A system and method for measuring the chromatic aberration of the atmosphere refraction based on the differential of color camera channels

Abstract

A system and method for measuring atmospheric chromatic aberration based on color camera channel differential analysis includes a transmitting device and a receiving device. The transmitting device comprises two lasers of different wavelengths, a first laser and a second laser, and a fiber coupler. Light beams of corresponding wavelengths, λ1 and λ2, are combined into a single beam via the fiber coupler. The receiving device comprises a telescope, a color camera, and a processor. The telescope receives the light after atmospheric transmission and inputs it into the color camera for imaging. The light is then input into the processor for analysis and processing. The dispersion generated by atmospheric transmission of the two beams of light of different wavelengths is separated via the RGB channels of the color camera. This invention utilizes a dual-wavelength, identical optical path color camera channel differential method, fundamentally resolving the issue of random jitter of the imaging spot caused by atmospheric turbulence affecting high-precision measurements. This method enables high-precision measurement of horizontal atmospheric chromatic aberration in complex underlying atmospheric environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of measuring chromatic aberration of haze, and in particular relates to a system and method for measuring chromatic aberration of haze based on color camera channel differential. Background Art

[0002] The concept of atmospheric aberration was first used in astronomical observations. When light passes through the atmosphere, it undergoes a certain degree of deflection, resulting in a certain deviation between the apparent elevation angle and the actual observed elevation angle. With the in-depth study of atmospheric aberration in various related fields, this concept is now widely used to study the effects of atmospheric refraction on light transmission. Quantitative analysis of atmospheric chromatic aberration is essential for high-precision optical axis calibration, atmospheric transmission, and tracking of lasers. A similar concept, atmospheric chromatic aberration, describes the varying degrees of atmospheric refraction experienced by light of different wavelengths during atmospheric transmission, i.e., the difference in deflection angle. Traditionally, atmospheric aberration has been calculated by observing relevant atmospheric parameters, obtaining profile data along the corresponding transmission path, and then using the atmospheric refractive index formula combined with the ray trajectory propagation equation to calculate the required atmospheric aberration and atmospheric chromatic aberration. However, in areas with low elevation angles or complex underlying surfaces, where the complex atmospheric structure precludes simple models from simulating the light transmission process, the resulting results are often inaccurate and subject to significant errors.

[0003] In order to improve observation accuracy and get rid of dependence on complex atmospheric parameters and models, optical imaging measurement methods are gradually attracting the attention of relevant scholars. This method generally uses two or more different wavelengths and processes their arrival angles to achieve direct measurement of atmospheric chromatic aberration. According to the measurement principle of the optical method, it can be known that the direct object of its measurement is atmospheric chromatic aberration, mainly because the measurement of atmospheric chromatic aberration does not require zero-point calibration, and it is easier to achieve high-precision measurement results through differential processing. However, zero-point calibration of atmospheric chromatic aberration is very difficult for high-precision optical imaging systems, especially in complex outdoor environmental conditions. It is impossible to achieve. However, atmospheric turbulence is a very important factor limiting optical measurement, especially the random jitter of the imaging spot will reduce the accuracy of the measurement results. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a system and method for measuring chromatic aberration of haze based on color camera channel difference. The specific technical solution is as follows:

[0005] A system for measuring atmospheric chromatic aberration based on color camera channel differential includes a transmitting device and a receiving device. The transmitting device is composed of two lasers with different wavelengths and a fiber coupler. The two lasers are a first laser and a second laser. Light with corresponding wavelengths λ1 and λ2 are combined into a single beam through the fiber coupler. The receiving device includes a telescope, a color camera, and a processor. The telescope receives light after being transmitted through the atmosphere and inputs it into the color camera for imaging. Finally, the light is input into the processor for analysis and processing. The dispersion generated by the two beams of light with different wavelengths being transmitted through the atmosphere is separated through the RGB channels of the color camera.

[0006] Specifically, the color camera is an Allied Vision industrial color camera.

[0007] Specifically, the telescope is a purely reflective Cassegrain structure.

[0008] Specifically, λ1 and λ2 are 450 nm and 650 nm, respectively.

[0009] Specifically, it also includes a card-type parallel light tube without color difference set at the output light of the emitting device for initial calibration of the color camera.

[0010] The method for measuring the chromatic aberration of the haze system based on the color camera channel difference mentioned above includes the following steps:

[0011] S1. Obtain the imaging result of the color camera, separate the RGB channels of the color image, obtain the final imaging position of the two light spots with different wavelengths, and calculate the centroids (x R ,y R ) and (x B ,y B ); Assuming the center of mass position when there is no dispersion is (x0, y0), the vertical wavelength differences of λ1 and λ2 are:

[0012]

[0013] Where a is the pixel size of the color camera, and f is the equivalent focal length of the telescope;

[0014] S2. Decompose the measurement result of the air gap into two parts of the R and B channels, namely

[0015]

[0016] Where θ R0 ,θ B0 represents the actual atmospheric difference in atmospheric transmission, and α represents the arrival angle fluctuation error caused by atmospheric turbulence;

[0017] According to the fact that the light sources with wavelengths λ1 and λ2 are transmitted through the atmosphere, the final arrival angle fluctuations are the same for the same measurement system. The expression formula for atmospheric chromatic aberration is obtained by using the channel difference between R and B of the color camera:

[0018]

[0019] S3. Initially calibrate the color camera; convert the light output by the fiber coupler into parallel light, place the calibration light source and the receiving device in a laboratory environment that is considered to have no atmospheric dispersion, and calculate the centroid coordinates of the light spot after channel separation (x RO ,y RO ) and (x RO ,y RO ), follow the same steps as steps S1-S2, and the static initial deviation of the fog color difference is obtained as:

[0020]

[0021] S4. Combined with the dispersion formula under standard air, calculate the veil difference and veil chromatic aberration for any wavelength under the same atmospheric conditions and transmission distance. The dispersion formula under standard air is:

[0022]

[0023] The wavelength of the air difference is expressed as

[0024]

[0025] The chromatic aberration between wavelengths λ3 and λ4 is expressed as:

[0026]

[0027] The advantages of the present invention are:

[0028] (1) The use of optical imaging methods eliminates the reliance on atmospheric model building and meteorological parameter acquisition, and enables high-precision measurement of horizontal cloud color differences in complex underlying atmospheric environments.

[0029] (2) By using the channel difference method of a dual-wavelength, same-optical-path color camera, the arrival angle fluctuation error term is separated by measuring the relative quantity of the atmospheric chromatic aberration between different wavelengths, which fundamentally solves the problem of random jitter of the imaging spot caused by atmospheric turbulence affecting high-precision measurement.

[0030] (3) The absolute quantity of the chromatic aberration requires the knowledge of the initial zero point, and its zero point calibration is very difficult for high-precision optical imaging systems, especially in complex outdoor environments. The color camera channel differential method of measuring the relative quantity of chromatic aberration not only solves the influence of random jitter of the light spot, but also avoids the operation of zero point calibration, making it more feasible in actual engineering applications.

[0031] (4) The initial calibration of the color camera by calibrating the light source avoids the systematic deviation caused by the color camera in the process of synthesizing color pictures, quantifies the influence of static deviation, and improves the accuracy of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a structural diagram of a system for measuring chromatic aberration of haze based on color camera channel difference.

[0033] Figure 2 This is the quantum efficiency diagram of the color camera.

[0034] Figure 3 This is a color imaging and channel separation diagram.

[0035] Figure 4 This is the structural diagram of the calibration light source.

[0036] In the picture:

[0037] 1. Transmitter; 11. First laser; 12. Second laser; 13. Fiber coupler; 2. Receiver; 21. Telescope; 22. Color camera; 23. Processor; 3. Card-type collimator. DETAILED DESCRIPTION

[0038] like Figure 1As shown, a system for measuring atmospheric chromatic aberration based on color camera channel differential analysis includes a transmitter 1 and a receiver 2, each placed at either end of the atmospheric path being measured. Transmitter 1 emits light, which is transmitted through the atmosphere and then received and processed by receiver 2 to produce the desired results. This measurement system is suitable for horizontal transmission over kilometer-scale paths and can monitor atmospheric chromatic aberration along the transmission path in real time. Transmitter 1 comprises two lasers of different wavelengths, a first laser 11 and a second laser 1312, and a fiber coupler. Light beams of corresponding wavelengths λ1 and λ2 are combined into a single beam via the fiber coupler, and can be considered to share the same optical path during atmospheric transmission. Receiver 2 comprises a telescope 21, a color camera 22, and a processor 23. Telescope 21 receives the light after atmospheric transmission and feeds it into color camera 22 for imaging. Finally, the light is fed into processor 23 for analysis and processing. The dispersion of the two beams of light generated by atmospheric transmission is separated by the RGB channels of color camera 22.

[0039] Specifically, the color camera 22 is an Allied Vision industrial color camera 22, and the corresponding quantum efficiency is as follows: Figure 2 As shown in the figure, λ1 and λ2 are 450 nm and 650 nm respectively. The telescope 21 adopts a pure reflective Cassegrain structure and does not produce additional dispersion.

[0040] Specifically, a card-type collimator 3 without color difference is set at the output light of the emitting device 1, and the emitting device 1 and the card-type collimator 3 are used as a calibration light source as a whole. Figure 4 shown.

[0041] The method for measuring the chromatic aberration of the fog system based on the color camera channel difference includes the following steps:

[0042] S1, obtain the imaging result of the color camera 22 as follows Figure 3 As shown, by separating the RGB channels of the color image, the final imaging positions of the two light spots with different wavelengths are obtained, and the centroids are obtained as (x R ,y R ) and (x B ,y B ); Assuming the center of mass position when there is no dispersion is (x0, y0), the vertical wavelength differences of λ1 and λ2 are:

[0043]

[0044] Where a is the pixel size of the color camera 22, and f is the equivalent focal length of the telescope 21. Under typical atmospheric conditions, vertical meteorological gradients primarily produce glare and chromatic aberration. In comparison, horizontal gradients produce less glare and chromatic aberration, which can be ignored. However, in some locations, such as fronts and land-sea boundaries, horizontal variations in meteorological elements are significant. The specific treatment is similar to that for the vertical direction, simply replacing the vertical parameters with horizontal ones.

[0045] S2. Decompose the measurement result of the air gap into two parts of the R and B channels, namely

[0046]

[0047] Where θ R0 ,θ B0 represents the actual atmospheric difference in atmospheric transmission, and α represents the arrival angle fluctuation error caused by atmospheric turbulence;

[0048] According to the fact that the light sources with wavelengths λ1 and λ2 are transmitted through the atmosphere, the final arrival angle fluctuations are the same for the same measurement system. Using the channel difference of the color camera 22R and B, the expression formula for the atmospheric chromatic aberration is obtained:

[0049]

[0050] The reasons for proving that the arrival angle fluctuations of light sources with wavelengths λ1 and λ2 during atmospheric transmission are the same for the same measurement system are as follows:

[0051] When a light beam propagates in the atmosphere, the influence of atmospheric turbulence on the measurement results must be considered. In this paper, we mainly focus on the influence of arrival angle fluctuation on the measurement results. In order to describe the integral effect of atmospheric turbulence on light beam propagation, Freid introduced the atmospheric coherence length r0:

[0052]

[0053] Where L is the transmission path length, β is the zenith angle, is the turbulent refractive index structure constant at height z, and k = 2π / λ is the wave number. From the above formula, it can be seen that the atmospheric coherence length r0 is proportional to λ 6 / 5 , that is, r0∝λ 6 / 5 The variance of arrival angle fluctuation caused by atmospheric turbulence can be expressed as:

[0054]

[0055] Where D is the receiving aperture, r0 is the atmospheric coherence length, and λ is the wavelength.

[0056] S3. Initially calibrate the color camera 22; the calibration light source converts the light output by the fiber coupler into parallel light, and places the calibration light source and the receiving device 2 in a laboratory environment that is considered to have no atmospheric dispersion. The coordinates of the centroid of the light spot after channel separation are calculated as (x RO ,y RO ) and (x BO ,y BO ), follow the same steps as steps S1-S2, and the static initial deviation of the fog color difference is obtained as:

[0057]

[0058] The imaging of color cameras can generally be divided into two types. One is a single-detector color camera, which uses a Bayer filter with a specific RGB arrangement to generate mosaic images of each channel, obtains a complete three-channel image through an interpolation algorithm, and finally synthesizes a color image. The other is a three-detector color camera, which uses a dichroic prism to generate complete three-channel images on three detectors respectively, and finally synthesizes a color image. The above two types of color cameras will produce some static initial deviations for high-precision chromatic aberration measurements. Since the color information of each channel in the former is incomplete, the missing color information can only be estimated through a difference algorithm, resulting in false color display, which has a certain impact on the centroid solution. Although the latter records complete color information through three detectors, it has extremely high requirements on the installation positions of the three detectors. Once there is a mismatch between pixels, it will also affect the final measurement results. The present application can eliminate the influence of static deviations and improve the accuracy of the measurement results by performing initial calibration of the color camera.

[0059] S4. Combined with the dispersion formula under standard air, calculate the veil difference and veil chromatic aberration for any wavelength under the same atmospheric conditions and transmission distance. The dispersion formula under standard air is:

[0060]

[0061] The wavelength of the air difference can be expressed as

[0062]

[0063] The chromatic aberration between wavelengths λ3 and λ4 is expressed as:

[0064]

[0065] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A system for measuring chromatic aberration of airborne particles based on color camera channel difference, characterized in that: The invention comprises a transmitting device (1) and a receiving device (2), wherein the transmitting device (1) is composed of two lasers with different wavelengths and a fiber coupler (13), wherein the two lasers are a first laser (11) and a second laser (12), and light with corresponding wavelengths λ1 and λ2 are combined into a single light beam through the fiber coupler (13); the receiving device (2) comprises a telescope (21), a color camera (22) and a processor (23), wherein the telescope (21) receives light after being transmitted through the atmosphere and inputs the light into the color camera (22) for imaging, and finally inputs the light into the processor (23) for analysis and processing, and the dispersion generated by the two light beams with different wavelengths being transmitted through the atmosphere is separated through the RGB channels of the color camera (22); The measurement steps include: S1. Obtain the imaging result of the color camera (22), separate the RGB channels of the color image, obtain the final imaging position of the light spots of two different wavelengths, and calculate the centroids (x R ,y R ) and (x B ,y B ); Assuming the center of mass position when there is no dispersion is (x0, y0), the vertical wavelength differences of λ1 and λ2 are: Where a is the pixel size of the color camera (22), and f is the equivalent focal length of the telescope (21); S2. Decompose the measurement result of the air gap into two parts of the R and B channels, namely Where θ R0 ,θ B0 represents the actual atmospheric difference in atmospheric transmission, and α represents the arrival angle fluctuation error caused by atmospheric turbulence; According to the fact that the light sources with wavelengths λ1 and λ2 are transmitted in the atmosphere, for the same measurement system, the resulting arrival angle fluctuations are the same, and the expression formula of the atmospheric chromatic aberration is obtained by using the channel difference of R and B of the color camera (22): S3. Initially calibrate the color camera (22); convert the light output by the fiber coupler (13) into parallel light, place the calibration light source and the receiving device (2) in a laboratory environment that is considered to have no atmospheric dispersion, and calculate the centroid coordinates of the light spot after channel separation (x RO ,y RO ) and (x RO ,y RO ), follow the same steps as steps S1-S2, and the static initial deviation of the fog color difference is obtained as: S4. Combined with the dispersion formula under standard air, calculate the veil difference and veil chromatic aberration for any wavelength under the same atmospheric conditions and transmission distance. The dispersion formula under standard air is: The wavelength of the air difference is expressed as The chromatic aberration between wavelengths λ3 and λ4 is expressed as:

2. The system for measuring chromatic aberration of air based on color camera channel difference according to claim 1, characterized in that: The color camera (22) is an Allied Vision industrial color camera (22).

3. The system for measuring chromatic aberration of air based on color camera channel difference according to claim 1, characterized in that: The telescope (21) is a purely reflective Cassegrain structure.

4. The system for measuring chromatic aberration of air based on color camera channel difference according to claim 1, characterized in that: λ1 and λ2 are 450nm and 650nm respectively.

5. The system for measuring chromatic aberration of air based on color camera channel difference according to claim 1, characterized in that: It also includes a card-type parallel light tube (3) without color difference arranged at the outgoing light of the emitting device (1) for initial calibration of the color camera (22).

6. A method for measuring a haze color difference system based on color camera channel difference according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Obtain the imaging result of the color camera (22), separate the RGB channels of the color image, obtain the final imaging position of the light spots of two different wavelengths, and calculate the centroids (x R ,y R ) and (x B ,y B ); Assuming the center of mass position when there is no dispersion is (x0, y0), the vertical wavelength differences of λ1 and λ2 are: Where a is the pixel size of the color camera (22), and f is the equivalent focal length of the telescope (21); S2. Decompose the measurement result of the air gap into two parts of the R and B channels, namely Where θ R0 ,θ B0 represents the actual atmospheric difference in atmospheric transmission, and α represents the arrival angle fluctuation error caused by atmospheric turbulence; According to the fact that the light sources with wavelengths λ1 and λ2 are transmitted in the atmosphere, for the same measurement system, the resulting arrival angle fluctuations are the same, and the expression formula of the atmospheric chromatic aberration is obtained by using the channel difference of R and B of the color camera (22): S3. Initially calibrate the color camera (22); convert the light output by the fiber coupler (13) into parallel light, place the calibration light source and the receiving device (2) in a laboratory environment that is considered to have no atmospheric dispersion, and calculate the centroid coordinates of the light spot after channel separation (x RO ,y RO ) and (x RO ,y RO ), follow the same steps as steps S1-S2, and the static initial deviation of the fog color difference is obtained as: S4. Combined with the dispersion formula under standard air, calculate the veil difference and veil chromatic aberration for any wavelength under the same atmospheric conditions and transmission distance. The dispersion formula under standard air is: The wavelength of the air difference is expressed as The chromatic aberration between wavelengths λ3 and λ4 is expressed as:

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