable laser light acousto-optic spectrum trace gas detection experiment device for teaching, including tunable laser source 1, light
Learn collimator 2, photoacoustic cell 3, photothermal conversion element 4, microphone 5, air inlet 6, gas outlet 7, light source driving 8, signal acquisition with
Processing circuit 9 and computer 10；Tunable laser source 1, optics collimator 2, photoacoustic cell 3 are sequentially connected in series, microphone 5, signal
Acquisition is sequentially connected in series with processing circuit 9 and light source driving 8；Photothermal conversion element 4 is installed on the non-arrival end of photoacoustic cell 3；Microphone 5
It is installed on 3 outer wall of photoacoustic cell；Signal acquiring and processing circuit 9 is connected with computer 10；Light source driving 8 receives signal acquisition and place
It manages the sinusoidal modulation signal that circuit 9 generates and current-modulation is carried out to tunable laser source 1；What tunable laser source 1 emitted
Laser is incident in photoacoustic cell 3 through optics collimator 2, is finally irradiated on photothermal conversion element 4；Photoacoustic cell 3 is equipped with air inlet
Mouth 6 and gas outlet 7；Microphone 5 is mounted on photoacoustic cell 3, for detecting the photoacoustic signal generated in photoacoustic cell 3；Signal acquisition
It is connected with the signal input part of processing circuit 9 with microphone 5, carries out digital signal after the photoacoustic signal that acquisition microphone 3 detects
Processing；Computer 10 is connected with Signal acquiring and processing circuit 9, the running parameter for setting signal acquisition and processing circuit 9
And the gas concentration measurement exported to Signal acquiring and processing circuit 9 is shown.
The tunable laser source 1 is the narrow linewidth semiconductor tunable laser light source of tunable wave length.
The tunable laser source 1 after current-modulation, modulated simultaneously by Output optical power and optical wavelength.
The photothermal conversion element 4 is the device with high photothermal conversion efficiency.
The photothermal conversion element 4 has wider absorption spectrum region, in the absorbing wavelength attachment of under test gas
Absorptance without significant change, keep the 2f component amplitude in the solid photoacoustic signal generated almost nil.
The core of the Signal acquiring and processing circuit 9 is can to measure first harmonic and second harmonic signal amplitude simultaneously
Signal detector.
The principles of the present invention are as follows: increasing a photothermal conversion element in traditional photoacoustic cell, modulation laser passes through
After under test gas, gas photoacoustic signal is generated, remaining light energy is converted to heat after being absorbed by photothermal conversion element, and makes closed
Gas generating period in photoacoustic cell expands with heat and contract with cold, and then generates solid photoacoustic signal.
According to Lambert-Bill law, under conditions of 1 < LC < α (v), the available light after gas absorbs
By force are as follows:
Ig(v)=I0(v)(1-exp(-α(v)LC))≈I0(v)α(v)LC (1)
In formula, I0It (v) is incident intensity, α (v) is absorption coefficient, and L absorbs Cheng Changdu, and C is the concentration of gas.
If the light after transmission gas is absorbed by photothermal conversion element completely, absorption coefficient of light μ (ν) are as follows:
μ (ν)=1- α (ν) LC ≈ 1 (2)
Microphone can be detected simultaneously by gas photoacoustic signal and solid photoacoustic signal, can using wavelength modulation spectrum technology
To obtain its photoacoustic signal are as follows:
In formula, AcellFor photoacoustic cell constant, m is the modulation amplitude of incident intensity, and η is that the optoacoustic of photothermal conversion element is converted
Efficiency, ε are the optoacoustic transfer efficiency of gas, H0And HnIt is the harmonic series that Fourier expansion generation is carried out to the absorption coefficient of gas
Number.
After locking phase is handled, obtains 1f signal and be respectively as follows: with 2f signal
At the center of gas absorption spectra, 1f signal approximate can simplify with 2f signal are as follows:
S1f=η mAcellI0 (6)
S2f=ε AcellI0H2LC (7)
1f signal at the center of gas absorption spectra be photothermal conversion element absorption intensity variation laser after generate
Solid photoacoustic signal, when gas concentration is smaller, amplitude is only related with laser power；2f signal is used for the optoacoustic of detection gas
Signal, amplitude and laser power and gas concentration are linear.
2f signal obtains 2f/1f signal divided by 1f signal, can indicate are as follows:
According to formula (8), the gas concentration of measurement can be indicated are as follows:
It can be seen that formula (9) are unrelated with power, therefore in the lower situation of gas concentration, it can be by measuring 2f/1f
The size of signal is finally inversed by the concentration of minimum gas to be measured, final to realize the calibration-free under tunable laser source changed power
Gas concentration measurement.
The utility model has the beneficial effects that it is only necessary to increase a photothermal conversion element in traditional photoacoustic cell
A background photo acoustic signal is introduced as reference, then uses 2f/1f ratio mensuration, can be realized and impart knowledge to students to Laser Photoacoustic Spectroscopy
The calibration-free of experimental provision measures, and considerably reduces the maintenance workload of device.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of the utility model.
Fig. 2 is the structural schematic diagram of test macro.
Fig. 3 is the first harmonic photoacoustic signal of measurement.
Fig. 4 is the second harmonic photoacoustic signal of measurement.
Fig. 5 is the relation curve that the 2f/1f value of measurement changes with acetylene gas concentration.
Fig. 6 is the 2f/1f value of measurement with the relation curve of laser power variation.
In figure: 1 tunable laser source；2 optics collimators；3 photoacoustic cells；4 photothermal conversion elements；5 microphones；6 air inlets
Valve；7 air outlet valves；The driving of 8 light sources；9 Signal acquiring and processing circuits；10 computers；11 Optical Fiber Winding devices；12 fiber couplers；
13 light power meters.
Specific embodiment
Specific embodiment of the present utility model is described in detail below in conjunction with technical solution and attached drawing.
A kind of tunable laser light acousto-optic spectrum trace gas detection experiment device for teaching, mainly includes tunable laser source
1, optics collimator 2, photoacoustic cell 3, photothermal conversion element 4, microphone 5, air inlet 6, gas outlet 7, light source driving 8, signal are adopted
Collection and processing circuit 9 and computer 10.Light source driving 8 receives the modulated signal of the generation of Signal acquiring and processing circuit 9 to adjustable
Humorous laser light source 1 carries out current-modulation, which is the superposed signal of sawtooth wave and sine wave, realizes to optical maser wavelength
Scanning and modulation；The laser that tunable laser source 1 issues is incident on photoacoustic cell 3 after optics collimator 2 carries out beam collimation,
Under test gas enters photoacoustic cell 3 by air inlet 6；Under test gas in photoacoustic cell 3 absorbs laser transition to high level, then exists
Heat is discharged during radiationless transition to ground state expands air generating period, and then generates the photoacoustic signal of gas,
Vibrate the surface of photothermal conversion element 4 in laser irradiation to photothermal conversion element 4 after transmission gas, while photo-thermal turns
Heat transfer after changing expands the gas generating period in photoacoustic cell into gas, generates photoacoustic signal；Microphone 7 will
The photoacoustic signal of detection is converted to the signal input part that Signal acquiring and processing circuit 9 is input to after electric signal, is existed by extracting
First harmonic and second harmonic at gas absorption spectra center can be finally inversed by under test gas according to 2f/1f calculated value
Concentration；Computer 10 is shown and is stored to measurement result；Finally, under test gas is discharged by gas outlet 7 from photoacoustic cell 3.
Wherein, tunable laser source 1 is narrow linewidth distributed feed-back (DFB) laser of tunable wave length, central wavelength
For 1532.83nm.Photoacoustic cell 3 is non-resonance photoacoustic cell.Photothermal conversion element 4 is multi-layer graphene piece.Signal acquiring and processing
The core of circuit 9 is good digital lock-in amplifier.
Fig. 2 is the structural schematic diagram of test macro.The laser that tunable laser source 1 emits passes through Optical Fiber Winding device 11
Afterwards, then by coupling ratio the fiber coupler 12 for being 1:99,1% light are incident on light power meter 13, supervise to light source power
It surveys, in addition 99% light is incident on photoacoustic cell.Change optical fiber by changing winding circle number of the optical fiber on Optical Fiber Winding device 11
Bending loss, obtain unused photo-acoustic excitation optical power, the utility model experiment device for teaching verified to photo-acoustic excitation with this
The calibration-free measurement capability of optical power change.
Fig. 3 is the first harmonic photoacoustic signal of measurement.Acetylene/nitrogen mixed gas of 100ppm is passed through into photoacoustic cell,
First harmonic photoacoustic signal amplitude under wavelength modulation is measured using phase lock amplifying technology.
Fig. 4 is the second harmonic photoacoustic signal of measurement.Acetylene/nitrogen mixed gas of 100ppm is passed through into photoacoustic cell,
Second harmonic photoacoustic signal amplitude under wavelength modulation is measured using phase lock amplifying technology.
Fig. 5 is the relation curve that the 2f/1f value of measurement changes with acetylene gas concentration.Be passed through into photoacoustic cell 0ppm,
Acetylene/nitrogen mixed gas of 20ppm, 40ppm, 60ppm, 80ppm, 100ppm are measured simultaneously using phase lock amplifying technology
Second harmonic and first harmonic photoacoustic signal amplitude at 1532.83nm wavelength, second harmonic signal amplitude is divided by first harmonic
There is preferable linear relationship between the obtained 2f/1f value of signal amplitude and gas concentration, responsiveness is obtained by linear fit
For 0.005531ppm-1。
Fig. 6 is the 2f/1f value of measurement with the relation curve of laser power variation.The second of 100ppm is passed through into photoacoustic cell
Alkynes/nitrogen mixed gas changes photo-acoustic excitation optical power by changing winding circle number of the optical fiber on Optical Fiber Winding device 11.It surveys
Test result shows that 2f/1f value hardly follows the change of light source power and changes, to demonstrate the utility model teaching experiment dress
Set the calibration-free measurement capability to photo-acoustic excitation optical power change.
Above description is merely a prefered embodiment of the utility model, it is noted that comes for those skilled in the art
It says, various modifications and changes may be made to the present invention.Within the spirit and principle of the utility model, made any to repair
Change, equivalent replacement, improvement etc., should be included within the scope of protection of this utility model.
Claims (5)
1. a kind of tunable laser light acousto-optic composes trace gas detection experiment device for teaching, which is characterized in that described is tunable
Laser Photoacoustic Spectroscopy trace gas detection experiment device for teaching includes tunable laser source (1), optics collimator (2), optoacoustic
Pond (3), photothermal conversion element (4), microphone (5), air inlet (6), gas outlet (7), light source driving (8), signal acquisition and place
Manage circuit (9) and computer (10)；Tunable laser source (1), optics collimator (2), photoacoustic cell (3) are sequentially connected in series, transaudient
Device (5), Signal acquiring and processing circuit (9) and light source driving (8) are sequentially connected in series；Photothermal conversion element (4) is installed on photoacoustic cell
(3) non-arrival end；Microphone (5) is installed on photoacoustic cell (3) outer wall；Signal acquiring and processing circuit (9) and computer (10) phase
Even；Light source drives (8) to receive the sinusoidal modulation signal of Signal acquiring and processing circuit (9) generation to tunable laser source (1)
Carry out current-modulation；The laser of tunable laser source (1) transmitting is incident in photoacoustic cell (3) through optics collimator (2), finally
It is irradiated on photothermal conversion element (4)；Photoacoustic cell (3) is equipped with air inlet (6) and gas outlet (7)；Microphone (5) is mounted on light
On sound pond (3), for detecting the photoacoustic signal generated in photoacoustic cell (3)；The signal input part of Signal acquiring and processing circuit (9)
It is connected with microphone (5), carries out Digital Signal Processing after the photoacoustic signal of acquisition microphone (3) detection；Computer (10) and letter
Number acquisition is connected with processing circuit (9), for setting signal acquisition and processing circuit (9) running parameter and to signal acquisition with
The gas concentration measurement of processing circuit (9) output is shown.
2. tunable laser light acousto-optic according to claim 1 composes trace gas detection experiment device for teaching, feature exists
In the tunable laser source (1) is the narrow linewidth semiconductor tunable laser light source of tunable wave length.
3. tunable laser light acousto-optic according to claim 1 or 2 composes trace gas detection experiment device for teaching, feature
It is, the photothermal conversion element (4) is the device with high photothermal conversion efficiency.
4. tunable laser light acousto-optic according to claim 1 or 2 composes trace gas detection experiment device for teaching, feature
It is, the Signal acquiring and processing circuit (9) is the signal that can measure first harmonic and second harmonic signal amplitude simultaneously
Detector.
5. tunable laser light acousto-optic according to claim 3 composes trace gas detection experiment device for teaching, feature exists
In the Signal acquiring and processing circuit (9) is the signal inspection that can measure first harmonic and second harmonic signal amplitude simultaneously
Survey device.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109490216A (en) * | 2019-01-07 | 2019-03-19 | 大连理工大学 | A kind of the Laser Photoacoustic Spectroscopy trace gas detection instrument and method of calibration-free |
| CN111220513A (en) * | 2020-03-23 | 2020-06-02 | 石家庄铁道大学 | Haze detection device and method based on digital phase locking and photoacoustic spectroscopy technology |
| CN112903595A (en) * | 2021-01-25 | 2021-06-04 | 安徽宝龙环保科技有限公司 | Online multicomponent gas analysis photoacoustic spectrometer |
| CN113533249A (en) * | 2021-06-09 | 2021-10-22 | 山东师范大学 | N2O detection system and method based on open optical path and wavelength modulation |
-
2019
- 2019-01-07 CN CN201920024251.1U patent/CN209372684U/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109490216A (en) * | 2019-01-07 | 2019-03-19 | 大连理工大学 | A kind of the Laser Photoacoustic Spectroscopy trace gas detection instrument and method of calibration-free |
| CN109490216B (en) * | 2019-01-07 | 2021-02-19 | 大连理工大学 | Calibration-free laser photoacoustic spectrum trace gas detection instrument and method |
| CN111220513A (en) * | 2020-03-23 | 2020-06-02 | 石家庄铁道大学 | Haze detection device and method based on digital phase locking and photoacoustic spectroscopy technology |
| CN112903595A (en) * | 2021-01-25 | 2021-06-04 | 安徽宝龙环保科技有限公司 | Online multicomponent gas analysis photoacoustic spectrometer |
| CN112903595B (en) * | 2021-01-25 | 2022-07-08 | 安徽宝龙环保科技有限公司 | Online multicomponent gas analysis photoacoustic spectrometer |
| CN113533249A (en) * | 2021-06-09 | 2021-10-22 | 山东师范大学 | N2O detection system and method based on open optical path and wavelength modulation |
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