Automatic calibratable gas detection system based on mid-infrared light and visible light cooperation

Abstract

The utility model discloses an automatic calibration gas detection system based on mid-infrared light and visible light cooperation relates to optical detection technical field, utilize optical lens group to combine and shoot mid-infrared laser and visible laser into multiple reflection pool, multiple reflection pool inside is equipped with high reflection mirror, and high reflection mirror passes through mirror frame installation, is equipped with stepping motor on the mirror frame and is used for adjusting the angle of high reflection mirror, utilizes mid-infrared detector to receive the laser of multiple reflection pool emission, control unit is used for receiving the detection signal of mid-infrared detector, and is used for driving stepping motor to adjust the angle of high reflection mirror. The utility model discloses can realize quick, intuitive initial calibration, and can realize online automatic calibration, maintains the best state of optical path, improves the long -term stability and reliability of system and provides hardware system.

Description

Technical Field

[0001] This utility model relates to the technical fields of optical detection, environmental monitoring, and automatic control, and in particular to an automatically calibrated gas detection system based on the synergy of mid-infrared light and visible light. Background Technology

[0002] The mid-infrared band (usually referring to wavelengths of 3-20 micrometers) is the fingerprint absorption region of most gas molecules. Mid-infrared laser absorption spectroscopy has the absolute advantages of high sensitivity and good selectivity in detecting gases (such as carbon dioxide, methane, carbon monoxide, volatile organic compounds, etc.).

[0003] To improve the detection limit, multiple reflection cell technology is usually used, which makes the laser reflect dozens to hundreds of times in a cell of finite size, greatly increasing the optical path and thus enhancing the interaction between the laser and the gas to be measured, making the weak absorption signal measurable.

[0004] Technical problems and defects of existing technologies: Calibration is extremely difficult: mid-infrared light is invisible to the human eye. During equipment debugging, installation, or maintenance, operators cannot directly observe the laser spot with the naked eye, making the process of precisely coupling the laser into the tiny entrance aperture of the multi-reflection cell and adjusting the high-reflection mirror to achieve a stable spot pattern exceptionally difficult and time-consuming. Currently, it is usually determined indirectly by experience, using expensive infrared observers, or repeatedly monitoring the output signal, which is extremely inefficient.

[0005] Poor long-term stability: During operation, the optical path may drift slightly due to factors such as changes in ambient temperature and mechanical vibration, which weakens the optical signal coupled to the detector, reduces detection sensitivity, or even causes the signal to be completely lost. Measurement needs to be interrupted for recalibration, making it impossible to achieve stable monitoring without human intervention for a long time. Utility Model Content

[0006] To overcome the shortcomings of the prior art, this utility model provides an automatically calibrated gas detection system based on the synergy of mid-infrared and visible light. This system provides a hardware system for achieving rapid and intuitive initial calibration, as well as for achieving online automatic calibration, maintaining the optimal state of the optical path, and improving the long-term stability and reliability of the system.

[0007] To achieve the above objectives, the present invention adopts the following technical solution, including: An automatically calibrated gas detection system based on the synergy of mid-infrared and visible light includes: a mid-infrared laser emitting unit, a visible light indicating laser unit, an optical lens group, a multiple reflection cell, and a mid-infrared detector. The mid-infrared laser emitting unit is used to emit mid-infrared laser; the visible light indicating laser unit is used to emit visible laser; the optical lens group is used to combine the mid-infrared laser and the visible laser and project them into the multiple reflection cell; The multiple reflection cell is provided with a gas inlet, an outlet, a laser incident hole, and an exit hole; the multiple reflection cell is provided with two or more high-reflection mirrors, which are used for multiple reflections of the laser in the multiple reflection cell to form a long optical path; the high-reflection mirrors are installed inside the multiple reflection cell by mirror frames, and the mirror frames are provided with stepper motors for adjusting the angle of the high-reflection mirrors. Mid-infrared detectors are used to receive laser light emitted from multiple reflection cells and to detect mid-infrared light signals that have attenuated after long-path absorption.

[0008] Preferably, the system further includes: a control unit; The control unit is used to receive the detection signal from the mid-infrared detector, drive the stepper motor on the high-reflectivity mirror mount to adjust the angle of the high-reflectivity mirror, and control the opening and closing of the mid-infrared laser emitting unit and the visible light indicating laser unit.

[0009] Preferably, the high-reflectivity mirror is fastened to the mirror frame with screws, and the stepper motor is mounted on the screws to drive the screws to rotate, thereby adjusting the angle of the high-reflectivity mirror.

[0010] Preferably, the multiple reflection cell is a Herriott type or White type multiple reflection cell.

[0011] Preferably, the optical lens group is specifically as follows: The visible laser beam passes through the first aperture and the first reflector before reaching the beam splitter, while the mid-infrared laser beam passes through the second aperture and the lens before reaching the beam splitter. The visible and mid-infrared laser beams are combined by the beam splitter, and the coaxial and collimated laser beams then pass through the second reflector and enter the multiple reflection cell.

[0012] Preferably, the mid-infrared laser emitting unit is a quantum cascade laser or an interband cascade laser.

[0013] Preferably, the visible laser is 635nm red light or 520nm green light, used as an indicator light.

[0014] Preferably, the visible light indicating laser unit is integrated into the mid-infrared laser emitting unit, or is separate from the mid-infrared laser emitting unit.

[0015] The advantages of this utility model are: (1) This utility model relates to a device that uses mid-infrared laser for high-sensitivity gas detection and integrates indicator light (visible laser) and automatic calibration conditions.

[0016] (2) This utility model utilizes coaxial indicator light (visible laser) to visualize the invisible mid-infrared optical path, reducing the calibration time for initial installation and daily maintenance from several hours to several minutes, greatly reducing the technical threshold and maintenance cost, and making calibration intuitive and efficient.

[0017] (3) This utility model uses a control unit to drive a stepper motor on the high-reflectivity mirror mount to adjust the angle of the high-reflectivity mirror. This can be used to automatically compensate for optical path offset during system operation, thereby maintaining the best detection state, improving the long-term stability and reliability of the system, and achieving a high degree of automation.

[0018] (4) This utility model sets a micro stepper motor on the screw of the high-reflectivity mirror frame, drives the stepper motor to rotate the screw, adjusts the angle of the high-reflectivity mirror, and thus realizes micro-scanning of the optical path.

[0019] (5) This utility model integrates the mid-infrared laser emitting unit and the visible light indicating laser unit into one design, without the need to introduce a complex external optical observation system. The overall structure is compact, the additional cost is low, and it is easy to achieve industrialization based on the existing technology. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the automatic calibration gas detection system of this utility model.

[0021] Figure 2 This is a schematic diagram of a high-reflectivity mirror frame.

[0022] Figure 3 This is a flowchart of the calibration method for the automatic calibration gas detection system of this utility model. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0024] Example 1 Depend on Figure 1 As shown, the present invention provides an automatically calibrated gas detection system based on the synergy of mid-infrared and visible light, comprising: a mid-infrared laser emitting unit, a visible light indicating laser unit, an optical lens group, a multiple reflection cell, a mid-infrared detector, and a control unit.

[0025] The mid-infrared laser emitting unit is used to emit mid-infrared laser light of a specific wavelength. The mid-infrared laser emitting unit can be a distributed feedback (DFB) quantum cascade laser (QCL), an interband cascade laser (ICL), or other tunable mid-infrared laser sources.

[0026] The visible light indicator laser unit is integrated into or separate from the mid-infrared laser emitting unit and is used to emit visible laser light (such as 635nm red light or 520nm green light) as an indicator light.

[0027] The mid-infrared laser emitting unit and the visible light indicating laser unit use precise optical mirrors to ensure that the emitted visible laser and mid-infrared laser are strictly coaxial and collimated, making the two laser beams completely overlap in space, as if they were one. Specifically, the visible laser emitted by the visible light indicating laser unit passes through the first aperture and the first reflector before reaching the beam splitter, while the mid-infrared laser emitted by the mid-infrared laser emitting unit passes through the second aperture and the lens before reaching the beam splitter. After the visible laser and the mid-infrared laser are combined by the beam splitter, the coaxial and collimated laser beam then passes through the second reflector and enters the multi-reflection cell.

[0028] The walls of the multiple reflection cell are equipped with gas inlets and outlets, as well as laser entrance and exit holes. Inside the cell are two or more high-reflectivity mirrors, forming an optical structure such as a Herriott or White type. The function of these mirrors is to allow the coaxial laser beam to undergo dozens to hundreds of reflections within the cell, creating a long optical path and enabling full interaction between the mid-infrared laser and the gas inside the cell. The high-reflectivity mirrors in the multiple reflection cell are fixed by a frame and their angles are adjustable. Specifically, [the text abruptly ends here, likely due to an incomplete sentence or missing information]. Figure 2 As shown, a miniature stepper motor is installed on the fastening screws of the high-reflectivity mirror frame. Driving the stepper motor causes the screws to rotate, thereby adjusting the angle of the high-reflectivity mirror. The multiple reflection cell is a Herriott or White type.

[0029] The mid-infrared detector is located at the laser entrance and exit aperture of the multiple reflection cell. It is used to receive the laser emitted from the multiple reflection cell, detect the mid-infrared light signal that has been attenuated after long optical path absorption, and convert it into an electrical signal.

[0030] The control unit is used to receive the detection signal from the mid-infrared detector, drive the stepper motor on the high-reflectivity mirror mount to adjust the angle of the high-reflectivity mirror, and control the opening and closing, current and temperature of the mid-infrared laser emitting unit and the visible light indicator laser unit.

[0031] The control unit is the system's control component. The control logic within the control unit can be implemented based on existing technology. This invention focuses on providing a hardware system for achieving rapid and intuitive initial calibration, as well as for enabling online automatic calibration, maintaining optimal optical path conditions, and improving the long-term stability and reliability of the system. The functions of the control unit include: Drive control function: used to control the on / off state, current and temperature of the mid-infrared laser emitting unit and the visible light indicating laser unit.

[0032] Signal processing function: Used to receive signals from mid-infrared detectors and calculate the concentration of the target gas through harmonic detection (such as wavelength modulation spectroscopy - WMS) and other technologies.

[0033] Automatic calibration function: includes a first calibration stage for initial optical path alignment based on visible laser, and a second calibration stage for dynamic optical path optimization based on detection signal feedback.

[0034] During the first calibration phase, the control unit shuts down the mid-infrared laser emitting unit and turns on the visible light indicating laser unit, allowing operators to perform manual or visually assisted automatic alignment based on the visible laser spot.

[0035] In the second calibration phase, the control unit monitors the signal strength and signal-to-noise ratio (SNR) in real time based on the detection signal from the mid-infrared detector, and determines whether both meet preset conditions. When either the strength or SNR does not meet the preset conditions, the control unit drives the stepper motor to adjust the angle of the high-reflectivity mirror and scans the optical path. During the scanning process, the control unit continuously monitors the signal strength and SNR, searches for a position where both the signal strength and SNR meet the preset conditions, and locks the optical path at that position. The preset conditions are: the strength is greater than a set strength threshold, and the SNR is lower than a set SNR threshold.

[0036] The control unit can be implemented using MCU, MPU, drive circuit, signal processing circuit, human-machine interaction / interface circuit, power management module, etc.

[0037] Example 2 like Figure 3 As shown, the calibration method for the automatically calibrated gas detection system of this invention includes two calibration stages: First calibration phase: In the initial state, initial rapid alignment is performed based on the indicator light, i.e., the visible laser.

[0038] During calibration mode or system startup, the control unit shuts down the mid-infrared laser emitting unit and activates only the visible light indicating laser unit. Operators can clearly see the bright visible laser spot's position on the entrance aperture of the multiple reflection cell and on each high-reflection mirror. By adjusting the angle of the high-reflection mirrors in the multiple reflection cell, all laser spots are aligned to their predetermined positions (ensuring the spots are evenly and closely distributed around the high-reflection mirrors on both sides of the multiple reflection cell), precise alignment of the basic optical path can be quickly achieved. This process is intuitive, efficient, and requires no external infrared observation equipment.

[0039] Second calibration phase: During operation, the angle of the high-reflectivity mirror is adjusted based on the detection signal from the mid-infrared detector to achieve closed-loop automatic calibration.

[0040] In normal detection mode, the system simultaneously or periodically activates both mid-infrared and visible lasers. The control unit performs the following closed-loop control: a. Signal quality monitoring: Real-time monitoring of relevant parameters such as signal strength and second harmonic peak signal-to-noise ratio received by the infrared detector, and determination of whether the strength and signal-to-noise ratio meet the preset conditions; b. Micro-scanning and optimization: When the intensity or signal-to-noise ratio does not meet the preset conditions, the control unit drives the stepper motor mounted on the high-reflectivity mirror mount. By driving the stepper motor, the screws on the high-reflectivity mirror mount are rotated, and the angle of the high-reflectivity mirror is finely adjusted to achieve a periodic deflection scan with a small amplitude, thus performing a micro-scan on the optical path. c. Feedback and Locking: During the scanning process, the signal strength and signal-to-noise ratio are continuously monitored. The position where both the strength and signal-to-noise ratio meet the preset conditions is found as the optimal signal point, and the optical path is locked at the optimal signal point, thereby realizing fully automatic calibration and compensation during operation and overcoming the influence of temperature drift and mechanical vibration.

[0041] This invention utilizes coaxial indicator light (visible laser) to visualize the invisible mid-infrared optical path, reducing the calibration time for initial installation and routine maintenance from several hours to several minutes, greatly lowering the technical threshold and maintenance costs, and making calibration intuitive and efficient.

[0042] This invention uses closed-loop feedback control to automatically compensate for optical path offset during system operation, maintain the best detection state, improve the long-term stability and reliability of the system, and has a high degree of automation.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automatically calibrable gas detection system based on the synergy of mid-infrared and visible light, characterized in that, The system includes: a mid-infrared laser emitting unit, a visible light indicating laser unit, an optical mirror group, a multiple reflection cell, and a mid-infrared detector; The mid-infrared laser emitting unit is used to emit mid-infrared laser; the visible light indicating laser unit is used to emit visible laser; the optical lens group is used to combine the mid-infrared laser and the visible laser and project them into the multiple reflection cell; The multiple reflection cell is provided with a gas inlet, an outlet, a laser incident hole, and an exit hole; the multiple reflection cell is provided with two or more high-reflection mirrors, which are used for multiple reflections of the laser in the multiple reflection cell to form a long optical path; the high-reflection mirrors are installed inside the multiple reflection cell by mirror frames, and the mirror frames are provided with stepper motors for adjusting the angle of the high-reflection mirrors. Mid-infrared detectors are used to receive laser light emitted from multiple reflection cells and to detect mid-infrared light signals that have attenuated after long-path absorption.

2. The automatically calibrable gas detection system based on the synergy of mid-infrared and visible light according to claim 1, characterized in that, The system also includes: a control unit; The control unit is used to receive the detection signal from the mid-infrared detector, drive the stepper motor on the high-reflectivity mirror mount to adjust the angle of the high-reflectivity mirror, and control the opening and closing of the mid-infrared laser emitting unit and the visible light indicating laser unit.

3. The automatically calibrable gas detection system based on the synergy of mid-infrared and visible light according to claim 1, characterized in that, The high-reflectivity mirror is fastened to the mirror frame with screws, and the stepper motor is mounted on the screws to drive the screws to rotate, thereby adjusting the angle of the high-reflectivity mirror.

4. The automatically calibrable gas detection system based on the synergy of mid-infrared and visible light according to claim 1, characterized in that, The multiple reflection cell is a Herriott type or White type multiple reflection cell.

5. The automatically calibrable gas detection system based on the synergy of mid-infrared and visible light according to claim 1, characterized in that, The optical lens assembly is specifically shown below: The visible laser beam passes through the first aperture and the first reflector before reaching the beam splitter, while the mid-infrared laser beam passes through the second aperture and the lens before reaching the beam splitter. The visible and mid-infrared laser beams are combined by the beam splitter, and the coaxial and collimated laser beams then pass through the second reflector and enter the multiple reflection cell.

6. The automatically calibrable gas detection system based on the synergy of mid-infrared and visible light according to claim 1, characterized in that, The mid-infrared laser emitting unit employs a quantum cascade laser or an interband cascade laser.

7. The automatically calibrable gas detection system based on the synergy of mid-infrared and visible light according to claim 1, characterized in that, The visible laser is either 635nm red light or 520nm green light, used as an indicator light.

8. The automatically calibrable gas detection system based on the synergy of mid-infrared and visible light according to claim 1, characterized in that, The visible light indicating laser unit is integrated into the mid-infrared laser emitting unit, or it can be separate from the mid-infrared laser emitting unit.

Images