Method for controlling resolution of laser active scanning gas imaging

Abstract

The application discloses a kind of laser active scanning gas imaging resolution regulation methods, belong to laser absorption spectroscopy gas imaging technical field.Minimal step angle resolution, detection distance, single-point sampling period, imaging time, scanning field angle, initial spot diameter and beam divergence angle are obtained.Under the condition of uniform grid scanning, angle resolution constraint value, sampling density constraint value and spot size constraint value are calculated respectively.According to the square sum of three kinds of constraint values, the predicted spatial resolution is obtained, and the constraint value with the maximum value is determined as the dominant constraint factor.At least one regulation parameter is determined according to the target spatial resolution and the dominant constraint factor, and the equipment is controlled to scan and image.The method can identify the resolution limiting factor under different detection distances, and quantitatively match the hardware parameters and operating parameters.

Description

Technical Field

[0001] This invention relates to the field of laser absorption spectroscopy gas imaging technology, and in particular to a method for adjusting the resolution of laser active scanning gas imaging. Background Technology

[0002] Active scanning gas imaging technology based on laser absorption spectroscopy typically uses a scanning mechanism to drive a laser telemetry module to scan a target area point by point, and forms a spatial distribution image of the gas based on the detection data obtained at each scanning location. This technology can be used for industrial leak monitoring and regional safety early warning. Spatial resolution is an important indicator for evaluating the performance of a gas imaging system, and it is affected by the accuracy of the scanning mechanism, the scanning range, the sampling time, the detection distance, and the propagation characteristics of the laser beam.

[0003] Chinese invention patent application CN 110140064 A (published on August 16, 2019, entitled "Method and System for Automatic Real-Time Adaptive Scanning Using an Optical Ranging System") discloses a scheme for performing a coarse scan based on the detection scene and dividing the range into range gates based on the distance information obtained from the coarse scan. This scheme can determine the characteristic distance and target angular resolution for different range gates and generate corresponding adaptive scanning trajectories. By adjusting the scanning area, angular resolution, and scanning rate, scanning of areas without effective return can be reduced, while maintaining target spatial resolution to a certain extent.

[0004] The aforementioned adaptive scanning scheme primarily determines the scanning angle and trajectory based on the relationship between the detection distance and the target spatial resolution. This scheme also considers factors such as the scanning frame rate, the number of measurement points, and the beam angle width. However, it does not incorporate the angular accuracy of the scanning mechanism, the in-plane sampling density determined by the imaging time and field of view, and the laser spot size into a unified spatial resolution calculation relationship. Furthermore, it does not determine the corresponding parameter adjustment objects based on the relative contributions of various limiting factors.

[0005] Chinese invention patent application CN 113655464 A (published on November 16, 2021, entitled "A Method for Improving the Spatial Resolution of SAM Imaging LiDAR") discloses a scheme that utilizes multiple SAM imaging lidar receiving and detection systems, and sets different optical parameters for each system to cover different distance segments. The detection data from each distance segment, after being recombined, can improve the range resolution for long-range detection. This scheme mainly relies on multiple optical systems, different system parameter configurations, and segmented data recombination; its parameter relationships and equipment structure differ from those of rotating active scanning gas imaging systems.

[0006] In the design and operation of laser active scanning gas imaging equipment, evaluating spatial resolution solely based on scanning angle or a single hardware parameter makes it difficult to determine whether current performance limitations are caused by scanning mechanism accuracy, scanning sampling density, or beam diffusion. This can lead to hardware performance mismatches during the system design phase. Furthermore, the lack of quantitative data during field operation makes it difficult to coordinate scanning field of view, imaging time, and spatial resolution when the detection distance changes.

[0007] Therefore, how to quantitatively evaluate the spatial resolution constraints formed by different physical factors in laser active scanning gas imaging systems, identify the main limiting factors at different detection distances, and match hardware and operating parameters accordingly has become an urgent technical problem to be solved. Summary of the Invention

[0008] The main objective of this invention is to provide a method for adjusting the resolution of laser active scanning gas imaging, which aims to quantitatively evaluate the spatial resolution constraints formed by different physical factors in a laser active scanning gas imaging system, identify the main limiting factors at different detection distances, and match hardware and operating parameters accordingly.

[0009] To achieve the above objectives, this invention proposes a laser active scanning gas imaging resolution control method, comprising using a scanning mechanism to drive a laser telemetry module to scan a target area and form a gas spatial distribution image, including: obtaining the minimum step angle resolution. Detection range Single-point sampling period Imaging time Scanning field of view Initial spot diameter and beam divergence angle ; Set the scan path to a uniform grid, where the number of row sampling points is the same as the number of column sampling points. The scan field of view is within the detection distance. The corresponding square scanning plane; according to Determine the angular resolution constraint value, based on Determine the sampling density constraint value, based on Determine the light spot size constraint value; according to Obtain the predicted spatial resolution The maximum value among the three types of constraint values ​​is determined as the dominant constraint factor; Based on target spatial resolution Based on the dominant constraint factor, determine at least one of the following control parameters: minimum step angle resolution, beam divergence angle, scanning field of view, and imaging time. Then, control the laser active scanning gas imaging device to perform scanning imaging according to these control parameters, so that... Not greater than .

[0010] Preferably, the single-point sampling period The equivalent cycle required to complete the localization and data acquisition of a scanning location, and , , , , , , .

[0011] Preferably, let the ideal total number of sampling points be... In actual scanning, let Set both the number of row sampling points and the number of column sampling points of the uniform grid to The total number of valid sampling points is Let the side length of the square scanning plane be... and in accordance with Determine the sampling density constraint value.

[0012] Preferably, when ,and , At that time, the current detection distance is determined as the near field, and... and The larger value in the range is determined as the dominant constraint factor in the near field.

[0013] Preferably, when When, reduce the minimum step angle resolution; when At the same time, at least one of the following is taken: extending the imaging time and reducing the scanning field of view.

[0014] Preferably, when , and When the decimal orders are the same, the current detection distance is determined as the mid-field transition zone, and the minimum step angle resolution, beam divergence angle, imaging time, and scanning field of view are evaluated at the same time; the same decimal orders mean that the integer part of the common logarithm of the three types of constraint values ​​is the same.

[0015] Preferably, when and When the spot size constraint value is determined as the dominant constraint factor, the beam divergence angle is reduced first, and at least one of the following is selected as a supplementary control parameter: reducing the scanning field of view and extending the imaging time.

[0016] Preferably, during the system design phase, a target working distance is given. Target spatial resolution In addition, the single-point sampling period, imaging time, scanning field of view, and initial spot diameter are determined by solving... Determine the maximum allowable step angle interval of the scanning mechanism and the maximum allowable beam divergence angle of the optical system.

[0017] Preferably, when the hardware parameters of the laser active scanning gas imaging device are fixed, the response to the detection distance... The scanning field of view is dynamically reduced or the imaging time is increased according to the parameters allowed by the equipment, and the calculation is recalculated after each adjustment. until .

[0018] Preferably, when the allowed target spatial resolution When the numerical value increases and the spatial precision requirement decreases, while satisfying Under the condition of increasing the scanning field of view and shortening the imaging time.

[0019] The above technical solution has the following advantages: This application calculates the angular resolution constraint value formed by the minimum step angular resolution, the sampling density constraint value formed by the scanning field of view and imaging time, and the spot size constraint value formed by laser beam propagation, respectively, so that mechanical scanning accuracy, scanning sampling strategy, and optical propagation characteristics can be reflected in a unified spatial resolution evaluation process. By coupling the three types of constraint values ​​with the square root of the sum of squares, the predicted spatial resolution at the current detection distance can be obtained; by determining the maximum value among the three types of constraint values ​​as the dominant constraint factor, the main limiting factors under the current operating conditions can be determined. Selecting at least one of the minimum step angular resolution, beam divergence angle, scanning field of view angle, or imaging time to adjust the dominant constraint factor helps to reduce ineffective adjustments to non-dominant parameters and enables hardware parameter matching during the system design stage. Under fixed hardware conditions, the operating parameters can be adjusted according to changes in detection distance, thereby establishing a quantitative correspondence between spatial resolution, scanning field of view, and imaging time. Attached Figure Description

[0020] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings, wherein: Figure 1 A graph showing the relationship between the angular resolution constraint value and the detection distance provided in the embodiments of this application.

[0021] Figure 2 The graph provided in this application illustrates the relationship between sampling density constraint values ​​at different detection distances and the scanning field of view and imaging time. Figure 2 In the diagram, 'a' represents the relationship when the detection distance D = 3m. Figure 2 In the diagram, b represents the relationship when the detection distance D = 5m. Figure 2In the diagram, 'c' represents the relationship when the detection distance D = 10m. Figure 2 The d in the figure represents the relationship when the detection distance D=20m.

[0022] Figure 3 The graph provided in this application illustrates the relationship between the sampling density constraint values ​​for different scanning range side lengths and the detection distance and imaging time. Figure 3 In the graph, 'a' represents the relationship when the side length of the scan range is equal to 1m. Figure 3 In the graph, 'b' represents the relationship when the side length of the scan range is equal to 2m. Figure 3 In the diagram, 'c' represents the relationship when the side length of the scan range is equal to 3m. Figure 3 The d in the figure represents the relationship when the side length of the scanning range is equal to 5m.

[0023] Figure 4 A flowchart of a laser active scanning gas imaging resolution control method provided in an embodiment of this application. Detailed Implementation

[0024] The following embodiments are used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Where there is no conflict, the technical features in these embodiments can be combined with each other. General data acquisition, program storage, communication, and control operations not specifically described can be implemented using conventional methods in the art. These conventional implementation methods do not replace the constraint value calculation, coupling processing, dominant constraint judgment, and parameter adjustment processes explicitly described below.

[0025] Example 1 See Figure 4 As shown, this embodiment provides a method for adjusting the resolution of laser active scanning gas imaging. This method is applied to a laser active scanning gas imaging device. The device includes a laser telemetry module, a scanning mechanism, a data acquisition module, and a control processing unit. The scanning mechanism drives the laser telemetry module to scan the target area according to a set scanning path. The data acquisition module collects detection data corresponding to each scanning position. The control processing unit receives operating parameters and hardware parameters, performs spatial resolution calculation, dominant constraint factor judgment, and parameter adjustment, and outputs control commands to the scanning mechanism and the data acquisition module.

[0026] In this embodiment, spatial resolution refers to the spatial scale between adjacent distinguishable sampling positions on the target plane. The smaller the spatial resolution value, the finer the distinguishable spatial structure. The control processing unit uses the scanning mechanism accuracy, scanning sampling density, and laser spot size as spatial resolution constraints for the mechanical motion dimension, time and field of view dimension, and optical propagation dimension, respectively.

[0027] Before performing spatial resolution calculation, the control processing unit obtains the minimum step angle resolution. Detection range Single-point sampling period Imaging time Scanning field of view Initial spot diameter and beam divergence angle Among them, the minimum step angle resolution The minimum angular interval that can be achieved between two adjacent scanning positions of the scanning mechanism; detection distance. The distance from the laser active scanning gas imaging device to the target plane; single-point sampling period. The equivalent cycle required to complete the positioning and data acquisition of a scanning position; initial spot diameter for The beam diameter at the system reference plane; beam divergence angle This is the equivalent full-angle divergence angle used to characterize the increase in spot diameter with propagation distance. Imaging time. The total time allocated to complete one frame of scanning imaging, the scanning field of view This represents the angular range covered by the current scan imaging. The calculation uses... , , , , , , Lengths are uniformly expressed in meters, times in seconds, and angles in radians. The attached diagram uses degrees for easy display; angles are labeled according to… The calculation is performed after converting to radians.

[0028] The control processing unit first determines whether the signal-to-noise ratio (SNR) of the current backlight signal reaches the detection threshold. The detection threshold is the minimum usable SNR value preset by the data acquisition module under the current operating mode through device calibration. When the SNR of the backlight signal reaches the detection threshold, the control processing unit inputs the current hardware parameters and operating parameters into the spatial resolution model. In this embodiment, the spatial resolution model is used to evaluate the spatial resolution formed by geometric and sampling factors, and does not include resolution degradation caused by backlight signal attenuation in the predicted spatial resolution.

[0029] The control processing unit is based on the minimum step angle resolution. and detection range The angular resolution constraint value is calculated and determined according to equation (1): (1) The angular resolution constraint value represents the minimum spatial interval formed when the minimum angular interval of the scanning mechanism is projected onto the target plane. With the minimum step angular resolution remaining constant, the angular resolution constraint value increases as the detection distance increases.

[0030] The control processing unit further calculates based on the single-point sampling period. and imaging time The ideal total number of sampling points for a frame of imaging is determined according to equation (2): (2) In this embodiment, the scanning path is set to a uniform grid. The number of row sampling points and column sampling points of the uniform grid are the same, and the scanning field of view is within the detection distance. This corresponds to a square scanning plane. In an ideal situation, For a perfect square, the number of sampling points per row is . In actual scanning, let Set both the number of row sampling points and the number of column sampling points to 1. The total number of valid sampling points is To ensure that the actual sampling time does not exceed .

[0031] The side length of the square scanning plane is determined according to formula (3): (3) The control processing unit calculates the sampling density constraint value based on the side length of the square scanning plane and the number of sampling points in a single row. The sampling density constraint value is determined according to equation (4): (4) The sampling density constraint value represents the spatial interval between adjacent scan positions in a uniform grid on the target plane. When When it is a perfect square, Equation (4) is equivalent to With the detection distance and single-point sampling period remaining unchanged, reducing the scanning field of view can decrease the scanning plane range, and extending the imaging time can increase the total number of sampling points. Both can reduce the sampling density constraint value.

[0032] The control processing unit also considers the initial spot diameter Beam divergence angle and detection range Calculate the spot size constraint value, which is determined according to equation (5): (5) The spot size constraint value represents the diameter of the spot formed when the laser beam propagates to the target plane. Gas detection information within the spot's coverage area is spatially averaged, making it difficult to distinguish gas distribution structures smaller than the spot size. With the initial spot diameter and beam divergence angle remaining constant, the spot size constraint value increases with increasing detection distance.

[0033] After obtaining the angular resolution constraint, sampling density constraint, and spot size constraint, the control processing unit couples the independent error synthesis relationship of the square root of the sum of the squares of the three types of constraint values ​​to predict the spatial resolution. Determine according to formula (6): (6) In equation (6), , , and The same length unit is used. The three types of constraint values ​​are retained separately for subsequent determination of the dominant constraint factor; the comprehensive calculation result represents the spatial resolution level under the combined effect of scanning mechanism accuracy, sampling density per unit area, and laser spot size.

[0034] The control processing unit compares the numerical relationships of the three types of constraint values. When one constraint value is greater than the other two, that value is identified as the dominant constraint factor. When the decimal orders of magnitude of the three types of constraint values ​​are the same, all three constraints are collectively identified as the main limiting factors in the mid-field transition zone. The same decimal orders of magnitude mean that the integer parts of the common logarithms of the three positive constraint values ​​are the same. The dominant constraint factor represents the constraint factor that imposes the greatest limitation on the prediction spatial resolution under the current parameter conditions. By simultaneously retaining the comprehensive prediction value and the individual constraint values, the control processing unit can determine... Is it not greater than the target spatial resolution? And identify the main physical factors that limit spatial resolution.

[0035] when ,and , At this time, the control processing unit treats the current distance range as near-field processing. Under near-field conditions, and The larger value in the range is determined as the dominant constraint factor, and the control parameters are selected accordingly.

[0036] when At that time, reducing the minimum step angle resolution can reduce the spacing between adjacent scan beams on the target plane; when At the same time, extending the imaging time increases the total number of sampling points in a frame, while reducing the scanning field of view increases the sampling density per unit area without changing the total number of sampling points. The control processing unit selects one or more of the parameters allowed by the device for adjustment and recalculates after each adjustment. until Or it may reach the device parameter boundary.

[0037] when , and When the decimal orders of magnitude are the same, the control processing unit uses the current distance range as the mid-range transition zone. Within the mid-range transition zone, three types of factors jointly limit the predicted spatial resolution. The control processing unit simultaneously evaluates the minimum step angle resolution, beam divergence angle, imaging time, and scanning field of view, and performs coordinated matching of the above parameters.

[0038] when and At this point, the control processing unit identifies beam spread as the primary limiting factor for the current spatial resolution. Therefore, it prioritizes reducing the beam divergence angle. If the beam divergence angle cannot be further reduced due to hardware limitations, the control processing unit can further reduce the scanning field of view or extend the imaging time to lower the sampling density constraint and improve the overall predicted spatial resolution.

[0039] During the system design phase, the control processing unit can receive multiple sets of candidate hardware parameters and operating parameters. Each set of candidate parameters includes at least the minimum step angular resolution, beam divergence angle, scanning field of view, imaging time, and target working distance. The control processing unit calculates angular resolution constraints, sampling density constraints, spot size constraints, and predicted spatial resolution for each set of candidate parameters, and compares the performance of different configurations based on the calculation results.

[0040] Given target working distance and target spatial resolution Then, the control processing unit performs reverse parameter matching. Reverse parameter matching is... To constrain the process, given a fixed single-point sampling period, imaging time, scanning field of view, and initial spot diameter, the maximum allowable step angle interval of the scanning mechanism can be calculated using equations (7) and (8), respectively. and the maximum beam divergence angle allowed by the optical system .

[0041] (7) (8) Equations (7) and (8) are used only when the values ​​within the square root are non-negative and the calculation results meet the conditions for legal parameter values; otherwise, the current fixed parameter combination does not constitute a feasible parameter set. The obtained parameters serve as the basis for selecting the scanning mechanism and designing the laser optical system.

[0042] In a deployed fixed hardware system, the minimum step angle resolution and beam divergence angle are determined by the device hardware. When the detection distance changes, the control processing unit recalculates the three types of constraint values ​​and .when At the same time, the control processing unit gradually reduces the scanning field of view or extends the imaging time according to the discrete parameter levels allowed by the equipment, and recalculates after each adjustment. until Or it may reach the device parameter boundary.

[0043] After determining the new scanning field of view, the control processing unit sends a field-of-view control command to the scanning mechanism to change the scanning angle range corresponding to one frame of image. After determining the new imaging time, the control processing unit sends a time control command to the scanning mechanism and the data acquisition module to adjust the scanning duration and total number of sampling points for one frame of image. The scanning mechanism drives the laser telemetry module to scan the target area according to the adjusted uniform grid path, and the data acquisition module collects detection data according to the corresponding single-point sampling period, thereby forming gas imaging data corresponding to the control parameters.

[0044] When the permissible target spatial resolution increases, meaning the required spatial detail decreases, the control processing unit can increase the scanning field of view and shorten the imaging time. Increasing the scanning field of view expands the target area covered by a single frame image, while shortening the imaging time improves the image update speed. The control processing unit performs these adjustments while meeting the current target spatial resolution, ensuring that the scanning range and imaging time match the actual monitoring requirements.

[0045] This embodiment calculates the constraints formed by mechanical scanning accuracy, scanning sampling density, and beam propagation size, and identifies the main performance bottlenecks through the numerical relationships of these three types of constraint values. Compared to adjusting the scanning angle solely based on the detection distance, this implementation can distinguish between different situations such as insufficient scanning mechanism accuracy, insufficient sampling point density, and excessive beam spread. The control processing unit can select appropriate adjustment parameters for the dominant constraint factors, thereby reducing ineffective adjustments to non-dominant parameters and performing quantitative matching between spatial resolution, scanning field of view, and imaging time.

[0046] Example 2 This embodiment illustrates the process of predicting the positive performance of spatial resolution. The control and processing unit of the laser active scanning gas imaging device pre-stores angular resolution constraint models, sampling density constraint models, spot size constraint models, and the coupling relationships between these three types of constraint values. The control and processing unit obtains the hardware and operational parameters to be evaluated through a parameter input interface, device configuration files, or device operating status data.

[0047] For any set of parameters to be evaluated, the control processing unit reads the minimum step angle resolution. Detection range Single-point sampling period Imaging time Scanning field of view Initial spot diameter and beam divergence angle .

[0048] The control processing unit first calculates the angular resolution constraint value according to equation (1).

[0049] Subsequently, the control processing unit determines the ideal total number of sampling points for a single frame imaging according to formula (2), and determines the actual number of row and column sampling points according to the rounding rules described in Example 1.

[0050] When the scanning path is a uniform grid, the number of row sampling points is the same as the number of column sampling points, and the scanning field of view corresponds to a square scanning plane, the control processing unit calculates the side length of the scanning plane according to formula (3).

[0051] The sampling density constraint value is determined according to equation (4).

[0052] The light spot size constraint value is determined according to formula (5).

[0053] After the control processing unit completes the calculation of the three types of constraint values, it obtains the prediction spatial resolution corresponding to the current parameter set according to equation (6). The dominant constraint factor is determined according to the comparison rules described in Example 1. The control processing unit also saves the values ​​of each sub-constraint to analyze and predict the main sources of spatial resolution limitations.

[0054] When multiple sets of hardware configurations or operating parameters need to be compared, the control processing unit sequentially reads each set of candidate parameters and obtains the predicted spatial resolution corresponding to each set of candidate parameters according to the same calculation process. Each set of candidate parameters may have different minimum step angle resolution, beam divergence angle, scanning field of view, or imaging time.

[0055] The control processing unit compares each predicted spatial resolution with the target spatial resolution and outputs whether each candidate parameter group meets the target requirements. Simultaneously, the control processing unit outputs the angular resolution constraint value, sampling density constraint value, spot size constraint value, and dominant constraint factor corresponding to each parameter group.

[0056] The above processing allows for comparison of spatial resolution performance using different combinations of scanning mechanisms, optical parameters, and operating parameters before equipment manufacturing or field deployment. This comparison is not limited to single-angle accuracy but considers the impact of both scanning sampling density and beam propagation size on spatial resolution.

[0057] like Figure 1 As shown, when the minimum step angular resolution is fixed, the angular resolution constraint value increases with the increase of the detection distance. Different minimum step angular resolutions correspond to different slopes of change. Therefore, after the target working distance is determined, it can be used... Figure 1 The corresponding calculation relationship is used to evaluate whether the angular accuracy of the scanning mechanism meets the spatial resolution requirements.

[0058] like Figure 2As shown in figures a to d, when the single-point sampling period is 1 ms, the corresponding sampling frequency is 1 kHz. For different detection distances, the sampling density constraint value changes with the scanning field of view and imaging time. When the scanning field of view increases relative to the current value, the scanning range on the target plane expands, and the sampling density constraint value increases; when the imaging time is extended relative to the current value, the total number of sampling points increases, and the sampling density constraint value decreases. Figure 2 The scanning field of view is displayed in degrees and converted to radians during calculation.

[0059] like Figure 3 As shown in a to d, when the single-point sampling period is 1ms and the corresponding sampling frequency is 1kHz, the sampling density constraint value changes with the detection distance and imaging time for different scanning range side lengths. When the detection distance increases, the sampling density constraint value under the same scanning range side length condition changes according to equation (4); extending the imaging time can increase the number of sampling points, thereby reducing the spatial interval between adjacent scanning points.

[0060] The control processing unit can be based on Figures 1 to 3 The corresponding calculation results are used to determine the impact of scanning angle accuracy, field of view, and imaging time on spatial resolution. Combined with the spot size constraint, the main performance bottlenecks of candidate configurations can be identified, avoiding hardware selection based solely on a single parameter.

[0061] Example 3 This embodiment illustrates the reverse parameter matching process during the system design phase.

[0062] First, set the target working distance for the laser active scanning gas imaging device. and target spatial resolution Simultaneously, the single-point sampling period, expected imaging time, scanning field of view, and initial spot diameter are set. These parameters serve as inputs for inverse parameter matching.

[0063] The control processing unit calculates the angular resolution constraint value based on the target working distance and the candidate minimum step angular resolution. The control processing unit also calculates the spot size constraint value based on the target working distance, the candidate beam divergence angle, and the initial spot diameter, and calculates the sampling density constraint value based on the imaging time, the single-point sampling period, and the scanning field of view.

[0064] For each set of candidate minimum step angle resolution and candidate beam divergence angle, the control processing unit obtains the corresponding [equation] according to equation (6). and judge Whether it is valid or not.

[0065] when When the current candidate parameter set is determined to be a feasible parameter set; when At that time, the control processing unit reduces the step angle interval or the beam divergence angle according to the preset discrete level of the candidate hardware parameters, and re-executes the calculation until a feasible parameter set is obtained or all candidate parameters are traversed.

[0066] After calculating the candidate parameters, the control processing unit determines the minimum step angle resolution required by the scanning mechanism and the maximum allowable beam divergence angle of the optical system from the feasible parameter set. The resulting parameters are used to guide the selection of the scanning mechanism and the optical system.

[0067] When angular resolution is the primary limiting factor, a scanning mechanism with a smaller step angle interval should be preferred. When spot size is the primary limiting factor, an optical configuration with a smaller beam divergence angle should be preferred. When sampling density is the primary limiting factor, the imaging time or scanning field of view can be further adjusted without changing the hardware.

[0068] This embodiment places hardware parameters and operational parameters within the same spatial resolution evaluation framework. After the target working distance and target spatial resolution are determined, it is possible to determine whether the scanning mechanism accuracy, beam divergence characteristics, and scanning sampling strategy meet the requirements, thereby reducing insufficient hardware specifications or performance redundancy caused by relying solely on experience in selection.

[0069] Example 4 This embodiment illustrates the on-site dynamic control process under fixed hardware conditions.

[0070] After the laser active scanning gas imaging device is installed, the minimum step angle resolution, initial spot diameter, and beam divergence angle are determined by the device hardware. During device operation, the control processing unit calculates and predicts the spatial resolution based on the current detection distance, scanning field of view, imaging time, and single-point sampling period.

[0071] When the detection distance changes, the control processing unit updates the detection distance. And recalculate , , and Then judge Whether it is valid or not.

[0072] like The control and processing unit maintains the current scanning field of view and imaging time. The scanning mechanism continues to operate according to the current scanning path, and the data acquisition module completes gas imaging data acquisition according to the current sampling cycle.

[0073] like The control processing unit determines the adjustable parameters based on the dominant constraint factor. Since the hardware parameters in this embodiment are fixed, the main adjustments during operation are the scanning field of view and the imaging time.

[0074] when and At this time, the control processing unit reduces the scanning field of view. After the scanning field of view is reduced, the scanning plane range corresponding to the same detection distance is reduced; with the total number of sampling points remaining unchanged, the spatial interval between adjacent scanning points is reduced accordingly.

[0075] The control processing unit can also extend the imaging time. With the imaging time extended, the total number of sampling points increases while the single-point sampling period remains unchanged. The number of row sampling points and column sampling points in the uniform grid increases accordingly, and the sampling density constraint value decreases.

[0076] After the control processing unit completes the parameter adjustment, it recalculates. .like If the conditions are not met, the control processing unit will output updated field-of-view control commands and imaging time control commands to the scanning mechanism and data acquisition module; if the conditions are still not met, the unit will continue to adjust the parameters according to the equipment's allowed parameter levels until the conditions are met or the parameter boundaries are reached.

[0077] The scanning mechanism determines the scanning boundary based on the new scanning field of view and performs a uniform grid scan within the scanning boundary. The data acquisition module completes the acquisition of one frame of gas imaging data based on the new imaging time. Thus, the device adapts to changes in detection distance by adjusting operating parameters without changing hardware parameters.

[0078] When the allowed target spatial resolution When the value increases, meaning the spatial precision requirement decreases, the control processing unit can perform adjustments in the opposite direction, and... Under the condition of increasing the scanning field of view and shortening the imaging time.

[0079] Increasing the scanning field of view expands the area covered by a single frame of imaging. Shortening the imaging time reduces the time required to complete one frame. This control method is suitable for operational situations requiring expanded monitoring range or increased image update speed.

[0080] Example 5 This embodiment illustrates the process of identifying dominant constraint factors and zonal control at different detection distances.

[0081] The control processing unit calculates angular resolution constraint values, sampling density constraint values, and spot size constraint values ​​at multiple detection distances. By comparing the relationship between these three types of constraint values ​​and detection distance, the main resolution limiting factors within different distance ranges can be identified.

[0082] Under near-field conditions, the laser spot size is relatively small. ,and , At that time, the control processing unit determines the current distance range as the near-field dominance zone.

[0083] Within the near-field dominance region, when When, prioritize reducing the minimum step angle resolution; when In such cases, priority should be given to extending the imaging time or reducing the scanning field of view.

[0084] Within the midfield transition zone, , and The decimal orders of magnitude are the same, and the three types of factors together limit the spatial resolution of the prediction.

[0085] The control processing unit simultaneously evaluates the minimum step angle resolution, beam divergence angle, scanning field of view, and imaging time within the mid-field transition zone. During system design, both scanning mechanism parameters and optical parameters can be adjusted simultaneously. For fixed hardware systems, the scanning field of view and imaging time can be adjusted as a key factor, and the achievable spatial resolution can be determined based on the current hardware conditions.

[0086] Under far-field conditions, the spot size increases with propagation distance. and At that time, the control processing unit determines the spot size as the dominant constraint factor.

[0087] During the system design phase, far-field modulation prioritizes reducing the beam divergence angle. Reducing the beam divergence angle slows down the rate at which the spot size increases with distance. For already deployed fixed hardware systems where the beam divergence angle cannot be dynamically changed, the scanning field of view can be reduced or the imaging time extended to decrease the sampling density constraint. This supplementary modulation cannot eliminate the physical limitations on spot size formation, but it can prevent the sampling density constraint from further reducing the overall spatial resolution.

[0088] Through the aforementioned zoned control, the control processing unit can select corresponding parameters based on the performance bottlenecks at different detection distances. Near-field control focuses on the accuracy of the scanning mechanism and sampling density, mid-field control focuses on multi-parameter coordination, and far-field control focuses on beam divergence characteristics.

[0089] Example 6 This embodiment illustrates the process of handling applicable conditions for the spatial resolution model.

[0090] Before performing spatial resolution prediction, the laser active scanning gas imaging device first acquires the current backlight signal, and the data acquisition module outputs data to evaluate signal quality. The control processing unit compares the current signal-to-noise ratio with the minimum usable signal-to-noise ratio threshold preset by the device calibration to determine whether the applicable conditions of the spatial resolution model are met.

[0091] When the signal-to-noise ratio of the reflected light signal reaches the detection threshold, the control processing unit executes... , and The calculation is performed according to equation (6). .

[0092] The predicted spatial resolution obtained in this embodiment is used to evaluate the resolving power of scanning geometry, sampling density, and light spot propagation. The predicted spatial resolution does not include resolution degradation caused by attenuation of the backlight signal, weak absorption signal, or increased noise.

[0093] When the signal-to-noise ratio of the returned light signal does not reach the detection threshold, the control processing unit does not perform coupling of the three types of constraint values, nor does it output spatial resolution adjustment commands based on the prediction results. By setting this applicable condition, the calculation results of the geometric and sampling models can be avoided from being directly used as the actual imaging resolution when the signal quality is insufficient.

[0094] Example 7 This embodiment illustrates the quantitative trade-off between scanning field of view and imaging time.

[0095] When the detection distance, single-point sampling period and hardware parameters remain unchanged, the control processing unit sets multiple sets of scanning field angle and imaging time combinations, and calculates the sampling density constraint value for each combination according to equation (4).

[0096] As the scanning field of view increases, the side length of the square scanning plane increases. If the imaging time remains constant, the total number of sampling points remains unchanged, but the sampling density constraint value increases.

[0097] As imaging time increases, the total number of sampling points increases. If the scanning field of view remains unchanged, the spatial interval between adjacent scanning points in a uniform grid decreases, and the sampling density constraint value decreases accordingly.

[0098] Control processing unit To constrain the selection process, feasible combinations are screened from multiple sets of scanning field-of-view and imaging time combinations. Compared to the current combination, for applications requiring higher spatial precision, a smaller scanning field-of-view or a longer imaging time is chosen; for applications requiring a larger monitoring range or a higher image update speed, a smaller scanning field-of-view or a longer imaging time is selected. Within the range, you can choose a larger scanning field of view or a shorter imaging time.

[0099] The above processing eliminates the need for independent manual setting of the scanning field of view and imaging time; instead, they are matched based on the detection distance, total number of sampling points, and target spatial resolution. This allows for the establishment of a calculable operational parameter relationship between monitoring range, imaging speed, and spatial resolution.

[0100] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit the scope of protection of this application. Those skilled in the art, without departing from the core technical concept of this application, can adjust the parameter input method, data transmission method, control execution method, and specific implementation of each step according to the actual equipment structure, detection distance, scanning range, and imaging time. When the above adjustments do not change the technical relationship between the separate calculation, coupling analysis, identification of the dominant constraint factor, and parameter adjustment of the scanning angular resolution constraint, sampling density constraint, and spot size constraint, they all constitute equivalent implementations of the technical solutions of this application.

[0101] The control processing unit, data acquisition module, scanning mechanism, and laser telemetry module described in the various embodiments of this application can be implemented using conventional hardware and software in the art. The modules can interact with each other via conventional communication interfaces for data and control commands. The control processing unit can call pre-stored programs to perform parameter reading, constraint value calculation, coupling processing, dominant constraint judgment, parameter matching, and control command output. The above-described conventional implementation does not change the computational logic and control relationship of the method in this application.

[0102] The technical solution of this application is not limited to the specific parameter combinations described in the embodiments. As long as the parameters used have the same physical meaning and can obtain the angular resolution constraint value, sampling density constraint value, spot size constraint value and predicted spatial resolution according to equations (1) to (6), they can be used to implement the method of this application. The sampling density constraint model described in this application is applicable to the conditions of uniform grid, the same number of row and column sampling points and the scanning field of view corresponding to a square scanning plane.

[0103] For the coupling processing of the three types of constraint values, the square root relationship of the sum of squares shown in Equation (6) is adopted, which matches the physical meaning and dimensions of each constraint value. The coupling processing is used both to obtain the predicted spatial resolution and to retain the individual constraint values ​​so as to identify the dominant constraint factors and select the corresponding control parameters.

Claims

1. A method for adjusting the resolution of laser active scanning gas imaging, comprising using a scanning mechanism to drive a laser telemetry module to scan a target area and form a spatial distribution image of the gas, characterized in that, Includes: obtaining the minimum step angle resolution Detection range Single-point sampling period Imaging time Scanning field of view Initial spot diameter and beam divergence angle ; Set the scan path to a uniform grid, with the number of row sampling points equal to the number of column sampling points. The scan field of view is within the detection distance. The corresponding square scanning plane; according to Determine the angular resolution constraint value, based on Determine the sampling density constraint value, based on Determine the light spot size constraint value; according to Obtain the predicted spatial resolution The maximum value among the three types of constraint values ​​is determined as the dominant constraint factor; Based on target spatial resolution Based on the dominant constraint factor, determine at least one of the following control parameters: minimum step angle resolution, beam divergence angle, scanning field of view, and imaging time. Then, control the laser active scanning gas imaging device to perform scanning imaging according to these control parameters, so that... Not greater than ; when ,and , At that time, the current detection distance is determined as the near field, and... and The larger value in the range is determined as the dominant constraint factor in the near field.

2. The laser active scanning gas imaging resolution control method according to claim 1, characterized in that, The single-point sampling period The equivalent cycle required to complete the localization and data acquisition of a scanning location, and , , , , , , .

3. The laser active scanning gas imaging resolution control method according to claim 2, characterized in that, Let the ideal total number of sampling points be In actual scanning, let Set both the number of row sampling points and the number of column sampling points of the uniform grid to The total number of valid sampling points is Let the side length of the square scanning plane be... and in accordance with Determine the sampling density constraint value.

4. The laser active scanning gas imaging resolution control method according to claim 1, characterized in that, when When, reduce the minimum step angle resolution; when At the same time, at least one of the following is taken: extending the imaging time and reducing the scanning field of view.

5. The laser active scanning gas imaging resolution control method according to claim 1, characterized in that, when , and When the decimal orders are the same, the current detection distance is determined as the mid-field transition zone, and the minimum step angle resolution, beam divergence angle, imaging time, and scanning field of view are evaluated and matched accordingly; the same decimal orders mean that the integer part of the common logarithm of the three types of constraint values ​​is the same.

6. The laser active scanning gas imaging resolution control method according to claim 1, characterized in that, when and When the spot size constraint value is determined as the dominant constraint factor, the beam divergence angle is reduced first, and at least one of the following is selected as a supplementary control parameter: reducing the scanning field of view and extending the imaging time.

7. The laser active scanning gas imaging resolution control method according to claim 1, characterized in that, During the system design phase, given the target working distance Target spatial resolution In addition, the single-point sampling period, imaging time, scanning field of view, and initial spot diameter are determined by solving... Determine the maximum allowable step angle interval of the scanning mechanism and the maximum allowable beam divergence angle of the optical system.

8. The laser active scanning gas imaging resolution control method according to claim 1, characterized in that, With the hardware parameters of the laser active scanning gas imaging device fixed, the response to the detection distance The scanning field of view is dynamically reduced or the imaging time is increased according to the parameters allowed by the equipment, and the calculation is recalculated after each adjustment. until .

9. The laser active scanning gas imaging resolution control method according to claim 8, characterized in that, When the allowed target spatial resolution When the numerical value increases and the spatial precision requirement decreases, while satisfying Under the condition of increasing the scanning field of view and shortening the imaging time.

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