CN108872147B - Laser generating device and gas concentration detection device based on TD L AS technology - Google Patents
Laser generating device and gas concentration detection device based on TD L AS technology Download PDFInfo
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- CN108872147B CN108872147B CN201810649214.XA CN201810649214A CN108872147B CN 108872147 B CN108872147 B CN 108872147B CN 201810649214 A CN201810649214 A CN 201810649214A CN 108872147 B CN108872147 B CN 108872147B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
Abstract
The invention relates to a laser generating device, in particular to a laser generating device and a gas concentration detection device based on a TD L AS technology, and the laser generating device based on the TD L AS technology comprises a main control unit, a modulation signal generating unit, a sawtooth wave signal generating unit, a signal superposition unit, a voltage-current conversion unit and a laser.
Description
Technical Field
The present invention relates to a laser generator, and more particularly, to a laser generator and a gas concentration detection device based on TD L AS technology.
Background
TD L AS (Tunable Diode L AS absorber spectroscopy) is a non-contact measurement method in which a photodetector and other elements are not in contact with the gas to be analyzed, and TD L AS is a non-contact, remote and high-precision detection technique based on Lambert beer's law, which uses laser wavelength modulation to pass through a characteristic absorption region of the gas to be detected, and the laser beam is absorbed by the gas to be detected to cause attenuation of laser intensity, the attenuation degree of which is proportional to the content of the gas to be detected, and the concentration of the gas to be detected can be obtained through the attenuation information of the laser intensity, so that the gas concentration value can be measured with high resolution, high selectivity and the like.
However, in the prior art, in the gas detection process by using the TD L AS technology, the detection accuracy of the detection system is affected by the temperature change of the laser, the pressure variation of the gas chamber, and the interference of other gases, so how to further improve the detection accuracy becomes a problem to be solved in the field.
Disclosure of Invention
The invention aims to solve the technical problem of low detection precision of a detection system in the prior art, and provides a laser generating device and a gas concentration detection device based on a TD L AS technology.
The invention provides a laser generating device based on a TD L AS technology, which comprises a main control unit, a modulation signal generating unit, a sawtooth wave signal generating unit, a signal superposition unit, a voltage-current conversion unit and a laser, wherein:
the modulation signal generating unit is used for generating a sine wave signal with a preset frequency;
the sawtooth wave signal generating unit is used for generating a sawtooth wave signal with a preset frequency;
the main control unit is respectively connected with the modulation signal generating unit and the sawtooth wave signal generating unit and is used for driving the modulation signal generating unit and the sawtooth wave signal generating unit to respectively generate a modulation sine wave with a specific frequency and a sawtooth wave signal with a specific frequency;
the signal superposition unit is respectively connected with the modulation signal generation unit and the sawtooth wave signal generation unit and is used for superposing the sine wave signal and the sawtooth wave signal to obtain a voltage driving signal and outputting the voltage driving signal to the voltage current conversion unit;
the voltage and current conversion unit is connected with the signal superposition unit and is used for converting the voltage driving signal into a current driving signal;
and a laser for generating a laser beam of a specific wavelength according to the current driving signal.
According to the laser generating device based on the TD L AS technology, the signal superposition unit superposes a sawtooth wave signal and a plurality of sections of sine wave signals with different frequencies to serve AS a voltage driving signal of a measuring period, the voltage driving signal is converted into a current driving signal required by a laser through the voltage current conversion unit, the laser generates a laser beam with a specific wavelength, and detection light and reference light are generated through the laser generating device, so that the complexity of instrument and equipment is greatly reduced, the cost is saved, the laser beam is a plurality of sections of lasers with different frequencies, only one laser beam achieves the effect of differential detection, the accurate value of gas concentration detection is effectively improved, and the influence of background noise is removed to a greater extent.
The invention also provides an embodiment of a gas concentration detection device based on the TD L AS technology, which comprises a detector, a gas concentration calculation unit and the laser generation device, wherein:
the detector is used for detecting the gas to be detected which selectively absorbs the laser beam in a measurement period and obtaining a gas detection value;
and the gas concentration calculating unit is used for obtaining the concentration of the gas to be detected according to the gas detection value of the detector.
The invention also provides an embodiment of a gas concentration detection device based on the TD L AS technology, which comprises a detector, a gas concentration calculation unit and the gas concentration detection device, wherein:
the detector is used for detecting the gas to be detected which selectively absorbs three sections of laser beams with different frequencies in a measurement period to obtain gas detection values corresponding to the three laser beams with different frequencies;
and the gas concentration calculating unit is used for obtaining gas concentration values corresponding to three different frequencies according to the gas detection values corresponding to the three different frequencies, and averaging the gas concentration values corresponding to the three different frequencies to obtain the concentration of the gas to be detected.
The gas concentration detection device based on the signal TD L AS technology of the invention superposes a sawtooth wave signal and a plurality of sections of sine wave signals with different frequencies through a signal superposition unit to be used AS a voltage driving signal of a measurement period, after the voltage driving signal is converted into a current driving signal required by a laser through a voltage current conversion unit, the laser generates a laser beam with a specific wavelength, and a detection light and a reference light are generated through a laser generating device, thereby greatly reducing the complexity of instrument and equipment and saving the cost.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment of a laser generating device based on TD L AS technology according to the present invention.
Fig. 2 is a schematic diagram of signal superposition of a signal superposition unit in the laser generating device based on the TD L AS technology.
Fig. 3 is a schematic structural diagram of another embodiment of the laser generating device based on TD L AS technology according to the present invention.
Fig. 4 is a schematic structural diagram of an embodiment of a gas concentration detection apparatus based on TD L AS technology according to the present invention.
In the figure: the device comprises a laser generating device 1, a main control unit 11, a modulation signal generating unit 12, a sawtooth wave signal generating unit 13, a signal superposition unit 14, a voltage-current conversion unit 15, a laser 16, a temperature control unit 17, a detector 2 and a gas concentration calculating unit 3.
Detailed Description
The following further describes embodiments of the present invention with reference to the drawings.
In order to solve the technical problem of low measurement accuracy in the prior art, an embodiment of the present invention provides a laser generator 1 based on TD L AS technology, and the laser generator 1 is used for detecting the concentration of a gas to further solve the technical problem proposed in the background art.
The invention provides a laser generating device 1 based on a TD L AS technology, AS shown in FIG. 1, the laser generating device 1 comprises a main control unit 11, a modulation signal generating unit 12, a sawtooth wave signal generating unit 13, a signal superposition unit 14, a voltage-current conversion unit 15 and a laser 16, wherein the modulation signal generating unit 12 is used for generating a sine wave signal with a preset frequency, the sawtooth wave signal generating unit 13 is used for generating a sawtooth wave signal with a preset frequency, the main control unit 11 is respectively connected with the modulation signal generating unit 12 and the sawtooth wave signal generating unit 13 and is used for driving the modulation signal generating unit and the sawtooth wave signal generating unit to respectively generate a modulation sine wave with a specific frequency and a sawtooth wave signal with a specific frequency, the signal superposition unit 14 is respectively connected with the modulation signal generating unit 12 and the sawtooth wave signal generating unit 13 and is used for superposing the sine wave signal and the sawtooth wave signal to obtain a voltage driving signal which is output to the voltage-current conversion unit 15, the voltage-current conversion unit 15 is connected with the signal superposition unit 14 and is used for converting the voltage driving signal into a current driving signal, the laser 16 is used for generating a voltage driving signal and is used for generating a laser beam according to specific technical component combination of the present invention, and the present invention can be implemented according to the specific technical knowledge and the above.
In specific implementation, the main control unit 11 may be an ARM main controller, the modulation signal generating unit 12 may be a DDS chip, the sawtooth wave signal generating unit 13 is a D/a digital-to-analog converter, the signal superimposing unit 14 is an operational amplifier chip with an independent enable terminal, the voltage-current converting unit 15 is implemented by an MOSFET, and the laser 16 is a distributed feedback laser.
The laser generator 1 of the present invention operates according to the following principle: the main control unit 11 controls the sawtooth wave signal generating unit 13 to send sawtooth wave signals to the signal superposition unit 14, the frequency of the sawtooth wave signals is 1-100Hz, and the main control unit 11 controls the modulation signal generating unit 12 to send sine wave signals to the signal superposition unit 14; the sawtooth wave signal and the sine wave signal are superposed together by the signal superposition unit 14 and then output to obtain a voltage driving signal, and the voltage and current conversion unit 15 converts the voltage driving signal into a current driving signal required by the laser 16 and then the laser 16 generates a laser beam with a specific wavelength. The frequency of the sawtooth signal is much smaller than the frequency of the sine wave signal, which in this embodiment is used to determine the wavelength of the laser beam and the sine wave signal is used to modulate the frequency of the laser beam.
In the present embodiment, the sine wave signal generated by the modulation signal generation unit 12 includes at least two sections of sine waves with different frequencies in one measurement period. Specifically, one measurement cycle is a fixed time length when the laser generating apparatus 1 performs gas concentration measurement. In this embodiment, the modulation signal generating unit 12 includes three sections of sine waves with different frequencies in one measurement period, and the three sections of sine waves with different frequencies are continuous and have the same generation time. Specifically, the frequency values of the three sine waves with different frequencies are increased in value or decreased in value within one measurement period.
In a specific implementation, the main control unit 11 controls the sawtooth wave signal generating unit 13 to send a sawtooth wave signal to the signal superimposing unit 14, and the frequency of the sawtooth wave generated by the sawtooth wave signal generating unit 13 is 10Hz, the main control unit 11 controls the modulated signal generating unit 12 to send a sine wave signal to the signal superimposing unit 14, the sine wave is a modulated signal, and the modulated signal generating unit 12 generates sine wave signals with frequencies of 4.5KHz, 5KHz and 5.5KHz respectively corresponding to three consecutive periods of the sawtooth wave signal, a schematic diagram of signal superimposing is shown in fig. 2, the sine wave signal with the frequency of 4.5KHz is superimposed with L segments of sawtooth wave signals, the sine wave signal with the frequency of 5KHz is superimposed with M segments of sawtooth wave signals, the sine wave signal with the frequency of 5.5KHz is superimposed with H segments of sawtooth wave signals, the duration of the three segments of signals constitutes a measurement period, that is, a voltage driving signal generated by the signal superimposing unit 14 is a sine wave signal with three consecutive periods of sinusoidal signals superimposed with three frequencies, that is a measurement period is three periods of sawtooth wave signal complexity, that the voltage driving unit 15 converts a voltage driving signal into a laser beam driving signal corresponding to a laser beam driving device, and a laser beam measuring device which greatly reduces the frequency of a laser beam driving device, and the laser beam measuring device which generates a laser beam with a laser beam driving device which generates a laser beam with a frequency of a laser beam with a frequency which corresponds to a laser beam.
In the specific implementation, since the temperature of the laser generating device 1 is a great interference factor in the gas concentration detection process, the accuracy of the laser generating device 1 in detecting the gas concentration is improved. As shown in fig. 3, the laser generator 1 further includes a temperature control unit 17, and the temperature control unit 17 is connected to the main control unit 11 and is configured to detect and maintain the temperature of the laser 16. The specific design of the temperature control unit 17 is not limited in this embodiment, and a temperature detection control scheme that is common in the prior art is selected. Specifically, the temperature control unit 17 may select a TEC temperature control module to maintain the temperature change in the laser generator 1 within a certain range, thereby ensuring the accuracy of gas concentration detection.
The laser generating device based on the TD L AS technology has the advantages that the signal superposition unit superposes sawtooth wave signals and multi-section sine wave signals with different frequencies to serve AS voltage driving signals of a measuring period, the voltage driving signals are converted into current driving signals required by a laser through the voltage current conversion unit, the laser generates laser beams with specific wavelengths, detection light and reference light are generated through the laser generating device, complexity of instrument and equipment is greatly reduced, cost is saved, the laser beams are multi-section lasers with different frequencies, only one laser beam achieves the effect of differential detection, the accurate value of gas concentration detection is effectively improved, the temperature control unit detects and maintains the temperature of the laser, and influence of background noise is removed to a greater extent.
The invention also provides a gas concentration detection device based on the TD L AS technology, AS shown in FIG. 4, the gas concentration detection device comprises a detector 2, a gas concentration calculation unit 3 and a laser generation device 1 AS in the above embodiment, wherein the detector 2 is used for detecting gas to be detected which selectively absorbs laser beams in a measurement period and obtaining gas detection values, the gas concentration calculation unit 3 is used for obtaining the concentration of the gas to be detected according to the gas detection values of the detector 2, in the gas concentration detection device, when sine wave signals comprise three sections of sine waves with different frequencies, the detector 2 is used for detecting the gas to be detected which selectively absorbs three sections of laser beams with different frequencies in a measurement period and obtaining gas detection values corresponding to the three laser beams with different frequencies, the gas concentration calculation unit 3 is used for obtaining gas concentration values corresponding to the three different frequencies according to the gas detection values corresponding to the three different frequencies and obtaining an average value of the gas concentration values corresponding to the three different frequencies, the detector 2 is used for converting the laser beam signals into electric signals, and since the laser beam signals are derived from voltage driving signals after being superimposed, the laser beam signals are used for obtaining the concentration values of the gas to be detected by the harmonic wave lines of the gas to be detected, the gas concentration values of the gas to be detected which are not repeated.
In a specific implementation, a main control unit 11 in a laser generation device 1 controls a sawtooth wave signal generation unit 13 to send a sawtooth wave signal to a signal superposition unit 14, the frequency of a sawtooth wave generated by the sawtooth wave signal generation unit 13 is 10Hz, the main control unit 11 controls a modulation signal generation unit 12 to send a sine wave signal to the signal superposition unit 14, the sine wave signal is a modulation signal, the modulation signal generation unit 12 correspondingly generates sine wave signals with the frequencies of 4.5KHz, 5KHz and 5.5KHz respectively on three continuous periods of the sawtooth wave signal, the sine wave signal with the frequency of 4.5KHz is superposed with L sections of sawtooth wave signals, the sine wave signal with the frequency of 5KHz is superposed with M sections of sawtooth wave signals, the sine wave signal with the frequency of 5.5KHz is superposed with H sections of sawtooth wave signals to form a measurement period, a voltage driving signal generated by the signal superposition unit 14 comprises two parts, one part is a sawtooth wave with the frequency of 10Hz, the other part is a sine wave, the three parts are respectively 4.5KHz, 5.5KHz and 5.5.5 KHz, the voltage driving signal is a sawtooth wave, the other part is a sawtooth wave, the three parts are a sawtooth wave signal, the sawtooth wave driving signal, the three parts are used for converting the sawtooth wave signal generated by a laser beam in a laser beam, the sawtooth wave signal generated in a laser beam, the sawtooth wave signal to obtain a laser beam, the laser beam is obtained by the laser beam, the laser beam is obtained by the laser beam, the.
According to the gas concentration detection device based on the TD L AS technology, a laser generator generates a bundle of laser with different multi-section frequencies to detect the concentration of gas to be detected, a detector obtains a gas detection value under each section of frequency by using a second harmonic detection technology, a gas concentration calculation unit obtains gas concentration values corresponding to a plurality of different frequencies according to the gas detection values corresponding to the plurality of sections of different frequencies, and then the gas concentration values are averaged to obtain the concentration of the gas to be detected, so that low-frequency noise interference is reduced, and the measurement precision is improved.
The foregoing embodiments and description have been presented only to illustrate the principles and preferred embodiments of the invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention as hereinafter claimed.
Claims (8)
1. The laser generating device based on the TD L AS technology is characterized by comprising a main control unit, a modulation signal generating unit, a sawtooth wave signal generating unit, a signal superposition unit, a voltage-current conversion unit and a laser, wherein:
the modulation signal generating unit is used for generating a sine wave signal with a preset frequency, and the sine wave signal comprises at least two sections of sine waves with different frequencies in one measuring period;
the sawtooth wave signal generating unit is used for generating a sawtooth wave signal with a preset frequency;
the main control unit is respectively connected with the modulation signal generating unit and the sawtooth wave signal generating unit and is used for driving the modulation signal generating unit and the sawtooth wave signal generating unit to respectively generate a modulation sine wave with a specific frequency and a sawtooth wave signal with a specific frequency;
the signal superposition unit is respectively connected with the modulation signal generation unit and the sawtooth wave signal generation unit, and is used for superposing the sine wave signal and the sawtooth wave signal to obtain a voltage driving signal and outputting the voltage driving signal to the voltage current conversion unit;
the voltage and current conversion unit is connected with the signal superposition unit and is used for converting the voltage driving signal into a current driving signal;
the laser is used for generating a laser beam with a specific wavelength according to the current driving signal.
2. The laser generating apparatus according to claim 1, wherein the sine wave signal includes three pieces of sine waves having different frequencies in one measurement period.
3. The laser generating apparatus according to claim 2, wherein the frequency values of the three sine waves with different frequencies are increased in value or decreased in value within one measurement period.
4. The laser generating apparatus of claim 1, further comprising a temperature control unit connected to the main control unit for detecting and maintaining the temperature of the laser.
5. The laser generating apparatus of claim 1, wherein the laser is a distributed feedback laser.
6. The laser generating device as claimed in claim 1, wherein the signal superimposing unit is an operational amplifier chip with an independent enable terminal.
7. A gas concentration detection apparatus based on TD L AS technology, comprising a detector, a gas concentration calculation unit, and a laser light generation apparatus according to any one of claims 1 to 6, wherein:
the detector is used for detecting the gas to be detected which selectively absorbs the laser beam in a measurement period and obtaining a gas detection value;
and the gas concentration calculating unit is used for obtaining the concentration of the gas to be detected according to the gas detection value of the detector.
8. A gas concentration detection apparatus based on TD L AS technology, comprising a detector, a gas concentration calculation unit, and the laser light generation apparatus of claim 2 or 3, wherein:
the detector is used for detecting the gas to be detected which selectively absorbs three sections of laser beams with different frequencies in a measurement period to obtain gas detection values corresponding to the three laser beams with different frequencies;
the gas concentration calculating unit is used for obtaining gas concentration values corresponding to three different frequencies according to the gas detection values corresponding to the three different frequencies, and averaging the gas concentration values corresponding to the three different frequencies to obtain the concentration of the gas to be detected.
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| CN110380334A (en) * | 2019-07-23 | 2019-10-25 | 南京霍普斯科技有限公司 | A kind of laser driving circuit with protection based on TDLAS |
| CN113109292B (en) * | 2020-01-13 | 2022-04-29 | 中国石油大学(华东) | Carbon isotope detection system based on TDLAS and detection method thereof |
| CN111289465B (en) * | 2020-03-24 | 2021-12-07 | 中国科学院长春光学精密机械与物理研究所 | TDLAS gas detection system and driving method thereof |
| CN111398216A (en) * | 2020-05-20 | 2020-07-10 | 中南大学 | Multi-frequency modulation method for gas concentration detection, gas concentration detection method and system |
| CN113097862B (en) * | 2021-04-16 | 2022-08-16 | 中国科学院长春光学精密机械与物理研究所 | Driving signal generating device |
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