Multi-wavelength laser based on MEMS galvanometer, multi-gas laser detector and detection method

Abstract

The invention discloses a multi-wavelength laser based on an MEMS galvanometer, a multi-gas laser detector and a detection method. The multi-wavelength laser comprises a laser tube shell, N laser chips, a light path assembly and the MEMS galvanometer, wherein the N laser chips, the light path assembly and the MEMS galvanometer are arranged in the laser tube shell; the optical path assembly comprises N lens groups and N optical isolators; the N laser chips are distributed in the laser tube shell in an array mode, and laser emitted by each laser chip is collimated by one lens group and stabilized by one optical isolator, and then is input into the MEMS galvanometer; and the MEMS galvanometer selectively outputs the laser with different optical axes as a detection light beam for measuring different gas components. The multi-gas laser detector comprises a multi-wavelength laser based on the MEMS galvanometer, a photoelectric detector, a laser driving unit, a signal conditioning unit and a controller. The device is simple in structure, small in size, low in power consumption and capable of achieving multi-component atmospheric environment gas detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser gas detection, and in particular relates to a multi-wavelength laser based on a MEMS galvanometer, a multi-gas laser detector and a detection method. Background Art

[0002] TDLAS technology (Tunable Diode Laser Absorption Spectroscopy) is based on tunable diode lasers and uses the "frequency-selective" characteristics of the gas molecules to measure the characteristics of the gas being measured. This technology successfully avoids the interference of other irrelevant gas components and has become the preferred solution for online gas detection systems with high precision and real-time requirements. This technology has a fast response speed, a low detection limit, and can simultaneously analyze multiple gas components, such as methane, carbon monoxide, carbon dioxide, oxygen, ammonia and other gases. Since the late 1990s, gas detection solutions and equipment based on TDLAS technology have emerged in large numbers, and various measurement methods such as fixed test systems, distributed test systems, and telemetry test systems have appeared in the field of industrial applications.

[0003] Based on the "fingerprint" characteristics of gas absorption spectra, a certain gas has a specific absorption spectrum, and a laser with a specific wavelength is required to detect a certain gas. In practical applications, if multiple gases need to be measured simultaneously, it is necessary to use multiple lasers with different central wavelengths for spectral scanning, and set up multiple detectors to detect laser signals of corresponding wavelengths; or the central wavelength of a laser is time-tuned to correspond to the absorption wavelengths of different measured gas components, and a spectrometer is used for reception or multiple detectors are set up for reception. However, due to the limited tunable wavelength range of the laser, there are few types of detectable gases. Therefore, most of the online gas detectors currently used in industry are detectors for a single gas component, such as methane detectors, acetylene detectors, oxygen detectors, etc., and it is difficult to detect multiple gases simultaneously with the same device.

[0004] At present, there are mainly the following technical problems in online detection of multi-component gases: 1. The lasers, detectors and gas chambers used for different gas components are different, and the optical paths of the multi-component gas real-time online detector are separated. Its cost is high, almost equal to the sum of the costs of several separate detectors. In addition, it is large in size, loose in structure, poor in portability and reliability, and is not conducive to inspection and maintenance. 2. Laser is the core component of TDLAS gas detector, and the "frequency-selective" characteristics of gas molecules mean that multi-gas detection requires multi-wavelength lasers, but there are currently no integrated lasers on the market. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention proposes a multi-wavelength laser, a multi-gas laser detector and a detection method based on a MEMS galvanometer.

[0006] The objective of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a multi-wavelength laser based on a MEMS galvanometer, comprising: A laser tube shell, and N laser chips, an optical path component and a MEMS galvanometer arranged in the laser tube shell; The optical path component includes N lens groups and N optical isolators; The N laser chips are distributed in the laser tube shell in an array, and the laser emitted by each laser chip is collimated by a lens group and stabilized by an optical isolator before being input into the MEMS galvanometer; The MEMS galvanometer selectively outputs lasers of different optical axes as detection beams for measuring different gas components; wherein the lasers emitted by each laser chip have a typical wavelength that is different from each other, and each typical wavelength corresponds to a typical absorption spectrum line or absorption spectrum peak of a certain gas component.

[0007] Based on the above, the optical isolator includes a first vertical polarization beam splitter, a Faraday magneto-optical rotator, and a second vertical polarization beam splitter which are arranged in sequence; The Faraday magneto-optical rotator is used to rotate the polarization direction of polarized light by 45°; The beam splitting surfaces of the first vertical polarization beam splitter and the second vertical polarization beam splitter are adjusted so that the polarization directions of the light beams passing through the two vertical polarization beam splitters form an angle of 45°.

[0008] Based on the above, the MEMS oscillator mirror adopts a one-dimensional MEMS oscillator mirror or a two-dimensional MEMS oscillator mirror.

[0009] Based on the above, the multi-wavelength laser further includes a TEC thermoelectric cooler and an NTC thermistor; The TEC thermoelectric cooler and the NTC thermistor are placed close to the laser chip; The NTC thermistor is used to detect the temperature of the laser chip in real time and feed it back to the external circuit control chip; The external circuit control chip controls the TEC thermoelectric cooler to adjust the temperature of the multi-wavelength laser to keep it within a constant range.

[0010] Based on the above, the multi-wavelength laser further includes an optical fiber; The MEMS galvanometer selectively couples different lasers into the optical fiber receiving surface, and the optical fiber outputs the light beam reflected by the MEMS galvanometer as a detection beam for measuring different gas components.

[0011] In a second aspect, the present invention provides a multi-gas laser detector, comprising the multi-wavelength laser based on MEMS galvanometer and at least one photodetector; Also includes a laser driving unit, a signal conditioning unit and a controller; The controller drives the multi-wavelength laser connected to the MEMS galvanometer through the laser driving unit, and is used to control the multi-wavelength laser based on the MEMS galvanometer to output a detection light beam; The controller controls the connection to the MEMS galvanometer to adjust the reflection angle of the MEMS galvanometer; The photoelectric detector receives the return light signal after passing through the detection area and being absorbed by the gas to be detected, and transmits it to the controller after photoelectric conversion; The signal conditioning unit is connected to the controller and is used to calculate the concentration information of the gas to be detected in the detection area according to the return light signal after photoelectric conversion, realize the simultaneous detection of multi-component gases, and finally send it to the controller for storage and display.

[0012] Based on the above, the controller adjusts the reflection angle of the MEMS galvanometer by controlling the MEMS galvanometer according to the different incident angles of the multiple laser beams of the multi-wavelength laser based on the MEMS galvanometer, so that the laser light intensity received by the photodetector is maintained within the predetermined range of concentration calculation, thereby realizing adaptive adjustment of light intensity and meeting the concentration calculation requirements.

[0013] In a third aspect, the present invention provides a detection method of the multi-gas laser detector, which is: (1) The laser driving unit drives N laser chips respectively to make them emit light stably; (ii) by adjusting the lens group and the optical isolator, the emitted light energy of the N laser chips can all be incident on the same position of the MEMS galvanometer; (iii) driving the MEMS galvanometer to rotate the MEMS galvanometer at different angles, thereby combining the outgoing laser beams for output; (iv) the emitted detection light beam is received by the photoelectric detector to complete the photoelectric conversion; (V) The converted current signal is sent to the signal conditioning unit through the IV conversion and signal conditioning circuit to complete the concentration calculation; (VI) Finally, the data is stored and displayed through the controller.

[0014] Compared with the prior art, the present invention has outstanding substantive features and significant progress, specifically: On one hand, the present invention combines a MEMS galvanometer and can make lasers with different incident angles emit from the same exit angle direction by controlling the angle of the MEMS galvanometer.

[0015] On the other hand, the present invention is based on laser absorption spectroscopy technology and combined with a MEMS galvanometer system. By controlling the angle of the MEMS galvanometer, lasers with different incident angles are emitted from the same exit angle direction; by processing the received light and calculating the concentration, multi-component gas detection is achieved. In addition, by collecting the received light intensity information, the reflector angle of the MEMS galvanometer is controlled to be corrected to ensure the stability of the received light intensity. The present invention has a simple structure, a small size, and low power consumption, and can achieve multi-component environmental gas detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a schematic diagram of the structure of Example 1 of the present invention.

[0018] Figure 2 It is a schematic diagram of the side structure of Example 1 of the present invention.

[0019] Figure 3 This is another side structural diagram of Example 1 of the present invention.

[0020] Figure 4 Schematic diagram of the structure of the optical isolator in Example 1 of the present invention.

[0021] Figure 5 This is a schematic diagram of the MEMS galvanometer structure in Example 1.

[0022] Figure 6 This is one of the irradiation modes of the multi-wavelength laser and the photodetector in Example 2.

[0023] Figure 7 This is another way of irradiating the multi-wavelength laser and the photodetector in Example 2.

[0024] Figure 8 This is the optical fiber spot diagram corresponding to LD1 in Example 2.

[0025] Fig. 9 This is the optical fiber spot diagram corresponding to LD2 in Example 2.

[0026] Fig.10 This is the optical fiber spot diagram corresponding to LD3 in Example 2.

[0027] Fig.11 This is the optical fiber spot diagram corresponding to LD4 in Example 2. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] Example 1 This embodiment provides a multi-wavelength laser based on a MEMS galvanometer. Figure 1-Figure 3 As shown, including: A laser tube shell 1, and N laser chips 2, an optical path component 3, a MEMS galvanometer 4 and an optical fiber 5 arranged in the laser tube shell 1; The optical path component 3 includes N lens groups 3-1 and N optical isolators 3-2; The N laser chips 2 are distributed in the laser tube housing 1 in an array, and the laser emitted by each laser chip 2 is collimated by a lens group 3-1 and stabilized by an optical isolator 3-2 before being input to the MEMS galvanometer 4; The MEMS galvanometer selectively couples different lasers into the optical fiber receiving surface, and the optical fiber 5 outputs the light beam reflected by the MEMS galvanometer as a detection light beam for measuring different gas components; wherein the laser emitted by each laser chip 2 has a typical wavelength that is different from each other, and each typical wavelength corresponds to a typical absorption spectrum line or absorption spectrum peak of a certain gas component.

[0030] In this embodiment, Figure 4 As shown, the optical isolator 3-2 includes a first vertical polarization beam splitter (PBS), a Faraday magneto-optical rotator and a second vertical polarization beam splitter (PBS) which are arranged in sequence; The Faraday magneto-optical rotator is used to rotate the polarization direction of polarized light by 45°; The beam splitting surfaces of the first vertical polarization beam splitter and the second vertical polarization beam splitter are adjusted so that the polarization directions of the light beams passing through the two vertical polarization beam splitters are at a 45° angle. In this way, the light beam incident from the right can just pass through the PBS on the left after passing through the Faraday rotator (see Figure 4 The polarization direction of the beam fed back from the left after passing through the Faraday rotator is perpendicular to the polarization direction of the PBS on the right (see Figure 4b), can only be reflected from the side and will not be transmitted through the PBS into the semiconductor laser. In this way, the optical isolator achieves the effect of isolating light feedback.

[0031] MEMS galvanometer is a miniature optical component based on micro-electromechanical system technology. It can control the direction and path of light. It has the advantages of small size, low power consumption, fast response speed and long life. It is used in optical systems such as fiber optic communication, projectors, scanning microscopes, etc. MEMS galvanometer is usually composed of a miniature metal reflective surface and electrodes, such as Figure 5 As shown. By applying an electric field on the reflective surface to control its vibration direction and angle, the reflection and refraction of light are achieved. The MEMS oscillator in this embodiment uses a one-dimensional MEMS oscillator or a two-dimensional MEMS oscillator.

[0032] In order to ensure the stability of the output wavelength of the laser, the multi-wavelength laser also includes a TEC thermoelectric cooler and an NTC thermistor 6; the TEC thermoelectric cooler and the NTC thermistor 6 are placed close to the laser chip; the NTC thermistor is used to detect the temperature of the laser chip in real time and feed it back to the external circuit control chip; the external circuit control chip controls the TEC thermoelectric cooler to adjust the temperature of the multi-wavelength laser to keep it within a constant range.

[0033] Example 2 This embodiment provides a multi-gas laser detector, comprising the multi-wavelength laser based on the MEMS galvanometer as described in Embodiment 1 and at least one photodetector; Also includes a laser driving unit, a signal conditioning unit and a controller; The controller drives the multi-wavelength laser connected to the MEMS galvanometer through the laser driving unit, and is used to control the multi-wavelength laser based on the MEMS galvanometer to output a detection light beam; The controller controls the connection to the MEMS galvanometer to adjust the reflection angle of the MEMS galvanometer; The photoelectric detector receives the return light signal after passing through the detection area and being absorbed by the gas to be detected, and transmits it to the controller after photoelectric conversion; The signal conditioning unit is connected to the controller and is used to calculate the concentration information of the gas to be detected in the detection area according to the return light signal after photoelectric conversion, realize the simultaneous detection of multi-component gases, and finally send it to the controller for storage and display.

[0034] Specifically, in the case of a multi-wavelength laser and a photodetector, if the light response wavelength range of a photodetector is sufficient, the following is used: Figure 6The reflection method shown in the figure; if the light response wavelength range of a photodetector is insufficient and two photodetectors are needed, a semi-transparent and semi-reflective mirror can be added to achieve it, such as Figure 7 shown.

[0035] Specifically, the controller adjusts the reflection angle of the MEMS galvanometer by controlling the MEMS galvanometer according to the different incident angles of the multiple laser beams of the multi-wavelength laser based on the MEMS galvanometer, so that the laser light intensity received by the photodetector is maintained within a predetermined range for concentration calculation, thereby realizing adaptive adjustment of light intensity and meeting the concentration calculation requirements.

[0036] At the same time, when testing different gases, the wavelength can be switched by adjusting the angles of the controller and the MEMS galvanometer to meet the needs of different gas detection.

[0037] The typical wavelengths of LD1, LD2, LD3, and LD4 lasers correspond to different gases, such as the wavelengths of CH4, H2S, CO, and O2 as shown in Table 1. The deflection angle range of the MEMS galvanometer, for example, 0 to 10°, is calculated through simulation design to calculate the initial angle value of the MEMS galvanometer placement. When the device is running, the reflection angle of the MEMS galvanometer can be adjusted to couple different wavelengths emitted by the array laser chip into the optical fiber. The spot intensity diagrams of the optical fiber receiving surface for the typical wavelengths of the four different lasers are respectively Figure 8 , Fig. 9 , Fig.10 and Fig.11 At this time, the light beam emitted by the optical fiber is used as the detection beam.

[0038] Table 1 Wavelengths of LD1, LD2, LD3 and LD4 lasers Example 3 This embodiment provides a detection method of the multi-gas laser detector, which is specifically: (1) The laser driving unit drives N laser chips respectively to make them emit light stably; (ii) by adjusting the lens group and the optical isolator, the emitted light energy of the N laser chips can all be incident on the same position of the MEMS galvanometer; (iii) driving the MEMS galvanometer to rotate the MEMS galvanometer at different angles, thereby combining the outgoing laser beams for output; (iv) the emitted detection light beam is received by the photoelectric detector to complete the photoelectric conversion; (V) The converted current signal is sent to the signal conditioning unit through the IV conversion and signal conditioning circuit to complete the concentration calculation; (VI) Finally, the data is stored and displayed through the controller.

[0039] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A multi-wavelength laser based on a MEMS galvanometer, characterized in that: include: A laser tube shell, and N laser chips, an optical path component and a MEMS galvanometer arranged in the laser tube shell; The optical path component includes N lens groups and N optical isolators; The N laser chips are distributed in the laser tube shell in an array, and the laser emitted by each laser chip is collimated by a lens group and stabilized by an optical isolator before being input into the MEMS galvanometer; The MEMS galvanometer selectively outputs lasers of different optical axes as detection beams for measuring different gas components; wherein the lasers emitted by each laser chip have a typical wavelength that is different from each other, and each typical wavelength corresponds to a typical absorption spectrum line or absorption spectrum peak of a certain gas component.

2. The multi-wavelength laser based on MEMS galvanometer according to claim 1, characterized in that: The optical isolator comprises a first vertical polarization beam splitter, a Faraday magneto-optical rotator and a second vertical polarization beam splitter which are arranged in sequence; The Faraday magneto-optical rotator is used to rotate the polarization direction of polarized light by 45°; The beam splitting surfaces of the first vertical polarization beam splitter and the second vertical polarization beam splitter are adjusted so that the polarization directions of the light beams passing through the two vertical polarization beam splitters form an angle of 45°.

3. The multi-wavelength laser based on MEMS galvanometer according to claim 1, characterized in that: The MEMS oscillator mirror is a one-dimensional MEMS oscillator mirror or a two-dimensional MEMS oscillator mirror.

4. The multi-wavelength laser based on MEMS galvanometer according to any one of claims 1 to 3, characterized in that: The multi-wavelength laser also includes a TEC thermoelectric cooler and an NTC thermistor; The TEC thermoelectric cooler and the NTC thermistor are placed close to the laser chip; The NTC thermistor is used to detect the temperature of the laser chip in real time and feed it back to the external circuit control chip; The external circuit control chip controls the TEC thermoelectric cooler to adjust the temperature of the multi-wavelength laser to keep it within a constant range.

5. The multi-wavelength laser based on MEMS galvanometer according to any one of claims 1 to 3, characterized in that: The multi-wavelength laser also includes an optical fiber; The MEMS galvanometer selectively couples different lasers into the optical fiber receiving surface, and the optical fiber outputs the light beam reflected by the MEMS galvanometer as a detection beam for measuring different gas components.

6. A multi-gas laser detector, characterized in that: A multi-wavelength laser based on a MEMS galvanometer as claimed in any one of claims 1 to 5 and at least one photodetector; Also includes a laser driving unit, a signal conditioning unit and a controller; The controller drives the multi-wavelength laser connected to the MEMS galvanometer through the laser driving unit, and is used to control the multi-wavelength laser based on the MEMS galvanometer to output a detection light beam; The controller controls the connection to the MEMS galvanometer to adjust the reflection angle of the MEMS galvanometer; The photoelectric detector receives the return light signal after passing through the detection area and being absorbed by the gas to be detected, and transmits it to the controller after photoelectric conversion; The signal conditioning unit is connected to the controller and is used to calculate the concentration information of the gas to be detected in the detection area according to the return light signal after photoelectric conversion, realize the simultaneous detection of multi-component gases, and finally send it to the controller for storage and display.

7. The multi-gas laser detector according to claim 6, characterized in that: The controller adjusts the reflection angle of the MEMS galvanometer by controlling the MEMS galvanometer according to the different incident angles of the multiple laser beams of the multi-wavelength laser based on the MEMS galvanometer, so that the laser light intensity received by the photodetector is maintained within a predetermined range for concentration calculation, thereby realizing adaptive adjustment of light intensity and meeting the concentration calculation requirements.

8. A detection method of the multi-gas laser detector according to claim 6 or 7, characterized in that: (1) The laser driving unit drives N laser chips respectively to make them emit light stably; (ii) by adjusting the lens group and the optical isolator, the emitted light energy of the N laser chips can all be incident on the same position of the MEMS galvanometer; (iii) driving the MEMS galvanometer to rotate the MEMS galvanometer at different angles, thereby combining the outgoing laser beams for output; (iv) the emitted detection light beam is received by the photoelectric detector to complete the photoelectric conversion; (V) The converted current signal is sent to the signal conditioning unit through the IV conversion and signal conditioning circuit to complete the concentration calculation; (VI) Finally, the data is stored and displayed through the controller.

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