High power laser system for thermal surface treatment applications with design size and power density

Abstract

A high power laser system for surface thermal treatment is configured with one or more laser sources that produce respective source beams having respective arbitrary powers and at a particular wavelength. The source light beam is transmitted to the laser head through a respective fiber optic bundle having an output end terminating within the laser head. An optical mixer is mounted in the laser head, the optical mixer having its own input face opposite the output end opposite the output end of the respective fiber bundle, the output ends of the respective fiber bundles together forming a predetermined spatial arrangement. The optical mixers are configured to receive the source output beams from the respective fiber output ends to combine and shape the coupled output beams into at least one system output beam that forms a beam spot having a desired power density distribution (PDD) and a desired shape.

Description

Technical Field

[0001] The present disclosure relates to a laser system for thermal surface treatment applications. Specifically, the present disclosure relates to a laser system in which a plurality of fiber bundles direct respective source beams, each having an arbitrary power density distribution (PDD), to an optical mixer configured to combine the source beams into a system output beam having a beam spot having a predetermined shape and a desired PDD on the irradiated surface. Background Art

[0002] Laser surface treatment is a thermal process that utilizes a high-power-density laser beam to heat a material surface in a non-contact manner. Traditional small-area and large-area laser processing technologies, such as laser cleaning, laser hardening, laser alloying, laser shock peening, and laser annealing, as well as laser cladding, laser 3D printing, and laser electroplating, offer a wealth of potential applications. Some of these prospects, at least partially realized, include, preferably (but not exclusively), drying printed water-based or solvent-based dispersions applied to large-area substrates or components.

[0003] For example, laser-based drying of anode and cathode layers has recently gained traction in battery manufacturing. To achieve the temperature range required to increase coating / drying speeds, previous research projects have shown that near-infrared wavelengths are particularly promising. This wavelength range is typically (but not exclusively) achieved with semiconductor or fiber lasers. Compared to conventional oven-drying processes, laser processing can reduce energy consumption. However, to date, laser processing has not been able to achieve the processing speeds required by industry. This limitation is being gradually overcome through increasing laser power and optimizing parameters.

[0004] The basic configuration of known laser drying systems is as follows: Figure 1 As shown, it comprises a fiber-coupled diode laser or fiber laser, which generates light that is transmitted via an optical fiber 1 to a laser head 2 for scanning a surface 3 to be processed along a scan line 4 . Figure 2 The figure shows a more detailed configuration of one of the known laser surface treatment systems for drying water-based electrodes for lithium-ion battery cells made of a slurry of active material powder, binder, solvent, conductive agent, and other additives. As the coating is conveyed below, the laser module scans the coating surface, such as Figure 2 , which shows the laser module in direct juxtaposition with the surface to be treated. However, in practice, the laser radiation is generated remotely and is transmitted through an optical fiber or waveguide and a laser head (such as Figure 1 shown) are fed into the process.

[0005] Heating with diode lasers allows for targeted, directed, and highly controllable contactless transfer of thermal energy to the material to be processed. However, power scaling of the drying process requires combining numerous diode lasers into bars and further stacking these bars. Using bulk optics, the outputs of multiple stacks can be sequentially combined based on geometric, polarization, and / or then wavelength criteria. The result is a combination of parallel beams of different polarizations and wavelengths coupled into a single waveguide, which typically has a large diameter and is associated with a variety of undesirable challenges. One of these challenges includes bending problems, which can affect the reliability of the waveguide, limiting further scaling, and the power distribution across the combined beam spot deviates from the desired power distribution (which can be uniform or non-uniform).

[0006] Regardless of the desired PDD, in order to convert any PDD into the desired PDD, it is known to implement an optical element, namely a beam shaper, which is configured to shape the PDD of essentially any beam. A variety of configurations of beam shapers are known, and include periodic microlens arrays, phase masks, and light pipes, all of which are used to obtain the desired PDD from any PDD. At the high powers required, limitations of such shapers may include power losses of up to 10%, manufacturing and maintenance costs, a large footprint, and low reliability. Based on the above, the industrial application of laser bar stack light sources may be limited.

[0007] It is therefore desirable to provide a laser system for thermally processing material powders, binders, solvents, inks, and various additives over large surface areas, wherein the laser system:

[0008] Overcoming the power limitations of known laser systems and the disadvantages associated with large diameter transmission waveguides; and

[0009] is configured with an optical mixer mounted in the laser head, the optical mixer being configured to simultaneously:

[0010] combining multiple laser source outputs, each with its own arbitrary PDD, into a single or multiple high-power system output beams for the illuminated surface area to provide a desired PDD distribution across the beam spot and area shape; and

[0011] The received outputs are shaped together to provide a predetermined shape and size to the illuminated surface area. Summary of the Invention

[0012] The disclosed direct diode laser system is configured with an optical system configured to control the system's output beam, which illuminates an area on a surface to be laser-treated, so that the output beam forms a beam spot on the surface that provides a predetermined shape and desired PDD for the area. The disclosed system is particularly (but not exclusively) advantageous for drying technology due to its power scalability and energy efficiency, meeting growing industry demands. The system includes a laser source operating over a wide power range, a fiber-based beam delivery system, and a laser head enclosing optical elements (further referred to as optical mixers) and an imaging system. The disclosed laser system provides the desired shape, size, and PDD for the laser-irradiated surface area.

[0013] According to one feature of the present disclosure, the laser source comprises one or more laser modules (LMs), each of which outputs a 1kW–5kW LM source beam, with the combined system output (depending on the number of laser modules) varying from 1kW to 100kW, with this range being extendable if necessary. Each LM comprises a solid-state laser selected from a plurality of direct diode lasers, pigtailed (fiber-coupled) laser diode (PLD) emitters, and associated output fibers. While diode lasers are the most efficient of the laser types mentioned, experiments have shown that fiber lasers, either alone or in combination with diode lasers, can be effective because the electrical-to-optical conversion efficiency (WPE) of fiber lasers is comparable to that of laser diodes. Therefore, the inventive system disclosed herein can be implemented using diode lasers or fiber lasers, or a combination thereof, and the details disclosed below based on pigtailed diode lasers are equally applicable to fiber lasers.

[0014] According to one aspect of the present disclosure, the arrangement of the downstream ends of the respective fiber bundles relative to the input face of the mixer is predetermined. Geometrically, the fiber end arrangement can be polygonal, circular, or irregular. The position of the fiber ends relative to the mixer's input face defines where any given LM output beam initially strikes the mixer's peripheral surface, which influences the PDD of the system's output beam to provide a desired PDD profile for the irradiated area. Multiple LMs can operate at different wavelengths and / or output powers. In fact, each individual LM can be configured with multiple PDDs operating at respective wavelengths that differ from one another. Thus, it may be desirable to group the LM outputs based on, for example, different wavelengths and / or different powers, resulting in multiple regions with different PDDs across the beam spot across the irradiated area. Alternatively, the PDD profile can be uniform across the output beam spot, and therefore the irradiated area. Another aspect of the present disclosure relates to the disclosed system in which the mixer is positioned at an angle other than a right angle relative to the surface to be laser-processed. Perhaps, given that life is never entirely black or white but rather has varying shades and hues, the shape of the mixer may affect not only the beam shape but also the PDD across the beam and the illuminated area. Once an orthogonally mounted mixer is angularly displaced relative to a surface, the shape of the beam spot and the shape of the illuminated area may differ from the corresponding beam spot shape associated with the mixer's normal position. The beam spot and area illuminated by the angularly displaced mixer may remain unchanged or narrow at one end, while widening at the other. A good example of these shape variations is a rectangular mixer, which, if tilted, provides a beam spot and illuminated area with a trapezoidal shape. Another example is a ring mixer, which, when displaced from its normal position, results in an elliptical illuminated area. This modification of the desired shape affects the PDD within the illuminated area: the portion of the beam and area that becomes narrower is characterized by a higher PDD than the portion that widens. If the goal is to provide uniform PDD, then deviations from the desired shape of the area clearly defeat this goal. However, replacing the rectangular mixer with a trapezoidal mixer restores the desired rectangular beam shape. While a uniform PDD is desirable in some applications, a non-uniform PDD may be preferred in other applications. In the example of the rectangular mixer, it is sufficient to simply tilt the rectangular mixer to receive the desired non-uniform PDD profile.

[0015] The foregoing and other features and advantages of the disclosed system are discussed in detail below. Furthermore, it should be understood that the foregoing information and the following detailed description are merely illustrative of various aspects and embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed aspects and features. Features disclosed herein may be combined with other features, and references to "one embodiment" and "an example" are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic being described can be included in at least one embodiment. The appearance of such terms herein does not necessarily refer to the same embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings, which are not intended to be drawn to scale. The drawings are included to provide illustration and further understanding of the various aspects and embodiments and are incorporated into and constitute a part of this specification, but are not intended to be a definition of the limits of any particular embodiment. The drawings, together with the remainder of the specification, serve to explain the principles and operation of the described and claimed aspects and embodiments. In the figures, each identical or nearly identical component illustrated in various figures is represented by a like number. For clarity, not every component may be labeled in every figure. In the figures:

[0017] Figure 1 Shows an exemplary laser system, preferably (but not exclusively) used for drying and coating technology;

[0018] Figure 2 One of the known laser systems for drying water-based electrodes made of slurry for lithium-ion battery cells is shown;

[0019] Figure 3A An exemplary laser system of the present invention is shown;

[0020] Figure 3B It shows Figure 3A A chart showing estimated annual energy and cost savings for systems operating at different wall-plug efficiency (WPE) states;

[0021] Figure 4A FIG3 shows a high power laser source of the system of the present invention;

[0022] Figure 4B is an optical schematic diagram of a single laser module (LM);

[0023] Figure 5A yes Figure 3A A side cross-sectional view of the laser head of the system of the present invention;

[0024] Figure 5B yes Figure 5A A simplified schematic diagram of the laser head;

[0025] Figure 6A shows an exemplary spatial arrangement of fiber bundle ends connected to corresponding quartz blocks in the laser head of FIG. 5 ;

[0026] Figure 6B Shown directly connected to Figure 5 and Figure 6A an optical fiber end portion of an optical element;

[0027] Figure 7 is an exemplary schematic perspective view of the optical element of FIG5 , the optical element being configured with an exemplary irregular shape;

[0028] Figure 8A shows a rectangular mixer incorporated into the laser system of the present invention and positioned at an angle relative to the surface to be laser processed, the angle being different from a right angle;

[0029] Figure 8B and Figure 8C Shown in Figure 8A PDD within the area irradiated by the system;

[0030] Figure 9A shows a ladder mixer incorporated into the laser system of the present invention;

[0031] Figure 9B 、 Figure 9C Shown in Figure 9A PDD within the area irradiated by the system;

[0032] Figure 10A The laser system of the present invention is shown with multiple angled laser heads provided with Figure 9A The corresponding mixer;

[0033] Figure 10B and Figure 10C Shown in Figure 10A Laser PDD within the surface area irradiated by the laser system;

[0034] Figure 11 Shown is a scanner Figure 10A The laser system of the present invention; and

[0035] Figure 12 Shown for Figure 2 A conceptual implementation of the laser system of the present invention for industrial-scale drying of water-based electrodes in a vacuum chamber; and

[0036] Figure 13 is an orthogonal view of an exemplary ladder mixer, which is incorporated into Figure 9A 、 Figure 10A and Figure 12 in the corresponding structure. DETAILED DESCRIPTION

[0037] To highlight the background of this invention, numerous laser systems based on various types of solid-state lasers have been tested in coating / drying applications, including the food industry, lithium-ion battery production, and other technologies that may require thermal surface treatment. While laser systems have proven more efficient than many traditional thermal treatment methods, several of these systems' shortcomings are well documented. One known drawback is the limited power scalability due to the large diameter delivery fiber(s) needed to guide the high power light required to meet industry-standard processing speeds. This is particularly relevant to systems based on laser rod stacks, which are favored for their high wall-plug efficiency (WPE). Such delivery fibers are susceptible to bending, resulting in excessive power loss and an impractical footprint. Furthermore, beam combining in these surface thermal treatment laser systems requires complex, cost-ineffective beam combiners. Another significant drawback of known laser systems involves the use of complex, cost-ineffective, and power-prone beam shapers, typically used to achieve a flat-top beam and known as a homogenizer.

[0038] In view of the above and other shortcomings of known hot surface laser systems, Figure 3A An exemplary laser system 10 configured in accordance with the inventive concept to overcome the aforementioned shortcomings of known systems is shown. The system 10 is configured with a high power laser source 12, producing, for example, 30 kW of output, which is transmitted to a laser / processing head 14 via a cable 16 that shields a plurality of feed optical fibers that transmit the respective outputs of the laser source 10 to the laser head 14. Figure 3A As shown, the system 10 is called DLS-ECO, which is known for its high WPE of up to or exceeding 50% and optical loss of less than 2% (and under certain conditions less than 1%). Obviously, different features of the system 10 can be used as long as the system meets industrial requirements such as processing speed.

[0039] Figure 3B Shown Figure 3A Estimated energy and cost savings for system 10 of the present invention operating at three different energy regimes. The least cost-effective regime corresponds to a 33% WPE, while system 20 operating at the most cost-effective regime has a 50% WPE. These examples are based on 298 working days, two shifts per day (i.e., 16 hours of operation per day), a 75% laser duty cycle per shift, and a chiller coefficient of performance (kW / kW) of 4.35.

[0040] refer to Figure 4A and Figure 4BThe high power laser source 12 is configured with a plurality of LMs 20, which are powered by respective power supply modules 22. The eight exemplary LMs 20 of the power supply 12 shown in the figure can each output 3750 W, with a total system output of 30 kW. Such a high power output of each LM 20 is due to the presence of multiple multi-mode (MM) high power laser diodes PLDs in each LM 20, such as Figure 4B Schematically illustrated. For exemplary purposes only, the illustrated LMs 20 are each powered by eighteen PLDs 24, each with nine individual laser diodes. The MM outputs of the individual PLDs 20 are directed through corresponding PLD output fibers 26. These fibers are further combined by a fiber combiner 28, which has an output fiber 30 that receives the LM output beams. Examples of the PLDs 24 configuration, their parameters, and characteristics are published at https: / / www.ipgphotonics.com and are incorporated herein by reference in their entirety.

[0041] The LM transmission fiber 30 guides the corresponding LM output beam to Figure 4A splicing module 25, where these optical fibers 30 are spliced ​​to corresponding feeder optical fibers 32 (see Figures 5 and Figure 3A , showing multiple feeding optical fibers 32 passing through the sleeve 16), thereby providing the laser source 12 and Figure 3A The optical communication between the laser heads 14 in FIG. Figure 4B The PLD 24 or other solid-state laser types in the embodiment can operate at the same or different operating wavelengths and have the same or different powers. Therefore, the LM 20 can output LM output beams of the same or different wavelengths and powers. Figure 4B The combiner 28 in FIG. 2 can be omitted, where the outputs of the individual LMs 20 are directly coupled to the corresponding transmission fibers 30. Figure 4A The splicing module 25 is connected to the feeding fiber 32. Regardless of whether there is a fiber combiner, the optical communication between the power supply 12 including multiple LMs 20 and the laser head 14 is achieved through multiple fiber bundles, each of which includes at least a transmission fiber and a feeding fiber spliced ​​together.

[0042] refer to Figure 5A and Figure 5BThe laser head 14 is provided with a housing 50 that receives the individual LM output fibers 30, which are coupled to corresponding feed fibers 32. The downstream ends of the individual feed fibers 32 each have corresponding downstream fiber ends, each of which is directly coupled to a few millimeters long AR-coated quartz block 34. The quartz block 34 is arranged so that the fiber ends are positioned in a predetermined arrangement relative to each other and relative to the input face 38 of the optical mixer 36. The optical mixer 36 is configured to combine the outputs from the individual feed fibers 32 into a single system output beam having a beam spot of the desired shape on the surface to be laser processed. The mixer 36 can include a variety of polygonal shapes or conical cross-sections, such as circular, elliptical, etc. In the normal position of the laser head 14 relative to the surface to be processed, the system output beam spot, and therefore the area illuminated, has the same shape as the mixer 36.

[0043] Figure 5A and Figure 5B The exemplary mixer 14 in FIG is a rectangular-shaped (here, 10 mm × 40 mm × 100 mm) block of quartz (n = 1.45). It is used to homogenize the emission from the input optical spot of the optical fiber through multiple reflections from the mixer's side surfaces. The mixer's input optical facet 38 and output optical facet 40 are each AR-coated at the PLD wavelength; the side surfaces are intentionally uncoated—they are largely in contact with air (n = 1.0), and only the mechanical fixings of the mixer are secured using high numerical aperture (NA) silicone (n = 1.38). This allows the mixer 14 to direct the emission from the input optical fiber to its output end facet 40 via total internal reflection, mixing them together.

[0044] Returning to the downstream ends of the respective feed fibers 32, their arrangement is critical to creating the desired PDD profile across the system output beam spot and the illuminated area, since the LM outputs coupled into the laser mixer 36 may have respective wavelengths and powers that differ from one another or may be non-uniform. As a result, the combined system output beams decoupled from the output facet 40 of the mixer 36 create a beam spot defining the illuminated area, formed by regions of uniform or non-uniform wavelength and, most importantly, power density. Thus, the PDD within the illuminated area can be uniform or non-uniform, such as increasing from one end region of the beam spot to the opposite end region, or having alternating regions of high and low PDD, or any other non-uniform power distribution that meets the process requirements.

[0045] An exemplary arrangement of the fiber end arrangement is Figure 6A and Figure 6B Specifically, Figure 6A A plurality of feeder fibers 32 are shown extending through respective supports 54 into element 56, which covers Figure 5B34 in the corresponding quartz blocks 34. The fiber ends are positioned to form a square arrangement. A variety of fiber end arrangements can be easily implemented by one of ordinary skill in the art. For example, the fiber ends can be configured so that the fiber ends / quartz blocks in one of the multiple rows straddle the corresponding fiber ends / blocks in an adjacent row. Alternatively, the fiber ends / blocks can be positioned to define one or more concentric or adjacent annular arrangements. In fact, any geometric arrangement of fiber ends can be envisioned within the scope of the present disclosure, as long as the corresponding positions are preliminarily calculated to produce a predetermined PDD of the output system beam. Importantly, the source beams guided in the corresponding feeding fibers 32 may have different PDDs and / or wavelengths, or may have uniform PDDs and / or wavelengths. Figure 6B A different structural modification is shown in which the fiber ends of the respective feed fibers 32 are directly coupled / fused to the input facet 38 of the mixer 36. As mentioned above, the spatial arrangement of the directly coupled fiber ends 32 is varied and is limited only by the desired PDD of the output system beam.

[0046] Back to Figure 5B In the mixer 36, there are two methods for directing the coupled LM beam between the input facet 38 and the output facet 40. One method utilizes the phenomenon of total internal reflection (TIR), according to which the coupled LM beam is incident on the interface between the peripheral wall 42 of the component 36 and the medium outside the peripheral wall 42 at an angle exceeding the critical angle of the interface. Another prerequisite for this phenomenon is a relationship between the refractive index of the corresponding material of the component 36 and the external medium, where the refractive index of the material is higher than that of the external medium. The component 36 is made of a transparent material, including but not limited to quartz, with a refractive index n = 1.45, which is higher than the refractive index of the external medium, such as air (n = 1.00). Due to the TIR phenomenon, the coupled beam undergoes multiple reflections from the peripheral wall 42. According to this method, only the input facet 38 and the output facet 40 of the component 36 can have the corresponding AR coating, which can be omitted under certain conditions. In addition to air, element 36 occasionally comes in contact with high numerical aperture (NA) silicone rubber (n = 1.38) at spaced locations where mechanical fixing components are required.

[0047] The multiple internal reflections of the beams enhance beam mixing along the entire length of the optical mixer 36 and cause the combined output system beam to exhibit a flat-top PDD characterized by a desired PDD over the irradiated area of ​​the surface to be laser treated. Thus, the laser irradiated area on the surface to be treated has a specified size, shape, and desired PDD. Preferably, the inner surface of the wall 42 is smooth, which minimizes diffusion power losses.

[0048] Another method of mixing beams in the mixer 36 includes coating its peripheral wall 42 with a metal or dielectric film that produces a mirror effect. This method is also applicable to mixers 36 of regular and irregular shapes. For example, Figure 7 As shown, multiple LM beams propagating along the initial path are coupled into element 36 through the vertical input side and incident on the inclined side 52. The latter redirects the incident light along a path perpendicular to the initial path, with the reflected beams emerging from the bottom of the structure as shown. Except for the input side and the output bottom side, the remaining peripheral sides are covered with a coating that reflects the light multiple times inward, which improves beam mixing. Figure 7 The shape shown is referred to as an irregular shape. One skilled in the art will readily recognize that various irregularly shaped mixers 36 may be configured and used herein without departing from the inventive concept of the disclosed system.

[0049] The size of the beam spot on the surface can be controlled by displacement of the laser head 14 along the z-axis. The laser head can also be provided with a zoom mechanism. Although the working distance in the exemplary system 10 is approximately between 0.1 meters and 5 meters, in some cases the working distance is increased to 20 meters, and the linearly varying beam spot on the surface to be processed generally has a constant PDD.

[0050] Figures 8A to 8C relates to a specific industrial application in which Figure 5B The mixer 36 extending along the axis AA' can be displaced from a normal position relative to the surface to be treated within an angular range of between about 0° and 65°. The angular displacement of the mixer may require replacement with a mixer of another shape to assist in arranging the fiber ends to provide an irradiated area with a desired PDD.

[0051] Those skilled in the art of optics will readily appreciate that if the mixer is displaced from its normal position, the beam spot and the illuminated area may take on a shape that is different from, for example, the shape of the mixer 36. In the normal position of the mixer 36 relative to the surface to be laser treated, the beam spot and the area have the same rectangular shape. However, if Figure 8B As shown, the beam spot and area are not rectangular, but are actually substantially trapezoidal. Due to this displacement, one end of the illuminated area 60 (end area 64 closest to the output end of the laser head 14) remains essentially unchanged, while the distal end area 62 expands. In other words, when the rectangular mixer 36 is displaced at certain angles, the rectangular shape of the beam spot takes on a trapezoidal cross-section. Of course, the trapezoidal cross-section affects the PDD distribution across the entire area 60, as shown in FIG. Figure 8B and Figure 8CAs clearly shown, the PDD of the wider end region 62 is lower than the PDD of the opposite end 64. One of ordinary skill in the art of optics will have no difficulty determining the desired angle within the aforementioned angular range to provide a region of predetermined size. Displacement of the laser head and mixer, or only the mixer within the laser head, at the desired angle can be achieved by utilizing well-known actuators, such as those receiving signals from a central processing unit, which is typically incorporated into systems like the system of the present disclosure.

[0052] Figures 9A to 9C 14 shows a solution to the problem discussed immediately above. In order to compensate for the PDD unevenness caused by the incident angle and distance, the mixer 66 of the laser head 14 is configured in a trapezoidal shape as shown in FIG. Figure 13 The angle between the non-parallel sides of the ladder mixer is a function of the angle of incidence. Therefore, Figures 9A to 9C The configuration disclosed in provides an illuminated surface area having a substantially rectangular shape, characterized by a Figures 8A to 8C One of the requirements of the disclosed system 10 is that the system be compact. For example, if the laser head 14 or the mixer 36 is pivoted 45 degrees, Figure 8A The vertical distance between the laser head and the surface to be processed is reduced by almost 50% compared to a normal mounted laser head.

[0053] Figures 10A to 10C The configuration of the system of the present invention is shown, which includes multiple Figure 9A One of the main advantages of having multiple laser heads 14 operating simultaneously includes improving the PDD in the area being illuminated. Figure 9A Compared to the single laser head shown, the simultaneous operation of several laser heads 14 improves the power scalability and the uniformity of the PDD over the illuminated area in proportion to the number of laser heads. Figure 10B and Figure 10C As shown, the PDD distribution on the area illuminated by the two laser heads is visually Figure 9B and Figure 9C The PDD distribution associated with a single laser head in the image is more constant.

[0054] Figure 11 shows a Figure 10AAnother advantage of the laser heads / mixers is the corresponding angular positions of the laser heads / mixers. Any given process may require the use of additional process equipment or components, such as optical and / or metrology equipment, powder delivery nozzles, and gas delivery nozzles, positioned between the illustrated laser heads. For example, in sintering / 3D printing applications, the illustrated configuration reduces processing time by 3 to 5 times, increasing process productivity. It also offers the possibility of using new materials, improving parameters, and significantly reducing part production costs.

[0055] Back to Figures 5A to 5B , the laser head 14 is further configured with an imaging system comprising an objective lens 44 (e.g., a spherical, cylindrical, or aspherical lens) and a plane or curved mirror located downstream of the component 36. Preferably, the objective lens 44 is an aspherical lens of complex shape that forms an image of the output end face 40 of the component 36 on the surface to be processed at a considerable working distance (e.g., 1450 mm). As shown in FIG5 , the objective lens 44 is spaced apart from the optical element 36. However, an alternative structure may have the optical element 36 and the objective lens 44 coupled to form a one-piece component. In either configuration, the size of the resulting image is substantially larger than the size of the output face 40, which in the example shown in the figure is 1300 mm x 300 mm. The working distance can be varied over hundreds of millimeters, with the image size varying linearly. However, the uniformity of the PDD of the irradiated area remains substantially unchanged and is less than 20%, or even less than 10%. The assembly of the laser head 14 is completed by installing a protective glass 46 covered with an AR coating and configured to protect the optical components within the laser head 14 from debris from the surface to be processed. In the context of the present disclosure, the imaging system can provide additional control over the PDD and shape of the beam spot and the illuminated area, if necessary, as will be readily understood by those skilled in the art of optics.

[0056] like Figure 12 As shown, the system 10 can be easily modified by adding additional systems operating with the same parameters or different parameters. For example, as shown, the complete set of components can have three identically configured systems 10, each system including a laser source 12 (with a configuration similar to that of the laser source 12). Figure 4A The configuration shown is identical) and the associated Figures 6 and Figure 7 Laser head 14 is shown. The number of systems 10 can be customized based on the customer's desired power density on the foil to be processed, as well as the length and width of the irradiated surface 50. Those skilled in the art will appreciate that each system can be controlled independently or centrally by a single control unit. Thus, the outputs of the various systems can be generated synchronously or in a time-independent manner to meet customer needs. The number of systems 10 is entirely determined by the customer's specifications.

[0057] about Figure 12 of multiple stations, and in view of the present disclosure, a single laser head can be used to receive source beams from various power sources. The optical mixer as disclosed above can be configured to provide multiple areas with the same PDD or different PDDs in the beam spot and the irradiated area. The speed of the conveyor belt conveying the foil must be adapted to the laser power distribution and power density. The aspects disclosed herein according to the present invention are not limited in their application to the details of the arrangement and construction of the components set forth in the following description or illustrated in the accompanying drawings. These aspects can assume other embodiments and can be practiced or implemented in various ways. The examples of specific embodiments provided herein are for illustrative purposes only and are not intended to be limiting. In particular, the actions, components, elements and features discussed in conjunction with any one or more embodiments are not intended to be excluded from similar roles in any other embodiment.

[0058] Having thus described several aspects of at least one example, it should be understood that various variations, modifications, and improvements will readily occur to those skilled in the art. For example, the examples disclosed herein may also be applied to other situations. Such variations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the appended claims. Therefore, the foregoing description and drawings are intended to be examples only.

Claims

1. A laser system for forming an area having a predetermined shape and a desired power density distribution (PDD) on a surface to be heat treated, comprising: a plurality of laser sources operable to controllably output respective source beams having respective uncontrolled PDDs; a plurality of optical fiber bundles that direct corresponding source light beams along a path; at least one laser head receiving a downstream optical fiber end portion of a corresponding optical fiber bundle; an optical mixer mounted in the laser head and positioned opposite the optical fiber end to receive, direct, and combine the source beams into a system output beam, wherein The optical mixer is configured to shape the system output beam so that the system output beam forms a beam spot of the predetermined shape defining the area, and The output fiber ends define a spatial arrangement that provides a desired power density distribution throughout the beam spot of the system output beam and within the surface area.

2. The high power laser system according to claim 1, wherein: The laser sources each include one or more fiber lasers, direct diode lasers, or pigtailed diode lasers, the fiber lasers, the direct semiconductor lasers, or the pigtailed diode lasers operating at the same power and wavelength, or the fiber lasers, the direct semiconductor lasers, or the pigtailed diode lasers operating at different powers and wavelengths.

3. The high power laser system according to claim 1, wherein: The shape of the optical mixer is selected from a regular polygon, an irregular polygon or a conical cross-section, and is configured with an input face and an output face spaced apart, the input face and the output face being bridged by a peripheral wall, and the input face and the output face are each provided with an AR coating or without an AR coating.

4. The high power laser system according to claim 3, wherein: The spatial arrangement of the optical fiber ends is configured such that, when coupled into the optical mixer, the coupled source light beam is incident on and reflected by the inner surface of the peripheral wall, the inner surface of the peripheral wall being coated with a metal coating or a dielectric coating.

5. The high power laser system according to claim 4, wherein: The optical mixer is made of a transparent material having a higher refractive index than that of the external medium, and the relationship between the refractive indices and the incident angle together produce a total internal reflection effect, wherein the coupled laser source beam is reflected multiple times by the peripheral surface, wherein the reflected laser beams are mixed together to produce the system output beam with the desired PDD.

6. The high power laser system according to claim 1, wherein: The output fiber ends of the respective fiber bundles are directly or indirectly coupled to the optical mixers.

7. The high power laser system according to claim 1, wherein: The spatial arrangement of the output fiber ends comprises a polygonal arrangement or a circular arrangement selected to provide a desired power density distribution throughout the system output beam and within the surface area, wherein the desired power density distribution is uniform or non-uniform.

8. The high power laser system according to claim 1, wherein: The mixer is displaceable between a normal position relative to the surface to be processed and a plurality of angular positions at angles controllably varying between 0° and 65° to provide a desired PDD and predetermined shape to the beam spot and the irradiated area.

9. The high power laser system according to claim 8, wherein: The optical mixer is configured with a trapezoidal shape that provides the beam spot with the predetermined shape and a desired uniform PDD to the area when the optical mixer is obliquely shifted to a predetermined angular position, the predetermined shape being rectangular.

10. The high power laser system of claim 9 , further comprising at least two spaced-apart laser heads having respective trapezoidal mixers, each of the trapezoidal mixers being tilted at the angle such that the corresponding system output beams overlap with each other to illuminate a rectangular shaped surface area having a uniform PDD that increases in proportion to the number of trapezoidal laser heads.

11. The high power laser system of claim 10, further comprising at least one or more system components positioned between the trapezoidal laser heads.

12. The high power laser system according to claim 1 , further comprising a plurality of additional optical laser heads, the optical laser heads being arranged in a predetermined spatial pattern to output corresponding system output beams, the corresponding system output beams forming corresponding beam spots, the corresponding beam spots having the same power density distribution and shape or having respective different power density distributions and shapes.

13. The high power laser system of claim 1 , further comprising an imaging system installed in the laser head downstream of the optical mixer, and the imaging system is configured with an optical device based on refraction or reflection mirrors, wherein: The imaging system includes one or more aspherical lenses, spherical lenses, cylindrical lenses, or flat mirrors or curved mirrors, wherein the optical mixer and the imaging system are spaced apart, or the optical mixer and the imaging system are coupled together to form a one-piece structure, or are spaced apart.

14. The high power laser system according to claim 11, wherein: The flat-top PDD of the system output beam is characterized by a non-uniformity of 1%-20%.

15. The high power laser system according to claim 8, wherein: The laser head can be displaced along the Z axis over a distance ranging from 0.1 m to 5 m to linearly vary the size of the surface area.

16. The high power laser system according to claim 1, wherein: The laser sources are combined in one or more laser modules, each laser module is capable of operating to output a source beam in the power range of 1kW-100kW, the source beam is coupled to an optical mixer of the one laser head, the optical mixer is configured to output a system output beam, the system output beam has a beam spot characterized by the predetermined shape and provides a desired PDD to the surface area, wherein the desired PDD is uniform or non-uniform.

17. The high power laser system according to claim 16, wherein: The laser module outputs a corresponding source light beam, and the accumulated source light beam has a corresponding uniform or non-uniform power PDD and a uniform or non-uniform output power.

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