An automatic beam drift compensation device for a high-power laser processing head

Abstract

The present invention discloses an automatic beam drift compensation device for a high-power laser processing head. The implementation process of the beam detection module includes: the main laser beam is first divided into a transmitted light and two reflected lights (detection lights) by two reflection surfaces of an optical wedge, and the two detection lights are respectively converged onto a position photodetector and a CMOS camera through a focusing lens. By fusing the data information of the position photodetector and the CMOS camera, the spot shape information obtained by the CMOS camera can be complementary to the high-precision angle measurement ability of the position photodetector, while ensuring high resolution and high response speed of detection, and improving the measurement accuracy of spots of various shapes. According to the angular offset Δθ of the beam measured by the beam detection module, it is judged whether the incident beam deflects relative to the incident direction, and the transmitted light is automatically compensated for the deflected beam by the beam compensation module, so that the outgoing beam and the incident beam maintain the same optical axis and exit perpendicular to the incident plane.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly relates to an automatic beam drift compensation device for a high-power laser processing head. Background Art

[0002] Due to the advantages of non-contact processing, processing flexibility, and a wide variety of processed materials, laser processing technology has currently been widely applied in industries such as aerospace, automotive, and electronics. During the laser processing process, it is often necessary to focus the laser beam to make it a laser spot with a very small area and a very high energy density in order to process the material. Among them, high-energy-density ultrafast lasers, due to their characteristics such as short pulse duration and high energy density, are suitable for the field of precision machining and manufacturing. At this time, the focal position plays a decisive role in the processing accuracy. Controlling the beam transmission and compensating for the change in the focal position is very important for improving the processing efficiency and quality.

[0003] In general laser processing equipment, optical fibers are mostly used for laser transmission. In this method, the laser optical fiber is directly mounted on the processing head. During the processing process, the optical fiber rotates and swings together with the processing head, thereby realizing the laser processing of parts. Due to the different properties of laser light sources, for high-energy-density ultrafast lasers, the beam can only be introduced into the laser processing head through an external optical path system and various optical elements are installed inside the processing head as a light guiding system to realize the deflection and scanning of the beam during the processing process. This form of beam transmission is called the "hard optical path" transmission method. Compared with the optical fiber transmission form, the "hard optical path" beam transmission method is more susceptible to opto-mechanical thermal deformation and environmental temperature, resulting in beam deflection and focal position change, and thus affecting the processing quality.

[0004] To solve the above problems, researchers have proposed solutions such as common-path compensation method, symmetric double-beam method, and sensor feedback regulation. Patent CN108592825A proposes an optoelectronic autocollimation device and method based on differential compensation. By making the measurement beam and the reference beam pass through the same path, the deviation between the beam measurement signal and the reference beam signal is used to passively compensate for the error caused by beam drift, thereby improving the beam accuracy. However, this method is mostly used for angle drift compensation and cannot compensate for lateral drift. For different defect compensations, more beams need to be separated for detection, which will reduce the quality of the laser beam. Moreover, this solution requires the two beams to return along the original optical path to the CCD sensor for detection, which is not suitable for laser processing heads that emit light in a single direction for a short time. Patent CN114289861A proposes a laser focus automatic compensation system, which improves the stability of the laser beam by the way of temperature sensor feedback to the computer and driving the collimating mirror to automatically correct. However, the stability of such a compensation system highly depends on the sensitivity of the sensor, and the feedback sensitivity is greatly affected by external environmental changes, and it occupies a large space and is not suitable for application scenarios with limited space. Summary of the Invention

[0005] To solve the problems existing in the above background technology, the present invention provides an automatic beam drift compensation device for a high-power laser processing head. According to the geometric optical principle related to the beam deflection angle, only by detecting the unidirectional main beam once, the compensation for the beam drift caused by the mirror deflection can be completed, and it has the characteristics of simple structure, high detection accuracy, low cost, fast response speed, smaller occupied space of the optical path, and improving the measurement accuracy of various shaped light spots.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides an automatic beam drift compensation device for a high-power laser processing head, including a beam detection module and a beam compensation module;

[0008] The beam detection module has the function of detecting the beam deflection by splitting the light, and includes an inclined first optical wedge, two focusing lenses, a position photodetector, and a CMOS camera. The incident beam emitted by the high-power laser processing head is divided into a transmitted light and two reflected lights by the two reflection surfaces of the inclined first optical wedge, and the two reflected lights are respectively converged onto the position photodetector and the CMOS camera through the corresponding focusing lenses;

[0009] The offsets ε x and ε y in the X and Y directions of the focused light spot at this time are obtained according to the following formula:

[0010] ;

[0011] ;

[0012] where k x and k y are the sensitivities of the position photodetector, i1, i2, i3, and i4 are the output currents of the light beam on the four quadrants of the position photodetector respectively, f is the focal length of the focusing lens, ∆C x and ∆C y are the central measurement errors. When the light spot is a uniform light spot or a Gaussian light spot, the central measurement error is zero, while when the light spot is an irregular light spot, the central measurement error is the difference between the center of the light spot measured by the position photodetector and the centroid position measured by the CMOS camera;

[0013] Then, the angular offset ∆θ of the light beam is obtained by the following formula:

[0014] ;

[0015] It is judged whether the incident light beam deflects relative to the incident direction according to the angular offset ∆θ of the light beam. If the incident light beam deflects relative to the incident direction, the transmitted light passes through the light beam compensation module to automatically compensate for the deflected light beam, so that the outgoing light beam and the incident light beam maintain the same optical axis and are perpendicular to the incident surface and exit.

[0016] In one specific embodiment, the light beam compensation module includes a second optical wedge. The two optical wedges form a physical model of a rotating double optical wedge prism. In the initial state, the first optical wedge and the second optical wedge are placed in opposite directions (that is, one optical wedge remains stationary and the other optical wedge rotates 180° relative to it. At this time, the generated deviation angle is zero, and the transmitted light does not deflect after passing through the second optical wedge). The transmitted light formed after passing through the second optical wedge is the outgoing light beam, which has the function of realizing the perpendicular exit of the outgoing light beam and keeping it on the same optical axis as the incident light beam by adjusting the independent rotation of each optical wedge according to the deflection situation of the incident light beam.

[0017] It should be noted that the installation of each optical element in the light beam compensation module is based on the geometric center of the optical mirror surface. An auxiliary light beam perpendicular to the incident light can be introduced and made to pass through the centers of each optical element in turn to ensure that the geometric centers of the optical mirror surfaces are on the same optical axis.

[0018] Further, if the light beam detection module detects that the incident light beam deflects by an angle ∆θ relative to the incident direction, the control platform controls the driver to make the first optical wedge and the second optical wedge rotate around the same axis respectively. When the outgoing light beam exits parallel to the optical axis, the relative rotation angle of the first optical wedge and the second optical wedge is:

[0019] ;

[0020] Among them, n is the refractive index of the optical wedge, and ɑ is the refraction angle of the optical wedge. Since the refraction angle and the material refractive index of the double optical wedge prism are fixed, the deflection effect of the optical wedge prism on the light beam is also relatively fixed.

[0021] Furthermore, the optical wedge is in the xoy plane. Under the action of the corresponding first driver on the main section of the optical wedge, the two optical wedges can freely rotate around the beam transmission axis z-axis respectively.

[0022] Specifically, after obtaining the angular offset ∆θ by the beam detection module, it is judged by the main control program whether the incident light beam is deflected. If the incident light beam is not deflected or the deflection amount is lower than the sensitivity of the detector, it is judged as no, and each first driver remains stationary; if it is judged that the incident light beam has been deflected, the calculated angular deflection amount is sent to each first driver to change the rotational motion of the first optical wedge and the second optical wedge. Each optical wedge prism of the double optical wedge prism rotates independently around the common axis. By reasonably setting the angular velocity and relative phase of the two prisms, the collimated output of the light beam incident at a specific deflection angle within a certain range is realized.

[0023] When only a single optical wedge rotates, the deflection of the light beam can be achieved by changing the relative rotation angle between the two optical wedges. However, the lateral offset of the output light beam cannot be completely canceled, and the central position of the light beam will move periodically with the rotation of the rotatable optical wedge, forming a trajectory similar to a "ring" or "spiral", and the complete automatic compensation function cannot be realized. Therefore, the reason for the present invention to adopt the relative rotation of the double optical wedges is that when both optical wedges can rotate, by symmetrically adjusting their angles, the deflection directions can be superimposed, and at the same time the lateral offset can be canceled (for example, when the double optical wedges rotate in opposite directions, the lateral displacements cancel each other), keeping the central position of the light beam almost unchanged, simplifying the optical path calibration and alignment. At the same time, the rotation of the double optical wedges can achieve sub-milliradian-level precision control, which is more suitable for complex laser processing requirements.

[0024] In this embodiment, the beam deflection compensation of the double optical wedge prism is adopted. The optical path system has a simple structure and is easy to integrate, and can be flexibly and conveniently installed in a high-power laser processing head with limited optical path space to complete the drift compensation of the output light beam. In addition, in order to reduce the influence of the thermal effect on the function of the beam drift compensation module, a water-cooled heat dissipation plate can be added to the integrated optical path for water-cooled heat dissipation to further improve the output light beam quality.

[0025] In another specific embodiment, an adjustable planar mirror is used to achieve automatic compensation after the beam deflection. The beam compensation module is placed on the transmitted beam path behind the first optical wedge. The beam compensation module includes a first right-angled prism mirror, a second right-angled prism mirror, a first adjustable planar mirror, a second driver, a third driver, and a second adjustable planar mirror. The transmitted light formed after passing through the first optical wedge is directly incident on the first right-angled prism mirror, and after reflection, it directly enters the second right-angled prism mirror. The reflected light is then incident on the first adjustable planar mirror and exits horizontally. Subsequently, the reflected beam enters the second adjustable planar mirror and forms an output beam. The beam compensation module has the function of achieving vertical output of the beam and keeping it on the same optical axis as the incident beam by adjusting the rotation and translation of the adjustable planar mirror according to the deflection of the incident beam. It should be noted that the installation of each part of the optical elements in the beam compensation module is based on the geometric center of the optical mirror surface. An auxiliary light incident vertically can be introduced and made to pass through the centers of each optical element in turn to ensure that the geometric centers of the optical mirror surfaces are on the same optical axis.

[0026] The second driver and the third driver are a servo motor and an electric control translation stage, or devices such as a piezoelectric ceramic actuator and a nano translation stage with higher adjustment accuracy are selected. However, the cost of the piezoelectric ceramic actuator and the nano translation stage is relatively high.

[0027] Further, if the incident beam is deflected, the second driver drives the first adjustable planar mirror to rotate by an angle of 1 / 2∆θ around the center of the mirror surface in the direction of the beam deflection, and the third driver drives the second adjustable planar mirror to translate forward and backward by ∆ L , where

[0028] ;

[0029] L 1 represents the horizontal distance between the centers of the first right-angled prism mirror and the second right-angled prism mirror, L 2 represents the vertical distance between the centers of the second right-angled prism mirror and the first adjustable planar mirror.

[0030] Further, when the incident beam is deflected counterclockwise relative to the incident direction, the second driver drives the first adjustable planar mirror to rotate counterclockwise by an angle of 1 / 2∆θ around the center of the mirror surface; when the incident beam is deflected clockwise relative to the incident direction, the second driver drives the first adjustable planar mirror to rotate clockwise by an angle of 1 / 2∆θ around the center of the mirror surface.

[0031] When the incident beam is deflected by ∆θ and is incident on the first right-angled prism mirror, it will produce approximately The height difference. By rotating the first adjustable planar mirror by 1 / 2∆θ around the center, the horizontal emission of the incident light beam on the first adjustable planar mirror can be achieved. At this time, the angles between the incident light and the emitted light and the first adjustable planar mirror and are both 45°±1 / 2∆θ. The positive or negative value is related to the deflection direction of the incident light beam. When the incident light beam deflects counterclockwise relative to the incident direction, the positive value is taken; otherwise, the negative value is taken.

[0032] Further, when the incident light beam deflects counterclockwise relative to the incident direction, the third driver drives the second adjustable planar mirror to translate backward by ∆ L ; when the incident light beam deflects clockwise relative to the incident direction, the third driver drives the second adjustable planar mirror to translate forward by ∆ L .

[0033] There will be an obvious forward and backward translation of the deflected light beam emitted horizontally by the first adjustable planar mirror compared with the emission situation when the light beam is not deflected. Therefore, it is necessary to perform beam flat drift compensation by adjusting the forward and backward movement of the second adjustable planar mirror so that the final emitted light beam is perpendicularly emitted with the same optical axis as the initial incident light beam. The forward and backward movement of the second adjustable planar mirror is also related to the deflection direction of the light beam. When the incident light beam deflects counterclockwise relative to the vertically incident direction, the mirror surface of the second adjustable planar mirror moves backward from the original position; otherwise, the mirror surface moves forward from the original position.

[0034] Further, the condition for the incident light beam not to deflect is that the angular offset ∆θ is 0 or the angular offset ∆θ is lower than the sensitivity of the position photodetector.

[0035] Further, the beam drift automatic compensation device further includes an adjustable focusing collimator. The incident light beam emitted by the high-power laser processing head enters the beam detection module after passing through the adjustable focusing collimator. The movable platform in the adjustable focusing collimator can ensure that the emitted light beam is focused on the plane to be processed.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. Affected by the thermal effect caused by the long-term light output of the processed laser, there is a slight angular deviation in the laser beam (generally less than the milliradian level). The commonly used method in the prior art is to directly use a photodetector to obtain the specific beam deflection value. However, the measurement accuracy of the photodetector is greatly affected by the spot shape and light intensity distribution, and large measurement errors will occur when the spot becomes an irregular-shaped spot instead of a uniform and regular spot. A beam drift automatic compensation device for a high-power laser processing head designed by the present invention, the beam detection module includes an optical wedge with a transmission coefficient much larger than the reflection coefficient, a focusing lens, a position photodetector, and a CMOS camera. The multi-source information complementary detection method combining the position photodetector and the CMOS camera is used in the beam detection module of the present invention. The main implementation process includes: the main laser beam is first divided into a transmitted light and two reflected lights (detection lights) by the two reflection surfaces of the obliquely placed optical wedge, and the two detection lights are respectively converged onto the position photodetector and the CMOS camera located at the focal plane through the focusing lens. By fusing the data information of the position photodetector and the CMOS camera, the spot shape information obtained by the CMOS camera can be complementary to the high-precision angle measurement ability of the position photodetector, improving the measurement accuracy of various-shaped spots while ensuring high resolution and high response speed of the detection.

[0038] 2. In the beam compensation module, beam deflection compensation using a double optical wedge prism is proposed. Each optical wedge prism of the double optical wedge prism rotates independently around the common axis and has the characteristic of being able to deflect the beam greatly. According to the principle of beam reversibility, by reasonably setting the angular velocities and relative phases of the two optical wedges, the collimated output of the beam incident at a specific deflection angle within a certain range is achieved, and the output beam and the incident beam remain on the same optical axis. The optical path compensation structure will not change the transmission position of the beam in the laser processing equipment. Based on the physical model of the double optical wedge prism, an automatic compensation scheme for beam drift is realized. The entire compensation structure realizes the automatic compensation after beam deflection with the design characteristics of low cost and light miniaturization, making the entire optical path system simple in structure and easy to integrate, and can be flexibly and conveniently installed in a high-power laser processing head with limited optical path space to complete the drift compensation of the output beam.

[0039] 3. Optionally, in the beam compensation module, it is proposed to use an adjustable plane mirror to realize the automatic compensation after beam deflection. According to the corresponding relationship between beam deflection and mirror deflection in geometric optics, the determined values of the rotation and translation of the adjustable plane mirror (compensation mirror surface) are obtained, and the obtained compensation values are directly fed back to the corresponding driver, realizing the compensation of beam drift in a simple and effective way and ensuring the coaxial and perpendicular output of the final output beam. In addition, the corresponding relationship between the beam deflection direction, the rotation direction of the adjustable plane mirror around the mirror center, and the horizontal movement direction of the adjustable plane mirror is also summarized. Description of the Drawings

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0041] Figure 1 It is the structural schematic diagram of the automatic beam drift compensation device for the high-power laser processing head in Embodiment 1;

[0042] Figure 2 It is the implementation flowchart of the automatic beam drift compensation device for the high-power laser processing head in Embodiment 1;

[0043] Figure 3 It is the ray tracing schematic diagram of the rotating double optical wedge prism in Embodiment 1;

[0044] Figure 4 It is the simulation schematic diagram of Embodiment 1;

[0045] Figure 5 It is the simulation result diagram of Embodiment 1;

[0046] Figure 6 It is the structural schematic diagram of the automatic beam drift compensation device for the high-power laser processing head in Embodiment 2;

[0047] Figure 7 It is the implementation flowchart of the automatic beam drift compensation device for the high-power laser processing head in Embodiment 2;

[0048] Figure 8 It is the principle schematic diagram of angular offset adjustment in Embodiment 2;

[0049] Figure 9 It is the principle schematic diagram of parallel offset adjustment in Embodiment 2;

[0050] Figure 10 It is the simulation schematic diagram of Embodiment 2;

[0051] Figure 11 It is the simulation result diagram of Embodiment 2;

[0052] Among them, the specific reference numerals are:

[0053] The first optical wedge 1, the first focusing lens 2, the position photodetector 3, the second focusing lens 4, the CMOS camera 5, the second optical wedge 6, the adjustable focus collimator 8, the first right-angle prism mirror 9, the second right-angle prism mirror 10, the first adjustable plane mirror 11, the second driver 12, the second adjustable plane mirror 13, the third driver 14, the third focusing lens 15. Specific embodiments

[0054] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0055] Embodiment 1

[0056] This embodiment provides an automatic beam drift compensation device for a high-power laser processing head, as Figure 1 and Figure 2 shown, which includes a beam detection module and a beam compensation module;

[0057] The beam detection module has the function of detecting and splitting the beam deflection, and includes an inclined first optical wedge 1, a first focusing lens 2, a second focusing lens 4, a position photodetector (PSD) 3, and a CMOS camera 5. The incident beam emitted by the high-power laser processing head is divided into a transmitted light and two reflected lights (detection lights) through the two reflection surfaces of the inclined first optical wedge 1, and the two reflected lights (detection lights) are respectively converged onto the position photodetector 3 and the CMOS camera 5 through the first focusing lens 2 and the second focusing lens 4;

[0058] The offsets ε x and ε y of the focused spot in the X and Y directions at this time are obtained according to the following formula:

[0059] ;

[0060] ;

[0061] where k x and k y are the sensitivities of the position photodetector 3, i1, i2, i3, and i4 are the output currents of the beam on the four quadrants of the position photodetector 3 respectively, f is the focal length of the focusing lens, ∆C x and ∆C y are the central measurement errors. When the spot is a uniform spot or a Gaussian spot, the central measurement error is zero, and when the spot is an irregular-shaped spot, the central measurement error is the difference between the spot center measured by the position photodetector 3 and the centroid position measured by the CMOS camera 5;

[0062] Furthermore, the angular offset ∆θ of the beam is obtained from the following formula:

[0063] ;

[0064] It is judged whether the incident light beam deflects relative to the incident direction according to the angular offset ∆θ of the light beam. The condition for the incident light beam not to deflect is that the angular offset ∆θ is 0 or the angular offset ∆θ is lower than the sensitivity of the position photodetector 3. If the incident light beam deflects relative to the incident direction, the transmitted light is automatically compensated for the deflected light beam by the light beam compensation module, so that the outgoing light beam is collinear with the incident light beam and exits perpendicular to the incident plane.

[0065] The light beam compensation module includes a second optical wedge 6. The two optical wedges form a physical model of a rotating double optical wedge prism. As Figure 3 shown, the optical wedges are in the xoy plane. Under the action of the corresponding first driver (not shown in the figure), the two optical wedges can freely rotate around the light beam transmission axis z-axis respectively. In the initial state, the first optical wedge 1 and the second optical wedge 6 are placed oppositely (that is, one optical wedge remains stationary and the other optical wedge rotates 180° relative to it. At this time, the generated deviation angle is zero, and the transmitted light does not deflect after passing through the second optical wedge 6). The transmitted light passing through the second optical wedge 6 forms the outgoing light beam, which has the function of realizing the perpendicular exit of the outgoing light beam and keeping it collinear with the incident light beam by adjusting the independent rotation of each optical wedge according to the deflection situation of the incident light beam. It should be noted that the installation of each part of the optical elements in the light beam compensation module is based on the geometric center of the optical mirror surface. An auxiliary light beam perpendicular to the incident direction can be introduced and made to pass through the centers of each optical element in turn to ensure that the geometric centers of the optical mirror surfaces are on the same optical axis.

[0066] Among them, if the beam detection module detects that the incident light beam deflects by an angle ∆θ relative to the incident direction, the control platform controls the driver to make the first optical wedge 1 and the second optical wedge 6 rotate around the same axis respectively. When the outgoing light beam exits parallel to the optical axis, the relative rotation angle of the first optical wedge 1 and the second optical wedge 6 is:

[0067] ;

[0068] where n is the refractive index of the optical wedge and ɑ is the refraction angle of the optical wedge. The refraction angle and material refractive index of the double optical wedge prism are fixed, so the deflection effect of the optical wedge prism on the light beam is also relatively fixed.

[0069] The specific working principle of the beam compensation module is as follows: After the angular offset ∆θ is obtained by the beam detection module, the main control program determines whether the incident beam is deflected. If the incident beam is not deflected or the deflection amount is lower than the sensitivity of the position photodetector 3, it is judged as no, and each first driver remains stationary. If it is determined that the incident beam has been deflected, the calculated angular deflection amount is sent to each first driver to change the rotational motion of the first optical wedge 1 and the second optical wedge 6. Each optical wedge prism of the double optical wedge prism rotates independently around the common axis. By reasonably setting the angular velocity and relative phase of the two prisms, the collimated output of the beam incident at a specific deflection angle within a certain range is achieved.

[0070] For the adjustable angular velocity range of the prism, its lower limit requirement is to satisfy the timely response to the perturbation or deflection of the beam. If a stepper motor is used, its minimum step angle determines the lower limit of the angular velocity, and the upper limit needs to be determined comprehensively according to the mechanical rotation mechanism, perturbation frequency, and control bandwidth. The reference value range is about 0.1 - 200 rad / s. Regarding the specific implementation of the rotation compensation of the double optical wedge mirror, hierarchical control can be performed based on the beam deflection requirement. When the beam offset is large, a higher angular velocity is adopted to quickly approach the target position. After approaching the target, it is switched to the low-speed mode, and high-precision control with a milliradian level is achieved through, for example, PID closed-loop control. At this time, the angular velocity curve shows a trapezoidal distribution: acceleration - constant speed - deceleration, avoiding mechanical shock caused by step changes and being suitable for high-precision systems.

[0071] Among them, the beam drift automatic compensation device further includes an adjustable focus collimator 8. The incident beam emitted by the high-power laser processing head enters the beam detection module after passing through the adjustable focus collimator 8. The movable platform in the adjustable focus collimator 8 can ensure that the output beam is focused on the plane to be processed.

[0072] Affected by the thermal effect caused by the long-term light emission of the processed laser, there is a slight angular deviation in the laser beam (generally less than the milliradian level). In the existing technology, the commonly used method is to directly use a photodetector to obtain the specific beam deflection value. However, the measurement accuracy of the photodetector is greatly affected by the spot shape and light intensity distribution, and large measurement errors will occur when the spot becomes an irregular-shaped spot rather than a uniform and regular spot. A beam drift automatic compensation device for a high-power laser processing head designed in this embodiment. The beam detection module includes an optical wedge with a transmission coefficient much larger than the reflection coefficient, a focusing lens, a position photodetector 3, and a CMOS camera 5. The multi-source information complementary detection method combining the position photodetector 3 and the CMOS camera 5 is used in the beam detection module. The main implementation process includes: the main laser beam is first divided into a transmitted light and two reflected lights (detection lights) by the two reflection surfaces of the obliquely placed optical wedge, and the two detection lights are respectively focused on the position photodetector 3 and the CMOS camera 5 located at the focal plane through the focusing lens. By fusing the data information of the position photodetector 3 and the CMOS camera 5, the spot shape information obtained by the CMOS camera 5 can be complementary to the high-precision angle measurement ability of the position photodetector 3, improving the measurement accuracy of various-shaped spots while ensuring high resolution and high response speed of detection.

[0073] In the beam compensation module, beam deflection compensation using a double optical wedge prism is proposed. Each optical wedge prism of the double optical wedge prism rotates independently around the common axis and has the characteristic of being able to deflect the beam greatly. Then, according to the principle of beam reversibility, by reasonably setting the angular velocities and relative phases of the two optical wedges, the collimated output of the beam incident at a specific deflection angle within a certain range is achieved, and the output beam and the incident beam remain on the same optical axis. The optical path compensation structure will not change the transmission position of the beam in the laser processing equipment. An automatic compensation scheme for beam drift is realized based on the physical model of the double optical wedge prism. The entire compensation structure realizes the automatic compensation after beam deflection with the design characteristics of low cost and light miniaturization, making the entire optical path system simple in structure and easy to integrate, and can be flexibly and conveniently installed in a high-power laser processing head with limited optical path space to complete the drift compensation of the output beam. In addition, in order to reduce the influence of the thermal effect on the function of the beam drift compensation module, a water-cooled heat dissipation plate can be added to the integrated optical path for water-cooled heat dissipation to further improve the quality of the output beam.

[0074] As Figure 4 shown, the deflection of the actual beam is amplified. When the deflection angle of the incident light is 3°, the corresponding deflection angles are formed by rotating the first optical wedge 1 and the second optical wedge 6. The comparison of the focused spot distributions obtained by the third focusing lens 15 is as Figure 5 shown. It can be clearly seen through the comparison that after compensating the drifting beam by the above method, the deflected beam can vertically exit from the center of the mirror surface again.

[0075] Embodiment 2

[0076] This embodiment provides an automatic beam drift compensation device for a high-power laser processing head. As shown in Figure 6 and Figure 7 , it includes a beam detection module and a beam compensation module. In this embodiment, the structure and specific detection principle of the beam detection module are the same as those in Embodiment 1. In this embodiment, an adjustable plane mirror is used to achieve automatic compensation after beam deflection. The beam compensation module is placed on the transmitted beam path behind the first optical wedge 1. The beam compensation module includes a first right-angle prism mirror 9, a second right-angle prism mirror 10, a first adjustable plane mirror 11, a second driver 12, a third driver 14, and a second adjustable plane mirror 13. The transmitted light formed after passing through the first optical wedge 1 is directly incident on the first right-angle prism mirror 9, and after reflection, it directly enters the second right-angle prism mirror 10. The reflected light is then incident on the first adjustable plane mirror 11 and exits horizontally. Subsequently, the reflected beam enters the second adjustable plane mirror 13 and forms an output beam. The beam compensation module has the function of adjusting the rotation and translation of the adjustable plane mirror according to the deflection of the incident beam, so as to achieve the vertical output of the beam and keep it on the same optical axis as the incident beam. It should be noted that the installation of each part of the optical elements in the beam compensation module is based on the geometric center of the optical mirror surface. An auxiliary light incident vertically can be introduced and made to pass through the centers of each optical element in turn to ensure that the geometric centers of the optical mirror surfaces are on the same optical axis.

[0077] Specifically, the second driver 12 and the third driver 14 are servo motors and electric control translation stages, or devices with higher adjustment accuracy such as piezoelectric ceramic brakes and nano translation stages are selected, but the cost of piezoelectric ceramic brakes and nano translation stages is relatively high.

[0078] Among them, if the incident beam deflects, the second driver 12 drives the first adjustable plane mirror 11 to rotate 1 / 2∆θ angle around the center of the mirror surface in the direction of beam deflection, and the third driver 14 drives the second adjustable plane mirror 13 to translate forward and backward by ∆ L , where

[0079] ;

[0080] L 1 represents the horizontal distance between the centers of the first right-angle prism mirror 9 and the second right-angle prism mirror 10, L 2 represents the vertical distance between the centers of the second right-angle prism mirror 10 and the first adjustable plane mirror 11.

[0081] Specifically, when the incident light beam deflects counterclockwise relative to the incident direction, the second driver 12 drives the first adjustable planar mirror 11 to rotate counterclockwise by an angle of 1 / 2∆θ around the center of the mirror surface; when the incident light beam deflects clockwise relative to the incident direction, the second driver 12 drives the first adjustable planar mirror 11 to rotate clockwise by an angle of 1 / 2∆θ around the center of the mirror surface.

[0082] As Figure 8 shown, when the incident light beam deflects by ∆θ and is incident on the first right-angle prism mirror 9, a height difference of approximately will be generated on the second right-angle prism mirror 10. By rotating the first adjustable planar mirror 11 by an angle of 1 / 2∆θ around the center, the horizontal emergence of the incident light beam on the first adjustable planar mirror 11 can be achieved. At this time, the angles between the incident light and the emergent light and the first adjustable planar mirror 11 are both 45°±1 / 2∆θ, and the positive or negative value depends on the deflection direction of the incident light beam. When the incident light beam deflects counterclockwise relative to the incident direction, the positive value is taken; otherwise, the negative value is taken.

[0083] As Figure 9 shown, when the incident light beam deflects counterclockwise relative to the incident direction, the third driver 14 drives the second adjustable planar mirror 13 to translate backward by ∆ L ; when the incident light beam deflects clockwise relative to the incident direction, the third driver 14 drives the second adjustable planar mirror 13 to translate forward by ∆ L .

[0084] There will be an obvious forward and backward translation of the deflected light beam emerging horizontally from the first adjustable planar mirror 11 compared with the emergence situation when the light beam does not deflect. Therefore, it is necessary to perform beam flat drift compensation by adjusting the forward and backward movement of the second adjustable planar mirror 13 so that the final emergent light beam is perpendicularly emergent with the same optical axis as the initial incident light beam. The forward and backward movement of the second adjustable planar mirror 13 is also related to the deflection direction of the light beam. When the incident light beam deflects counterclockwise relative to the vertically incident direction, the mirror surface of the second adjustable planar mirror 13 translates backward from its original position; conversely, the mirror surface translates forward from the original position.

[0085] As Figure 10 shown, the deflection of the actual light beam is amplified. When the deflection angle of the incident light beam is 4°, after the rotation and translation of the first adjustable planar mirror 11 and the second adjustable planar mirror 13, the focused spot situation obtained by the third focusing lens 15 is as Figure 11 shown. It can be clearly seen by comparison that after compensating the drifting light beam by the above method, the deflected light beam can emerge vertically from the center of the mirror surface again.

[0086] In this embodiment, in the beam compensation module, it is proposed to use an adjustable plane mirror to achieve automatic compensation after beam deflection. According to the corresponding relationship between beam deflection and mirror surface deflection in geometric optics, the definite numerical values of the rotation and translation of the adjustable plane mirror (compensation mirror surface) are obtained, and the obtained compensation values are directly fed back to the corresponding drivers, realizing the compensation of beam drift in a simple and effective way, ensuring the coaxial and perpendicular output of the final outgoing beam. In addition, the corresponding relationships between the beam deflection direction, the rotation direction of the adjustable plane mirror around the center of the mirror surface, and the horizontal movement direction of the adjustable plane mirror are also summarized.

[0087] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An automatic compensation device for beam drift of a high-power laser processing head, characterized in that: It includes a beam detection module and a beam compensation module; The beam detection module includes a tilted first optical wedge, two focusing lenses, a position photodetector and a CMOS camera. The incident light beam emitted by the high-power laser processing head is divided into a transmitted light and two reflected lights through two reflecting surfaces of the tilted first optical wedge. The two reflected lights are respectively converged to the position photodetector and the CMOS camera through corresponding focusing lenses. The offset of the focused spot in the X and Y directions at this time is obtained according to the following formula: x and ε y for: ； ； Among them, k x and k y is the sensitivity of the position photodetector, i1, i2, i3, i4 are the output currents of the light beam in the four quadrants of the position photodetector, f is the focal length of the focusing lens, ∆C x and ∆C y is the center measurement error. When the light spot is a uniform light spot or a Gaussian light spot, the center measurement error is zero. When the light spot is an irregular light spot, the center measurement error is the difference between the center of the light spot measured by the position photodetector and the centroid position measured by the CMOS camera. The angular deviation ∆θ of the light beam is obtained by the following formula: ； Whether the incident light beam is deflected relative to the incident direction is determined according to the angular offset ∆θ of the light beam. If the incident light beam is deflected relative to the incident direction, the transmitted light is automatically compensated for the deflected light beam by the light beam compensation module, so that the outgoing light beam maintains the same optical axis as the incident light beam and is emitted perpendicular to the incident surface.

2. The automatic beam drift compensation device for a high-power laser processing head according to claim 1, characterized in that: The beam compensation module includes a second optical wedge. In an initial state, the first optical wedge and the second optical wedge are placed opposite to each other, and the transmitted light formed after the transmitted light passes through the second optical wedge is the outgoing beam.

3. The automatic beam drift compensation device for a high-power laser processing head according to claim 2, characterized in that: If the incident light beam is deflected, the relative rotation angle of the first optical wedge and the second optical wedge is adjusted. for: ； Where n is the refractive index of the wedge and ɑ is the refraction angle of the wedge.

4. The automatic beam drift compensation device for a high-power laser processing head according to claim 3, characterized in that: The optical wedge is in the xoy plane, and the main cross section of the optical wedge is under the action of the corresponding first driver, and the two optical wedges can rotate freely around the light beam transmission axis z axis.

5. The automatic beam drift compensation device for a high-power laser processing head according to claim 1, characterized in that: The beam compensation module comprises a first right-angle prism reflector, a second right-angle prism reflector, a first adjustable plane reflector, a second driver, a third driver, and a second adjustable plane reflector; the transmitted light formed after passing through the first optical wedge is directly incident on the first right-angle prism reflector, and directly enters the second right-angle prism reflector after reflection, and the reflected light is then incident on the first adjustable plane reflector and emitted horizontally, and then the reflected light beam enters the second adjustable plane reflector and forms an emitted light beam.

6. The automatic beam drift compensation device for a high-power laser processing head according to claim 5, characterized in that: If the incident light beam is deflected, the second driver drives the first adjustable plane mirror to rotate 1 / 2∆θ around the center of the mirror, and the third driver drives the second adjustable plane mirror to translate forward and backward ∆ L ; in, ; L 1 represents the horizontal distance between the center of the first right-angle prism reflector and the center of the second right-angle prism reflector, L 2 represents the vertical distance between the center of the second right-angle prism reflector and the center of the first adjustable plane reflector.

7. The automatic beam drift compensation device for a high-power laser processing head according to claim 6, characterized in that: When the incident light beam is deflected counterclockwise relative to the incident direction, the second driver drives the first adjustable plane reflector to rotate counterclockwise around the center of the mirror surface by an angle of 1 / 2∆θ; when the incident light beam is deflected clockwise relative to the incident direction, the second driver drives the first adjustable plane reflector to rotate clockwise around the center of the mirror surface by an angle of 1 / 2∆θ.

8. The automatic beam drift compensation device for a high-power laser processing head according to claim 7, characterized in that: When the incident light beam deflects counterclockwise relative to the incident direction, the third driver drives the second adjustable plane reflector to translate backward by ∆ L ; When the incident light beam deflects clockwise relative to the incident direction, the third driver drives the second adjustable plane reflector to translate forward ∆ L .

9. The automatic beam drift compensation device for a high-power laser processing head according to claim 1, characterized in that: The condition that the incident light beam is not deflected is that the angular offset ∆θ is 0 or the angular offset ∆θ is lower than the sensitivity of the position photodetector.

10. The automatic beam drift compensation device for a high-power laser processing head according to claim 1, characterized in that: The automatic compensation device for beam drift also includes a focus-adjustable collimator. The incident beam emitted by the high-power laser processing head passes through the focus-adjustable collimator and then enters the beam detection module.

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