Laser remote sensing two-dimensional scanning imaging device and method thereof

Abstract

The application discloses a kind of laser remote sensing two-dimensional scanning imaging device and method thereof, it is related to gas spectrum detection field.The concentration field measurement of scene is realized by two-dimensional intermittent scanning, can realize the quick leak diagnosis, evaluation and the quick positioning of leak point;During concentration measurement process, laser spot is static, and motion noise is not introduced, the accuracy of concentration measurement is improved;Intermittent movement of spot is realized using optical modulation, without complex intermittent motion mechanism, more economical in cost, longer service life;Without mechanical scanning device frequently start-stop in two-dimensional scanning process, reduce the time consumption brought by motion acceleration and deceleration process, improve the frame rate of system scanning, realize the quick scanning of high dynamic gas cloud.

Description

Technical Field

[0001] This invention relates to the field of gas spectral detection, specifically to remote sensing and rapid source tracing of gas leaks, and more specifically to a TDLAS scanning imaging device. This device includes two modulation lenses, a laser, a receiving optical system, a detector, and a signal processing module. It can modulate the orientation of the emitted laser to form intermittent light spots, and combined with TDLAS spectral detection technology, achieve two-dimensional scanning measurement of gas leak concentration. While detecting the leak concentration, it can also achieve two-dimensional imaging of the leaking gas, quickly locating the leak point, which is of great significance for improving the detection and prevention of toxic and harmful gas leaks. Background Technology

[0002] Gas leak detection and mitigation are of great significance. TDLAS gas leak detection technology enables non-contact, long-distance detection of gas leaks; however, due to the limitations of its single-point laser, the detection area is limited. Detecting multiple areas requires deploying multiple devices, resulting in high deployment and maintenance costs. While equipping TDLAS with a pan-tilt unit can expand its detection area, the current pan-tilt unit movement speed is relatively slow, allowing only single-point detection per rotation, and it cannot achieve rapid multi-point measurement of dynamic gas clouds. When a gas leak is detected, it is often necessary to dispatch inspection personnel to the site for re-inspection. To meet the analytical needs of accurate leak source location, a more effective method is to use gas imaging technology. Gas imaging technology mainly uses focal plane array detectors or infrared cameras for direct imaging. However, it is greatly affected by ambient temperature, making it difficult to detect low-volume leaks and unable to assess the initial stages of a leak, mostly limiting itself to qualitative rather than accurate quantitative analysis. TDLAS scanning technology can achieve two-dimensional scanning of gas leakage concentration. These technologies (Pang Tao, Xia Hua, Wu Bian, et al. Methane gas spectral imaging method based on double wedge scanning mirror [J]. Acta Physica Sinica, 2024, 73(11): 114202.; Qingdao Aoride Electronics Co., Ltd., A laser telemetry instrument with galvanometer imaging and a gas concentration information imaging method: CN111929275A [P]. 2023-08-18.) use mechanical galvanometers or rotating prisms to modulate the emission angle. Considering that TDLAS single-point concentration measurement needs to remain stationary for a period of time during laser wavelength modulation, existing technologies are difficult to achieve rapid intermittent scanning through mechanical movement, and the scanning cycle is as long as 10s or more, which cannot achieve rapid imaging of dynamic gas clouds. In view of the above problems, this patent proposes a lens motion modulation laser emission orientation, which replaces mechanical movement with optical modulation to quickly form intermittent light spots, improves the TDLAS scanning speed, and realizes high-speed two-dimensional imaging of dynamic gas clouds. Summary of the Invention

[0003] To address the limitations of existing TDLAS single-point measurement and monitoring range, and the inability to quickly scan and monitor dynamic air clouds due to mechanical scanning limitations in multi-point scanning, a laser telemetry two-dimensional scanning imaging device and method are proposed.

[0004] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0005] A laser telemetry two-dimensional scanning imaging device, characterized in that it includes a laser emitting module, an intermittent spot modulation module, a receiving optical module, a photoelectric detection module, and a data acquisition and processing module;

[0006] The laser emission module is used to modulate and emit laser light;

[0007] The intermittent spot modulation module is used to generate a spot that moves intermittently in space;

[0008] The receiving optical module is used to converge diffused light;

[0009] The data acquisition and processing module includes a detector and related processing circuits, used to acquire data, synchronize azimuth angles, and calculate concentration.

[0010] The intermittent spot modulation module includes a horizontal azimuth modulation lens, a vertical azimuth modulation lens, a motor, a control drive unit, and an angle measurement unit. The horizontal azimuth modulation lens is used to achieve horizontal position modulation of the spot; the vertical azimuth modulation lens is used to achieve vertical modulation of the spot; the motor is used to move the horizontal and vertical azimuth modulation lenses; the control drive unit is used to control the position and speed of the motor; and the angle measurement unit is used to measure the position of the horizontal and vertical azimuth modulation lenses, thereby achieving the measurement of the spot position.

[0011] Furthermore, the laser emitting module needs to modulate the emitted laser during a concentration measurement. During the modulation process, the laser spot is stationary in space. After completing a concentration measurement, the spot instantly jumps to the next spatial position.

[0012] Furthermore, the intermittent spot modulation module achieves intermittent spot movement by driving the lens with a motor, eliminating the need for frequent motor starts and stops, and also eliminating the need for an additional mechanical intermittent movement mechanism.

[0013] Furthermore, the horizontal azimuth modulation lens and the vertical azimuth modulation lens have the same structure, both being ring-shaped structures. The ring-shaped structure includes different zones, each with a different refractive power, while the same zone has the same refractive power.

[0014] Furthermore, the modulated laser is incident on the first modulation lens at a fixed angle. As the lens moves, the laser hits different sections of the modulation lens. Within the same section, the exit angle is consistent. When crossing sections, the laser exit angle changes instantaneously.

[0015] Furthermore, the modulation period of the laser emission module is less than the time it takes for the modulation lens to move through one partition.

[0016] Furthermore, one of the two modulation lenses is a fast lens and the other is a slow lens; after the fast lens moves to scan a row or column, the slow lens moves through a partition to scan the next row or column.

[0017] A laser telemetry two-dimensional scanning imaging method includes the following steps:

[0018] Step 1: By injecting different currents into the laser of the laser emitting module, the wavelength of the emitted laser is modulated.

[0019] Step 2: The intermittent spot modulation module drives the fast mirror and the slow mirror to move at a constant speed. When the fast mirror moves through a partition, the laser emission module modulates the time period of one complete cycle.

[0020] Step 3: After passing through a fast mirror and a slow mirror, the modulated laser hits the target in the scene and produces diffuse reflection.

[0021] Step 4: The receiving optical module focuses the diffusely reflected modulated laser onto the detector, and performs photoelectric conversion, signal amplification, acquisition, and concentration calculation of the modulated laser signal through related processing circuits.

[0022] Step 5: The data acquisition and processing module acquires the angles of the fast and slow mirrors output by the angle measurement unit of the intermittent spot modulation module. Based on these two angles, it calculates the index position of the current concentration in the two-dimensional array and stores it in the corresponding storage address.

[0023] Step 6: Repeat steps 1 to 5 until the intermittent spot modulation module controls the laser to complete the two-dimensional scanning of the entire scene.

[0024] Furthermore, this method is applied to gas leak scanning imaging.

[0025] Furthermore, in step 5, when measuring the angle, the collected position and the lens partition distribution are related. Different spatial positions correspond to different partitions, and different partitions correspond to different lens displacements.

[0026] The beneficial effects of this invention are as follows:

[0027] By using two-dimensional intermittent scanning, the concentration field of the scene can be measured, enabling rapid leak diagnosis, assessment, and quick location of leak points;

[0028] During concentration measurement, the laser spot is static, which does not introduce motion noise and improves the accuracy of concentration measurement.

[0029] Using optical modulation to achieve intermittent movement of the light spot eliminates the need for complex intermittent movement mechanisms, making it more economical in terms of cost and extending its service life.

[0030] The two-dimensional scanning process eliminates the need for frequent starting and stopping of the mechanical scanning device, reducing the time consumed by the acceleration and deceleration process, improving the system's scanning frame rate, and enabling rapid scanning of highly dynamic atmospheric clouds. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the modulation optical path of the modulation lens of the present invention. By controlling the included angle of the lens, the direction of the emission angle can be adjusted.

[0032] Figure 2 This is a diagram showing the module configuration of the present invention.

[0033] Figure 3 This is a circular arrangement of the modulation lenses of the present invention.

[0034] Figure 4 This is a cross-sectional optical path diagram of the circular arrangement of the modulation lenses of the present invention.

[0035] Figure 5 This describes the linear arrangement of the modulation lenses in this invention.

[0036] Figure 6 This is a cross-sectional optical path diagram of the linear arrangement of the modulation lenses of the present invention. Detailed Implementation

[0037] Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] like Figure 2 As shown, this embodiment provides a laser telemetry two-dimensional scanning imaging device, which can perform rapid two-dimensional scanning imaging of leaking gas clouds without contacting the leaking gas, thereby locating the leak source. The device includes a laser emitting module, an intermittent spot modulation module, a receiving optical module, a photoelectric detection module, and a data acquisition and processing module.

[0039] The laser emission module is used to modulate and emit laser light. Taking methane detection as an example, its modulation range is 1653.7nm ± 0.5nm; the laser spot emitted by the laser emitter has a diameter of less than 1mm within 10cm.

[0040] The intermittent spot modulation module uses optical modulation to realize a spatially intermittently moving spot, without the need for a complex intermittent motion mechanism or mechanical start-stop, and can achieve rapid two-dimensional intermittent scanning of the laser spot;

[0041] The receiving optical module is used to converge diffuse reflected light. It consists of a series of lenses to focus the diffuse reflected light onto the photodetector and further expand the field of view. In this embodiment, the field of view (FOV) is expanded to ±12°.

[0042] The data acquisition and processing module includes a photodetector and related processing circuits, used to control the laser modulation of the laser emitter, control the intermittent spot modulation module, acquire photodiode data, synchronize the spot azimuth angle, and calculate the concentration. The concentration calculation method can be direct absorption or wavelength modulation. The diameter of the detector surface is 2mm.

[0043] The intermittent spot modulation module includes a horizontal azimuth modulation lens, a vertical azimuth modulation lens, a motor, a control drive unit, and an angle measurement unit. The horizontal azimuth modulation lens is used to achieve horizontal position modulation of the spot; the vertical azimuth modulation lens is used to achieve vertical modulation of the spot; the motor is used to move the modulation lens; the control drive unit is used to control the position and speed of the motor; and the angle measurement unit is used to measure the position of the modulation lens, thereby measuring the position of the spot.

[0044] During a concentration measurement, the laser emission module needs to modulate the emitted laser wavelength. During wavelength modulation, the emitted laser spot must be spatially stationary. After completing one concentration measurement, the spot instantly jumps to the next spatial position; this modulation period is typically less than 1 ms. Figure 3 , Figure 4 As shown, one implementation of the modulation lens in this example is a circular lens. The modulation lens is divided into different zones along different central angles. The refractive power of the lens is different in different zones, but the refractive power is the same in the same zone.

[0045] In this example, the modulated laser is incident perpendicularly onto the first modulation lens, and its optical path is as follows: Figure 1 As shown. For the same zone, the angle of the emitted light is determined by the angle between the two reflecting surfaces and the refractive index of the lens. n Controlled, and modulated by the first lens, the angle between the outgoing and incoming directions is: ;

[0046] Pick n =1.5, When taking the values ​​shown in the table below, the corresponding launch angles are as follows:

[0047] Table 1. Relationship between the modulation angle and the emission angle of the first lens in Example 1;

[0048] ;

[0049] According to Table 1 To achieve the first lens, ten sector lenses with different angles are fabricated and stitched together. In this example, the scanning spot is a 10*10 array, with a scanning angle range of ±11° both horizontally and vertically. The second lens can use the same parameters as the first lens. By adjusting the relative positions of the two lenses, modulation in different directions can be achieved. One possible relative positional relationship is as follows: Figure 5 As shown, the light beam first enters the rightmost sector of the first lens, achieving horizontal modulation, and then enters the uppermost sector of the second lens, achieving vertical modulation. Since the exit angle of the first lens is not perpendicular to the incident angle of the second lens, the range of vertical angles obtained after passing through the second lens is shown in Table 2.

[0050] Table 2. Relationship between the modulation angle and the emission angle of the second lens in Example 1;

[0051] ;

[0052] A motor drives the lens to rotate at a constant speed. The laser illuminates different sections of the modulation lens. Within the same section, the emission angle is consistent; when crossing sections, the laser emission angle changes instantaneously. The modulation period of the laser emission module (i.e., one concentration measurement cycle) is less than the time it takes for the modulation lens to move through one section. The intermittent spot modulation module achieves intermittent spot movement by driving the lens with a motor, eliminating the need for frequent motor starts and stops or additional mechanical intermittent movement mechanisms. The two modulation lenses are a block mirror and a slow mirror, moving at a slower speed. After the fast mirror scans one row or column, the slow mirror moves through one section to scan the next row or column. For a 10Hz scanning speed, the corresponding rotation speed of the first modulation lens is 100 r / s, and the rotation speed of the second lens is 10 r / s. A single click can be used to drive both lenses to rotate synchronously at a fixed speed ratio via a speed-changing mechanism. For a 10*10@10Hz scanning requirement, the laser modulation period is less than 1ms. In this example, the distance between the modulation lens and the laser source is less than 10cm, and the laser spot diameter can be controlled within 1mm. In this example, the diameters of the first and second lenses are 32mm, so the path length of the light spot scanning in the same sector is greater than 10mm. Considering the transition between the two sectors, the actual usable path length is 8mm. The 10*10 array is required to be scanned within 80ms, and each measurement is required to be scanned within 0.64ms, that is, the laser modulation period is 640ns.

[0053] Unlike traditional TDLAS two-dimensional scanning, this scheme uses optical modulation of the laser emission direction to achieve intermittent movement of the light spot, ensuring that the light remains constant during the concentration measurement process. At the same time, it simplifies the galvanometer or intermittent mechanism for light spot modulation and improves the speed of two-dimensional scanning.

[0054] like Figure 6 As shown, in this example, in addition to using a circular arrangement of fan-shaped mirrors, a linear arrangement of prism mirrors can also be used. For the linear arrangement scheme, a linear motor can be used to drive it.

[0055] It is worth noting that multiple circular lenses can be combined to form a modulation lens. By adjusting the rotational gear ratio of different modulation lenses, a more refined spatial angular distribution can be achieved. For example, the first sub-modulation lens can achieve modulation in 10 horizontal directions. If a second sub-modulation lens is cascaded in the optical path, and its modulation quantity is also 10, then the lens group composed of the two sub-lenses can achieve modulation in 100 horizontally subdivided directions. The rotational gear ratio of the first sub-lens and the second sub-lens is 1:10.

[0056] This embodiment provides a laser telemetry two-dimensional scanning imaging method that can rapidly scan and image a leaking gas cloud without contacting the leaking gas, thereby locating the leak source. This method uses the gas leak scanning imaging device described in Embodiment 1. Specifically, it includes the following steps:

[0057] Step 1: By injecting different currents into the laser of the laser emitting module, the wavelength of the emitted laser is modulated. The modulation period is 640ns. Further dynamic modulation of the wavelength is achieved by using a sine wave with a period of 10ns.

[0058] Step 2: The intermittent spot modulation module drives the fast mirror to move at a period of 100Hz and the slow mirror to move at a period of 10Hz. The fast mirror moves through one zone in 1ms and the slow mirror moves through one zone in 10ms.

[0059] Step 3: The wavelength-modulated laser is incident on the fast mirror at a fixed angle. After passing through the fast mirror, it is deflected in the horizontal direction; after passing through the slow mirror, it is deflected in the vertical direction and illuminates the target in the scene, producing diffuse reflection.

[0060] Step 4: The receiving optical module focuses the diffusely reflected light signal onto the detector through the lens group. The processing circuit realizes photoelectric conversion, signal amplification, acquisition and concentration calculation of the detection signal. For the wavelength modulation concentration measurement method, the processing circuit includes a phase lock-in to demodulate the signal.

[0061] Step 5: The data acquisition and processing module acquires the angles of the fast and slow mirrors output by the angle measurement unit of the intermittent spot modulation module. Based on these two angles, it calculates the index position of the current concentration in the two-dimensional array and stores it in the corresponding storage address. One method for calculating the index is as follows:

[0062] ;

[0063] in and These are the column and row indexes, respectively. and These are the measurement angles for fast and slow motion, respectively; and These are the horizontal and vertical modulation angle step sizes, respectively. This indicates rounding down to the nearest integer.

[0064] Step 6: Repeat steps 1 to 5 until the intermittent spot modulation module controls the laser to complete the two-dimensional scanning of the entire scene.

[0065] The laser telemetry two-dimensional scanning imaging device and method of the present invention utilizes multiple modulation lenses to achieve intermittent scanning of the laser spot, ensuring the spatial static state of the laser spot during the laser wavelength modulation process and its rapid transition between different spatial positions during concentration measurement. This eliminates the problems of limited service life and low dynamic response rate caused by complex intermittent mechanisms and frequent start-stops.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0067] This invention discloses a laser telemetry two-dimensional scanning imaging device and method. The laser telemetry two-dimensional scanning imaging device includes a laser emitting module, an intermittent spot modulation module, a receiving optical module, a photoelectric detection module, and a data acquisition and processing module. The laser telemetry two-dimensional scanning imaging method achieves intermittent scanning of the laser spot through the combined movement of multiple modulation lenses, overcoming the problems of limited service life and low dynamic response rate caused by complex intermittent mechanisms and frequent start-stop operations.

Claims

1. A laser telemetry two-dimensional scanning imaging device, characterized in that: It includes a laser emission module, an intermittent spot modulation module, a receiving optical module, a photoelectric detection module, and a data acquisition and processing module; The laser emitting module is used to modulate and emit laser light. During a concentration measurement, the laser emitting module needs to modulate the emitted laser light. During the modulation of the laser light, the spot of the emitted laser light is stationary in space. After completing a concentration measurement, the spot of light instantly jumps to the next spatial position. The intermittent spot modulation module is used to generate a spatially intermittently moving spot; the intermittent spot modulation module drives the fast mirror and the slow mirror to move at a constant speed. When the fast mirror moves through a partition, the laser emission module realizes the modulation of one completion time period. The receiving optical module is used to converge diffused light; The data acquisition and processing module includes a detector and related processing circuits, used to acquire data, synchronize azimuth angles, and calculate concentration. The intermittent spot modulation module includes a horizontal azimuth modulation lens, a vertical azimuth modulation lens, a motor, a control drive unit, and an angle measurement unit. The horizontal azimuth modulation lens is used to achieve horizontal position modulation of the spot. The vertical azimuth modulation lens is used to achieve vertical modulation of the light spot, the motor is used to realize the movement of the horizontal azimuth modulation lens and the vertical azimuth modulation lens, the control drive unit is used to control the position and speed of the motor, and the angle measurement unit is used to measure the position of the horizontal azimuth modulation lens and the vertical azimuth modulation lens, thereby realizing the measurement of the position of the light spot. The horizontal azimuth modulation lens and the vertical azimuth modulation lens have the same structure, which is a ring structure. The ring structure includes different zones, and the refractive power of the different zones is different, while the refractive power of the same zone is the same.

2. The laser telemetry two-dimensional scanning imaging device as described in claim 1, characterized in that, The intermittent spot modulation module achieves intermittent spot movement by driving the lens with a motor, eliminating the need for frequent motor starts and stops, and also eliminating the need for an additional mechanical intermittent movement mechanism.

3. The laser telemetry two-dimensional scanning imaging device as described in claim 1, characterized in that, The modulated laser is incident on the first modulation lens at a fixed angle. As the lens moves, the laser hits different sections of the modulation lens. Within the same section, the exit angle is consistent. When crossing sections, the laser exit angle changes instantaneously.

4. The laser telemetry two-dimensional scanning imaging device as described in claim 1, characterized in that, The modulation period of the laser emission module is less than the time it takes for the modulation lens to move through one partition.

5. The laser telemetry two-dimensional scanning imaging device as described in claim 1, characterized in that, One of the two modulation lenses is a fast lens and the other is a slow lens; after the fast lens moves to scan a row or column, the slow lens moves through a partition to scan the next row or column.

6. A scanning imaging method using the laser telemetry two-dimensional scanning imaging device as described in claim 1, characterized in that, Includes the following steps: Step 1: By injecting different currents into the laser of the laser emitting module, the wavelength of the emitted laser is modulated. Step 2: The intermittent spot modulation module drives the fast mirror and the slow mirror to move at a constant speed. When the fast mirror moves through a partition, the laser emission module modulates the time period of one complete cycle. Step 3: After passing through a fast mirror and a slow mirror, the modulated laser hits the target in the scene and produces diffuse reflection. Step 4: The receiving optical module focuses the diffusely reflected modulated laser onto the detector, and performs photoelectric conversion, signal amplification, acquisition, and concentration calculation of the modulated laser signal through related processing circuits. Step 5: The data acquisition and processing module acquires the angles of the fast and slow mirrors output by the angle measurement unit of the intermittent spot modulation module. Based on these two angles, it calculates the index position of the current concentration in the two-dimensional array and stores it in the corresponding storage address. Step 6: Repeat steps 1 to 5 until the intermittent spot modulation module controls the laser to complete the two-dimensional scanning of the entire scene.

7. The scanning imaging method as described in claim 6, characterized in that, This method was applied to gas leak scanning imaging.

8. The scanning imaging method as described in claim 6, characterized in that, In step 5, when measuring the angle, the collected position and the lens partition distribution are related. Different spatial positions correspond to different partitions, and different partitions correspond to different lens displacements.

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