Diffuse reflection imaging method laser parameter measurement method and system

Abstract

The invention belongs to the field of optical data measurement, and particularly relates to a diffuse reflection imaging method laser parameter measurement method and system. The measuring method comprises the following steps of: controlling the diffuse reflection target plate to rotate, so that a light spot rotates by taking the center of the light spot as a symmetric point; imaging the light spots on the diffuse reflection target plate; acquiring the real-time power density of a plurality of fixed point positions in the light spot through a detector; acquiring a power density distribution diagram according to the light spot image and the real-time power density of the plurality of fixed point positions; and calculating laser parameters according to the power density distribution image. The invention mainly solves the problem of speckle elimination in the laser parameter measurement technology by the diffuse reflection imaging method, and greatly improves the measurement precision of the measurement method by the diffuse reflection imaging method.

Description

Technical Field

[0001] The invention belongs to the field of optical data measurement, and in particular relates to a diffuse reflection imaging laser parameter measurement method and system. Background Art

[0002] Accurately measuring the intensity and spatial-temporal distribution parameters of the laser spot is the most direct and effective means to evaluate the performance of high-energy laser emission systems and study the atmospheric transmission characteristics of high-energy lasers.

[0003] When measuring laser parameters for large-size spots for high-power, long-distance transmission, analyzing and studying parameters such as spot centroid jitter, spot energy, spot diameter, and spot peak power density will be able to intuitively reflect the performance of the high-energy laser launch system and the atmospheric transmission characteristics of high-energy lasers.

[0004] In the performance evaluation of the high-energy laser launch system and the study of the atmospheric transmission characteristics of the high-energy laser, the spot intensity distribution image is first obtained through the system, and the spot image is processed and calculated to obtain the corresponding measurement parameters, thereby realizing the performance evaluation of the high-energy laser launch system and the study of the atmospheric transmission characteristics of the high-energy laser.

[0005] In the imaging system, the characteristics of the diffuse reflection screen surface and the coherence of the laser have a decisive influence on the speckle phenomenon. When the properties of the diffuse reflection screen surface are different, the speckle on the spot image obtained by the measurement system will have different characteristics. In the field of laser parameter measurement, the imaging quality and measurement accuracy of the system are seriously affected by the laser speckle. Therefore, a diffuse reflection imaging laser parameter measurement system and method are urgently needed. Summary of the invention

[0006] In view of the above problems, the present invention discloses a diffuse reflection imaging laser parameter measurement method, which comprises the following steps:

[0007] Control the rotation of the diffuse reflection target plate so that the light spot rotates symmetrically with its own center;

[0008] Imaging the light spot on the diffuse reflection target plate;

[0009] Acquiring real-time power density of multiple fixed-point positions within the light spot through a detector;

[0010] Obtain a power density distribution diagram based on the spot image and the real-time power density at multiple fixed-point positions;

[0011] The laser parameters are calculated according to the power density distribution image.

[0012] Furthermore, the step of obtaining a power density distribution diagram according to the spot image and the real-time power density at multiple fixed positions specifically includes the following steps:

[0013] Acquiring the real-time power density value detected by the detector while collecting the spot image;

[0014] Calculate the conversion coefficient between the mean value of the regional pixel value in the image and the power density by combining the real-time power density and the spot image;

[0015] The conversion coefficient is introduced into the light spot image to obtain a power density distribution image of the entire light spot.

[0016] Furthermore, the calculation of the conversion coefficient between the mean value of the regional pixel value in the image and the power density by combining the real-time power density and the spot image specifically includes the following steps:

[0017] Obtaining the average pixel value corresponding to the detector installation position in the spot image;

[0018] Calculate the average real-time power density of multiple detectors;

[0019] The average real-time power density value is divided by the real-time average pixel value to obtain a conversion coefficient between the mean value of the regional pixel value in the spot image and the power density.

[0020] Furthermore, the step of obtaining the real-time power density of multiple fixed positions in the light spot through the detector further includes calibrating the detector, and the specific calibration steps are as follows:

[0021] Using a stable laser to emit laser light with a predetermined power density toward the diffuse reflection target plate;

[0022] Get the output value of the detector;

[0023] A conversion coefficient between the output value of the detector and the power density is calculated according to the predetermined power density and the output value.

[0024] Furthermore, when the diffuse reflection target plate rotates T times within one exposure time, the contrast of the light spot is reduced to T 1 / 2 times.

[0025] In another embodiment of the present invention, a diffuse reflection imaging laser parameter measurement device is also disclosed, the parameter measurement device comprising a diffuse reflection target plate, an imaging camera assembly, a drive motor, a first photoelectric detector module and a data processing unit;

[0026] The diffuse reflection target plate is used to receive the emitted laser of the laser;

[0027] The imaging camera assembly is used to collect a grayscale image of a light spot on a diffuse reflection target plate;

[0028] The driving motor is used to drive the diffuse reflection target plate to rotate with its center as the rotation center;

[0029] The first photoelectric detection module is used to receive the grayscale image and convert it into a digital signal to transmit to the data processing unit;

[0030] The data processing unit is used to execute the diffuse reflection imaging laser parameter measurement method described in any one of the above embodiments.

[0031] Furthermore, the diffuse reflection target plate adopts diffuse reflection micro-coefficient optical material.

[0032] Furthermore, a sampling hole is provided on the diffuse reflection target plate, and a sampling optical fiber, an attenuation scattering plate, an extinction channel, a second photodetector and a detector are sequentially arranged on the back of the sampling hole.

[0033] Furthermore, there are multiple sampling holes, which are evenly arranged outwards with the diffuse reflection center position as the origin.

[0034] In another embodiment of the present invention, a computer-readable storage medium is disclosed. The medium stores a computer program. When the computer program is run, the diffuse reflection imaging laser parameter measurement method described in any one of the above embodiments is executed.

[0035] The present invention mainly solves the problem of speckle elimination in the diffuse reflection imaging method for measuring laser parameters, and greatly improves the measurement accuracy of the diffuse reflection imaging method.

[0036] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 A flow chart of a diffuse reflection imaging laser parameter measurement method according to an embodiment of the present invention is shown;

[0039] Figure 2 A schematic diagram of diffuse reflection imaging in the prior art is shown;

[0040] Figure 3 A schematic diagram of speckle formation is shown;

[0041] Figure 4 A schematic diagram of the structure of a detector channel in an embodiment of the present invention is shown.

[0042] In the figure: 1. sampling optical fiber; 2. attenuation scattering plate; 3. extinction channel; 4. second photodetector. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, the present invention discloses a diffuse reflection imaging laser parameter measurement method, the measurement method comprising the following steps:

[0045] Control the rotation of the diffuse reflection target plate so that the light spot rotates symmetrically with its own center;

[0046] Imaging the light spot on the diffuse reflection target plate;

[0047] Acquiring real-time power density of multiple fixed-point positions within the light spot through a detector;

[0048] Obtain a power density distribution diagram based on the spot image and the real-time power density at multiple fixed-point positions;

[0049] The laser parameters are calculated according to the power density distribution image.

[0050] Specifically, Figure 2 As shown in the figure, the diffuse reflection imaging method uses a camera to collect information about the laser beam irradiated on the diffuse reflection screen. After obtaining the image information of the light spot, some data processing methods can be used to accurately obtain the temporal and spatial distribution of the intensity of the laser beam. The measuring beam is directly irradiated on the standard diffuse reflection screen, and then the camera is used to sample and analyze the light spot image on the diffuse reflection screen.

[0051] In the diffuse reflection imaging measurement system, the surface of the diffuse reflection screen is relatively rough, so the surface of the target plate can be regarded as composed of many irregularly distributed surface elements. When a highly coherent laser is irradiated on the surface of the target plate, each surface element can be regarded as a diffraction unit, and the entire surface is equivalent to a phase grating composed of a large number of diffraction units. Since a large number of surface elements are irregularly distributed, the interference effect will change dramatically and irregularly with the change of the observation point, thus forming a diffraction pattern with an irregularly distributed granular structure, such as Figure 3If the surface of an object is imaged by an optical system, as long as the point spread function of the imaging system has a sufficient "width" and can cover enough facets on the surface of the object after being converted to the object plane, the light from these facets will coherently superimpose at the same image point, thus forming speckle.

[0052] Through the analysis of the causes of speckle, it can be seen that the characteristics of the diffuse reflection screen surface and the coherence of the laser have a decisive influence on the speckle phenomenon. When the properties of the diffuse reflection screen surface are different, the speckle on the spot image obtained by the measurement system will have different characteristics. In the field of laser parameter measurement, the imaging quality and measurement accuracy of the system are seriously affected by laser speckle.

[0053] For the problem of speckle suppression in the diffuse reflection imaging measurement system, it must be done under the premise that the laser energy and beam quality will not be affected. The roughness of the diffuse reflection screen is the main reason affecting the speckle. The distribution of speckle in the image is closely related to the coherence of the light source and the standard deviation of the diffuse reflection screen surface. In addition, the incident angle of the laser beam and the coherence length of the incident laser will also affect the speckle in the image. When the coherence length of the laser beam is long, speckle will appear when it is irradiated on the surface of any object. However, when the coherence length of the laser is short, the factor affecting the speckle is mainly the roughness of the irradiated object surface. For the high-energy laser spot parameter measurement system using diffuse reflection imaging, what must be ensured in solving its speckle problem is to ensure that the characteristics of the incident laser itself are not damaged. Therefore, the focus of solving the speckle problem is to start from the characteristics of the diffuse reflection screen. As can be seen from Formula 1, the parameter speckle contrast C that characterizes the speckle strength of the laser spot image is equal to the standard deviation σ of the spot image I Divide by the mean value I of the speckle image. In order to reduce the speckle contrast in the spot image, we can consider reducing the image standard deviation. For the spot image, the standard deviation σ I It can be calculated by formula 2.

[0054]

[0055] In the above formula, M and N are the pixel sizes of the spot image, is the pixel value of the image, and is the average value of the pixel values ​​in the image. In the laser parameter measurement system of the camera imaging method, the reason for the high speckle contrast is due to the uneven position of the diffuse reflection screen surface.

[0056] In this embodiment, by rapidly rotating the diffuse reflection screen, the position of the light spot rapidly rotates with its own center as the origin within one exposure time. The laser is stably irradiated on the diffuse reflection screen, and the light spot image collected by the measurement system theoretically does not change in its irradiation position, and the speckle contrast of the image does not change either. At this time, the temporal and spatial distribution of the light spot intensity is more accurate.

[0057] At the same time, the detector is used to collect data from multiple fixed positions on the diffuse reflection target plate to obtain the real-time power density of the fixed position on the light spot. Exemplarily, a sampling hole is opened on the diffuse reflection target plate, and a detector is fixedly installed on the back of the diffuse reflection target plate at the corresponding position. When the diffuse reflection target plate rotates, the detector rotates with the diffuse reflection target plate to ensure that the detector can output a valid measurement value when the light spot shakes on the diffuse reflection target plate. By combining imaging with the detector, the power density distribution image of the light spot is accurately obtained. Finally, the laser parameters are calculated through the power density distribution image.

[0058] Furthermore, the step of obtaining a power density distribution diagram according to the spatiotemporal distribution of the light spot intensity and the absolute power density at multiple fixed positions specifically includes the following steps:

[0059] Acquiring the real-time power density value detected by the detector while collecting the spot image;

[0060] Calculate the conversion coefficient between the mean value of the regional pixel value in the image and the power density by combining the real-time power density and the spot image;

[0061] The conversion coefficient is introduced into the light spot image to obtain a power density distribution image of the entire light spot.

[0062] Specifically, a single detector can obtain the real-time power density value of the sampling hole position in the spot, and combine the temporal and spatial distribution data of the spot intensity in the same area in the spot image to calculate the power density of the entire spot image. Multiple sampling holes are evenly distributed at different positions of the spot, and a high-precision power density distribution map of the spot can be obtained.

[0063] Furthermore, the step of obtaining a conversion coefficient between a mean value of a regional pixel value in an image and a power density according to the real-time power density and the data collected by the detector specifically includes the following steps:

[0064] Obtaining the average pixel value corresponding to the detector installation position in the spot image;

[0065] Calculate the average real-time power density of multiple detectors;

[0066] The average real-time power density value is divided by the real-time average pixel value to obtain a conversion coefficient between the mean value of the regional pixel value in the spot image and the power density.

[0067] Specifically, the power density detected by the detector is the power density in the sampling hole area of ​​the diffuse reflection target plate. The average pixel value of the sampling hole area can be obtained through the spot image. The power density value of a single pixel in the sampling hole area can be obtained by dividing the value detected by the detector by the average pixel value of the sampling hole area.

[0068] Furthermore, before obtaining the absolute power density of the light spot at multiple fixed positions on the diffuse reflection target plate through the detector, the detector is also calibrated. The specific calibration steps are as follows:

[0069] Using a stable laser to emit laser light with a predetermined power density toward the diffuse reflection target plate;

[0070] Get the output value of the detector;

[0071] A conversion coefficient between the output value of the detector and the power density is calculated according to the predetermined power density and the output value.

[0072] Specifically, when calibrating the detector, a diffuse reflection target plate is irradiated with a laser of known parameters, and the detector outputs an AD value after being irradiated. The conversion coefficient between the power density and the AD value output by the detector can be calculated in combination with a predetermined power density.

[0073] Furthermore, when the diffuse reflection target plate rotates T times within one exposure time, the contrast of the light spot is reduced to T 1 / 2 times.

[0074] Specifically, by setting the rotation speed of the diffuse reflection target plate, the accuracy of parameter measurement can be effectively controlled.

[0075] In another embodiment of the present invention, a diffuse reflection imaging laser parameter measurement device is also disclosed, the parameter measurement device comprising a diffuse reflection target plate, an imaging camera assembly, a drive motor, a first photodetector module and a data processing unit;

[0076] The diffuse reflection target plate is used to receive the emitted laser of the laser;

[0077] The imaging camera assembly is used to collect a grayscale image of a light spot on a diffuse reflection target plate;

[0078] The driving motor is used to drive the diffuse reflection target plate to rotate with its center as the rotation center;

[0079] The first photoelectric detection module is used to receive the grayscale image and convert it into a digital signal for transmission to a data processing unit;

[0080] The data processing unit is used to execute the diffuse reflection imaging laser parameter measurement method described in any one of the above embodiments.

[0081] Furthermore, the diffuse reflection target plate adopts diffuse reflection micro-coefficient optical material.

[0082] Specifically, the diffuse reflection target plate adopts diffuse reflection micro-coefficient optical material, which has the characteristics of high damage threshold, reliable structure, and good maintainability.

[0083] Preferably, the imaging camera assembly includes a digital camera, a lens, an attenuation plate and a filter that are set up at one time. The imaging camera assembly is used to collect a grayscale image of the incident light spot and perform distortion correction on it.

[0084] Further, such as Figure 4 As shown, a sampling hole is provided on the diffuse reflection target plate, and a sampling optical fiber 1, an attenuation scattering plate 2, an extinction channel 3, a second photodetector 4 and a detector are arranged in sequence on the back of the sampling hole.

[0085] Specifically, photoelectric conversion is achieved through the sampling optical fiber 1, the attenuation scattering plate 2, the second photodetector 4 and the detector, and the power density value is output after the electrical signal passes through the data processing module.

[0086] Furthermore, there are multiple sampling holes, which are evenly arranged outwards with the diffuse reflection center position as the origin.

[0087] Specifically, multiple sampling holes are evenly arranged outwardly to more accurately obtain the real-time power density of the light spot.

[0088] In another embodiment of the present invention, a computer-readable storage medium is disclosed. The medium stores a computer program. When the computer program is run, a diffuse reflection imaging laser parameter measurement method as described in any one of the above embodiments is executed.

[0089] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diffuse reflection imaging laser parameter measurement method, characterized in that: The measuring method comprises the following steps: Control the rotation of the diffuse reflection target plate so that the light spot rotates symmetrically with its own center; Imaging the light spot on the diffuse reflection target plate; Acquiring real-time power density of multiple fixed-point positions within the light spot through a detector; Obtain a power density distribution diagram based on the spot image and the real-time power density at multiple fixed-point positions; The laser parameters are calculated according to the power density distribution image.

2. The method for measuring laser parameters by diffuse reflection imaging according to claim 1, characterized in that: The step of obtaining a power density distribution diagram according to the light spot image and the real-time power density at multiple fixed positions specifically includes the following steps: Acquiring the real-time power density value detected by the detector while collecting the spot image; Calculate the conversion coefficient between the mean value of the regional pixel value in the image and the power density by combining the real-time power density and the spot image; The conversion coefficient is introduced into the light spot image to obtain a power density distribution image of the entire light spot.

3. The method for measuring laser parameters by diffuse reflection imaging according to claim 2, characterized in that: The step of calculating the conversion coefficient between the mean value of the regional pixel value in the image and the power density by combining the real-time power density with the spot image specifically comprises the following steps: Obtaining the average pixel value corresponding to the detector installation position in the spot image; Calculate the average real-time power density of multiple detectors; The average real-time power density value is divided by the real-time average pixel value to obtain a conversion coefficient between the mean value of the regional pixel value in the spot image and the power density.

4. The method for measuring laser parameters by diffuse reflection imaging according to claim 1, characterized in that: The step of obtaining the real-time power density of multiple fixed positions in the light spot through the detector further includes calibrating the detector. The specific calibration steps are as follows: Using a stable laser to emit laser light with a predetermined power density toward the diffuse reflection target plate; Get the output value of the detector; A conversion coefficient between the output value of the detector and the power density is calculated according to the predetermined power density and the output value.

5. The method for measuring laser parameters by diffuse reflection imaging according to claim 1, characterized in that: When the diffuse reflection target plate rotates T times within one exposure time, the contrast of the light spot is reduced to T 1 / 2 times.

6. A diffuse reflection imaging laser parameter measurement device, characterized in that: The parameter measurement device includes a diffuse reflection target plate, an imaging camera assembly, a drive motor, a first photoelectric detector module and a data processing unit; The diffuse reflection target plate is used to receive the emitted laser of the laser; The imaging camera assembly is used to collect a grayscale image of a light spot on a diffuse reflection target plate; The driving motor is used to drive the diffuse reflection target plate to rotate with its center as the rotation center; The first photoelectric detection module is used to receive the grayscale image and convert it into a digital signal to transmit to the data processing unit; The data processing unit is used to execute the diffuse reflection imaging laser parameter measurement method according to any one of claims 1 to 4.

7. The diffuse reflection imaging laser parameter measurement device according to claim 6, characterized in that: The diffuse reflection target plate adopts diffuse reflection micro-coefficient optical material.

8. The diffuse reflection imaging laser parameter measurement device according to claim 6, characterized in that: A sampling hole is provided on the diffuse reflection target plate, and a sampling optical fiber (1), an attenuation scattering plate (2), an extinction channel (3), a second photoelectric detector (4) and a detector are arranged in sequence on the back of the sampling hole.

9. The diffuse reflection imaging laser parameter measurement device according to claim 8, characterized in that: There are multiple sampling holes, which are evenly arranged outwards with the diffuse reflection center position as the origin.

10. A computer-readable storage medium, characterized in that: The medium stores a computer program, and after the computer program is run, a diffuse reflection imaging laser parameter measurement method as described in any one of claims 1 to 5 is executed.

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