Automatic compensation device for beam drift of high-power laser processing head

Abstract

The invention discloses a light beam drift automatic compensation device of a high-power laser processing head, and the implementation process of a light beam detection module comprises the following steps: a laser main light beam is firstly divided into transmission light and two beams of reflection light (detection light) by two reflection surfaces of an optical wedge, and the two beams of detection light are respectively converged on a position photoelectric detector and a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) camera through a focusing lens; through data information fusion of the position photoelectric detector and the CMOS camera, light spot shape information obtained by the CMOS camera can be complementary with the high-precision angle measurement capability of the position photoelectric detector, and the measurement precision of light spots in various shapes is improved while high resolution and high response speed of detection are ensured. Whether the incident light beam deflects relative to the incident direction or not is judged according to the angular offset theta, measured by the light beam detection module, of the light beam, and the transmitted light automatically compensates the deflected light beam through the light beam compensation module, so that the emergent light beam and the incident light beam keep the same optical axis and are emergent perpendicular to the incident plane.

Description

Technical Field

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

[0002] Laser processing technology has been widely used in aerospace, automotive, electronics and other industries due to its advantages such as non-contact processing, processing flexibility, and a wide variety of processing materials. In the process of laser processing, it is often necessary to focus the laser beam to make it a laser point with a very small area and high energy density in order to process the material. Among them, high-energy-density ultrafast lasers are suitable for precision processing and manufacturing due to their short pulse duration and high energy density. At this time, the focus position plays a decisive role in the processing accuracy. It is very important to improve the processing efficiency and quality by controlling the transmission of the beam and compensating for the change of the focus position.

[0003] In general laser processing equipment, optical fiber is mostly used for laser transmission. This method directly mounts the laser fiber on the processing head. During the processing, the optical fiber rotates and swings with the processing head, thereby realizing laser processing of parts. Due to the different properties of laser light sources, for high-energy-density ultrafast lasers, the light beam can only be introduced into the laser processing head through an external optical path system and various optical components are installed inside the processing head as a light guide system to achieve the deflection and scanning of the light beam during the processing process. This type of light beam transmission is called a "hard light path" transmission method. Compared with optical fiber transmission, the light beam transmission method using a "hard light path" is more susceptible to the thermal deformation of the optical machine and the ambient temperature, resulting in beam deflection and changes in the focal position, which in turn affects the processing quality.

[0004] In order to solve the above problems, researchers have proposed solutions such as common optical path compensation method, symmetrical dual beam method and sensor feedback control. Patent CN108592825A proposes a photoelectric self-collimation 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 angular drift compensation, and cannot compensate for flat drift. For different defect compensation, more beams need to be separated for detection, which will reduce the quality of the laser beam. Moreover, this solution requires the two beams of light to be returned to the CCD sensor along the original optical path for detection, which is not suitable for use in 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 feeding back the computer through a temperature sensor and driving the collimator to automatically correct. However, the stability of such compensation systems is highly dependent on the sensitivity of the sensor, the sensitivity of the feedback is greatly affected by changes in the external environment, and the large space occupied is not suitable for space-constrained application scenarios. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned background technology, the present invention provides an automatic beam drift compensation device for a high-power laser processing head. According to the geometric optical principles related to the beam deflection angle, the device can complete the compensation of the beam drift by the mirror deflection only through a single detection of the unidirectional main light beam. The device has the characteristics of simple structure, high detection accuracy, low cost, fast response speed, smaller optical path space occupied and improved measurement accuracy of light spots of various shapes.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides an automatic beam drift compensation device for a high-power laser processing head, comprising a beam detection module and a beam compensation module; The beam detection module has the function of splitting and detecting beam deflection, and includes a tilted 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 through the two reflection surfaces of the tilted first optical wedge. The two reflected lights are respectively converged to the position photodetector and the CMOS camera through the 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 yis 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.

[0007] In one specific embodiment, the beam compensation module includes a second optical wedge, and the two optical wedges form a rotating double-wedge prism physical model. In the initial state, the first optical wedge and the second optical wedge are placed oppositely (that is, one of the optical wedges remains stationary, and the other optical wedge is relatively rotated 180°. At this time, the deflection angle generated 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 an outgoing light beam, which has the function of realizing the vertical emission 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 of the incident light beam.

[0008] It should be noted that the installation of each optical element in the beam compensation module is based on the geometric center of the optical mirror. A beam of vertically incident auxiliary light can be introduced and passed through the center of each optical element in turn to ensure that the geometric center of the optical mirror is on the same optical axis.

[0009] Furthermore, if the beam detection module detects that the incident beam is deflected by an angle of ∆θ relative to the incident direction, the control platform controls the driver to rotate the first optical wedge and the second optical wedge around the same axis respectively. When the outgoing beam is parallel to the optical axis, the relative rotation angle of the first optical wedge and the second optical wedge is for: ; Where n is the refractive index of the wedge, and ɑ is the refractive angle of the wedge. The refractive angle and material refractive index of the double wedge prism are fixed, so the deflection effect of the wedge prism on the light beam is also relatively fixed.

[0010] Furthermore, the optical wedges are in the xoy plane, and the main cross-section of the optical wedges is acted upon by the corresponding first driver, so that the two optical wedges can freely rotate around the light beam transmission axis z-axis.

[0011] Specifically, after the angular offset ∆θ is obtained by the light beam detection module, the main control program is used to determine 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 determined as no, and each first driver remains stationary. If it is determined that the incident light beam has been deflected, the control program sends the calculated angular deflection amount 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 emission of the light beam incident at a specific deflection angle within a certain range is achieved.

[0012] If only a single wedge is rotated, the beam can be deflected by changing the relative rotation angle between the two wedges, but the lateral offset of the outgoing beam cannot be completely offset, and the center position of the beam will move periodically with the rotation of the rotatable wedge, forming a "ring" or "spiral" trajectory, and the complete automatic compensation function cannot be achieved. Therefore, the reason why the present invention adopts the relative rotation of the double wedges is that when both wedges can rotate, the deflection directions can be superimposed by symmetrically adjusting the angles of the two wedges, and the lateral offset can be offset (such as when the double wedges rotate in opposite directions, the lateral displacements cancel each other), keeping the center position of the beam almost unchanged, simplifying the optical path calibration and alignment, and the double wedge rotation can achieve sub-milliradian precision control, which is more suitable for complex laser processing requirements.

[0013] In this embodiment, a double wedge prism is used for beam deflection compensation. The optical path system has a simple structure and is easy to integrate. It 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 thermal effects on the function of the beam drift compensation module, a water-cooled heat sink can be added to the integrated optical path for water cooling and heat dissipation to further improve the output beam quality.

[0014] In another specific embodiment, an adjustable plane reflector is used to realize automatic compensation after the light beam is deflected. The light beam compensation module is placed on the transmission light beam line after the first optical wedge. The light beam compensation module includes 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 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. The reflected light is then incident on the first adjustable plane reflector and emitted horizontally. Then the reflected light beam enters the second adjustable plane reflector and forms an outgoing light beam. The light beam compensation module has the function of realizing the vertical emission of the light beam and keeping it on the same optical axis with the incident light beam by adjusting the rotation and translation of the adjustable plane reflector according to the deflection 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. A beam of vertically incident auxiliary light can be introduced and made to pass through the center of each optical element in turn to ensure that the geometric center of the optical mirror is on the same optical axis.

[0015] The second driver and the third driver are servo motors and electric-controlled translation stages, or piezoelectric ceramic brakes and nano-translation stages with higher adjustment accuracy, but the cost of piezoelectric ceramic brakes and nano-translation stages is relatively high.

[0016] Furthermore, if the incident light beam is deflected, the first adjustable plane reflector is driven by the second driver to rotate 1 / 2∆θ around the center of the mirror surface in the direction of the light beam deflection, and the second adjustable plane reflector is driven by the third driver to translate forward and backward by ∆ 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.

[0017] Furthermore, 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.

[0018] When the incident light beam is deflected by ∆θ and incident on the first right-angle prism reflector, it will produce approximately By rotating the first adjustable plane reflector around the center by 1 / 2∆θ, the incident light beam can be horizontally emitted from the first adjustable plane reflector. and Both are 45°±1 / 2∆θ. The positive and negative values ​​are related to the deflection direction of the incident light beam. When the incident light beam is deflected counterclockwise relative to the incident direction, a positive value is taken, otherwise a negative value is taken.

[0019] Furthermore, 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 .

[0020] Compared with the deflected light beam emitted horizontally by the first adjustable plane reflector, there will be obvious front-to-back translation when the light beam is not deflected. Therefore, it is necessary to compensate for the beam drift by adjusting the front-to-back movement of the second adjustable plane reflector so that the final emitted light beam and the initial incident light beam can be vertically emitted on the same optical axis. The front-to-back movement of the second adjustable plane reflector is also related to the deflection direction of the light beam. When the incident light beam deflects counterclockwise relative to the vertical incident direction, the mirror surface of the second adjustable plane reflector moves backward from the original position, and vice versa.

[0021] Furthermore, 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.

[0022] Furthermore, the automatic compensation device for beam drift also includes a focus-adjustable collimator, and the incident beam emitted by the high-power laser processing head enters the beam detection module after passing through the focus-adjustable collimator. The movable platform in the focus-adjustable collimator can ensure that the outgoing beam is focused on the plane to be processed.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. Affected by the thermal effect caused by the long-term light emission of the processing laser, the laser beam has a slight angular deviation (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 shape of the light spot and the light intensity distribution. When the light spot becomes an irregular light spot instead of a uniform regular light spot, a large measurement error will occur. The present invention is a device for automatically compensating beam drift of a high-power laser processing head. The beam detection module includes an optical wedge with a transmittance much larger than a reflection coefficient, a focusing lens, a position photodetector, and a CMOS camera. The beam detection module of the present invention uses a multi-source information complementary detection method combining a position photodetector and a CMOS camera. The main implementation process includes: the main laser beam is first divided into transmitted light and two beams of reflected light (detection light) by two reflective surfaces of an inclined optical wedge. The two beams of detection light are then respectively converged to the position photodetector and the CMOS camera located at the focal plane 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 complement the high-precision angle measurement capability of the position photodetector, thereby improving the measurement accuracy of various shapes of spots while ensuring high resolution and high response speed of detection.

[0024] 2. The beam compensation module proposes beam deflection compensation of double wedge prism. Each wedge prism of the double wedge prism rotates independently around the common axis, and has the characteristic of being able to deflect the beam to a large extent. Then, according to the principle of beam reversibility, by reasonably setting the angular velocity and relative phase of the two wedges, the collimated output of the beam incident at a specific deflection angle within a certain range is achieved. The outgoing beam and the incident beam remain on the same optical axis, and 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 wedge prism, an automatic compensation scheme for beam drift is implemented. The entire compensation structure realizes automatic compensation after beam deflection with its low-cost, lightweight and miniaturized design features, making the entire optical path system simple in structure and easy to integrate. It 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 outgoing beam.

[0025] 3. Optionally, in the beam compensation module, it is proposed to use an adjustable plane mirror to realize automatic compensation after the beam is deflected. According to the correspondence between the beam deflection and the mirror deflection in geometric optics, the determined values ​​of the rotation and translation of the adjustable plane mirror (compensation mirror) are obtained, and the obtained compensation value is directly fed back to the corresponding driver. The compensation of the beam drift is realized in a simple and effective way, ensuring the coaxial vertical output of the final output beam. In addition, the correspondence between the beam deflection direction and the rotation direction of the adjustable plane mirror around the mirror center and the horizontal movement direction of the adjustable plane mirror is summarized. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Figure 1 This is a structural principle diagram of the automatic beam drift compensation device of the high-power laser processing head in Example 1; Figure 2 This is a flow chart of the implementation of the automatic compensation device for beam drift of a high-power laser processing head in Example 1; Figure 3 Schematic diagram of ray tracing of the rotating double wedge prism in Example 1; Figure 4 It is a simulation schematic diagram of Example 1; Figure 5 This is a simulation result diagram of Example 1; Figure 6 This is a structural principle diagram of the automatic beam drift compensation device of the high-power laser processing head in Example 2; Figure 7 This is a flow chart of the implementation of the automatic compensation device for beam drift of a high-power laser processing head in Example 2; Figure 8 This is a schematic diagram of the principle of angular offset adjustment in Example 2; Fig. 9 It is a schematic diagram of the principle of parallel offset adjustment in Example 2; Fig.10 It is a simulation schematic diagram of Example 2; Fig.11 This is a simulation result diagram of Example 2; Among them, the specific drawings are marked as: A first optical wedge 1, a first focusing lens 2, a position photodetector 3, a second focusing lens 4, a CMOS camera 5, a second optical wedge 6, an adjustable focus collimator 8, a first right-angle prism reflector 9, a second right-angle prism reflector 10, a first adjustable plane reflector 11, a second driver 12, a second adjustable plane reflector 13, a third driver 14, and a third focusing lens 15. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0029] Example 1 This embodiment provides a device for automatically compensating beam drift of a high-power laser processing head. Figure 1and Figure 2 As shown, it includes a beam detection module and a beam compensation module; The beam detection module has the function of splitting and detecting 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 beams of reflected light (detection light) through the two reflection surfaces of the inclined first optical wedge 1. The two beams of reflected light (detection light) are respectively converged to the position photodetector 3 and the CMOS camera 5 through the first focusing lens 2 and the second focusing lens 4; 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 3, i1, i2, i3, i4 are the output currents of the light beam on the four quadrants of the position photodetector 3, 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 3 and the centroid position measured by the CMOS camera 5. 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 based on the angular offset ∆θ of the light beam. 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 3. 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 beam compensation module, so that the outgoing light beam and the incident light beam maintain the same optical axis and are emitted perpendicular to the incident surface.

[0030] The beam compensation module includes a second optical wedge 6, and the two optical wedges form a rotating double-wedge prism physical model, such as Figure 3As shown, the optical wedge is in the xoy plane, and the main section of the optical wedge is under the action of the corresponding first driver (not shown in the figure), and the two optical wedges can rotate freely around the z axis of the light beam transmission axis. In the initial state, the first optical wedge 1 and the second optical wedge 6 are placed oppositely (that is, one of the optical wedges remains stationary, and the other optical wedge rotates 180° relatively. At this time, the deflection angle generated is zero, and the transmitted light does not deflect after passing through the second optical wedge 6). The transmitted light formed after the transmitted light passes through the second optical wedge 6 is the outgoing light beam, which has the function of realizing the vertical emission of the outgoing light beam and keeping it on the same optical axis with the incident light beam by adjusting the independent rotation of each optical wedge according to the deflection of the incident light 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. A beam of vertically incident auxiliary light can be introduced and made to pass through the center of each optical element in turn to ensure that the geometric center of the optical mirror is on the same optical axis.

[0031] If the beam detection module detects that the incident beam is deflected by an angle of ∆θ relative to the incident direction, the control platform controls the driver to rotate the first optical wedge 1 and the second optical wedge 6 around the same axis. When the outgoing beam is parallel to the optical axis, the relative rotation angle of the first optical wedge 1 and the second optical wedge 6 is for: ; Where n is the refractive index of the wedge, and ɑ is the refractive angle of the wedge. The refractive angle and material refractive index of the double wedge prism are fixed, so the deflection effect of the wedge prism on the light beam is also relatively fixed.

[0032] 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 is used to determine 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 determined to be no, and each first driver remains stationary; if it is determined that the incident beam has been deflected, the control program sends the calculated angular deflection amount 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 emission of the light beam incident at a specific deflection angle within a certain range is achieved.

[0033] For the adjustable angular velocity range of the prism, its lower limit is required to meet the requirement of timely response to the disturbance or deflection of the light beam. If a stepper motor is used, its minimum step angle determines the lower limit of the angular velocity, while the upper limit needs to be determined comprehensively based on the mechanical rotation mechanism, disturbance frequency and control bandwidth. The reference value range is about 0.1 to 200 rad / s. Regarding the specific implementation of the dual-optical wedge mirror rotation compensation, hierarchical control can be performed based on the beam deflection requirements. When the beam offset is large, a higher angular velocity is used to quickly approach the target position. After approaching the target, it switches to a low-speed mode and achieves milliradian-level accuracy through, for example, PID closed-loop control. At this time, the angular velocity curve is trapezoidal in distribution: acceleration-uniform speed-deceleration, which avoids mechanical shock caused by step changes and is suitable for high-precision systems.

[0034] 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 outgoing beam is focused on the plane to be processed.

[0035] Due to the thermal effect caused by the long-term light emission of the processing laser, the laser beam has a slight angular deviation (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 shape of the light spot and the light intensity distribution. When the light spot becomes an irregular light spot instead of a uniform and regular light spot, a large measurement error will occur. The embodiment is designed to provide an automatic beam drift compensation device for a high-power laser processing head. The beam detection module includes an optical wedge with a transmittance coefficient much larger than a reflection coefficient, a focusing lens, a position photodetector 3, and a CMOS camera 5. The beam detection module uses a multi-source information complementary detection method combining the position photodetector 3 and the CMOS camera 5. The main implementation process includes: the main laser beam is first divided into transmitted light and two beams of reflected light (detection light) by the two reflective surfaces of the tilted optical wedge. The two beams of detection light are then respectively converged to 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 complement the high-precision angle measurement capability of the position photodetector 3, thereby improving the measurement accuracy of various shapes of spots while ensuring the high resolution and high response speed of the detection.

[0036] The beam compensation module proposes a beam deflection compensation of a double wedge prism. Each wedge prism of the double wedge prism rotates independently around a common axis, and has the characteristic of being able to deflect the beam to a large extent. Then, according to the principle of beam reversibility, by reasonably setting the angular velocity and relative phase of the two wedges, the collimated output of the beam incident at a specific deflection angle within a certain range is achieved. The output beam and the incident beam remain on the same optical axis, and the optical path compensation structure does not change the transmission position of the beam in the laser processing equipment. Based on the physical model of the double wedge prism, an automatic compensation scheme for beam drift is implemented. The entire compensation structure realizes automatic compensation after beam deflection with its low-cost and miniaturized design features, making the entire optical path system simple in structure and easy to integrate. It 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 thermal effects on the function of the beam drift compensation module, a water-cooled heat sink can be added to the integrated optical path for water cooling to further improve the output beam quality.

[0037] Depend on Figure 4 As shown, the deflection of the actual light beam is magnified. When the deflection angle of the incident light is 3°, the first optical wedge 1 and the second optical wedge 6 are rotated to form a corresponding deflection angle. The focus spot distribution obtained by the third focusing lens 15 is compared as shown in FIG. Figure 5 By comparison, it can be clearly seen that after the drift beam is compensated by the above method, the deflected beam can be emitted vertically from the center of the mirror again.

[0038] Example 2 This embodiment provides a device for automatically compensating beam drift of a high-power laser processing head. Figure 6 and Figure 7As shown, it includes a beam detection module and a beam compensation module. The structure and specific detection principle of the beam detection module in this embodiment are the same as those of the beam detection module in Example 1. In this embodiment, an adjustable plane reflector is used to realize automatic compensation after the beam is deflected. The beam compensation module is placed on the transmission beam line after the first optical wedge 1. The beam compensation module includes a first right-angle prism reflector 9, a second right-angle prism reflector 10, a first adjustable plane reflector 11, a second driver 12, a third driver 14, and a second adjustable plane reflector 13; the transmitted light formed after the first optical wedge 1 is directly incident on the first right-angle prism reflector 9, and directly enters the second right-angle prism reflector 10 after reflection. The reflected light is then incident on the first adjustable plane reflector 11 and emitted horizontally, and then the reflected light beam enters the second adjustable plane reflector 13 again and forms an emitted light beam. The beam compensation module has the function of realizing the vertical emission of the light beam and keeping it on the same optical axis as the incident light beam by adjusting the rotation and translation of the adjustable plane reflector according to the deflection of the incident light beam. It should be noted that the installation of each optical element in the beam compensation module is based on the geometric center of the optical mirror. A beam of vertically incident auxiliary light can be introduced and passed through the center of each optical element in turn to ensure that the geometric center of the optical mirror is on the same optical axis.

[0039] Specifically, the second driver 12 and the third driver 14 are servo motors and electric-controlled translation stages, or piezoelectric ceramic brakes and nano-translation stages with higher adjustment accuracy, but the cost of piezoelectric ceramic brakes and nano-translation stages is relatively high.

[0040] If the incident light beam is deflected, the first adjustable plane reflector 11 is driven by the second driver 12 to rotate 1 / 2∆θ around the center of the mirror surface in the direction of the light beam deflection, and the second adjustable plane reflector 13 is driven by the third driver 14 to translate forward and backward by ∆ L ,in, ; L 1 represents the horizontal distance between the centers of the first right-angle prism reflector 9 and the second right-angle prism reflector 10, L 2 represents the vertical distance between the center of the second right-angle prism reflector 10 and the center of the first adjustable plane reflector 11.

[0041] Specifically, when the incident light beam is deflected counterclockwise relative to the incident direction, the second driver 12 drives the first adjustable plane reflector 11 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 12 drives the first adjustable plane reflector 11 to rotate clockwise around the center of the mirror surface by an angle of 1 / 2∆θ.

[0042] Depend on Figure 8As shown in FIG. 1 , when the incident light beam is deflected by ∆θ and incident on the first right-angle prism reflector 9, a light beam of approximately By rotating the first adjustable plane reflector 11 around the center by 1 / 2∆θ, the incident light beam can be horizontally emitted from the first adjustable plane reflector 11. At this time, the angle between the incident light and the emitted light and the first adjustable plane reflector 11 is and Both are 45°±1 / 2∆θ. The positive and negative values ​​are related to the deflection direction of the incident light beam. When the incident light beam is deflected counterclockwise relative to the incident direction, a positive value is taken, otherwise a negative value is taken.

[0043] Depend on Fig. 9 As shown, when the incident light beam deflects counterclockwise relative to the incident direction, the third driver 14 drives the second adjustable plane reflector 13 to translate backward ∆ L When the incident light beam deflects clockwise relative to the incident direction, the third driver 14 drives the second adjustable plane reflector 13 to translate forward ∆ L .

[0044] The deflected light beam emitted horizontally by the first adjustable plane reflector 11 will produce obvious front-to-back translation compared with the emission state when the light beam is not deflected. Therefore, it is necessary to compensate for the light beam drift by adjusting the front-to-back movement of the second adjustable plane reflector 13 so that the final emitted light beam and the initial incident light beam can be vertically emitted on the same optical axis. The front-to-back movement of the second adjustable plane reflector 13 is also related to the deflection direction of the light beam. When the incident light beam deflects counterclockwise relative to the vertical incident direction, the mirror surface of the second adjustable plane reflector 13 moves backward from the original position, and vice versa.

[0045] Depend on Fig.10 As shown, the deflection of the actual light beam is magnified. When the deflection angle of the incident light beam is 4°, after the rotation and translation of the first adjustable plane reflector 11 and the second adjustable plane reflector 13, the focusing spot obtained by the third focusing lens 15 is as shown in FIG. Fig.11 By comparison, it can be clearly seen that after the drift beam is compensated by the above method, the deflected beam can be emitted vertically from the center of the mirror again.

[0046] In the beam compensation module of this embodiment, it is proposed to use an adjustable plane mirror to realize automatic compensation after the beam is deflected. According to the corresponding relationship between the beam deflection and the mirror deflection in geometric optics, the determined values ​​of the rotation and translation of the adjustable plane mirror (compensation mirror) are obtained, and the obtained compensation value is directly fed back to the corresponding driver. The compensation of the beam drift is realized in a simple and effective way, and the coaxial vertical output of the final output beam is ensured. In addition, the corresponding relationship between the beam deflection direction and the rotation direction of the adjustable plane mirror around the mirror center and the horizontal movement direction of the adjustable plane mirror is summarized.

[0047] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An automatic beam drift compensation device for 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 surface, 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.

Images