Laser welding head with dual movable mirrors providing beam shifting capability

Abstract

A laser welding head with a movable mirror can be used to perform welding operations, for example, using an oscillating pattern and / or a seam finding / tracking and following function. The movable mirror provides an oscillating function of one or more beams within a relatively small field of view, for example, defined by a scanning angle of 1° to 2°. The movable mirror can be a galvanometer mirror that can be controlled by a control system including a galvanometer controller. The laser welding head can also include a diffractive optical element to shape the moving beam or beams. The control system can also be used to control a fiber laser, for example, in response to the position of the beam relative to the workpiece and / or a sensed condition in the welding head (such as a thermal condition near one of the mirrors).

Description

[0001] This application is a divisional application of a patent application (international application date June 20, 2016, application number 201680036032.4, invention name “Laser welding head with double movable mirrors providing beam movement function”).

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 182,211, filed on June 19, 2015, and U.S. Provisional Patent Application No. 62 / 294,731, filed on February 12, 2016, both of which are incorporated herein by reference in their entirety. Technical Field

[0004] The present invention relates to laser welding, and more particularly to a laser welding head having dual movable reflecting mirrors providing a beam moving function, and a laser welding system and method using the laser welding head. Background Art

[0005] Lasers, such as fiber lasers, are often used for material processing applications, such as welding. Conventional laser welding heads include a collimator for collimating the laser and a focusing lens for focusing the laser onto a target area to be welded. The beam can be moved in various patterns to weld two structures along a seam (e.g., using a stir welding technique). One method of moving the beam for stir welding is to rotate the beam using a rotating prism optic to form a rotating or spiral pattern. Another way to move the beam for welding is to pivot or move the entire welding head on an XY stage to form a zigzag pattern. These conventional methods of moving the beam to perform a welding pattern do not allow for rapid and precise movement of the beam. Summary of the invention

[0006] According to one embodiment, a laser welding head includes: a collimator configured to be coupled to an output fiber of a fiber laser; and at least a first movable mirror and a second movable mirror configured to receive a collimated laser beam from the collimator and to move the laser beam on a first axis and a second axis only within a limited field of view defined by a scanning angle of about 1° to 2°. The laser welding head also includes: a focusing lens configured to focus the laser beam relative to a workpiece while the laser beam is moving.

[0007] According to another embodiment, a laser welding head includes: a collimator configured to be coupled to an output fiber of a fiber laser; at least a first movable mirror and a second movable mirror configured to receive a collimated laser beam from the collimator and to move the laser beam on a first axis and a second axis; and at least a first thermal sensor and a second thermal sensor, respectively, proximate to the first movable mirror and the second movable mirror and configured to detect a thermal condition. The laser welding head also includes: a focusing lens configured to focus the laser beam.

[0008] According to another embodiment, a laser welding head includes: a collimator module, which includes a collimator, the collimator is configured to be coupled to an output fiber of a fiber laser; and an oscillator module, which is coupled to the collimator module. The oscillator module includes: at least a first movable mirror and a second movable mirror, which are configured to receive a collimated laser beam from the collimator and move the laser beam on a first axis and a second axis. The laser welding head also includes: a core block module, which is coupled to the oscillator module. The core block module includes at least a focusing lens, which is configured to focus the laser beam.

[0009] According to another embodiment, a laser welding system includes: a fiber laser including an output fiber; and a welding head coupled to the output fiber of the fiber laser. The welding head includes: a collimator configured to be coupled to the output fiber of the fiber laser; at least a first movable mirror and a second movable mirror configured to receive a collimated laser beam from the collimator and move the laser beam on a first axis and a second axis; and a focusing lens configured to focus the laser beam. The laser welding system also includes: a control system for controlling the position of at least the fiber laser and the mirrors.

[0010] According to another embodiment, a laser welding head includes: a collimator configured to be coupled to an output fiber of a fiber laser; at least a first movable mirror and a second movable mirror configured to receive a collimated laser beam from the collimator and move the laser beam on a first axis and a second axis; and a focusing lens configured to focus the laser beam. The laser welding head also includes: at least one of a gas assist attachment and a gas knife attachment proximate to the focusing lens to assist welding.

[0011] According to another embodiment, a laser welding head includes: a collimator configured to be coupled to an output fiber of a fiber laser; at least one diffractive optical element configured to receive a collimated laser beam from the collimator and to shape the collimated laser beam; and at least a first movable mirror and a second movable mirror configured to receive the shaped laser beam from the diffractive optical element and to move the shaped laser beam on a first axis and a second axis. The laser welding head also includes: a focusing lens configured to focus the laser beam relative to a workpiece while the laser beam is moving. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These and other features and advantages will be better understood from the following detailed description read in conjunction with the accompanying drawings, in which:

[0013] Figure 1 is a schematic block diagram of a system including a laser welding head having dual movable mirrors according to an embodiment of the present invention.

[0014] Figure 1A is a schematic diagram of a focused laser beam having a relatively small range of motion provided by dual mirrors to facilitate seam finding and / or wobbling in accordance with an embodiment of the present invention.

[0015] FIG. 2A to FIG. 2D is a schematic diagram illustrating different wobble patterns that can be produced by a welding head including dual mirrors for beam movement according to an embodiment of the present invention.

[0016] Figure 3A is a micrograph of a welded workpiece having a weld seam formed by a laser using a stir welding function with a figure-8 oscillating pattern according to an embodiment of the present invention.

[0017] Figure 3B yes Figure 3A Micrograph of a cross section of the welded workpiece and weld shown.

[0018] Figure 3C is a micrograph of a welded workpiece having a weld seam formed by a laser without a wobble pattern.

[0019] Figure 3D yes Figure 3C Micrograph of a cross section of the welded workpiece and weld shown in .

[0020] Figure 4 is an exploded view of a laser welding head having dual movable mirrors for beam movement according to an embodiment of the present invention.

[0021] Figure 5 and Figure 6 is Figure 4 A perspective view of a collimator module used in a laser welding head is shown.

[0022] Figure 7 is Figure 4 A perspective view of a wobbler module used in a laser welding head is shown.

[0023] Figure 8 is Figure 4 Exploded view of the wobbler module used in the laser welding head shown.

[0024] Fig. 9 is Figure 4 A partially cut-away side view of a wobbler module used in a laser welding head is shown.

[0025] Fig.10 is a perspective view of the inside of the wiggler module with the water cooling restriction holes and thermal sensors.

[0026] Fig.11 is an exploded view of the core block module, which includes Figure 4 Focusing and window housing used in a laser welding head shown.

[0027] Fig.12 is an exploded view of the focus and window housing, which has Figure 4 Protective window used in laser welding head shown.

[0028] Fig.13 and Fig.14 yes Figure 4 A perspective view of a laser welding head is shown, wherein the collimator module, the wobbler module, and the core block module are assembled together and emit a focused beam.

[0029] Fig.15 yes Fig.13 and Fig.14 Schematic diagram of the optical path within the laser welding head is shown.

[0030] Fig.16 is a schematic block diagram of a laser welding head having dual movable mirrors and diffractive optics according to an embodiment of the present invention.

[0031] Fig.17A and Fig. 17B The circular spot produced by the diffractive optical device and the rectangular spot after shaping are shown respectively.

[0032] Fig. 17C The donut-shaped spot produced by the beam shaping optics is shown.

[0033] 18A to 18CRectangular light spots of different sizes produced by different diffractive optics are shown.

[0034] Fig.19 A pattern of light spots is shown, produced by a multi-beam fiber laser coupled to a laser welding head, according to an embodiment of the present invention.

[0035] Fig. 20 A pattern of a shaped spot is shown, produced by a multi-beam fiber laser coupled to a laser welding head including diffractive optics, according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] A laser welding head with a movable mirror according to an embodiment of the present invention can be used to perform welding operations, for example, using a swinging pattern and / or a seam finding / tracking and following function. The movable mirror provides a swinging movement function of one or more light beams within a relatively small field of view, for example, defined by a scanning angle of 1° to 2°. The movable mirror can be a galvanometer mirror, and the reflection can be controlled by a control system including a galvanometer controller. The laser welding head can also include a diffractive optical element to shape the one or more moving light beams. The control system can also be used to control a fiber laser, for example, in response to the position of the light beam relative to the workpiece and / or a sensed state in the welding head (such as a thermal state near one of the mirrors).

[0037] refer to Figure 1 , the laser welding system 100 includes a laser welding head 110, which is coupled to an output fiber 111 of a fiber laser 112 (e.g., using a connector 111a). The laser welding head 110 can be used to perform welding on a workpiece 102, for example, by welding a seam 104 to form a weld 106. The laser welding head 110 and / or the workpiece 102 can be moved relative to each other along the direction of the seam 104. The laser welding head 110 can be located on a moving stage 114 to move the welding head 110 relative to the workpiece 102 along at least one axis (e.g., along the length of the seam 104). Additionally or alternatively, the workpiece 102 can be located on a moving stage 108 to move the workpiece 102 relative to the laser welding head 110.

[0038] The fiber laser 112 may include an ytterbium fiber laser capable of producing laser light in the near infrared spectral range (e.g., 1060 to 1080 nm). The ytterbium fiber laser may be a single mode or multi-mode continuous wave ytterbium fiber laser; in some embodiments, the laser is capable of producing a laser beam with a power of up to 1 kW; in other embodiments, the laser is capable of producing a laser beam with a power of up to 50 kW. Examples of the fiber laser 112 include the YLRSM series or YLR HP series lasers available from IPG Photonics. The fiber laser 112 may also include a multi-beam fiber laser, such as the type disclosed in International Application No. PCT / US2015 / 45037, filed on August 13, 2015, entitled “Multibeam Fiber Laser System,” which is capable of selectively transmitting one or more laser beams through multiple optical fibers.

[0039] The laser welding head 110 generally includes: a collimator 122 for collimating the laser beam from the output optical fiber 111; at least a first movable mirror 132 and a second movable mirror 134 for reflecting and moving the collimated beam 116; and a focusing lens 142 for focusing and transmitting the focused beam 118 to the workpiece 102. In the embodiment shown in the figure, a fixed mirror 144 is also used to guide the collimated laser beam 116 from the second movable mirror 134 to the focusing lens 142. The collimator 122, the movable mirrors 132 and 134, and the focusing lens 142 and the fixed mirror 144 can be provided in separate modules 120, 130, 140, which can be coupled together, as described in detail later. For example, if the mirrors 132 and 134 are arranged to reflect light from the second mirror 134 toward the focusing lens 142, the laser welding head 110 can also be constructed without the fixed mirror 144.

[0040] The movable mirrors 132 and 134 can pivot about different axes 131 and 133 to move the collimated beam 116 and, therefore, the focused beam 118 relative to the workpiece 102 on at least two different perpendicular axes 2, 4. The movable mirrors 132 and 134 can be galvanometer mirrors that can be moved by a galvanometer motor that can quickly reverse direction. In other embodiments, other mechanisms such as stepper motors can be used to move the mirrors. The use of movable mirrors 132 and 134 in the laser welding head 110 allows the laser beam 118 to be moved accurately, controllably, and quickly without having to move the entire welding head 110 and without having to use a rotating prism to facilitate seam finding and following and / or beam swinging.

[0041] In an embodiment of the welding head 110, as Figure 1AAs shown, the movable mirrors 132 and 134 pivot the light beam 118 within a scan angle α of less than 10° and more specifically about 1° to 2°, thereby moving the light beam 118 only within a relatively small field of view (e.g., less than 30×30 mm), thereby allowing the beam to swing. In contrast, conventional laser scanning heads generally provide the movement function of the laser beam within a larger field of view (e.g., greater than 50×50 mm or even as large as 250×250 mm) and are designed to accommodate larger fields of view and scan angles. Therefore, the use of movable mirrors 132 and 134 in the laser welding head 110 to provide only a relatively small field of view is counterintuitive and contrary to the conventional wisdom that a wider field of view is provided when using a galvanometer scanner. Limiting the field of view and scan angle provides many advantages when using galvanometer mirrors in the welding head 110 (e.g., by achieving faster speeds, allowing use with cheaper components such as lenses, and by allowing use with accessories such as air knives and / or gas assists).

[0042] In an exemplary embodiment of the welding head 110, the second mirror 134 can have approximately the same size as the first mirror 132 due to the smaller field of view and scanning angle. In contrast, conventional galvanometer scanners typically use a larger second mirror to provide a larger field of view and scanning angle, and the larger second mirror can limit the speed of movement in at least one axis. Therefore, the smaller size of the second mirror 134 in the welding head 110 (e.g., approximately the same size as the first mirror 132) enables the mirror 134 to move at a faster speed compared to the larger mirror that provides a large scanning angle in a conventional galvanometer scanner.

[0043] The focusing lens 142 may include known focusing lenses for laser welding heads and have various focal lengths, ranging from 100 mm to 1000 mm, for example. Conventional laser scanning heads use multi-element scanning lenses, such as Fθ lenses, flat field lenses, or telecentric lenses, which have larger diameters (e.g., 300 mm diameter lenses for 33 mm diameter beams) to focus the beam within a larger field of view. Because the movable reflectors 132 and 134 move the beam within a relatively small field of view, a larger multi-element scanning lens (e.g., an Fθ lens) is not required or used. In one embodiment of a welding head 110 according to the present invention, a 50 mm diameter plano-convex F300 focusing lens can be used to focus a beam of approximately 40 mm in diameter for movement within a field of view of approximately 15×5 mm. The use of a smaller focusing lens 142 also allows the use of accessories, such as air knives and / or gas-assisted accessories, at the end of the welding head 110. The larger scanning lenses required for conventional laser scanning heads limit the use of these accessories.

[0044] Other optical devices such as beam splitters can also be used in the laser welding head 110 to separate the laser beam so as to provide at least two spots for welding (e.g., on both sides of the weld). Additional optical devices can also include diffractive optical devices and can be positioned between the collimator 122 and the mirrors 132, 134, which will be described in detail later.

[0045] A protective window 146 may be provided in front of the lens 142 to protect the lens and other optical devices from debris generated by the welding process. The laser welding head 110 may also include a welding head accessory 116, such as an air knife for providing a high-speed gas flow through the protective window 146 or the focusing lens 142 to remove debris; and / or a gas assist accessory for delivering a shielding gas coaxially or off-axis to the welding point to suppress the welding plume. Thus, the laser welding head 110 with a movable reflector can be used with existing welding head accessories.

[0046] The embodiment of the laser welding system 100 shown in the figure also includes a detector 150, such as a camera, for detecting and locating the seam 104, for example, at a position in front of the beam 118. Although the camera / detector 150 is schematically shown on one side of the welding head 110, the camera / detector 150 can be directed through the welding head 110 to detect and locate the seam 104.

[0047] The embodiment of the laser welding system 100 shown in the figure also includes a control system 160 for controlling the positioning of the fiber laser 112, the movable mirrors 132, 134 and / or the movable stages 108, 114, for example, in response to the sensed conditions in the welding head 110, the detected position of the seam 104 and / or the movement and / or position of the laser beam 118. The laser welding head 110 may include sensors, such as a first thermal sensor 162 and a second thermal sensor 164, which are close to the corresponding first movable mirror 132 and second movable mirror 134 to sense thermal conditions. The control system 160 is electrically connected to the sensors 162 and 164 to receive data to monitor the thermal conditions near the movable mirrors 132 and 134. The control system 160 can also monitor the welding operation by receiving data from the camera / detector 150 (e.g., data indicating the detected position of the seam 104).

[0048] The control system 160 can control the fiber laser 112, for example, by shutting down the laser, changing a laser parameter (e.g., laser power), or adjusting any other adjustable laser parameter. The control system 160 can shut down the fiber laser 112 in response to a sensed condition in the laser welding head 110. The sensed condition can be a thermal condition sensed by one or both of the sensors 162 and 164 and a symptom of a mirror failure or other condition resulting in high temperatures caused by the high power laser.

[0049] The control system 160 can shut down the fiber laser 112 by triggering a safety interlock. The safety interlock is disposed between the output fiber 111 and the collimator 122 such that when the output fiber 111 is disconnected from the collimator 122, the safety interlock state is triggered and the laser is shut down. In the embodiment shown in the figure, the laser welding head 110 includes an interlock path 166 that extends the safety interlock feature to the movable mirrors 132 and 134. The interlock path 166 extends between the output fiber 111 and the control system 160 to allow the control system 160 to trigger the safety interlock state in response to a potentially dangerous condition detected in the laser welding head 110. In this embodiment, the control system 160 can cause the safety interlock state to be triggered via the interlock path 166 in response to a predetermined thermal condition detected by one or both sensors 162, 164.

[0050] The control system 160 can also control laser parameters (e.g., laser power) in response to the movement or position of the beam 118 without shutting down the laser 112. If one of the movable mirrors 132 and 134 moves the beam 118 out of range or too slowly, the control system 160 can reduce the laser power to dynamically control the energy of the spot to avoid damage caused by the laser. The control system 160 can also control the selection of laser beams in a multi-beam fiber laser.

[0051] The control system 160 may also control the positioning of the movable mirrors 132 and 134 in response to the position of the seam 104 detected by the camera / detector 150, for example, to correct the position of the focused beam 118 to find, track and / or follow the seam 104. The control system 160 may identify the position of the seam 104 by using data from the camera / detector 150, thereby finding the seam 104, and then move one or both of the mirrors 132 and 134 until the beam 118 coincides with the seam 104. As the beam 118 moves along the seam to perform welding, the control system 160 may continuously adjust or correct the position of the beam 118 by moving one or both of the mirrors 132 and 134 so that the beam coincides with the seam 104, thereby following the seam 104. The control system 160 may also control one or both of the movable mirrors 132 and 134 to provide a swing function during welding, as described in more detail later.

[0052] Thus, the control system 160 includes a laser control and a mirror control working together to control the laser and the mirror together. The control system 160 may include, for example, known hardware (e.g., a general purpose computer) and software for controlling a fiber laser and a galvanometer mirror. For example, existing galvanometer control software may be used and modified to allow the galvanometer mirror to be controlled as described herein.

[0053] FIG. 2A to FIG. 2D An example of an oscillating pattern is shown that may be used to perform stir welding of seam 204. As used herein, "oscillating" refers to reciprocating movement of a laser beam (eg, in two axes) and within a relatively small field of view defined by a scan angle of less than 10°. Figure 2A and Figure 2B The circular pattern and the figure-eight pattern sequentially formed along the seam 204 are respectively shown. Figure 2C and Figure 2D A zigzag pattern and a wavy pattern are shown, respectively, formed along the seam 204. Although certain oscillating patterns are shown, other oscillating patterns are also within the scope of the present invention. One advantage of using a movable mirror in the laser welding head 110 is the ability to move the beam according to a variety of different oscillating patterns.

[0054] FIG. 3A to FIG. 3D shows the figure-8 swing pattern ( Figure 3A and Figure 3B ) and the conventional unmanipulated beam ( Figure 3C and Figure 3D ) compared with the welds formed. In one example ( Figure 3A and Figure 3B), two sheets of aluminum 6061-T6 alloy were welded using a spot with a diameter of 2 mm, moving in a 90° figure-of-eight pattern, oscillating at a frequency of 300 Hz, a power of 2.75 kW, a speed of 3.5 m / min, and a gap of 0.012 inches. In another example ( Figure 3C and Figure 3D ), two sheets of aluminum 6061-T6 alloy were welded using a beam spot without oscillation, a power of 2.0 kW, a speed of 3.5 m / min, and a gap of 0.012 inches. As shown in the figure, the weld quality on the surface with the figure-eight oscillation was improved compared to the unoperated beam. In particular, compared to Figure 3C In comparison, Figure 3A As shown, the uniformity of the weld is improved. Figure 3B The cross section in also shows (with Figure 3D The reduction in area at the weld is smaller than that at the 204 weld because the figure-eight oscillating pattern more effectively bridges the gap of the joint 204. The laser welding systems and methods described herein can also be used to improve welding with materials that are typically difficult to weld, such as titanium.

[0055] Figures 4 to 15 An embodiment of a laser welding head 410 is shown in greater detail. Although one specific embodiment is shown, other embodiments of the laser welding heads and systems and methods described herein are also within the scope of the present invention. Figure 4 As shown, the laser welding head 410 includes a collimator module 420, a wobbler module 430, and a core block module 440. The wobbler module 430 includes the first movable mirror and the second movable mirror discussed above, and is coupled between the collimator module 420 and the core block module 440.

[0056] Figure 5 and Figure 6 The collimator module 420 is shown in more detail. Figure 5 As shown, the input end 421 of the collimator module 420 is configured to be coupled to an output fiber connector and includes a fiber interlock connector 425 that is connected to the output fiber connector (not shown) to provide a safety interlock when the output fiber is disconnected. Figure 6 As shown, the output end 423 of the collimator module 420 is configured to be connected to the oscillator module 430 (see Figure 4 ) and includes a fiber interlock connector 427 to extend the safety interlock path into the oscillator module 430. The collimator module 420 may include a collimator (not shown) having a pair of fixed collimating lenses, such as the type known for use in laser welding heads. In other embodiments, the collimator may include other lens configurations, such as movable lenses that enable adjustment of the size and / or focus of the light spot.

[0057] Figures 7 to 10 The oscillator module 430 is shown in more detail. The embodiment of the oscillator module 430 shown in the figure includes: an input hole 431, which is used to connect to the collimator module 420; and an output hole 433, which is used to connect to the core block module 440 (see Figure 4 ). The input hole 431 may include a water cooling restriction hole.

[0058] like Figure 8 As shown, the embodiment of the oscillator module 430 shown in the figure also includes a first galvanometer 436 and a second galvanometer 438 for moving the galvanometer mirrors 432 and 434 around different vertical axes. Known galvanometers for laser scanning heads can be used. Galvanometers 436 and 438 can include a connection portion 437 for connecting to a galvanometer controller (not shown). The galvanometer controller can include hardware and / or software for controlling the galvanometers to control the movement of the mirrors and thereby control the movement and / or positioning of the laser beam. Known galvanometer control software can be used and can be modified to provide the functions described herein, such as seam finding, oscillation patterns, and communication with the laser.

[0059] like Figure 7 As shown, the oscillator module 430 includes a fiber interlock connector 435 for connecting to the collimator fiber interlock connector 427. The oscillator module 430 also includes a galvanometer fiber interlock connector 437 for connecting to a galvanometer controller. Therefore, the safety interlock extends to the oscillator module 430 and the galvanometer controller. The galvanometer controller can be configured to trigger a safety interlock state, for example, in response to a sensed condition within the oscillator module 430.

[0060] like Fig. 9 and Fig.10 As shown, the oscillator module 430 includes thermal probes 462 and 464, which are respectively adjacent to each of the reflectors 432 and 434. The thermal probes 462 and 464 sense thermal conditions (e.g., temperature) at corresponding locations within the oscillator module 430 and can be connected to a galvanometer controller via a galvanometer connection 437. In this way, the galvanometer controller can monitor the thermal probes 462 and 464 to determine whether a predetermined condition occurs, such as a high temperature indicating a potential dangerous condition within the oscillator module 430. For example, if one of the movable reflectors 432 and 434 fails, a high power laser directed into the oscillator module 430 may not be properly reflected and a dangerous condition may result. Therefore, the galvanometer controller can trigger a safety interlock to shut down the laser in response to the dangerous condition. The thermal probes can include known sensors, such as a bimetallic strip inside a ceramic.

[0061] Fig.11 The core block module 440 is shown in more detail. The core block module 440 includes a fixed reflector (not shown); the reflector redirects the light beam received from the oscillator module 430 to the focusing lens 442 and then to the workpiece. As shown, the core block module 440 includes a core block housing 441 and a focus and window housing 443 coupled to one side of the core block housing 441. A camera module (not shown) can be coupled to the opposite side of the core block housing 441 to monitor the focused light beam and / or the workpiece within the field of view provided by the focus and window housing 443.

[0062] The focusing and window housing 443 houses the focusing lens 442 and the protective window 446. Fig.12 As shown, the protective window 446 may be removable and replaceable. The focus and window housing 443 also houses a window state monitoring circuit 470 having sensors such as a thermistor 472 and a photodiode 474 for monitoring the state of the protective window 446. The core block housing 441 also includes: a state monitoring connector 475 for connecting to the state monitoring circuit 470 in the focus and window housing 443; and a weld monitor connector 477 for connecting to a weld head monitor (not shown).

[0063] Fig.13 and Fig.14 An assembled laser welding head 410 is shown, wherein each of the modules 420, 430, 440 is coupled together and emits a focused beam 418. The laser beam coupled to the collimator module 420 is collimated, and the collimated beam is directed to the wobbler module 430. The wobbler module 430 uses a mirror to move the collimated beam, and directs the moved collimated beam to the core block module 440. The core block module 440 then focuses the moved beam, and the focused beam 418 is directed to a workpiece (not shown).

[0064] Fig.15 The path of the collimated light beam 416 inside the oscillator module 430 and the core block module 440 coupled together is shown. As shown, the collimated light beam 416 input into the oscillator module is reflected from the first galvanometer mirror 432 to the second galvanometer mirror 434, and then reflected from the fixed mirror 444 within the core block module and output from the core module. The fixed mirror 444 can be an infrared mirror to allow use with a camera for monitoring the light beam 416.

[0065] refer to Fig.16, further embodiments of a laser welding head 1610 and a laser welding system with movable mirrors are described in more detail. This embodiment of the laser welding head 1610 also includes at least one shaping diffractive optical element 1626 for shaping the beam. The beam shaping diffractive optical element 1626 is located between the collimator 1622 and the movable mirrors 1632, 1634 in the welding head 1610. The beam shaping diffractive optical device 1626 shapes the collimated beam, and then the shaped beam is moved by the mirrors 1632 and 1634 as described above.

[0066] An example of a beam shaping diffractive optical element 1626 includes a top hat beam shaping element that receives a beam having a Gaussian profile and a circular spot (e.g. Fig.17A ) and produces a shaped laser beam with a uniform square or "top hat" profile and a rectangular or square spot, such as Fig. 17B Other beam shaping diffractive optical elements may include, but are not limited to: a diffractive beam splitting element that converts an input beam into a 1-D or 2-D array of beamlets; a ring generator element that shapes an input beam into a ring or a series of rings; and a diffractive vortex lens that shapes an input beam into a donut-shaped ring, such as Fig. 17C shown.

[0067] Therefore, different beam shaping diffractive optical elements 1626 can be used to provide beams of different shapes and / or sizes. By eliminating the high power concentration at the center of the beam, the annular spot can also have a more uniform power distribution. 18A to 18C As shown, different diffractive optical elements can provide rectangular beams with different sizes, thereby enabling different "brush sizes" and resolutions for welding and other applications. For example, for smaller areas or around edges where higher resolution is desired, a smaller spot or "brush size" can be used.

[0068] In an embodiment, the beam shaping diffractive optical element 1626 is located in the beam shaping module 1624, which is removably positioned between the collimator module 1620 and the wobbler module 1630, for example as previously described. Thus, beam shaping modules 1624 having different diffractive optical devices can be used interchangeably in the welding head 1610. The beam shaping module 1624 can also provide a safety interlock path 1666 as described above.

[0069] In another embodiment, the welding head 1610 can be coupled to a multi-beam fiber laser 1612 that can selectively transmit multiple beams. An example of a multi-beam fiber laser is described in more detail in International Application No. PCT / US2015 / 45037, filed on August 13, 2015, entitled “Multibeam Fiber Laser System,” which is incorporated herein by reference in its entirety. The multiple beams can have different characteristics, such as different modes, powers, energy densities, profiles, and / or sizes. For example, Fig.19 Multiple beams of different sizes are shown. Multiple beams can be transmitted simultaneously, or individual beams with different characteristics can be separately and selectively transmitted at different times to provide different operations (e.g., heating, welding, and post-processing). Fig. 20 As shown, the multiple beams can also be shaped by the diffractive optical device 1626 to produce multiple shaped beams. In this way, the shape and / or size of the multiple beams can be changed to facilitate different operations or applications using the multi-beam fiber laser 1612 and / or different diffractive optical elements 1626. For example, for some welding applications, one or more beams can be shaped into a ring or donut shape to provide a more uniform power distribution.

[0070] Thus, the laser welding head with a movable mirror according to the embodiments described herein allows for better control of the movement, size, and / or shape of the laser beam for various welding applications. Thus, the embodiments of the laser welding head with a movable mirror and the welding systems and methods described herein can be used to form stronger, smoother, and more uniform welds.

[0071] Although the principles of the present invention have been described herein, it should be understood by those skilled in the art that such description is by way of example only and not as a limitation on the scope of the present invention. In addition to the exemplary embodiments shown and described herein, other embodiments may be envisioned within the scope of the present invention. Modifications and substitutions made by those of ordinary skill in the art are considered to fall within the scope of the present invention; the present invention is not limited except to the extent defined by the appended claims.

Claims

1. A laser welding method, comprising: generating a raw laser beam from a laser; collimating the raw laser beam in the welding head; reflecting a collimated laser beam from at least first and second movable mirrors in the welding head and moving the at least first and second movable mirrors according to an oscillating pattern on first and second axes within only a limited field of view defined by a scan angle of about 1° to 2° to move the beam relative to a workpiece; and The moving light beam is focused onto the workpiece to perform welding.

2. The laser welding method according to claim 1, further comprising: At least one of the laser welding head and the workpiece is moved relative to each other while the light beam is moved with the first movable mirror and the second movable mirror.

3. The laser welding method according to claim 1, further comprising: Movement of the at least first and second movable mirrors is controlled such that the light beam moves in the wobbling pattern over the workpiece during welding.

4. The laser welding method according to claim 1, wherein: At least a portion of the workpieces being welded is aluminum.

5. The laser welding method according to claim 1, wherein: Generating the laser beam includes generating a laser beam in the near infrared spectral range from an ytterbium fiber laser.

6. The laser welding method according to claim 1, wherein: Generating the laser beam includes generating the laser beam from a fiber laser having an active optical fiber selected from the group consisting of optical fibers doped with erbium, thorium, holmium, and combinations thereof.

7. The laser welding method according to claim 1, further comprising: The movement of the at least first and second movable mirrors is controlled so that the light beam follows the seam to be welded.

8. The laser welding method according to claim 7, further comprising: The position of the seam to be welded is detected before the seam, and wherein the movement is controlled to adjust the positioning of the light beam in response to the detected position of the seam to be welded.

9. The laser welding method according to claim 8, further comprising: Movement of at least one of the first movable mirror and the second movable mirror is controlled such that the light beam moves in the oscillating pattern over the joint to be welded.

10. The laser welding method according to claim 1, further comprising: The collimated light beam is shaped.

11. The laser welding method according to claim 10, wherein: Shaping the collimated light beam includes passing the collimated laser beam through a diffractive optical element.

12. The laser welding method according to claim 1, further comprising: Laser power is adjusted in response to the movement and / or positioning of the light beam.

13. The laser welding method according to claim 1, further comprising: The laser is turned off in response to sensing proximity to at least one of the first movable mirror and the second movable mirror.

14. The laser welding method according to claim 13, wherein: The sensed condition is a thermal condition.

15. The laser welding method according to claim 1, further comprising: Gas is delivered to the weld point from a gas assist accessory mounted on the laser welding head.

16. The laser welding method according to claim 1, characterized in that: The wobbling pattern is selected from the group consisting of a circular pattern, a figure-8 pattern, a zigzag pattern, and a wave pattern.

17. A laser welding method, comprising: providing a laser for generating a raw laser beam; A laser welding head is provided, the laser welding head being used to: collimate the raw laser beam in the laser welding head, move the collimated laser beam relative to a workpiece in an oscillating pattern within a limited field of view, and focus the moved beam on the workpiece as the beam moves in the oscillating pattern, the laser welding head being configured with at least a first movable mirror and a second movable mirror, the at least first movable mirror and second movable mirror being configured to move the beam according to the oscillating pattern on a first axis and a second axis within a limited field of view defined only by a scanning angle of about 1° to 2°; and At least one translation stage is provided for moving at least one of the laser welding head and the workpiece relative to each other while moving the beam across the workpiece in an oscillating pattern.

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