A Gaussian laser spot energy distribution measurement method and device

Abstract

The present invention relates to a Gaussian laser spot energy distribution measurement method and device, wherein a laser output unit outputs Gaussian laser, and a distance measuring unit is arranged in conjunction with the laser output unit to obtain distance measuring data. When the projection method is used to measure the spot energy, the light intensity distribution of the spot is corrected by an image deflection correction method to obtain a corrected spot energy distribution diagram. The image acquisition unit is arranged on the side of the laser output unit to receive and output the laser diffusely reflected back from the projection area. The present invention aims at infrared laser fixed-point shooting to obtain the spot morphology; for the problem of distortion of the spot energy distribution diagram caused by the tilt of the projection area, the design scheme eliminates the distortion, ensures the quality of the spot energy distribution acquisition, and lays the foundation for subsequent optical path shaping and spot morphology analysis.

Description

Technical Field

[0001] The present invention relates to the technical fields of measurement of intensity, speed, spectral composition, polarization, phase or pulse characteristics of infrared light, visible light and ultraviolet light; colorimetry; and radiation high temperature determination method, and in particular to a Gaussian laser spot energy distribution measurement method and device. Background Art

[0002] Infrared lasers are mainly used for material processing, such as cutting, welding and heat treatment, but with the development of technology, the requirements for the processing of laser fiber spot morphology and spot shaping have become more stringent and extensive. Therefore, it is necessary to study the energy distribution diagram of high-power infrared lasers.

[0003] Laser photography technology is a technology that uses laser as a light source to capture the energy distribution of a light spot. Lasers can provide precise lighting and imaging effects due to their high monochromaticity, directionality, and brightness, especially in low-light environments or when high-contrast and high-resolution imaging is required. Traditional laser photography technology usually involves the selection of laser light sources, the guidance and focusing of laser beams, and the optimization of matching imaging systems, aiming to achieve accurate energy distribution; however, the problem of distortion of the light spot energy distribution diagram caused by the deflection of the projection area still exists, which leads to distortion of the light spot phase and poor quality of irradiation distribution acquisition.

[0004] The Chinese patent with publication number CN114370935A discloses a CCD target surface laser energy distribution measurement system and method based on image fusion, which sets a series of step-changing interference laser powers, and obtains a grayscale image of the CCD detector under orthogonal placement at each interference laser power; then uses orthogonal compensation to perform data fusion on the image under equal power conditions, and finally compensates and superimposes the fused image according to a linear relationship to obtain the final image distribution information, and obtains the CCD target surface laser energy distribution information based on the final image distribution information. Its disadvantage is that the tilt of the projection area during the process of spot imaging is not considered to produce energy distribution distortion, which affects the quality of spot acquisition.

[0005] The Chinese patent with the publication number CN115185096A discloses a device and method for adjusting the energy distribution of a 3D printing laser beam using an aspheric lens. The device includes an aspheric lens installed in the housing of the device. By changing the coefficient c and coefficient k of the aspheric lens, the energy distribution of the light beam incident on the aspheric lens is adjusted. The coefficient c represents the curvature at the vertex of the aspheric lens, and k represents the cone coefficient. The present invention uses an aspheric lens to adjust the energy distribution of the light spot and the light spot scanning line beam, so that the light spot presents the characteristics of low energy in the middle and high energy at the edge, thereby making the energy of the scanning line beam locally flat-topped, improving the uniformity of the 3D printing laser energy distribution, and is conducive to improving the quality of SML metal 3D laser printing. And by changing the diameter of the Gaussian beam incident on the aspheric lens, the energy distribution of the incident beam can be adjusted more conveniently, thereby meeting the different requirements of different printing materials and processes for the energy distribution of the light spot. Starting from adjusting the energy distribution of the light spot, the patent still does not propose an effective solution to the objective problem of energy map distribution map distortion caused by the tilt of the projection area.

[0006] Therefore, when using a sensor to shoot an infrared laser spot, the problem of energy distribution distortion caused by the tilt of the projection area needs to be solved urgently. Summary of the invention

[0007] The present invention solves the problems existing in the prior art and provides a Gaussian laser spot energy distribution measurement method and device, which utilizes Gaussian laser to illuminate the target area and uses a special sensor to capture the reflected infrared light to generate a visible image, thereby solving the problem of spot energy distribution distortion caused by the tilt of the projection area in the spot capture technology.

[0008] The technical solution adopted by the present invention is a Gaussian laser spot energy distribution measuring device, a projection surface is provided in conjunction with the measuring device, and the measuring device comprises:

[0009] A laser output unit, used for outputting Gaussian laser to the projection surface;

[0010] A distance measuring unit is provided in conjunction with the laser output unit and is used to obtain distance measuring data. When the light spot energy is measured by the projection method, the light intensity distribution of the light spot is corrected by the image deflection correction method to obtain a corrected light spot energy distribution diagram;

[0011] An image acquisition unit is arranged at the side of the laser output unit and is used to receive and output the laser diffusely reflected by the projection area.

[0012] Preferably, the distance measuring unit and the light source outlet of the laser output unit are located at the same end surface and face the projection area; the distance measuring unit comprises a second distance measuring instrument, a first distance measuring instrument and a third distance measuring instrument which are sequentially arranged on the outside of the laser output unit.

[0013] Preferably, the laser power density emitted by the laser output unit is less than 50% of the material ablation threshold in the projection area.

[0014] Preferably, the area of ​​the projection surface satisfy,

[0015]

[0016] Wherein, Z0 is the distance between the light source outlet of the laser output unit and the projection area, and NA is the numerical aperture of the laser output unit.

[0017] A measuring method of the Gaussian laser spot energy distribution measuring device adopts a projection method to measure the spot energy, and corrects the light intensity distribution of the spot by an image deflection correction method to obtain a corrected spot energy distribution diagram.

[0018] Preferably, a projection area is set in the imaging area of ​​the light source outlet of the laser output unit, and the distances X1 and X2 from the first rangefinder and the second rangefinder on the side of the light source outlet to the light source outlet are obtained, and the distances Y3 and Y4 from the first rangefinder and the third rangefinder on the side of the light source outlet to the light source outlet are obtained, and the distances L1, L2, and L3 from the first rangefinder, the second rangefinder, and the third rangefinder to the projection area and pointing to the end point of the light spot are obtained, and the length of the major axis of the light spot is measured. and the length of the minor axis of the light spot satisfy,

[0019]

[0020] .

[0021] Preferably, based on the angle between the projection area and the x-axis and y-axis projections, the projected measurement length of any point of the light spot on the x-axis and y-axis is , the measured distance from this point to the center of the light spot is ;

[0022] Calculate the actual long axis length after correction of the long axis and short axis measurement length of the spot , actual minor axis length ,

[0023]

[0024]

[0025] The corrected actual distance from any point of the light spot to the center of the light spot satisfy,

[0026] .

[0027] Preferably, , where I is the energy intensity of the Gaussian spot, which is determined by the maximum output power of the laser, k=1,2,3, The spot energy intensity of the long axis and short axis of the laser spot after correction, They are the length ratios of the major axis, minor axis and distance from any point on the laser spot to the center of the spot before and after correction, , .

[0028] The present invention relates to a Gaussian laser spot energy distribution measurement method and device, wherein a laser output unit is used to output Gaussian laser, and a distance measuring unit is arranged in conjunction with the laser output unit to obtain distance measuring data. When a projection method is used to measure the spot energy, an image deflection correction method is used to correct the light intensity distribution of the spot to obtain a corrected spot energy distribution diagram. The image acquisition unit is arranged on the side of the laser output unit to receive and output the laser diffusely reflected back by the projection area.

[0029] The beneficial effects of the present invention are that the spot morphology can be obtained by fixed-point shooting with infrared laser; the distortion problem of the spot energy distribution diagram caused by the tilt of the projection area is eliminated by the design scheme, thereby ensuring the quality of the spot energy distribution acquisition and laying the foundation for subsequent optical path shaping and spot morphology analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the measuring device of the present invention;

[0031] Figure 2 It is a schematic diagram of an embodiment of the present invention for measuring the actual correction value of the major axis;

[0032] Figure 3 It is a structural schematic diagram of the laser output unit in the present invention;

[0033] Figure 4 It is a structural schematic diagram of the image acquisition unit in the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0035] The present invention relates to a Gaussian laser spot energy distribution measuring device, wherein a projection surface is provided in conjunction with the measuring device, and the measuring device comprises:

[0036] A laser output unit 201, used to output Gaussian laser to the projection surface;

[0037] A distance measuring unit, arranged in conjunction with the laser output unit 201, is used to obtain distance measuring data. When the light spot energy is measured by the projection method, the light intensity distribution of the light spot is corrected by the image deflection correction method to obtain a corrected light spot energy distribution diagram;

[0038] An image acquisition unit is disposed on the side of the laser output unit 201 and is used to receive and output the laser diffusely reflected by the projection area.

[0039] The distance measuring unit and the light source outlet of the laser output unit 201 are located at the same end face and face the projection area; the distance measuring unit includes a second distance measuring instrument 202, a first distance measuring instrument 205 and a third distance measuring instrument 203 which are sequentially arranged outside the laser output unit 201.

[0040] The laser power density emitted by the laser output unit 201 is less than 50% of the ablation threshold of the material in the projection area.

[0041] Projection surface area satisfy,

[0042]

[0043] Wherein, Z0 is the distance between the light source outlet of the laser output unit 201 and the projection area, and NA is the numerical aperture of the laser output unit 201 .

[0044] In the present invention, the laser output unit 201 is composed of a laser head 401 and a protective mirror 402. The protective mirror 402 is located at the output end of the laser head 401. The laser passes through the protective mirror 402 and enters the scattering system and is projected onto the projection area.

[0045] In the present invention, the rangefinders are respectively placed above, below and at the far end of the receiving end of the image acquisition unit, and are used to measure the distances from multiple positions in the projection area to the light source.

[0046] In the present invention, the image acquisition unit is composed of an industrial camera 501 and a laser protection lens 502. The laser protection lens 502 is located at the lens end of the industrial camera 501 and is used to reduce the influence of diffuse reflected light on the lens imaging quality. A filter is also arranged in front of the industrial camera 501 to reduce high-power laser exposure behavior. In order to ensure that the image acquisition unit can receive the reflected infrared laser beam and reduce the image distortion error, the industrial camera 501 and the laser output device should be arranged on the same side and fixed on the same plane by a mechanical device.

[0047] In the specific implementation of the present invention, the distance between the projection area and the light source (laser output unit 201) satisfies the requirement of being greater than 2m and less than 5m, so as to prevent the spot exposure caused by being too close and the low energy in the center area of ​​the spot caused by being too far, which are not conducive to analyzing the spot morphology;

[0048] The distance between the rangefinder and the light source outlet should be no more than 50cm to prevent the measurement value from being too far away and affecting the experimental data; the distance between the rangefinder and the projection area is generally greater than 2m to ensure that the light spot is not too small to cause high exposure and affect the observation of the light spot morphology, and not too large to cause the image pixel spacing to be too large, making it difficult to analyze the light spot morphology;

[0049] The industrial camera 501 is visible to light beams within the wavelength range of the laser, and the response rate of the industrial camera 501 to light beams within the wavelength range is not less than 70%.

[0050] The present invention also relates to a Gaussian laser spot energy distribution measurement method. When the spot energy is measured by a projection method, the light intensity distribution of the spot is corrected by an image deflection correction method to obtain a corrected spot energy distribution diagram.

[0051] In the present invention, the output laser is projected to the projection area, and the image acquisition unit acquires the spot morphology. During the process, the projection area may be tilted, such as Figure 2 As shown in the figure, the energy distribution of the light spot is distorted. Therefore, the long axis and short axis of the light spot are measured and the equation is established based on the distance between the set rangefinder and the light source outlet and the projection area. Finally, the length of the long axis and short axis of the actual light spot is calculated, and the energy distribution diagram distortion in the projection area is corrected after the gray value of the light spot is extracted.

[0052] During the process, in addition to the major axis and minor axis, any point Q of the light spot is also taken to add correction to ensure the accuracy of the correction.

[0053] In the present invention, the light source outputs laser light, and its wavelength satisfies the requirement of being less than 10600nm and greater than 800nm, so as to ensure that the example can be applied to most application scenarios; the measurable distance of the rangefinder is not less than 50m, so as to ensure the accuracy of the measurement data.

[0054] In the present invention, in order to prevent the visible light from affecting the irradiation distribution of the light spot, it should be ensured that the light spot morphology is obtained in a closed environment without light.

[0055] Specifically, a projection area is set in the imaging area of ​​the light source outlet of the laser output unit 201, and the distances X1 and X2 from the first rangefinder 205 and the second rangefinder 202 on the side of the light source outlet to the light source outlet are obtained, and the distances Y3 and Y4 from the first rangefinder 205 and the third rangefinder 203 on the side of the light source outlet to the light source outlet are obtained, and the distances L1, L2, and L3 from the first rangefinder 205, the second rangefinder 202, and the third rangefinder 203 to the projection area and pointing to the end point of the light spot are obtained, and the length of the major axis of the light spot is measured. and the length of the minor axis of the light spot satisfy,

[0056]

[0057] .

[0058] Based on the angle between the projection area and the x-axis and y-axis projections, the projected measurement length of any point Q on the x-axis and y-axis is , the measured distance from this point to the center of the light spot is ;

[0059] Calculate the actual long axis length after correction of the long axis and short axis measurement length of the spot , actual minor axis length ,

[0060]

[0061]

[0062] The corrected actual distance from any point Q of the light spot to the center of the light spot satisfy,

[0063] .

[0064] In the present invention, The acquisition is based on measurement.

[0065] , where I is the energy intensity of the Gaussian spot, which is determined by the maximum output power of the laser, k=1,2,3, The spot energy intensity of the long axis and short axis of the laser spot after correction, They are the length ratios of the major axis, minor axis and distance from any point on the laser spot to the center of the spot before and after correction, , .

[0066] That is, when the spot diagram expands or contracts in a certain direction, the energy distribution diagram expands or contracts accordingly.

[0067] In the present invention, I should be no greater than 50 kW to prevent image exposure. Usually greater than 80% to ensure the accuracy of the correction.

[0068] Furthermore, considering , with I as light intensity, G as grayscale value, k and b as proportional coefficient and offset respectively, based on the corrected light spot, the grayscale value at each point of the light spot is extracted, and the image data is fused using orthogonal compensation. The images are compensated and superimposed according to the linear relationship to obtain the final image distribution information, and the laser energy distribution information of the laser light source is obtained based on the final image distribution information.

[0069] In the present invention, the value range of G is usually 0 to 255 (for 8-bit images) or 0 to 65535 (for 16-bit images). The grayscale value is used to quantify the brightness of each pixel in the image. k and b are respectively the proportional coefficient and the offset. These parameters depend on specific conditions such as camera response and exposure time. This relationship is usually linear, which means that the increase in grayscale value is proportional to the increase in energy. Imagej software is used to extract the grayscale value distribution, which is then input into the software for simulation. The grayscale value of the light spot is converted by the above formula to obtain the light spot irradiance map, which can also be used for the above I k Validation of formula.

[0070] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A Gaussian laser spot energy distribution measuring device, wherein a projection surface is provided in conjunction with the measuring device, characterized in that: The measuring device comprises: A laser output unit, used for outputting Gaussian laser to the projection surface; A distance measuring unit is provided in conjunction with the laser output unit and is used to obtain distance measuring data. When the light spot energy is measured by the projection method, the light intensity distribution of the light spot is corrected by the image deflection correction method to obtain a corrected light spot energy distribution diagram; An image acquisition unit is arranged at the side of the laser output unit and is used to receive and output the laser diffusely reflected by the projection area.

2. The Gaussian laser spot energy distribution measuring device according to claim 1, characterized in that: The distance measuring unit and the light source outlet of the laser output unit are located at the same end surface and face the projection area; the distance measuring unit comprises a second distance measuring instrument, a first distance measuring instrument and a third distance measuring instrument which are sequentially arranged outside the laser output unit.

3. The Gaussian laser spot energy distribution measuring device according to claim 1, characterized in that: The laser power density emitted by the laser output unit is less than 50% of the ablation threshold of the material in the projection area.

4. The Gaussian laser spot energy distribution measuring device according to claim 1, characterized in that: Projection surface area satisfy, ， Wherein, Z0 is the distance between the light source outlet of the laser output unit and the projection area, and NA is the numerical aperture of the laser output unit.

5. A method for measuring the energy distribution of a Gaussian laser spot according to any one of claims 1 to 4, characterized in that: When the projection method is used to measure the light spot energy, the light intensity distribution of the light spot is corrected by the image deflection correction method to obtain the corrected light spot energy distribution diagram.

6. The measuring method according to claim 5, characterized in that: A projection area is set in the imaging area of ​​the light source outlet of the laser output unit, and the distances X1 and X2 from the first rangefinder and the second rangefinder on the side of the light source outlet to the light source outlet are obtained, and the distances Y3 and Y4 from the first rangefinder and the third rangefinder on the side of the light source outlet to the light source outlet are obtained, and the distances L1, L2, and L3 from the first rangefinder, the second rangefinder, and the third rangefinder to the projection area and pointing to the end point of the light spot are obtained respectively, and the length of the major axis of the light spot is measured. and the length of the minor axis of the light spot satisfy, ， 。 7. The measuring method according to claim 6, characterized in that: Based on the angle between the projection area and the x-axis and y-axis projections, the projected measurement length of any point of the light spot on the x-axis and y-axis is , the measured distance from this point to the center of the light spot is ; Calculate the actual long axis length after correction of the long axis and short axis measurement length of the spot , actual minor axis length , ， ； The corrected actual distance from any point of the light spot to the center of the light spot satisfy, 。 8. The measuring method according to claim 7, characterized in that: , where I is the energy intensity of the Gaussian spot, which is determined by the maximum output power of the laser, k=1,2,3, The spot energy intensity of the long axis and short axis of the laser spot after correction, They are the length ratios of the major axis, minor axis and distance from any point on the laser spot to the center of the spot before and after correction, , .

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