CN109856078B - Optical gas detection system - Google Patents
Optical gas detection system Download PDFInfo
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- CN109856078B CN109856078B CN201910039538.6A CN201910039538A CN109856078B CN 109856078 B CN109856078 B CN 109856078B CN 201910039538 A CN201910039538 A CN 201910039538A CN 109856078 B CN109856078 B CN 109856078B
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Abstract
The invention relates to the field of gas detection, in particular to an optical gas detection system. An optical gas detection system comprising: a laser for generating a first laser beam; an optical gas absorption cell; an optical lens; a laser center wavelength locking device; the first laser beam penetrates through the optical lens to generate a second laser beam emitted to the optical gas absorption cell, and the first laser beam is reflected by the optical lens to generate a third laser beam emitted to the laser central wavelength locking device; the second laser beam is used for detecting the concentration of the gas to be detected, the laser center wavelength locking device is used for calibrating the center wavelength of the laser by using the third laser beam, and the intensity of the second laser beam is greater than that of the third laser beam. According to the optical gas detection system, the center wavelength of the laser is measured and calibrated through the laser center wavelength locking device, and the accuracy of concentration measurement is guaranteed.
Description
Technical Field
The invention relates to the field of gas detection, in particular to an optical gas detection system.
Background
When the infrared spectrum analysis technology is applied to gas detection of the gas to be detected, the concentration of the gas to be detected can be calculated according to the absorption intensity of the gas to be detected on an infrared light source. In the process of using the laser applied to the infrared spectroscopic analysis technology, the central wavelength of the laser changes due to environmental change or device aging, so that the gas concentration measurement is inaccurate.
Disclosure of Invention
Based on the optical gas detection system, the central wavelength of the laser can be calibrated in real time, and the accuracy of concentration measurement is guaranteed.
An optical gas detection system comprising:
a laser for generating a first laser beam;
the optical gas absorption cell contains gas to be detected;
an optical lens; and
the laser center wavelength locking device is connected with the laser;
wherein the first laser beam transmits through the optical lens to generate a second laser beam directed to the optical gas absorption cell, and the first laser beam is reflected by the optical lens to generate a third laser beam directed to the laser center wavelength locking device; and
the second laser beam is used for detecting the concentration of the gas to be detected, the laser center wavelength locking device is used for calibrating the center wavelength of the laser by using the third laser beam, and the intensity of the second laser beam is greater than that of the third laser beam.
In one embodiment, the optical gas absorption cell comprises:
the accommodating cavity is used for accommodating gas to be detected; and
the window sheet is arranged on the side wall of the accommodating cavity and is used as the optical lens;
the first laser beam penetrates through the window sheet to generate a second laser beam emitted to the accommodating cavity, and meanwhile, the first laser beam is reflected by the window sheet to generate a third laser beam emitted to the laser central wavelength locking device.
The calibration of the central wavelength of the laser can be carried out by utilizing the useless light reflected by the window sheet on the premise of not changing the structure of the original optical gas absorption cell.
In one embodiment, the window sheet is a wedge-shaped lens, so that the optical interference phenomenon is avoided.
In one embodiment, the laser center wavelength locker comprises:
a measurement module containing a reference gas; the measuring module is used for receiving and absorbing the third laser beam to obtain the real-time central wavelength of the laser;
the analysis module comprises an analysis unit and a storage unit, the analysis unit is connected with the measurement module, and the storage unit stores standard central wavelength;
the control module is respectively connected with the laser and the analysis module so as to control the real-time central wavelength of the laser in real time;
the analysis module receives the real-time central wavelength obtained by the measurement module and compares the real-time central wavelength with the standard central wavelength to obtain the deviation of the real-time central wavelength relative to the standard central wavelength; and
a control module controls the laser to lock the real-time center wavelength to the standard center wavelength based on the received deviation.
In one embodiment, the measurement module comprises:
a focusing lens for focusing the third laser beam.
In one embodiment, the measurement module further comprises:
and the infrared detector is used for detecting the third laser beam absorbed by the reference gas.
In one embodiment, the reference gas and the gas to be measured have the same composition.
In one embodiment, the gas concentration in the measurement module is set according to the range of the system, the optical path length of the gas module to be measured and the length of the measurement module.
In one embodiment, the laser is a semiconductor laser.
In one embodiment, the control module is a semiconductor refrigeration module for controlling the center wavelength of the laser by controlling the temperature of the laser.
In one embodiment, the laser is a TO package laser, is low in cost and is suitable for mass application.
In the optical gas detection system, the optical lens respectively transmits and reflects the first laser beam emitted by the laser to generate the corresponding second laser beam and the corresponding third laser beam, the second laser beam is used for being incident to the optical gas absorption cell to detect the concentration of the gas to be detected, and the third laser beam is used for being incident to the laser center wavelength locking device to measure and calibrate the center wavelength of the laser, so that the optical gas detection system can monitor and correct the wavelength drift of the laser in the using process in real time, the accuracy of the measurement result is ensured, and the intensity of the second laser beam is greater than that of the third laser beam, thereby avoiding the waste of laser energy.
Drawings
FIG. 1 is a schematic diagram of an optical gas detection system in one embodiment;
FIG. 2 is a schematic diagram of a center wavelength locker of a laser according to an embodiment;
FIG. 3 is a schematic diagram of an optical gas detection system in another embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not delimit the invention.
Fig. 1 is a schematic structural diagram of an optical gas detection system in an embodiment, and as shown in fig. 1, an optical gas detection system 10 includes a laser 100, an optical gas absorption cell 200, an optical lens 300, and a laser center wavelength locking device 400, where the laser 100 can generate a first laser beam, the optical gas absorption cell 200 contains a gas to be detected, and the laser center wavelength locking device 400 is connected to the laser 100 and can be used to measure and calibrate the center wavelength of the laser 100 in real time, so as to lock the center wavelength of the laser 100 at a standard center wavelength; the first laser beam is incident on the optical lens 300, is transmitted and reflected by the optical lens, and is respectively transmitted to generate a second laser beam and is reflected to generate a third laser beam, the second laser beam is incident on the optical gas absorption cell 200 to detect the concentration of the gas to be detected, and the third laser beam is incident on the laser center wavelength locking device 400 to measure the center wavelength of the laser 100, and correspondingly adjust the center wavelength of the laser 100 to the standard center wavelength.
Specifically, the laser 100 is selected according to the gas to be detected, and it needs to be satisfied that when the actual center wavelength of the laser 100 is at the standard center wavelength, the absorption of the gas to be detected to the second laser beam (i.e., the laser emitted by the laser 100) is strongest; the optical gas absorption cell 200 has an incident mirror and an exit mirror, the second laser beam can be reflected by the incident mirror and the reflection mirror for multiple times after entering the optical gas absorption cell 200, and is transmitted in the optical gas absorption cell 200 by multiple times of return transmission, during which the second laser beam is absorbed by the gas to be measured, and the concentration of the gas to be measured can be obtained by interpretation according to the absorption intensity.
Further, the intensity of the second laser beam is greater than the intensity of the third laser beam, and the intensity may be power or energy, and the intensity is power when the laser 100 is a continuous wave laser and the intensity is energy when the laser 100 is a pulse laser; the second laser beam is a laser beam which transmits through the optical lens when the first laser beam irradiates the optical lens 300, the third laser beam is a laser beam which is reflected by the optical lens when the first laser beam irradiates the optical lens 300, that is, the second laser beam and the third laser beam are generated simultaneously when the first laser beam irradiates the optical lens, the sum of the intensity of the corresponding second laser beam and the intensity of the corresponding third laser beam is less than or equal to the intensity of the first laser beam, and considering that a certain light loss is generated when the first laser beam irradiates the optical lens, the sum of the intensity of the second laser beam and the intensity of the third laser beam is less than the intensity of the first laser beam; when the third laser beam is used for measuring and calibrating the central wavelength of the laser, the requirement on the intensity of the third laser beam is not high, and meanwhile, the second laser beam is reflected for multiple times in the process of propagating the optical gas absorption cell 200, so that the energy loss is large, and higher intensity is required. Therefore, the intensity of the second laser beam is higher than that of the third laser beam, which ensures the accuracy of concentration measurement and avoids unnecessary energy waste.
In one embodiment, the optical lens 300 is a window sheet of the optical gas absorption cell 200. The optical gas absorption cell 200 includes an accommodating chamber for accommodating a gas to be measured and a window sheet disposed on a sidewall of the accommodating chamber to serve as the optical lens 300; the first laser beam penetrates through the window sheet to generate a second laser beam emitted to the accommodating cavity, and the first laser beam is reflected by the window sheet to generate a third laser beam emitted to the laser center wavelength locking device. In general, a light beam for measuring the concentration of a gas to be measured needs to enter the optical gas absorption cell 200 through a window sheet, and inevitably undergoes reflection during the passage through the window sheet, the first laser beam is reflected by the window sheet to generate a third laser beam, and the third laser beam is used for center wavelength locking of the laser 100, avoiding waste of optical energy.
Specifically, the window sheet may be coated with a specific optical film to control the reflectivity and transmittance of the window sheet, thereby controlling the intensity ratio of the second laser beam and the third laser beam.
It should be noted that the optical lens 300 can be disposed independently of the optical gas absorption cell 200, and when disposed independently, the installation and adjustment are more convenient, and the disassembly and replacement are also convenient.
In one embodiment, the window piece is a wedge-shaped lens. The wedge-shaped lens is provided with a first surface and a second surface, the first surface and the second surface are in a non-parallel state, the first laser beam enters the first surface, the second laser beam is formed by transmission on the first surface, the first laser beam is reflected by the first surface to generate the third laser beam, the second laser beam is transmitted to the second surface of the wedge-shaped lens, the second laser beam is transmitted and reflected by the second laser beam on the second surface again to form a fourth laser beam and a fifth laser beam respectively, the fourth laser beam enters the optical gas absorption cell 200 to measure the concentration of the gas to be measured, the fifth laser beam is turned back to the first plane and is transmitted by the first plane again to generate the sixth laser beam, the first surface and the second surface of the wedge-shaped lens are not parallel, and the third laser beam and the sixth laser beam are not interfered, so that the measurement accuracy is guaranteed.
FIG. 2 is a schematic diagram of a laser center wavelength locker, according to an embodiment, as shown in FIG. 2, the laser center wavelength locker 400 may include a measurement module 410, an analysis module 420, and a control module 430; wherein the measurement module 410 has a reference gas chamber, a reference gas with a certain concentration is contained in the reference gas chamber, the third laser beam propagates to the measurement module 410, propagates in the reference gas chamber, and is absorbed by the reference gas to obtain the wavelength of the third laser beam, so as to obtain the real-time center wavelength of the laser 100; the analysis module 420 includes an analysis unit and a storage unit, the analysis unit is connected to the measurement module 410, and can accept the real-time center wavelength measured by the measurement module 410, meanwhile, the storage unit stores a standard center wavelength, and the analysis module 420 can compare the real-time center wavelength with the standard center wavelength and calculate a deviation of the real-time center wavelength with respect to the standard center wavelength; the control module 430 is connected to the laser 100 and the analysis module 420, respectively, and is capable of receiving the deviation obtained by the analysis module 420, and controlling the laser 100 according to the deviation to control the real-time center wavelength of the laser 100 in real time, and lock the real-time center wavelength to the standard center wavelength. Specifically, in the actual using process, the laser center wavelength locking device 400 may be integrated with the optical gas absorption cell 200, or may be separately disposed, and may be determined according to the actual assembly requirement.
In one embodiment, the measurement module 410 includes a focusing lens and an infrared detector; the focusing lens is used for converging the third laser beam and focusing the third laser beam on the surface of the infrared detector, so that the system fault tolerance of the optical gas detection system 10 is enhanced; and the infrared detector receives the third laser beam absorbed by the reference gas and detects the intensity of the third laser beam so as to acquire the central wavelength of the third laser beam.
In one embodiment, the reference gas has the same composition as the gas to be measured. It should be noted that the reference gas and the gas to be measured do not need to be gases with a single component, and only need to ensure that both gases react with the laser, for example, the gas component to be measured is ammonia gas, and the reference gas and the gas to be measured may both be single ammonia gas or mixed gas of nitrogen gas and ammonia gas, where nitrogen gas is background gas, does not react with laser light, does not affect measurement accuracy, or may use two different background gases to respectively form two mixed gases.
In one embodiment, the reference gas concentration in the measurement module 410 can be set according to the optical path length of the optical gas absorption cell 200 and the optical path length of the reference gas chamber of the measurement module 410. For example, taking a laser ammonia gas detection system as an example, the range of the laser ammonia gas detection system is 0 to 100ppm, the optical path length of the optical gas absorption cell of the laser ammonia gas detection system is 1000mm, and the optical path length of the reference gas chamber is 5mm, then the concentration of the reference gas in the reference gas chamber = (the upper limit of the concentration of the gas to be detected = 0.5) = the optical path of the optical gas absorption cell 200/the optical path of the reference gas chamber =100 × 0.5 × 1000/5=10000ppm.
In one embodiment, the laser 100 is a TO package laser, and the outgoing laser of the TO package laser is directly incident TO the optical detection system without transmission through an optical fiber, so that the laser requirements of each wavelength band can be met, the integration is easier, and the TO package laser is moderate in price and suitable for mass application. In one embodiment, the laser 100 is a semiconductor laser, which has a small size, a long lifetime, and a low price.
In one embodiment, the control module 430 may be a semiconductor refrigeration module operable to control the temperature of the laser 100 to control its corresponding real-time center wavelength. Specifically, the emission wavelength of the semiconductor laser generally increases with the temperature rise, and the temperature drift coefficient of the wavelength is generally 0.3 nm/K-0.4 nm/K, so that the temperature of the semiconductor laser can be controlled through the semiconductor refrigeration module, and the corresponding real-time central wavelength is adjusted to the standard central wavelength.
The optical gas detection system of the present application is described in detail below with reference to specific applications:
FIG. 3 is a block diagram of an optical gas detection system in another embodiment, as shown in FIG. 3, an optical gas detection system includes a laser, an optical gas absorption cell, a window sheet, and a laser center wavelength locker (indicated by a dashed box in the figure), wherein the window sheet is a part of the optical gas absorption cell and is used for incidence of a laser beam, and the laser center wavelength locker includes a focusing lens, a reference gas, and an infrared detector; specifically, the laser emits a first laser beam, the first laser beam is transmitted to the window sheet, the second laser beam is generated through transmission of the window sheet, and meanwhile the first laser beam is reflected by the window sheet to generate a third laser beam. The second laser beam enters the cavity of the optical gas absorption cell and is absorbed by gas to be detected in the cavity of the optical gas absorption cell, so that the concentration of the gas to be detected is obtained, the third laser beam enters the reference gas chamber of the laser central wavelength locking device after being focused by the focusing lens, is absorbed by the reference gas in the reference gas chamber and is detected by the infrared detector, so that the central wavelength of the third laser beam is obtained, so that the real-time central wavelength of the laser is obtained, and the semiconductor refrigeration module (not shown in the figure) correspondingly controls the laser according to the difference value between the real-time central wavelength and the standard wavelength, so that the real-time central wavelength of the laser is locked at the standard central wavelength.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.
Claims (8)
1. An optical gas detection system, comprising:
a laser for generating a first laser beam;
the optical gas absorption cell contains gas to be detected;
an optical lens; and
the laser center wavelength locking device is connected with the laser;
wherein the first laser beam transmits through the optical lens to generate a second laser beam directed to the optical gas absorption cell, and the first laser beam is reflected by the optical lens to generate a third laser beam directed to the laser center wavelength locking device; and
the second laser beam is used for detecting the concentration of the gas to be detected, the laser center wavelength locking device is used for calibrating the real-time center wavelength of the laser to a standard center wavelength by using the third laser beam, and the intensity of the second laser beam is greater than that of the third laser beam; wherein:
the optical gas absorption cell includes:
the accommodating cavity is used for accommodating gas to be detected; and
the window sheet is arranged on the side wall of the accommodating cavity and is used as the optical lens;
the first laser beam penetrates through the window sheet to generate a second laser beam emitted to the accommodating cavity, and the first laser beam is reflected by the window sheet to generate a third laser beam emitted to the laser central wavelength locking device;
the laser center wavelength locking device comprises:
a measurement module containing a reference gas; the measurement module is used for receiving the third laser beam and absorbing the third laser beam through the reference gas so as to obtain the real-time central wavelength of the laser;
the measurement module includes:
a focusing lens for focusing the third laser beam before being absorbed by the reference gas.
2. The optical gas detection system of claim 1 wherein the window pane is a wedge-shaped lens.
3. The optical gas detection system of claim 1 wherein the laser center wavelength locker comprises:
the analysis module comprises an analysis unit and a storage unit, the analysis unit is connected with the measurement module, and the storage unit stores standard central wavelength;
the control module is respectively connected with the laser and the analysis module so as to control the real-time central wavelength of the laser in real time;
the analysis module receives the real-time central wavelength obtained by the measurement module and compares the real-time central wavelength with the standard central wavelength to obtain the deviation of the real-time central wavelength relative to the standard central wavelength; and
a control module controls the laser to lock the real-time center wavelength to the standard center wavelength based on the received deviation.
4. The optical gas detection system of claim 3, wherein the measurement module further comprises:
and the infrared detector is used for detecting the third laser beam absorbed by the reference gas.
5. The optical gas detection system of claim 3, wherein the reference gas is the same composition as the gas under test.
6. The optical gas detection system of claim 3, wherein the laser is a semiconductor laser.
7. The optical gas detection system of claim 6 wherein the control module is a semiconductor refrigeration module for controlling the center wavelength of the laser by controlling the temperature of the laser.
8. The optical gas detection system of any one of claims 1-7, wherein the laser is a TO package laser.
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| CN113841041A (en) * | 2019-06-27 | 2021-12-24 | 株式会社堀场制作所 | Analysis device |
| CN110554002A (en) * | 2019-09-30 | 2019-12-10 | 大连艾科科技开发有限公司 | Hydrogen sulfide concentration detection module, hydrogen sulfide concentration telemeter and application |
| CN112782119A (en) * | 2020-12-30 | 2021-05-11 | 汉威科技集团股份有限公司 | Laser gas detection method and system capable of monitoring wavelength |
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