Python-based device and method for testing light beam quality of mid-infrared special-shaped structure light beam

Abstract

The invention discloses a device and a method for testing the quality of a mid-infrared special-shaped structure light beam based on python. According to the device, a CCD intelligent mobile system comprises a ball screw transmission guide rail, a stepping motor A and a CCD camera; the light beam intensity automatic attenuation system comprises a hollow rotating table, an attenuation sheet and a stepping motor B; the reflective dispersion-free focusing system comprises an off-axis parabolic mirror M1 and an off-axis parabolic mirror M2; the control system is connected with the stepping motor A, the stepping motor B and the CCD camera. The method comprises the following steps: after light beams are attenuated by the attenuation sheet, reflecting by the reflector to obtain reflected light; the special-shaped structure light beam light spots are transmitted to the control system through the CCD camera, and the control system automatically attenuates and weakens stray light in the special-shaped structure light beam light spots according to a set threshold value. Based on an image tracking capture technology, capturing a light spot in the specially-shaped structure light beam, calculating the light beam intensity, the light spot radius and the divergence angle of the light spot, and finally obtaining M2. The device and the method can automatically and accurately test the quality of the light beam.

Description

Technical Field

[0001] The invention belongs to the technical fields of intelligent control technology and mid-infrared beam quality testing, and specifically relates to a beam quality testing device and method for a mid-infrared special-shaped structure beam based on Python. Background Art

[0002] With the development of science and technology, laser has become an inseparable part of our lives. From laser cutting to laser communication, from medical surgery to laser printing, laser technology has been widely used in various fields. In laser technology, beam quality is a key parameter, which directly affects the performance and application effect of laser.

[0003] Beam quality is one of the important indicators to measure the performance of laser beam, usually expressed in M. 2 Factor M 2 The factor describes the deviation of the actual laser beam from the ideal Gaussian beam. 2 The closer the value is to the theoretical value (the minimum theoretical value is 1), the higher the beam quality is and the closer it is to an ideal Gaussian beam. A high-quality beam means that the laser beam has better focusing performance and can transmit more energy in a smaller area, which is critical for many precision processing and high-demand applications.

[0004] Laser beam quality is one of the key factors that determine laser performance, and directly affects the application effect and efficiency of lasers in various fields. Understanding and improving beam quality is of great significance for optimizing laser systems, improving processing accuracy and efficiency, and ensuring operational safety. With the continuous advancement of science and technology, the research and optimization of laser beam quality will continue to promote the development and application of laser technology, bringing more innovation and progress to all walks of life.

[0005] Although today's beam quality test devices have many advantages, they also have some significant shortcomings. For example, these devices have insufficient attenuation capabilities for lasers, which can easily damage the equipment during high-power laser testing; interference fringes caused by reflections are mixed with ring light, affecting the accuracy of the measurement; and the lack of intelligence makes it impossible to automatically handle complex test tasks. Summary of the invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention provides a beam quality testing device and method for a mid-infrared special-shaped structured light beam based on Python. The device has a high degree of intelligence and can automatically realize accurate testing of the beam quality. The method has a simple implementation process and can perform reliable and accurate evaluation of the beam quality for different types of light beams.

[0007] The present invention provides a Python-based mid-infrared special-shaped structure beam quality testing device, comprising a control system, a CCD intelligent moving system, a beam intensity automatic attenuation system and a reflective dispersion-free focusing system;

[0008] The CCD intelligent mobile system includes a ball screw transmission guide rail, a stepper motor A and a CCD camera; the ball screw transmission guide rail includes a lead screw and a slider mounted on the lead screw; the output shaft of the stepper motor A is connected to the lead screw in the ball screw transmission guide rail to provide a driving force for the ball screw transmission guide rail; the CCD camera is mounted on the slider in the ball screw transmission guide rail to collect high-definition image data;

[0009] The automatic beam intensity attenuation system comprises a hollow rotating table, an attenuation sheet and a stepper motor B. The hollow rotating table is used to rotate clockwise or counterclockwise. The attenuation sheet is installed on the hollow rotating table and is arranged opposite to the CCD camera to adjust the intensity of the laser to meet the measurement requirements. The output shaft of the stepper motor B is connected to the input end of the hollow rotating table to provide driving force for the hollow rotating table to drive the attenuation sheet to rotate clockwise or counterclockwise.

[0010] The reflective dispersion-free focusing system is arranged between the attenuation plate and the CCD camera, and the reflective dispersion-free focusing system comprises an off-axis parabolic reflector M1 and an off-axis parabolic reflector M2; the off-axis parabolic reflector M1 is distributed at an angle with the attenuation plate, and is used to receive the output light of the attenuation plate and reflect it out; the off-axis parabolic reflector M2 is distributed at an angle with the off-axis parabolic reflector M1, and is used to receive the output light of the off-axis parabolic reflector M1 and reflect it to the CCD camera;

[0011] The off-axis parabolic reflector M1 and the off-axis parabolic reflector M2 are polished and plated with gold or silver, or plated with a high-reflection dielectric film in the 1800-3000nm band, with a reflectivity of >97%. The reflector adopts an off-axis parabola, 90-degree reflection, a reflection focal length of 200mm in the incident direction, a parent focal length of 100mm, and a reflection wavefront distortion of <λ / 4, ensuring that the special-shaped beam is transmitted without distortion, and does not introduce accessory astigmatism and dispersion;

[0012] The control system has a python platform and a built-in communication module. The control system is connected to the stepper motor A, the stepper motor B and the CCD camera respectively, and is used to drive the stepper motor A and the stepper motor B to move, to control the CCD camera to move, to receive high-definition image data of the CCD camera, and to optimize the special-shaped structure beam and measure the beam quality based on the high-definition image data.

[0013] Furthermore, in order to improve the control accuracy, the ball screw transmission guide is a high-precision ball screw.

[0014] As a preferred embodiment, the attenuation type of the attenuation plate is absorption type, the response wavelength is 1800~3000nm, and its absorption rate increases clockwise in the tangential direction of the center angle to satisfy α=kθ, wherein α is the absorption rate, θ is the azimuth angle in polar coordinates, α takes a value between 0dB and 30dB, k is the absorption coefficient of the attenuation plate material for 1800~3000nm laser, and the surface wavefront distortion is <λ / 4.

[0015] As a preference, the control system is a laptop computer or a desktop computer.

[0016] In the present invention, a CCD camera is mounted on a slider in a ball screw transmission guide rail, and at the same time, a stepper motor A is used to drive the screw of the ball screw transmission guide rail, so that the displacement change of the CCD camera can be automatically controlled. The attenuation plate is mounted on a hollow rotating table, and the movement of the hollow rotating table is driven by a stepper motor B, so that the rotation movement of the attenuation plate can be automatically controlled. A reflective dispersion-free focusing system composed of two off-axis parabolic reflectors is arranged between the CCD camera and the attenuation plate, and the astigmatism and dispersion in the attenuated laser beam can be effectively removed by two consecutive reflections, thereby ensuring that the measurement beam entering the CCD camera is pure, and the imaging accuracy is effectively ensured. The CCD camera, stepper camera A and stepper camera B are connected simultaneously by a control system, and the stepper camera A and stepper camera B can be closed-loop controlled based on the analysis of the image captured by the CCD camera, so that the displacement of the CCD camera and the rotation angle of the attenuation plate can be automatically adjusted.

[0017] The device integrates a CCD intelligent moving system and an automatic beam intensity attenuation system to achieve precise positioning and intensity adjustment of the beam, ensuring the reliability of the test results. The innovative combination of the invention makes the beam quality test process more automated and intelligent, and is applicable to multiple fields such as laser technology and optical communications.

[0018] Specifically, compared with the prior art, the present invention has the following advantages:

[0019] (1) Unlike other devices, this device is based on the Python platform and has higher intelligence, flexibility and controllability. At the same time, through the use of the Python platform, it can also be further compatible with AI algorithms, allowing it to easily integrate machine learning and deep learning models, thereby realizing intelligent decision-making and automated control. In addition, Python's rich libraries and frameworks provide strong support for data processing and algorithm development, further improving the performance and adaptability of the system. The device can not only quickly respond to the needs of different application scenarios, but also improve operational efficiency and intelligence through continuous learning and optimization. This flexible architecture allows users to customize according to specific needs, thereby achieving more efficient resource utilization and innovative applications.

[0020] (2) This device has an automatic attenuation function, which is not available in other beam quality test devices. This function can monitor and automatically adjust the intensity of the light beam in real time according to the light intensity presented in the CCD to ensure that the output beam is in the optimal working range. Through precise light intensity detection, the device can effectively suppress the phenomenon of beam oversaturation and prevent image distortion and inaccurate data caused by excessive light intensity. The introduction of the automatic attenuation function not only improves the reliability and accuracy of the test, but also provides important protection for the CCD camera. When the light intensity exceeds the preset threshold, the system will automatically reduce the intensity of the light beam, thereby avoiding damage to the CCD camera. This intelligent protection mechanism ensures the long-term stable operation of the equipment and reduces equipment failures and maintenance costs caused by excessive light.

[0021] (3) The system in this device can automatically select the best processing strategy according to different spot shapes and characteristics, thereby optimizing the spot of the special-shaped structured beam. This intelligent adjustment capability enables the system to maintain efficient working state when facing complex optical environments and application requirements. This not only improves processing speed and accuracy, but also helps to maintain stable output quality during long-term operation.

[0022] (4) The attenuation plate in this device is placed at an angle, which is conducive to eliminating or reducing the influence of stray light and interference fringes. This design can effectively change the propagation path of light, so that a certain deviation angle is formed between the incident light and the attenuation plate, thereby reducing unnecessary light reflection and scattering. In this way, the attenuation plate can effectively absorb and attenuate unnecessary stray light when the light beam passes through, thereby improving the overall quality of the light beam.

[0023] The present invention also provides a beam quality testing method of a mid-infrared special-shaped structured beam based on Python, using a beam quality testing device of a mid-infrared special-shaped structured beam based on Python, comprising the following steps:

[0024] Step 1: Pre-enter the motion parameters of stepper motor A and stepper motor B in the Python platform;

[0025] Step 2: Use the laser to output the laser beam and send it into the attenuation plate. The attenuation plate is used to adjust the intensity of the laser to make it suitable for the measurement requirements. Then the adjusted laser beam is emitted to the off-axis parabolic reflector M1, and then reflected by the off-axis parabolic reflector M1 to the off-axis parabolic reflector M2, and then reflected by the off-axis parabolic reflector M2 to the CCD camera. In this process, the astigmatism and dispersion in the beam are weakened through the reflection process of the off-axis parabolic reflector M1 and the off-axis parabolic reflector M2 to obtain a pure test beam; the annular spot image of the test beam is collected by the CCD camera and transmitted to the control system; the control system analyzes and processes the annular spot image based on the python platform to obtain the physical quantity information of the test beam. The specific process is as follows:

[0026] S21: Perform data preprocessing and filtering on the annular light spot image, capture the light spot through image tracking and capture technology, and further determine the center of the annular light spot (x c ,y c ), and then use formula (1) and formula (2) to transform the image coordinate system to the spot center coordinate system to obtain the new coordinates (x′, y′);

[0027] x′=xx c (1);

[0028] y′=yy c (2);

[0029] S22: extract the intensity distribution along the x-axis and the y-axis by integration or projection; for the intensity I(x′, y′) of the light spot at the position (x′, y′), obtain the intensity distribution along the x-axis and the y-axis according to formula (3) and formula (4) respectively;

[0030]

[0031]

[0032] S23: First, the I x (x′) and I y (y′) is smoothed to reduce the influence of noise, and then normalized according to formula (6) and formula (5) to obtain the laser intensity data I′ of the x-axis x (x′) and y-axis laser intensity data I′ y (y′), where I′ x (x′), I′ y (y′) is the intensity distribution of the light beam on the x-axis and y-axis;

[0033]

[0034]

[0035] In the formula, I x，min is the minimum intensity of the x-axis spot, I x，max is the maximum intensity of the x-axis spot, I y，min is the minimum intensity of the y-axis spot, I y，max is the maximum value of the y-axis spot intensity;

[0036] Step 3: The control system 4 compares the real-time physical quantity information with the set threshold value. When the real-time physical quantity information does not reach the set threshold value, the control system 4 controls the stepper motor A1.1 to operate so as to adjust the attenuation of the incident laser beam by rotating the angle of the attenuation plate 2.2. At the same time, the stepper motor B2.3 is controlled to operate so as to adjust the lateral displacement of the CCD camera 1.3 so as to obtain a high-quality annular spot image. This adjustment process is repeated until the real-time physical quantity information reaches or exceeds the set threshold value, and the annular spot image in the current state is recorded, and step 4 is executed.

[0037] Step 4: Based on the annular spot image in the current state, the beam quality M of the special-shaped end beam is measured. 2 The specific process of evaluation and measurement is as follows:

[0038] S41: constructing an intensity profile of the light beam by measuring the intensity distribution at different positions;

[0039] S42: Measure the minimum radius ω0 of the light beam at the focus through experiments;

[0040] S43: At different propagation positions z, the measurement beam is calculated according to formula (7): Intensity radius ω(z);

[0041]

[0042] In the formula, z R represents the Rayleigh length;

[0043] S44: Calculate the divergence angle θ according to formula (8);

[0044]

[0045] In the formula, λ represents the wavelength of light;

[0046] S45: Calculate the beam quality M according to formula (9) 2 ;

[0047]

[0048] Preferably, in step 1, the motion parameters of the stepper motor A1.1 include rotation speed, rotation direction and number of rotations; the motion parameters of the stepper motor B2.3 include rotation speed, rotation direction and number of rotations.

[0049] Preferably, in step three, the physical quantity information includes beam intensity and beam radius.

[0050] As a preference, in step 2 S21, data preprocessing includes denoising, normalization and background subtraction.

[0051] As a preferred embodiment, in step 2 S21, the filtering process adopts Gaussian filtering technology and mean filtering technology.

[0052] As a preference, in step 2 S21, the image tracking and capturing technology includes a centroid method or a Hough transform.

[0053] The present invention has a simple implementation process. It realizes intelligent extraction of CCD data and measurement of beam quality through the Python platform, and can quickly acquire and process beam data, which is convenient for subsequent accurate analysis. Through data preprocessing and filtering, interference can be effectively eliminated and the clarity of beam imaging can be improved.

[0054] The present invention uses measurement of multivariate M 2 The method can reliably and accurately evaluate the beam quality for different types of beams. For the annular light presented by the Laguerre-Gaussian beam, the M in the x and y directions can be measured. 2 For Hermite-Gaussian beams, a combination of individual and unified measurements can be used to obtain multiple M 2 ,In this way, a comprehensive evaluation of the beam quality is provided, and this method provides a new way to measure beam quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a structural schematic diagram of the beam quality testing device in the present invention;

[0056] Figure 2 is a flow chart of the beam quality testing method of the present invention;

[0057] Figure 3 In the embodiment of the present invention, LG 01 Schematic diagram of the incident light spot and light wavelength displayed by the light beam in the CCD;

[0058] Figure 4 In the embodiment of the present invention, LG 01 M of the beam 2 Schematic diagram of measurement results.

[0059] In the figure: 1. CCD intelligent moving system, 1.1. Stepper motor A, 1.2. Ball screw transmission guide, 1.3. CCD camera; 2. Automatic beam intensity attenuation system, 2.1. Hollow rotating table, 2.2. Attenuation plate, 2.3. Stepper motor B; 3. Reflective dispersion-free focusing system, 3.1. Off-axis parabolic reflector M1, 3.2. Off-axis parabolic reflector M2; 4. Control system. DETAILED DESCRIPTION

[0060] like Figure 1 As shown, the present invention provides a beam quality testing device for a mid-infrared special-shaped structured beam based on Python, comprising a control system 4, a CCD intelligent moving system 1, a beam intensity automatic attenuation system 2 and a reflective dispersion-free focusing system 3;

[0061] The CCD intelligent mobile system 1 includes a ball screw transmission guide 1.2, a stepper motor A1.1 and a CCD camera 1.3; the ball screw transmission guide 1.2 includes a screw and a slider mounted on the screw; the output shaft of the stepper motor A1.1 is connected to the screw in the ball screw transmission guide 1.2, and is used to provide a driving force for the ball screw transmission guide 1.2; the CCD camera 1.3 is installed on the slider in the ball screw transmission guide 1.2, and is used to collect high-definition image data; in this way, it is only necessary to precisely control the stepper motor A1.1, and then the screw can be used to drive the slider to drive the CCD camera 1.3 to move, thereby realizing automatic control of the movement of the CCD camera 1.3.

[0062] The automatic light beam intensity attenuation system 2 includes a hollow rotating table 2.1, an attenuation plate 2.2 and a stepper motor B2.3. The hollow rotating table 2.1 is used to rotate clockwise or counterclockwise. The attenuation plate 2.2 is installed on the hollow rotating table 2.1 and is distributed relative to the CCD camera 1.3, and is used to adjust the intensity of the laser to make it suitable for the measurement requirements. The output shaft of the stepper motor B2.3 is connected to the input end of the hollow rotating table 2.1, and is used to provide a driving force for the hollow rotating table 2.1 to drive the attenuation plate 2.2 to rotate clockwise or counterclockwise. For the automatic light beam intensity attenuation system 2, the stepper motor B2.3 can be used to drive the hollow rotating table 2.1 to drive the attenuation plate 2.2 to rotate. In this way, the rotation angle of the attenuation plate 2.2 can be accurately adjusted by precisely controlling the stepper motor B2.3. In this way, the size of the induced light intensity can be effectively adjusted, thereby avoiding the situation of excessive light intensity and the damage of the CCD camera 1.3.

[0063] The reflective dispersion-free focusing system 3 is arranged between the attenuation plate 2.2 and the CCD camera 1.3, and the reflective dispersion-free focusing system 3 includes an off-axis parabolic reflector M13.1 and an off-axis parabolic reflector M23.2; the off-axis parabolic reflector M13.1 is distributed at an angle to the attenuation plate 2.2, and is used to receive the output light of the attenuation plate 2.2 and reflect it out; the off-axis parabolic reflector M23.2 is distributed at an angle to the off-axis parabolic reflector M13.1, and is used to receive the output light of the off-axis parabolic reflector M13.1 and reflect it to the CCD camera 1.3; the reflective dispersion-free focusing system 3 effectively reduces the astigmatism and dispersion of the light beam by reflection, thereby ensuring that the CCD camera 1.3 can obtain a pure light beam to ensure that an accurate image can be obtained.

[0064] As a preferred embodiment, the off-axis parabolic reflector M13.1 and the off-axis parabolic reflector M23.2 are polished and plated with gold or silver, or plated with a high-reflection dielectric film in the 1800-3000nm band, with a reflectivity of >97%. The reflector adopts an off-axis parabola, 90-degree reflection, a reflection focal length of 200mm in the incident direction, a parent focal length of 100mm, and a reflection wavefront distortion of <λ / 4, ensuring that the special-shaped light beam is transmitted without distortion, and does not introduce accessory astigmatism and dispersion;

[0065] The control system 4 has a python platform and a built-in communication module. The control system 4 is connected to the stepper motor A1.1, the stepper motor B2.3 and the CCD camera 1.3 respectively, and is used to drive the stepper motor A1.1 and the stepper motor B2.3 to operate, to control the CCD camera 1.3 to operate, to receive high-definition image data from the CCD camera 1.3, and to perform special-shaped structure light beam optimization and light beam quality measurement based on the high-definition image data.

[0066] As a further optimization, the Python platform is built on the ESP32 development board. The Python platform can capture the light spot through image tracking and capture. At the same time, it can perform multi-dimensional M for special-shaped structured beams. 2 Specifically, for Laguerre-Gaussian beams and Hermite-Gaussian beams, image tracking capture and measurement technology can adapt to different beam environments and measure M 2 For the Laguerre-Gaussian beam LG m,n The presented annular light, select different z positions, obtain multiple sets of beam cross-section diagrams, measure the beam diameter in the x and y directions, and calculate the M in the x and y directions 2 For the Hermite-Gaussian beam HG m，nFor the presented special-shaped structure beam, select different z positions to obtain multiple groups of beam cross-section diagrams. When the spot contains two sub-spots, the system tracks and captures the sub-spots, measures the beam diameters in the x and y directions respectively, and then measures the beam diameters of the complete spot in the x and y directions, and calculates a total of 6 M in the x and y directions. 2 ; When the spot contains 4 sub-spots, the system tracks and captures the sub-spots, measures the beam diameters in the x and y directions respectively, and then measures the beam diameters of the complete spot in the x and y directions, and calculates a total of 10 M in the x and y directions. 2 There are n sub-spots, corresponding to 2(n+1) M 2 .

[0067] Further preferably, a USB interface, a power driver, a relay and a power supply are connected to the ESP32 development board;

[0068] In order to improve the control accuracy, the ball screw transmission guide 1.2 is a high-precision ball screw.

[0069] As a preferred embodiment, as a preferred embodiment, the attenuation type of the attenuation plate 2.2 is absorption type, the response wavelength is 1800~3000nm, and its absorption rate increases clockwise with the tangential direction of the center angle to satisfy a=kθ, wherein α is the absorption rate, θ is the azimuth angle in polar coordinates, α is between 0dB and 30dB, k is the absorption coefficient of the attenuation plate material to 1800~3000nm laser, and the surface wavefront distortion is <λ / 4.

[0070] As a preference, the control system 4 is a laptop or desktop computer, which, as a core control processing component, can optimize the special-shaped structure light beam and also complete operations such as measuring the light beam quality.

[0071] In the present invention, a CCD camera is mounted on a slider in a ball screw transmission guide rail, and at the same time, a stepper motor A is used to drive the screw of the ball screw transmission guide rail, so that the displacement change of the CCD camera can be automatically controlled. The attenuation plate is mounted on a hollow rotating table, and the movement of the hollow rotating table is driven by a stepper motor B, so that the rotation movement of the attenuation plate can be automatically controlled. A reflective dispersion-free focusing system composed of two off-axis parabolic reflectors is arranged between the CCD camera and the attenuation plate, and the astigmatism and dispersion in the attenuated laser beam can be effectively removed by two consecutive reflections, thereby ensuring that the measurement beam entering the CCD camera is pure, and the imaging accuracy is effectively ensured. The CCD camera, stepper camera A and stepper camera B are connected simultaneously by a control system, and the stepper camera A and stepper camera B can be closed-loop controlled based on the analysis of the image captured by the CCD camera, so that the displacement of the CCD camera and the rotation angle of the attenuation plate can be automatically adjusted.

[0072] The device integrates a CCD intelligent moving system and an automatic beam intensity attenuation system to achieve precise positioning and intensity adjustment of the beam, ensuring the reliability of the test results. The innovative combination of the invention makes the beam quality test process more automated and intelligent, and is applicable to multiple fields such as laser technology and optical communications.

[0073] like Figure 2 As shown, the present invention also provides a beam quality testing method of a mid-infrared special-shaped structure beam based on Python, using a beam quality testing device of a mid-infrared special-shaped structure beam based on Python, comprising the following steps:

[0074] Step 1: Pre-enter the motion parameters of the stepper motor A1.1 and the motion parameters of the stepper motor B2.3 in the python platform; as a preferred embodiment, the motion parameters of the stepper motor A1.1 include rotation speed, rotation direction and number of rotations; the motion parameters of the stepper motor B2.3 include rotation speed, rotation direction and number of rotations.

[0075] Step 2: Use a laser to output a laser beam and send it to the attenuation plate 2.2. Use the attenuation plate 2.2 to adjust the intensity of the laser to make it suitable for the measurement requirements, and then emit the adjusted laser beam to the off-axis parabolic reflector M13.1, then reflect it to the off-axis parabolic reflector M23.2 through the off-axis parabolic reflector M13.1, and then reflect it to the CCD camera 1.3 through the off-axis parabolic reflector M23.2. In this process, the astigmatism and dispersion in the beam are weakened through the reflection process of the off-axis parabolic reflector M13.1 and the off-axis parabolic reflector M23.2 to obtain a pure test beam; use the CCD camera 1.3 to collect the annular spot image of the test beam and transmit it to the control system 4;

[0076] The control system 4 analyzes and processes the annular spot image based on the Python platform to obtain the physical quantity information of the test beam. The specific process is as follows:

[0077] S21: Perform data preprocessing and filtering on the annular light spot image, capture the light spot through image tracking and capture technology, and further determine the center of the annular light spot (x c ,y c ), and then use formula (1) and formula (2) to transform the image coordinate system to the spot center coordinate system to obtain new coordinates (x′, y′); as a preferred embodiment, data preprocessing includes denoising, normalization and background subtraction. As a preferred embodiment, filtering uses Gaussian filtering technology and mean filtering technology. As a preferred embodiment, image tracking and capturing technology includes centroid method (calculating the centroid of light intensity) or Hough transform (detecting circular features).

[0078] x′=xxc (1);

[0079] y′=yy c (2);

[0080] S22: extract the intensity distribution along the x-axis and the y-axis by integration or projection; for the intensity I(x′, y′) of the light spot at the position (x′, y′), obtain the intensity distribution along the x-axis and the y-axis according to formula (3) and formula (4) respectively;

[0081]

[0082]

[0083] S23: First, the I x (x′) and I y (y′) is smoothed to reduce the influence of noise. Common methods include moving average method, low-pass filtering, etc.; then normalized according to formula (4) and formula (5) for subsequent processing and analysis to obtain the laser intensity data I' of the x-axis x (x′) and y-axis laser intensity data I′ y (y′), where I′ x (x′), I′ y (y′) is the intensity distribution of the light beam on the x-axis and y-axis, which can be represented in the form of a one-dimensional array;

[0084]

[0085]

[0086] In the formula, I x，min is the minimum intensity of the x-axis spot, I x，max is the maximum intensity of the x-axis spot, I y，min is the minimum intensity of the y-axis spot, I y，max is the maximum value of the y-axis spot intensity;

[0087] Step 3: The control system 4 compares the real-time physical quantity information with the set threshold value. When the real-time physical quantity information does not reach the set threshold value, the control system 4 controls the stepper motor A1.1 to operate so as to adjust the attenuation of the incident laser beam by rotating the angle of the attenuation plate 2.2. At the same time, the stepper motor B2.3 is controlled to operate so as to adjust the lateral displacement of the CCD camera 1.3 so as to obtain a high-quality annular spot image. This adjustment process is repeated until the real-time physical quantity information reaches or exceeds the set threshold value, and the annular spot image in the current state is recorded, and step 4 is executed.

[0088] As a preferred embodiment, the physical quantity information includes beam intensity and beam radius. As a further preferred embodiment, the beam intensity is used as the main comparison reference parameter, wherein the set threshold is also a set beam intensity threshold;

[0089] Step 4: Based on the annular spot image in the current state, the beam quality M of the special-shaped end beam is measured. 2 The specific process of evaluation and measurement is as follows:

[0090] S41: The transverse intensity distribution of the laser beam is approximately Gaussian in shape, and the intensity profile of the beam can be constructed by measuring the intensity distribution at different positions;

[0091] S42: The minimum radius ω0 of the light beam at the focus (or near the focus) is measured experimentally. ω0 is usually the minimum diameter or the narrowest part of the light spot. If the experimental measurement cannot be directly obtained, it can also be estimated based on the beam size at other positions and the propagation properties of the beam.

[0092] S43: At different propagation positions z (at a certain distance from the focus), the measurement beam is calculated according to formula (7): Intensity radius ω(z); This data reflects the expansion of the light spot as the propagation distance of the light beam increases.

[0093]

[0094] In the formula, z R represents the Rayleigh length;

[0095] S44: Calculate the divergence angle θ according to formula (8);

[0096]

[0097] In the formula, λ represents the wavelength of light;

[0098] S45:M 2 Indicates the degree of deviation of the beam from the ideal Gaussian beam. In the ideal case, the M of the fundamental mode Gaussian beam 2 is equal to 1, while for other types of beams, the beam quality will be greater than 1, the annular Laguerre-Gaussian beam LG p，1 M 2 The theoretical value of is 2p+l+1. Hermite-Gaussian beam HG m，n M 2 The theoretical value of is m+n+1. In practice, due to astigmatism and wavefront phase distortion, its M 2 will be greater than the theoretical value. Specifically, the beam quality M is calculated according to formula (9): 2 ;

[0099]

[0100] Laser beam M 2 The closer it is to the theoretical value, the smaller the divergence angle, the better the beam quality, and the stronger the focusing performance. As a preferred method, the calculated beam quality M 2 Draw the beam image.

[0101] The present invention will be further described below in conjunction with specific embodiments:

[0102] Embodiment 1:

[0103] 1. Experimental environment:

[0104] The experiments were conducted in a laboratory with a temperature controlled at 20±1°C and a relative humidity of 40%-50% to ensure the stability of the optical components.

[0105] 2. Equipment composition:

[0106] (1) Laser: LG with an output wavelength of 1960nm beam.

[0107] (2) CCD intelligent movement system: High-precision stepper motor A drives the ball screw transmission guide to realize the movement of the CCD camera, and its movement accuracy can reach 0.1mm.

[0108] (3) Automatic beam intensity attenuation system: adjustable optical attenuator, automatically adjusts the beam intensity, uses attenuation sheet OD0-1, with a radius of 25mm.

[0109] (4) Reflective dispersion-free focusing system: uses a high-reflectivity gold-plated parabolic mirror with a reflective focal length of 200 mm.

[0110] (5) Control system: monitor beam parameters in real time and output beam quality indicators.

[0111] 3. Experimental steps:

[0112] (1) Install the laser on the experimental bench and ensure that its optical axis is aligned with the test area. Install the CCD camera on the slider of the ball screw transmission guide to ensure that it can capture the light spot on the beam path and connect the control system to facilitate data collection. Set the beam intensity automatic attenuation system and the reflective dispersion-free focusing system between the laser and the CCD camera.

[0113] (2) Set the laser power to 10mW and wait for the beam to stabilize. After the beam is attenuated by the attenuation plate, it is reflected by the reflector to reduce the astigmatism and dispersion of the beam, and obtain the reflected light in the 1800-3000nm band. Move the CCD camera position through the python platform, and the CCD camera transmits the special-shaped structure beam spot to the control system (laptop or desktop). The control system implements automatic attenuation according to the set threshold, weakens the stray light in the special-shaped structure beam spot, and controls the beam at 0.6mW.

[0114] (3) The Python platform uses image tracking and capture technology to capture the light spot in the special-shaped structure beam, calculate its beam intensity, light spot radius and divergence angle, and after multiple measurements of M 2 The results show that M x 2 =2.6, M y 2 =2.4 indicates that the beam quality is good and close to the theoretical value of 2. Figure 3 and Figure 4 shown.

[0115] The present invention has a simple implementation process. It realizes intelligent extraction of CCD data and measurement of beam quality through the Python platform, and can quickly acquire and process beam data, which is convenient for subsequent accurate analysis. Through data preprocessing and filtering, interference can be effectively eliminated and the clarity of beam imaging can be improved.

[0116] The present invention uses measurement of multivariate M 2 The method can reliably and accurately evaluate the beam quality for different types of beams. For the annular light presented by the Laguerre-Gaussian beam, the M in the x and y directions can be measured. 2 For Hermite-Gaussian beams, a combination of individual and unified measurements can be used to obtain multiple M 2 ,In this way, a comprehensive evaluation of the beam quality is provided, and this method provides a new way to measure beam quality.

Claims

1. A Python-based mid-infrared special-shaped structure beam quality testing device, comprising a control system (4); characterized in that: It also includes a CCD intelligent moving system (1), an automatic beam intensity attenuation system (2) and a reflective dispersion-free focusing system (3); The CCD intelligent mobile system (1) comprises a ball screw transmission guide rail (1.2), a stepper motor A (1.1) and a CCD camera (1.3); the ball screw transmission guide rail (1.2) comprises a lead screw and a slider mounted on the lead screw; the output shaft of the stepper motor A (1.1) is connected to the lead screw in the ball screw transmission guide rail (1.2) to provide a driving force for the ball screw transmission guide rail (1.2); the CCD camera (1.3) is mounted on the slider in the ball screw transmission guide rail (1.2) to collect high-definition image data; The beam intensity automatic attenuation system (2) comprises a hollow rotating table (2.1), an attenuation plate (2.2) and a stepping motor B (2.3); the hollow rotating table (2.1) is used to perform a clockwise or counterclockwise rotation; the attenuation plate (2.2) is mounted on the hollow rotating table (2.1) and is arranged relative to the CCD camera (1.3) to adjust the intensity of the laser so that it is suitable for measurement requirements; the output shaft of the stepping motor B (2.3) is connected to the input end of the hollow rotating table (2.1) to provide a driving force for the hollow rotating table (2.1) to drive the attenuation plate (2.2) to perform a clockwise or counterclockwise rotation; The reflective dispersion-free focusing system (3) is arranged between the attenuation plate (2.2) and the CCD camera (1.3), and comprises an off-axis parabolic reflector M1 (3.1) and an off-axis parabolic reflector M2 (3.2); the off-axis parabolic reflector M1 (3.1) is arranged at an angle with the attenuation plate (2.2), and is used to receive the output light of the attenuation plate (2.2) and reflect it out; the off-axis parabolic reflector M2 (3.2) is arranged at an angle with the off-axis parabolic reflector M1 (3.1), and is used to receive the output light of the off-axis parabolic reflector M1 (3.1), and reflect it to the CCD camera (1.3); The off-axis parabolic reflector M1 (3.1) and the off-axis parabolic reflector M2 (3.2) are polished and plated with gold or silver, or plated with a high-reflection dielectric film in the 1800-3000nm band, with a reflectivity of >97%. The reflector adopts an off-axis parabola, 90-degree reflection, a reflection focal length of 200mm in the incident direction, a parent focal length of 100mm, and a reflection wavefront distortion of <λ / 4, ensuring that the special-shaped light beam is transmitted without distortion, and does not introduce accessory astigmatism and dispersion; The control system (4) has a python platform and a built-in communication module. The control system (4) is respectively connected to the stepper motor A (1.1), the stepper motor B (2.3) and the CCD camera (1.3), and is used to drive the stepper motor A (1.1) and the stepper motor B (2.3) to move, to control the CCD camera (1.3) to move, to receive high-definition image data from the CCD camera (1.3), and to optimize the special-shaped structure beam and measure the beam quality based on the high-definition image data.

2. According to claim 1, a Python-based mid-infrared special-shaped structure beam quality testing device is characterized in that: The ball screw transmission guide rail (1.2) is a high-precision ball screw.

3. According to claim 2, a Python-based mid-infrared special-shaped structure beam quality testing device is characterized in that: The attenuation type of the attenuation plate (2.2) is absorption type, the response wavelength is 1800-3000nm, and its absorption rate increases clockwise in the tangential direction of the center angle to satisfy α=kθ, wherein α is the absorption rate, θ is the azimuth angle in polar coordinates, α takes a value between 0dB and 30dB, k is the absorption coefficient of the attenuation plate material for 1800-3000nm laser, and the surface wavefront distortion is <λ / 4.

4. The beam quality testing device of a mid-infrared special-shaped structure beam based on Python according to claim 3 is characterized in that: The control system (4) is a notebook computer or a desktop computer.

5. A method for testing the beam quality of a mid-infrared special-shaped structured beam based on Python, using a device for testing the beam quality of a mid-infrared special-shaped structured beam based on Python as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Pre-enter the motion parameters of stepper motor A (1.1) and stepper motor B (2.3) in the Python platform; Step 2: Use a laser to output a laser beam and send it to an attenuation plate (2.2). Use the attenuation plate (2.2) to adjust the intensity of the laser to make it suitable for the measurement requirements. Then, the adjusted laser beam is emitted to the off-axis parabolic reflector M1 (3.1). Then, it is reflected by the off-axis parabolic reflector M1 (3.1) to the off-axis parabolic reflector M2 (3.2). Then, it is reflected by the off-axis parabolic reflector M2 (3.2) to the CCD camera (1.3). In this process, the astigmatism and dispersion in the beam are weakened by the reflection process of the off-axis parabolic reflector M1 (3.1) and the off-axis parabolic reflector M2 (3.2), so as to obtain a pure test beam. Use the CCD camera (1.3) to collect the annular spot image of the test beam and transmit it to the control system (4). The control system (4) analyzes and processes the annular spot image based on the python platform to obtain the physical quantity information of the test beam. The specific process is as follows: S21: Perform data preprocessing and filtering on the annular light spot image, capture the light spot through image tracking and capture technology, and further determine the center of the annular light spot (x c ,y c ), and then use formula (1) and formula (2) to transform the image coordinate system to the spot center coordinate system to obtain the new coordinates (x′, y′); x′=x-x c (1); y′=yy c (2); S22: extract the intensity distribution along the x-axis and the y-axis by integration or projection; for the intensity I(x′, y′) of the light spot at the position (x′, y′), obtain the intensity distribution along the x-axis and the y-axis according to formula (3) and formula (4) respectively; S23: First, the I x (x′) and I y (y′) is smoothed to reduce the influence of noise, and then normalized according to formula (4) and formula (5) to obtain the laser intensity data I′ of the x-axis x (x′) and y-axis laser intensity data I′ y (y′), where I′ x (x′), I′ y (y′) is the intensity distribution of the light beam on the x-axis and y-axis; In the formula, I x,min is the minimum intensity of the x-axis spot, I x,max is the maximum intensity of the x-axis spot, I y,min is the minimum intensity of the y-axis spot, I y,max is the maximum value of the y-axis spot intensity; Step 3: The control system (4) compares the real-time physical quantity information with a set threshold value. When the real-time physical quantity information does not reach the set threshold value, the control system (4) controls the stepper motor A (1.1) to operate so as to adjust the attenuation of the incident laser beam by rotating the angle of the attenuation plate (2.2). At the same time, the stepper motor B (2.3) is controlled to operate so as to adjust the lateral displacement of the CCD camera (1.3) so as to obtain a high-quality annular spot image. This adjustment process is repeated until the real-time physical quantity information reaches or exceeds the set threshold value, and the annular spot image in the current state is recorded, and step 4 is executed. Step 4: Based on the annular spot image in the current state, the beam quality M of the special-shaped end beam is measured. 2 The specific process of evaluation and measurement is as follows: S41: constructing an intensity profile of the light beam by measuring the intensity distribution at different positions; S42: Measure the minimum radius ω0 of the light beam at the focus through experiments; S43: At different propagation positions z, the measurement beam is calculated according to formula (7): Intensity radius ω(z); In the formula, z R represents the Rayleigh length; S44: Calculate the divergence angle θ according to formula (8); In the formula, λ represents the wavelength of light; S45: Calculate the beam quality M according to formula (9) 2 ; 6. The beam quality testing device of a mid-infrared special-shaped structure beam based on Python according to claim 5, characterized in that: In step 1, the motion parameters of the stepper motor A (1.1) include rotation speed, rotation direction and number of rotations; the motion parameters of the stepper motor B (2.3) include rotation speed, rotation direction and number of rotations.

7. The beam quality testing device of a mid-infrared special-shaped structure beam based on Python according to claim 5, characterized in that: In step three, the physical quantity information includes beam intensity and beam radius.

8. The beam quality testing device of a mid-infrared special-shaped structure beam based on Python according to claim 5, characterized in that: In step 2 S21, data preprocessing includes denoising, normalization and background subtraction.

9. The beam quality testing device of a mid-infrared special-shaped structure beam based on Python according to claim 5, characterized in that: In step 2 S21, the filtering process uses Gaussian filtering technology and mean filtering technology.

10. The beam quality testing device of a mid-infrared special-shaped structure beam based on Python according to claim 5, characterized in that: In step 2 S21 , the image tracking and capturing technology includes a centroid method or a Hough transform.

Images