A wedge mirror frosting and dewing judgment method and device based on image processing

Abstract

The application discloses a wedge mirror frosting and dewing judgment method and device based on image processing and belongs to the technical field of atmospheric optical measurement equipment. The method comprises the following steps: collecting images of stars after being split by a double-wedge mirror in real time and converting the images into gray-scale images; identifying star targets by adopting a YOLO series light model and extracting starlight spots of regions of interest; calculating three characteristic indexes of spot gray-scale uniformity, spot edge sharpness and star target contrast for each spot region of interest; obtaining an ambient temperature and a dew point temperature, combining preset judgment thresholds of the three characteristic indexes in S3, adopting a continuous frame judgment rule and judging whether frosting and dewing phenomena exist on the surface of the double-wedge mirror; and according to a frosting and dewing judgment result, controlling the start-stop and heating power of a transparent heating film on the surface of the double-wedge mirror, simultaneously monitoring image deformation states in a heating process and dynamically adjusting heating parameters. The application can realize automatic and accurate judgment of frosting and dewing of the double-wedge mirror.

Description

Technical Field

[0001] This invention belongs to the technical field of atmospheric optical measurement equipment, specifically relating to a method and device for judging frost and dew on a wedge mirror based on image processing. Background Technology

[0002] The atmospheric coherence length measurement instrument is a core device for characterizing atmospheric turbulence and is widely used in astronomical observation, atmospheric optics research, and laser communication link evaluation. The DIMM (Differential Image Motion Monitor) atmospheric coherence length measurement instrument has a double wedge mirror at its front end. It uses the wedge mirrors to separate images to track and measure stellar targets. The optical properties of the wedge mirror surfaces directly determine the separation accuracy and image quality, thus affecting the reliability of atmospheric coherence length parameter inversion.

[0003] In autumn and winter, when the ambient temperature is below the dew point and the diurnal temperature range is large, dew or even frost easily condenses on the surface of the wedge mirror, causing light scattering, image blurring, and inaccurate identification of stellar targets, and in severe cases, measurement interruption. Current technologies for handling frost and condensation on wedge mirrors mainly rely on manual wiping or passive insulation, which has the following drawbacks: First, the response is delayed; by the time manual detection and handling of frost and condensation occur, the equipment has already experienced measurement errors or interruptions, making real-time intervention impossible. Second, passive insulation has limited effectiveness and cannot adapt to temperature and humidity changes in different regions and at different times, and it easily leads to increased equipment size and energy consumption. Third, some active heating solutions lack precise frost and condensation judgment logic; blind heating not only wastes energy but also causes image distortion due to thermal expansion and contraction of the wedge mirror, further affecting measurement accuracy.

[0004] Current applications of image processing technology in atmospheric optical equipment are mostly focused on stellar target identification and turbulence parameter calculation. There is a lack of specific methods for judging frost and condensation on wedge mirrors, particularly a lack of precise judgment logic combining stellar image characteristics and ambient temperature. This fails to meet the all-weather, automated, and high-precision operational requirements of atmospheric coherence length measuring instruments. Therefore, there is an urgent need to develop an image processing-based method and device for judging frost and condensation on wedge mirrors, enabling automatic and accurate identification and intelligent heating control. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for determining frost and condensation on a wedge mirror based on image processing, used in a DIMM atmospheric coherence length measuring instrument, wherein a double wedge mirror is provided at the front end of the DIMM atmospheric coherence length measuring instrument, and the surface of the double wedge mirror is coated with a transparent heating film, comprising:

[0007] S1. Image Acquisition: Real-time acquisition of images of stars after they have been imaged by the double wedge mirror, and conversion into grayscale images;

[0008] S2. Region of Interest Extraction for Star Spots: The YOLO series of lightweight models are used to identify stellar targets and extract the regions of interest for stellar spots.

[0009] S3. Feature index calculation: For each region of interest of the light spot, calculate three feature indices: gray-scale uniformity of the light spot, edge sharpness of the light spot, and contrast of the star target.

[0010] S4. Frost and Dew Point Judgment: Obtain the ambient temperature and dew point temperature, combine them with the judgment thresholds of the three characteristic indicators in S3, and use the continuous frame judgment rule to determine whether there is frost or dew on the surface of the double wedge mirror.

[0011] S5. Heating Control: Based on the frost and condensation judgment results of S4, control the start and stop of the transparent heating film on the surface of the double wedge mirror and the heating power, while monitoring the image deformation state during the heating process and dynamically adjusting the heating parameters.

[0012] A wedge mirror frost / dew determination device based on image processing, used in a DIMM atmospheric coherence length measuring instrument, comprising:

[0013] Image acquisition module: used to acquire images of stars after they have been imaged by the double wedge mirror in real time and transmit them to the image processing module;

[0014] Image processing module: Electrically connected to image acquisition module, temperature acquisition module, heating module and control module, used to convert the acquired image into a grayscale image, extract the region of interest of the light spot through the target detection algorithm, calculate three feature indicators: grayscale uniformity of the light spot, edge sharpness of the light spot and contrast of the star target, and perform frost and dew judgment;

[0015] Temperature acquisition module: used to acquire ambient temperature and dew point temperature in real time, and transmit the acquired data to the image processing module;

[0016] Heating module: includes a transparent heating film with a partitioned heating design coated on the surface of the double wedge mirror and a heating drive unit; the heating drive unit receives control commands from the image processing module to realize the start and stop of the heating film and power adjustment;

[0017] Control module: Implemented by control software running on an embedded computer, it connects to the image processing module, heating module, and temperature acquisition module. It is used to coordinate the work of each module, receive and store three characteristic index data, ambient temperature and dew point temperature data, frost and dew judgment results, and heating control records, and reserves parameter interfaces; it also supports docking with the original star tracking and coherence length calculation modules of the DIMM atmospheric coherence length measuring instrument.

[0018] The present invention has the following beneficial effects:

[0019] (1) Achieve automatic and accurate judgment of frost and dew on double wedge mirror: This invention combines three core feature indicators of star image (spot gray uniformity, edge sharpness, target contrast) with ambient temperature and dew point temperature, and adopts continuous frame judgment rules to avoid misjudgment of single indicators or instantaneous frames. The judgment accuracy is high and no manual intervention is required. It solves the problems of lagging manual detection of frost and large judgment error in the prior art, and meets the all-weather automatic operation requirements of DIMM atmospheric coherence length measuring instrument.

[0020] (2) Avoiding the risk of image deformation caused by heating: During the heating control process, the present invention monitors the image deformation status in real time and balances the requirements of anti-condensation of the double wedge mirror and image stability by dynamically adjusting the heating power and pausing heating, effectively avoiding the thermal expansion and contraction of the double wedge mirror due to blind heating, thereby ensuring the accuracy of star recognition and the reliability of atmospheric coherence length measurement data.

[0021] (3) Strong environmental adaptability and low energy consumption: The present invention uses a transparent heating film, which does not affect the image splitting function and light transmission of the double wedge mirror; through precise judgment and zone heating and dynamic power adjustment, energy waste is reduced; and the parameters can be finely adjusted according to the temperature and humidity characteristics of different regions to adapt to complex environments of -25℃~45℃ and relative humidity ≤90%, significantly improving the environmental adaptability of the equipment.

[0022] (4) Good integration and strong practicality: The method and device of the present invention can be directly integrated into the DIMM atmospheric coherence length measuring instrument, and can be seamlessly connected with the original YOLO star recognition module, control system and parameter calculation module of the equipment. There is no need to make significant modifications to the original equipment structure and code. The transformation is easy and the cost is controllable. It can be widely used in astronomical observation, atmospheric optics research and other related scenarios, and has extremely high practical value and promotion prospects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the DIMM atmospheric coherence length measuring instrument; where 1-double wedge mirror; 2-image acquisition and temperature control module; 3-control module; 4-two-dimensional scanning turntable;

[0024] Figure 2 This is a flowchart of the image processing-based wedge mirror frost and condensation judgment method of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] This invention provides a method for determining frost and condensation on a wedge mirror based on image processing, used in a DIMM atmospheric coherence length measuring instrument. For example... Figure 1 As shown, the DIMM atmospheric coherence length measuring instrument includes: a two-dimensional scanning turntable 4, with a double wedge mirror 1 mounted at its upper front end, and a telescope and an image acquisition and temperature control module 2 mounted at the rear end of the double wedge mirror 1. The image acquisition and temperature control module 2 integrates an image acquisition module and a temperature acquisition module, and is installed at the rear end of the double wedge mirror 1 to acquire stellar images and various temperature data. The two-dimensional scanning turntable is used for stellar target tracking to achieve stellar imaging for measuring atmospheric coherence length. The DIMM atmospheric coherence length measuring instrument also includes a control module 3 electrically connected to the image acquisition and temperature control module 2 and the two-dimensional scanning turntable 4, used to coordinate the operation of each component / module. The surface of the double wedge mirror 1 is coated with a transparent heating film.

[0027] like Figure 2 As shown, the image processing-based wedge mirror frost / condensation determination method of the present invention includes the following steps:

[0028] S1, Image Acquisition: Real-time acquisition of images of stars after passing through the double wedge mirror (1-minute image) and conversion of them into grayscale images.

[0029] S2, Region of Interest (ROI) Extraction: The grayscale image is used to identify stars by a target detection algorithm, and the region of interest (ROI) corresponding to each star is extracted. The target detection algorithm adopts the YOLO (You Only Look Once) series of lightweight models, which are adapted to the computing power requirements of the embedded processing unit of the device and can stably identify stars with brightness no less than magnitude 3 (i.e., magnitude 1, magnitude 2, and magnitude 3).

[0030] S3, Feature metric calculation: For each spot ROI, three feature metrics are calculated, specifically including:

[0031] Spot gray uniformity: Extract gray data within the ROI of the spot, calculate the gray mean and gray standard deviation, and calculate the spot gray uniformity using the formula: Spot gray uniformity = 1 - (Gray standard deviation / Gray mean). Then normalize the spot gray uniformity to the range of 0-1. The closer the spot gray uniformity is to 1, the more uniform the gray distribution.

[0032] Spot edge sharpness: Gaussian blur noise reduction is performed on the spot ROI, the gradient magnitude in the x and y directions is calculated, and the average value of the gradient magnitude is taken as the edge sharpness. The greater the edge sharpness, the clearer the spot edge.

[0033] Star target contrast: Construct an expanded background ROI centered on the spot ROI, subtract the spot area from the background ROI, and calculate the average gray value of the background. The star target contrast is calculated using the formula: Star target contrast = (Spot gray value - Background gray value) / Background gray value. The star target contrast is then normalized to the range of 0-1. The higher the star target contrast, the more obvious the difference between the star target and the background.

[0034] S4, Frost and Dew Detection: Obtain the ambient temperature and dew point temperature, preset the judgment thresholds for three feature indicators, and use the continuous frame judgment rule to judge frost and dew. Specifically, when there are two or more feature indicators lower than the corresponding preset judgment thresholds in N consecutive grayscale images, and the ambient temperature is lower than the dew point temperature, it is determined that there is frost and dew on the surface of the double wedge mirror 1; otherwise, it is determined that there is no frost and dew. The judgment thresholds for the three feature indicators can be finely adjusted according to the regional temperature and humidity characteristics.

[0035] S5, Heating Control: Based on the frosting / condensation judgment result of S4, control the start / stop of the transparent heating film on the surface of the double wedge mirror and the heating power, while monitoring the image deformation state during the heating process and dynamically adjusting the heating parameters. The specific control logic is as follows:

[0036] If frost or condensation is detected, the transparent heating film on the surface of the double wedge mirror 1 is activated to heat the double wedge mirror 1 in sections at the rated power.

[0037] During the heating process, the relative position deviation of the two stars after the double wedge mirror image is calculated in real time, and the distortion rate of the light spot shape is monitored to check the image deformation status. When the distortion rate of the light spot shape exceeds the judgment threshold, the heating power is reduced. If the distortion rate of the light spot shape continues to rise, the heating is temporarily stopped. When the three characteristic indicators of N consecutive frames of grayscale images have returned to the normal range, the heating is stopped. After the temperature stabilizes, the low-power heating is restarted to prevent frost and condensation from forming again.

[0038] If no frost or condensation is detected, or if all three characteristic indicators of N consecutive grayscale images return to the normal range after heating, stop heating, return to S1, and continue monitoring.

[0039] Furthermore, in S1, the grayscale image conversion method is to convert the image into a grayscale image of the corresponding format by directly converting the format or by calculating the pixel grayscale, so as to ensure the accuracy of the grayscale data.

[0040] Furthermore, in S2, the lightweight YOLO model is YOLOv8-nano (YOLO version 8 - lightweight version), trained and optimized using a dedicated stellar dataset. This dataset contains images of stars at different magnitudes and atmospheric turbulence intensities. Data augmentation (rotation, scaling, noise overlay, and lighting simulation) enhances the model's generalization ability, solving the challenge of distinguishing low-magnitude stars from background noise.

[0041] Furthermore, in S3, before calculating the three feature indicators, the validity of the ROI is checked to ensure that the ROI is within the grayscale image range and is not an empty ROI, so as to avoid calculation errors or device crashes due to invalid ROIs.

[0042] Furthermore, in S4, the determination threshold is calibrated by the following method: under normal conditions of no condensation and no interference in the double wedge mirror 1, multiple frames of star images are acquired, and the average value of the three characteristic indicators is calculated as the basic threshold. Then, the basic threshold is corrected according to the temperature and humidity characteristics of the equipment deployment area, and the corrected value is set as the determination threshold. The determination threshold is then fine-tuned by the control module 3 to improve adaptability.

[0043] The present invention further provides an image processing-based wedge mirror frost / dew determination device for use in a DIMM atmospheric coherence length measuring instrument, comprising:

[0044] Image acquisition module: used to acquire images of stars after they have passed through the double wedge mirror in 1 minute in real time, and transmit them to the image processing module;

[0045] Image processing module: Electrically connected to image acquisition module, temperature acquisition module, heating module, and control module 3, it is used to convert the acquired images into grayscale images, extract the ROI of the light spot through a target detection algorithm, calculate three feature indicators: grayscale uniformity of the light spot, edge sharpness of the light spot, and contrast of the star target, and perform frost and dew judgment; the image processing module has a built-in feature calculation unit to realize the rapid calculation of the three feature indicators, adapting to the real-time measurement requirements of the equipment;

[0046] Temperature acquisition module: used to acquire ambient temperature and dew point temperature in real time, and transmit the ambient temperature and dew point temperature data to the image processing module to provide data support for frost and dew judgment and heating control; the temperature acquisition module is set as a temperature sensor.

[0047] Heating module: includes a transparent heating film, such as an ITO (indium tin oxide) transparent heating film, coated on the surface of the double wedge mirror 1, and a heating drive unit. The transparent heating film has a light transmittance of ≥95%, uniform heating, low power consumption, and a total power control within 5W, and is compatible with the equipment power supply system. The heating drive unit receives control commands from the image processing module to realize the start and stop of the heating film and power adjustment.

[0048] Control Module 3: Implemented by control software running on an embedded computer, it connects to the image processing module, heating module, and temperature acquisition module. It coordinates the work of each module, receives and stores three characteristic index data, ambient temperature and dew point temperature data, frost and dew judgment results, and heating control records. It has reserved parameter interfaces for fine-tuning parameters such as threshold and heating power. It also supports interface with the original star tracking and coherence length calculation modules of the DIMM atmospheric coherence length measuring instrument to ensure the overall coordinated operation of the equipment.

[0049] Furthermore, in the image processing module, the target detection algorithm accelerates inference through TensorRT (Tensor Inference Engine), controlling the recognition time of a single frame image to within 10ms, meeting the real-time measurement requirements of the device; at the same time, an adaptive confidence threshold mechanism is introduced to dynamically adjust the confidence threshold for star recognition based on the current image signal-to-noise ratio, further reducing the false negative and false positive rates of star recognition.

[0050] Furthermore, the transparent heating film of the heating module adopts a zoned heating design, which can achieve precise heating according to the frost and condensation conditions in different areas of the double wedge mirror 1, reduce energy waste, and reduce the risk of image distortion caused by local overheating.

[0051] After extracting the ROI, the image processing module adds a spot morphology screening step to remove false spot ROIs caused by noise and atmospheric turbulence interference. The added spot morphology screening rule is to retain spot ROIs with a circularity between 0.7 and 1.0 and an area within a preset reasonable range, further improving the accuracy of feature index calculation.

[0052] The temperature acquisition module also collects the surface temperature of the double wedge mirror 1 in real time and transmits it to the control module 3. The control module 3 combines the surface temperature of the double wedge mirror 1 with the ambient temperature and dew point temperature to adjust the heating power of the double wedge mirror 1 in a coordinated manner to avoid the surface temperature of the double wedge mirror 1 being too high or too low.

[0053] The N value in the continuous frame determination rule can be manually fine-tuned by the control module 3 to adapt to the temperature and humidity fluctuation frequency of different regions. The value of N ranges from 3 to 10 frames, with a default value of 5 frames.

[0054] The heating drive unit of the heating module has a built-in over-temperature protection module. When the surface temperature of the double wedge mirror 1 exceeds the preset safety threshold (default 50℃), the heating power supply is automatically cut off to prevent damage to the double wedge mirror 1.

[0055] Example 1: A method for judging frost and condensation on a wedge mirror based on image processing;

[0056] This embodiment is applied to a certain model of DIMM atmospheric coherence length measuring instrument (with a double wedge mirror 1 at the front end, the surface of which is coated with an ITO (indium tin oxide) transparent heating film). The equipment operates in the autumn and winter seasons, with an ambient temperature range of -25℃ to 45℃ and a relative humidity of 60% to 90%. The specific implementation steps are as follows:

[0057] S1, Image Acquisition: The device's image acquisition module acquires a black-and-white image of the star after it passes through the double wedge mirror in real time, and transmits it to the image processing module; the acquired image is converted into a specified format to ensure accurate grayscale data.

[0058] S2, ROI extraction: The trained and optimized lightweight YOLO series model is used to identify stars in the grayscale image; after identification, the two star ROIs corresponding to the first image of the double wedge mirror are extracted, and the validity of the ROIs is checked to ensure that the ROIs are completely within the grayscale image range.

[0059] S3, Feature index calculation: For each spot ROI, calculate three feature indices respectively.

[0060] Spot grayscale uniformity: Extract grayscale data within the ROI of the spot, calculate the mean grayscale value, and then calculate the grayscale uniformity of the spot.

[0061] Spot edge sharpness: Gaussian blur noise reduction is performed on the spot ROI by calculating the gradient in the x and y directions and taking the average gradient magnitude;

[0062] Star target contrast: With the spot ROI as the center, a background ROI is constructed by expanding outward according to a preset ratio. After deducting the effective area of ​​the spot within the background ROI, the average gray value of the background in that area is calculated. The star target contrast is calculated using the formula: Star target contrast = (Spot gray value - Background gray value) / Background gray value. The result is normalized to the range of 0-1. The larger the value, the more significant the gray value difference between the star target and the background.

[0063] S4, Frost / Dew Condensation Detection: The ambient temperature is obtained through the temperature acquisition module. Dew point temperature is The preset threshold values ​​for the three feature indicators are: light spot grayscale uniformity threshold value. Threshold for determining the sharpness of light spot edges 2. Stellar target contrast determination threshold Current ambient temperature Below dew point temperature However, all three characteristic indicators were higher than the corresponding thresholds, indicating that there was no frost or condensation on the surface of the double wedge mirror 1. The process was then returned to the image acquisition step for continuous monitoring.

[0064] Simulating frost and condensation scenarios: artificially lowering the ambient temperature to Dew point temperature maintained This causes dew to condense on the surface of the double wedge mirror 1. At this point, the three characteristic indicators of the ROI (Region of Interest) in the acquired grayscale image become: [Indicators related to the grayscale uniformity of the spot]. Sharpness of the light spot edge stellar target contrast ;continuous In the frame image, all three indicators are below the preset threshold, and the ambient temperature... Below dew point temperature The presence of condensation was determined.

[0065] S5, Heating Control: The ITO transparent heating film is activated, heating in zones at a rated power of 5W; during heating, the relative position deviation and beam distortion rate of the two stars are calculated in real time, and the heating time is adjusted accordingly. Afterwards, the light spot distortion rate reached 0.6%, so the heating power was reduced to 3W; the heating time continued. Afterwards, the three characteristic indicators of the light spot were restored to: light spot grayscale uniformity. Sharpness of the light spot edge stellar target contrast ,continuous Once the frame rate stabilizes and meets the standard, heating is stopped, and the equipment returns to normal measurement status.

[0066] Example 2: A wedge mirror frost / condensation detection device based on image processing;

[0067] The apparatus in this embodiment corresponds to the method in Embodiment 1 and is applied to the same model of DIMM atmospheric coherence length measuring instrument, specifically including:

[0068] Image acquisition module: Employs a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, configured to correspond with the device's lens and double wedge mirror, ensuring clear acquisition of images of stars after they have passed through the double wedge mirror for one minute;

[0069] Image processing module: It adopts an embedded processor, integrates computing unit and neural network target detection model, and accelerates inference through TensorRT. The time consumption of single frame image recognition and single frame single spot feature index calculation meets the real-time measurement requirements.

[0070] Temperature acquisition module: includes several temperature sensors for acquiring ambient temperature and dew point temperature, with a measurement accuracy of ±0.1℃, and communicates with the image processing module via serial port;

[0071] Heating module: It adopts ITO transparent heating film with 95% light transmittance and has two heating areas, corresponding to the two image division areas of the double wedge mirror 1; the heating drive unit adopts a dedicated controller to realize heating start / stop and power adjustment;

[0072] Control module: An embedded processor is used to coordinate the work of each module. It supports manual fine-tuning of parameters such as threshold parameters and heating power. It can store nearly 30 days of characteristic index data, temperature data and heating control records, which is convenient for equipment maintenance and data analysis. At the same time, it seamlessly connects with the original star tracking and coherence length calculation modules of the DIMM atmospheric coherence length measuring instrument to ensure the overall coordinated operation of the equipment.

[0073] The above description is merely an embodiment of the present invention and does not limit the scope of the invention. Any equivalent structural or procedural transformations made based on the description and drawings of this invention, or direct or indirect applications in other related system fields, are similarly included within the protection scope of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for judging frost and dew on a wedge mirror based on image processing, characterized in that, Used in a DIMM atmospheric coherence length measuring instrument, the DIMM atmospheric coherence length measuring instrument has a double wedge mirror at its front end, and the surface of the double wedge mirror is coated with a transparent heating film, including: S1. Image Acquisition: Real-time acquisition of images of stars after they have been imaged by the double wedge mirror, and conversion into grayscale images; S2. Region of Interest Extraction for Star Spots: The YOLO series of lightweight models are used to identify stellar targets and extract the regions of interest for stellar spots. S3. Feature index calculation: For each region of interest of the light spot, calculate three feature indices: gray-scale uniformity of the light spot, edge sharpness of the light spot, and contrast of the star target. S4. Frost and Dew Point Judgment: Obtain the ambient temperature and dew point temperature, combine them with the judgment thresholds of the three characteristic indicators in S3, and use the continuous frame judgment rule to determine whether there is frost or dew on the surface of the double wedge mirror. S5. Heating Control: Based on the frost and condensation judgment results of S4, control the start and stop of the transparent heating film on the surface of the double wedge mirror and the heating power, while monitoring the image deformation state during the heating process and dynamically adjusting the heating parameters.

2. The method for determining frost and dew on a wedge mirror based on image processing according to claim 1, characterized in that, The DIMM atmospheric coherence length measuring instrument includes: a two-dimensional scanning turntable, with a double wedge mirror mounted at the upper front end of the turntable, and a telescope and an image acquisition and temperature control module mounted at the rear end of the double wedge mirror; the image acquisition and temperature control module integrates the image acquisition module and the temperature acquisition module, and is installed at the rear end of the double wedge mirror, for acquiring stellar images and various temperature data; the two-dimensional scanning turntable is used for stellar target tracking to achieve stellar imaging; it also includes a control module electrically connected to the image acquisition and temperature control module and the two-dimensional scanning turntable respectively.

3. The method for determining frost and dew on a wedge mirror based on image processing according to claim 1, characterized in that, In S3, before calculating the three feature indicators, the region of interest of the spot is checked for validity to ensure that the region of interest of the spot is within the grayscale image range and is not an empty region of interest.

4. The method for determining frost and dew on a wedge mirror based on image processing according to claim 1, characterized in that, In S3, the method for calculating the gray uniformity of the spot is as follows: extract the gray data in the region of interest of the spot, calculate the gray mean and gray standard deviation, and calculate the gray uniformity of the spot using the formula: gray uniformity of spot = 1 - (gray standard deviation / gray mean), and normalize the gray uniformity of the spot to the range of 0-1. The method for calculating the edge sharpness of the light spot is as follows: Gaussian blur noise reduction is performed on the region of interest of the light spot, the gradient magnitudes in the x and y directions are calculated, and the average value of the gradient magnitudes is taken as the edge sharpness. The method for calculating the contrast of a star target is as follows: Construct an expanded background region of interest centered on the region of interest of the light spot, subtract the light spot region from the background region of interest, and calculate the average gray value of the background. Calculate the star target contrast using the formula: Star target contrast = (average gray value of light spot - average gray value of background) / average gray value of background, and normalize the star target contrast to the range of 0-1.

5. The method for determining frost and dew on a wedge mirror based on image processing according to claim 1, characterized in that, In step S4, the continuous frame determination rule is as follows: when two or more feature indicators in multiple consecutive grayscale images are lower than the corresponding determination threshold, and the ambient temperature is lower than the dew point temperature, it is determined that there is frost or condensation on the surface of the double wedge mirror.

6. The method for determining frost and dew on a wedge mirror based on image processing according to claim 1, characterized in that, In step S4, under normal conditions with no condensation and no interference on the double wedge mirror, multiple frames of star images are acquired, and the average values ​​of the three characteristic indicators are calculated as the basic threshold. The basic threshold is then corrected according to the temperature and humidity characteristics of the region, and the corrected value is set as the judgment threshold. The judgment threshold is then fine-tuned through the control module.

7. The method for determining frost and dew on a wedge mirror based on image processing according to claim 1, characterized in that, In step S5, the control logic is as follows: if it is determined that there is frost or condensation, the transparent heating film on the surface of the double wedge mirror is activated to heat the double wedge mirror in sections with the rated power. After heating is started, the relative position deviation of the two stars after the double wedge mirror image splitting and the light spot shape distortion rate are calculated in real time. When the light spot shape distortion rate exceeds the judgment threshold, the heating power is reduced. If the light spot shape distortion rate continues to rise, heating is temporarily stopped. When the three characteristic indicators of N consecutive frames of grayscale images have returned to the normal range, low-power heating is restarted after the temperature stabilizes to prevent frost and condensation from forming again. If no frost or condensation is detected, or if all three characteristic indicators of N consecutive grayscale images return to the normal range after heating, stop heating, return to S1, and continue monitoring.

8. A wedge mirror frost / dew determination device based on image processing, characterized in that, For DIMM atmospheric coherence length measurement instruments, including: Image acquisition module: used to acquire images of stars after they have been imaged by the double wedge mirror in real time and transmit them to the image processing module; Image processing module: Electrically connected to image acquisition module, temperature acquisition module, heating module and control module, used to convert the acquired image into a grayscale image, extract the region of interest of the light spot through the target detection algorithm, calculate three feature indicators: grayscale uniformity of the light spot, edge sharpness of the light spot and contrast of the star target, and perform frost and dew judgment; Temperature acquisition module: used to acquire ambient temperature and dew point temperature in real time, and transmit the acquired data to the image processing module; Heating module: includes a transparent heating film with a partitioned heating design coated on the surface of the double wedge mirror and a heating drive unit; the heating drive unit receives control commands from the image processing module to realize the start and stop of the heating film and power adjustment; Control module: Implemented by control software running on an embedded computer, it connects to the image processing module, heating module, and temperature acquisition module. It is used to coordinate the work of each module, receive and store three characteristic index data, ambient temperature and dew point temperature data, frost and dew judgment results, and heating control records, and reserves parameter interfaces; it also supports docking with the original star tracking and coherence length calculation modules of the DIMM atmospheric coherence length measuring instrument.

9. The wedge mirror frost / dew judgment device based on image processing according to claim 8, characterized in that, After extracting the region of interest (ROI) of the light spot, the image processing module adds a light spot morphology screening step to remove false light spot ROIs. The light spot morphology screening rule is to retain light spot ROIs with a circularity between 0.7 and 1.0 and an area within a preset reasonable range.

10. The wedge mirror frost / dew judgment device based on image processing according to claim 8, characterized in that, The temperature acquisition module also collects the surface temperature of the double wedge mirror in real time and transmits it to the control module. The control module combines the surface temperature of the double wedge mirror with the ambient temperature and dew point temperature to adjust the heating power of the double wedge mirror in a coordinated manner. The heating drive unit of the heating module has a built-in over-temperature protection module. When the surface temperature of the double wedge mirror exceeds the preset safety threshold, it automatically cuts off the heating power to prevent damage to the double wedge mirror.

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