CN213903954U - Laser scanning device capable of changing size and shape of laser focus spot - Google Patents
Laser scanning device capable of changing size and shape of laser focus spot Download PDFInfo
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- CN213903954U CN213903954U CN202023284695.0U CN202023284695U CN213903954U CN 213903954 U CN213903954 U CN 213903954U CN 202023284695 U CN202023284695 U CN 202023284695U CN 213903954 U CN213903954 U CN 213903954U
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Abstract
The invention provides a laser scanning device capable of changing the size and the shape of a light spot at a laser focus position, which comprises: the device comprises a laser source, a collimating lens group, a beam expanding lens group and a micro lens array, wherein the micro lens optical unit is provided with N x N array-type arranged micro lens optical units and is used for homogenizing the beam after beam expansion to form uniform light intensity distribution output and change light spot energy into flat-top distribution; a scanning galvanometer system; and a field lens system; the collimating lens group is arranged on a moving platform which can move back and forth along the optical axis direction, and the size of a light spot at the position of a laser focus is changed through the back and forth movement of the moving platform; the laser focus is at the midpoint of the incident focuses of the beam expanding lens group and the micro lens array. The laser scanning device and the scanning method provided by the invention can provide stable spot output with adjustable spot size and shape at the laser focus position, and the energy distribution of the laser spots is changed from the traditional Gaussian distribution into uniform flat-top distribution, thereby realizing the homogenization treatment of light intensity.
Description
Technical Field
The invention relates to the technical field of laser beam scanning, in particular to a laser scanning device capable of changing the size and the shape of a light spot at a laser focus position.
Background
In the fields of laser processing and laser reconstruction such as laser scanning, polishing, welding, cutting, surface shaping, marking, laser cladding processing and the like, high-power laser beam output is utilized, and after optical processing such as collimation, convergence and the like, the surface of an object to be processed is correspondingly processed. The laser beam output by the existing laser is usually a round parallel beam, the energy is distributed in a gaussian shape, the beam is directly focused by a collimating and focusing lens and then is irradiated to the processing surface, the energy of the formed round, rectangular and linear facula is also distributed in a gaussian shape, the central energy of the facula is too high, the peripheral energy of the facula is low, when processing (such as cladding, cleaning, surface shaping and the like) is carried out, a higher overlapping rate is usually needed, and the processing efficiency and uniformity are affected.
The common improvement in the prior art is beam shaping to change the laser energy distribution, including optical waveguide reflective shapers, compound eye beam shaper, and telecentric telescope systems. The optical waveguide reflection shaper introduces an optical waveguide into an optical system, so that incident laser is reflected for multiple times in the system, laser beams are uniformly distributed, and the internal optical path structure is complex; the compound eye beam-equalizing shaper divides and superposes incident laser beams, and the energy loss rate is high; the telescope system with the diaphragm only isolates a region with low peripheral energy, only a central region with high energy is reserved, the telescope system belongs to pseudo-uniform distribution, and the size and the shape of a light spot at the position of a laser focus are not adjustable.
Disclosure of Invention
The invention aims to provide a laser scanning device capable of changing the size and the shape of a light spot at the position of a laser focus, aims to provide the light spot with uniformly distributed energy at the laser focus, converts a Gaussian beam output by laser into a flat-top beam, and can be applied to the fields of laser scanning, polishing, marking, welding, cutting, surface flatness increasing and surface roughness reducing.
In order to achieve the above object, a first aspect of the present invention provides a laser scanning device capable of changing the size and shape of a spot at a laser focus position, comprising:
a laser source for being driven to emit a laser beam;
the collimating lens group is used for collimating the light beam emitted by the laser source;
the beam expanding lens group is used for carrying out zooming and beam expanding on the collimated light beam;
the micro lens array is provided with N x N array-arranged micro lens optical units and is used for homogenizing the light beams after beam expansion to form uniform light intensity distribution output and change light spot energy into flat-top distribution, wherein N is a positive integer greater than or equal to 1;
a scanning galvanometer system; and
a field lens system;
the collimating lens group is arranged on a moving platform which can move back and forth along the optical axis direction, and the size of a light spot at the position of a laser focus is changed through the back and forth movement of the moving platform;
the laser focus is positioned at the midpoint of the incident focuses of the beam expanding lens group and the micro lens array.
Preferably, the distance of the collimating lens group which can move back and forth is controlled to be +/-100 mm.
Preferably, the beam expanding lens group adopts a Galileo beam expanding lens and is composed of a positive lens and a negative lens in combination.
Preferably, the beam expanding lens is composed of a plano-convex lens and a plano-concave lens, and one sides of the planes of the plano-convex lens and the plano-concave lens are placed to face each other.
Preferably, the beam expanding lens group adopts a kepler type beam expanding lens and is formed by combining two convex lenses with positive focal length.
Preferably, the beam expanding lens group comprises a fixed zoom beam expander or a zoom beam expander.
Preferably, the microlens array is a Refractive (ROE) microlens array, which includes N ROE microlens optical units, and subdivides, refracts and focuses the expanded light beam onto the focal plane, and realizes uniform output by overlapping of fine light spots on the focal plane, so as to form uniform light intensity distribution.
Preferably, the microlens array is a Diffractive (DOE) microlens array, and includes N DOE microlens optical units, and after the expanded light beam is subdivided and diffracted, the light beam is output uniformly on the focal plane by interference between the fine light spots on the focal plane, so as to form uniform light intensity distribution.
Preferably, the field lens is positioned at the exit end of the scanning galvanometer and is configured to focus the light beam scanned and output by the galvanometer; and the emergent end of the field lens is also provided with a protective lens.
According to the above embodiments of the present invention, there are significant advantages in that:
according to the laser processing device, the light path is optimized and designed, the light spots of Gaussian distribution output by the traditional laser are optimized and changed into flat-top distribution, so that the light intensity is uniformly distributed, meanwhile, the loss of the light power is low, and when the laser scanning, the laser cleaning, the surface shaping, the marking, the welding and the cutting are carried out, the surface flatness is increased, the surface roughness is reduced and the like, the efficiency and the utilization rate of the laser processing can be improved, and the overlapping rate of the light spots is reduced.
It should be understood that all combinations of the foregoing concepts and additional concepts described in greater detail below can be considered as part of the inventive subject matter of this disclosure unless such concepts are mutually inconsistent. In addition, all combinations of claimed subject matter are considered a part of the presently disclosed subject matter.
The foregoing and other aspects, embodiments and features of the present teachings can be more fully understood from the following description taken in conjunction with the accompanying drawings. Additional aspects of the present invention, such as features and/or advantages of exemplary embodiments, will be apparent from the description which follows, or may be learned by practice of specific embodiments in accordance with the teachings of the present invention.
Drawings
The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Embodiments of various aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
fig. 1 is a schematic diagram of a laser scanning device capable of changing the spot size and profile of a laser focal point according to an exemplary embodiment of the present invention.
FIGS. 2a and 2b are graphs comparing the energy distribution of a Gaussian distribution spot before homogenization with the energy distribution of a flat-topped spot after homogenization according to the present invention.
Detailed Description
In order to better understand the technical content of the present invention, specific embodiments are described below with reference to the accompanying drawings.
In this disclosure, aspects of the present invention are described with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the present disclosure are not necessarily intended to include all aspects of the invention. It should be appreciated that the various concepts and embodiments described above, as well as those described in greater detail below, may be implemented in any of numerous ways, as the disclosed concepts and embodiments are not limited to any one implementation. In addition, some aspects of the present disclosure may be used alone, or in any suitable combination with other aspects of the present disclosure.
The laser scanning device capable of changing the spot size and the profile of the laser focus position in combination with the exemplary embodiment shown in fig. 1 includes: the scanning galvanometer system comprises a laser source 10, a collimating lens group 20, a beam expanding lens group 30, a micro-lens array 40, a scanning galvanometer system 50 and a field lens 60.
The laser source 10, as a laser output head, is driven to emit a laser beam. Preferably, the laser source 10 can select different laser output powers in different application scenarios.
And a collimating lens group 20 for collimating the light beam emitted from the laser light source. In an embodiment of the present invention, the collimating lens group may include one or more collimating lenses, such as a biconvex lens or a plano-convex lens made of fused silica, which adjust the divergence angle of the light beam to change the incident divergent light path into a parallel light path for output.
The beam expanding lens group 30 is used for zooming and expanding the collimated light beam.
The beam expanding lens group 30 may be implemented based on a galilean design or a keplerian design. In the embodiment using the Galileo beam expanding lens, the Galileo beam expanding lens is composed of a positive lens and a negative lens. To minimize the phase difference, the beam expanding lens is composed of a plano-convex lens and a plano-concave lens, and one sides of the planes of the two are placed to face each other.
In the embodiment adopting the kepler type beam expanding lens, the beam expanding lens group adopts the kepler type beam expanding lens and is formed by combining two convex lenses with positive focal length.
In an alternative embodiment, the expanded beam lens assembly 30 is a lens made of fused silica material to meet the requirements of high and low power applications from 10W to 20000W. In a specific application, the beam expanding lens group 30 can be a fixed zoom beam expander or a zoom beam expander, and the zoom range can preferably reach 1.5 to 10 times.
And the micro lens array is provided with N-N array-arranged micro lens optical units and is used for homogenizing the light beams after beam expansion to form uniform light intensity distribution output and change the light spot energy into flat-top distribution, wherein N is a positive integer greater than or equal to 1.
As shown in fig. 1, the laser source 10 is driven and excited by the laser driving circuit to emit a laser beam; after the light beam is collimated by the collimating lens assembly 20, the collimated light beam enters the beam expanding lens assembly 30 for zooming and expanding; the light beams output by expanding beam enter the micro lens array 40, and the incident light beams are homogenized through a refraction type (ROE) micro lens array or a diffraction type (DOE) micro lens array to form flat-top laser spots with uniformly distributed light intensity; the collimating lens group, the beam expanding lens group and the micro lens array are coaxially designed in terms of main optical axes, namely the collimating lens group, the beam expanding lens group and the micro lens array are coaxially designed in terms of centers of projection in the direction along the optical path; and scanning the light beam by the scanning galvanometer system and outputting the light beam towards the surface of the workpiece to be processed, converging the light beam output by scanning to the surface of the workpiece through the field lens, and controlling the coverage area of the output light beam.
In a preferred embodiment, as shown in fig. 1, the collimating lens group 20 is mounted on a moving platform 21 that can move back and forth along the optical axis direction, and the spot size of the laser focal position is changed by the back and forth movement of the moving platform. The distance of the movable platform 21 capable of moving back and forth is controlled within ± 100mm to control the collimating lens group to move a corresponding distance along the direction of the optical axis, so that the size of a light spot at the laser focus position can be adjusted. The laser focus is at the midpoint of the incident focuses of the beam expanding lens group and the micro lens array.
In an alternative embodiment, referring to fig. 1, the microlens array is a Refractive (ROE) microlens array, which includes N ROE microlens optical units, and divides, refracts and focuses the expanded light beam onto the focal plane, and realizes uniform output by overlapping of the fine light spots on the focal plane, so as to form uniform light intensity distribution. Thus, a Refractive (ROE) microlens array can spatially divide a laser wave into a plurality of minute portions, each of which is focused on a focal plane by a corresponding microlens (e.g., a micro-scale optical unit), and spots are overlapped, thereby realizing light homogenization in a specific region and precise shaping of a laser beam.
In another embodiment, the microlens array is a Diffractive (DOE) microlens array, which includes N DOE microlens optical units, and divides and diffracts the expanded light beam at the focal plane, so as to achieve uniform output by interference between the fine light spots on the focal plane, thereby forming a uniform light intensity distribution. Thereby, the phase of the light is modulated and changed by the surface relief structure (e.g., a micro-scale spherical mirror, an aspherical mirror, a cylindrical mirror, a prism, etc.) of the DOE microlens array. The laser beam is diffracted after passing through each diffraction optical unit, and generates interference at the focal plane of the lens to form uniform light intensity distribution.
In the embodiment of the invention, the array structure of the microlens array can comprise an order of design from 1 × 1 to 500 × 500, and in a special demand field, the array structure formed by more microlens optical units can be used for realizing the homogenization treatment of the light intensity.
Therefore, through the optimized design of the laser source 10, the collimating lens group 20, the beam expander lens group 30 and the micro lens array 40, a laser beam shaping mechanism is formed, stable spot output with adjustable spot size and shape at the laser focus position is provided, and the energy distribution of laser spots can be changed from traditional Gaussian distribution to uniform flat-top distribution.
In an alternative embodiment, different coatings may be applied to the lens (such as the aforementioned collimating, beam expanding, and light homogenizing lens) according to the wavelength of the laser, and the lens is suitable for lasers with different wavelength bands, such as lasers in the 200-3000nm wavelength range.
The collimating lens group, the beam expanding lens group and the micro lens array can be provided with the lens base with the water cooling structure in a matched mode, and therefore the collimating lens group, the beam expanding lens group and the micro lens array can work stably for a long time and prolong the service life.
By combining the comparison schematic diagrams shown in fig. 2 and 2b, a collimating lens with a laser fiber core diameter of 50 micrometers and a focal length of 100 millimeters, a beam expander group of 2 times, a DOE homogenizing lens group arranged in a 20x20 array, and a field lens with a focal length of 150 millimeters are taken as examples, light spots obtained after excitation, beam collimation, beam expansion and homogenization according to the embodiment of the method are tested by a laser morphology tester, and through the implementation of the invention, the energy of the laser light spots is changed from original gaussian distribution into uniform flat-top distribution, so that the uniform distribution of the energy of the light spots at the laser focus is realized.
As shown in connection with fig. 1, scanning galvanometer system 50 employs an f-theta galvanometer or turning mirror. In the exemplary embodiment of the invention, the reflector base is cooled by water, and the temperature drift is less than 10 μ rad/K. The optical resolution is 12 mu rad, the repeated positioning precision is 2 mu rad, and the long-term drift of 8 hours is less than 100 mu rad. The aperture of the input aperture of the galvanometer is 15-30 mm. The lens material of the scanning galvanometer system comprises fused quartz, silicon or silicon carbide material.
Referring to fig. 1, a field lens 60 is located at the exit end of the scanning galvanometer and is configured to focus the light beam scanned out by the galvanometer. Therefore, the light beams at the tail end of the optical fiber can be effectively converged by the field lens, and the output light beams can be controlled in a small area.
Optionally, two or more pieces of composite focusing lens, aspheric focusing lens, and concentric focusing lens may be used to converge the light beam according to different application scenarios and requirements. The parameters of the field lens are: the effective focal length is 160 mm and 450mm, and the scanning range is 80X 80mm2 to 300X 300mm 2. The light beam transmittance is more than 96%, and the bearable maximum laser power is 20000W.
Referring to fig. 1, the exit end of the field lens is further provided with a protective lens 70. Through the design of the protective lens arranged outside the field lens, the field lens is effectively prevented from being polluted and damaged due to dust falling, and the service life of the lens is prolonged.
One to two air knives are selected according to the laser power and the size of splash particles during the application of laser scanning, marking, welding, cutting, surface flatness increasing, surface roughness reducing and the like, so that the splash is prevented from being sputtered on the protective lens.
According to the laser beam scanning of the foregoing embodiment of the present invention, in the applications of laser scanning, marking, welding, cutting, increasing surface flatness and reducing surface roughness, the laser power is selected as follows:
the parameters selected during laser marking are 5-100W of laser power, 10-10000mm/s of scanning speed and 10-100000Hz of laser frequency.
The parameters selected during welding are laser power of 500-.
The parameters selected during cutting are laser power of 500-.
The parameters selected when the surface flatness is increased and the surface roughness is reduced are 10-5000W of laser power, 5-5000mm/s of scanning speed and 10-100000Hz of laser frequency.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.
Claims (10)
1. A laser scanning device capable of changing the spot size and shape of a laser focus position is characterized by comprising:
a laser source for being driven to emit a laser beam;
the collimating lens group is used for collimating the light beam emitted by the laser source;
the beam expanding lens group is used for carrying out zooming and beam expanding on the collimated light beam;
the micro lens array is provided with N x N array-arranged micro lens optical units and is used for homogenizing the light beams after beam expansion to form uniform light intensity distribution output and change light spot energy into flat-top distribution, wherein N is a positive integer greater than or equal to 1;
a scanning galvanometer system; and
a field lens system;
the collimating lens group is arranged on a moving platform which can move back and forth along the optical axis direction, and the size of a light spot at the position of a laser focus is changed through the back and forth movement of the moving platform;
the laser focus is positioned at the midpoint of the incident focuses of the beam expanding lens group and the micro lens array.
2. The apparatus of claim 1, wherein the collimating lens group is configured to move back and forth within a range of ± 100 mm.
3. The apparatus of claim 1, wherein the beam expanding lens group is a galileo beam expanding lens, and is composed of a positive lens and a negative lens.
4. The apparatus of claim 3, wherein the beam expander lens is composed of a plano-convex lens and a plano-concave lens, and the two planar sides of the plano-convex lens and the plano-concave lens are disposed opposite to each other.
5. The apparatus according to claim 1, wherein the beam expanding lens group is a keplerian beam expanding lens, and is composed of two positive focal length convex lenses.
6. The apparatus of claim 1, wherein the beam expanding lens group comprises a fixed zoom beam expander or a zoom beam expander.
7. The apparatus according to any of claims 1-6, wherein the micro lens array is a Refractive (ROE) micro lens array, comprising N ROE micro lens optical units, and the expanded light beam is subdivided, refracted and focused onto the focal plane, and the overlapping of the fine spots on the focal plane realizes uniform output, resulting in uniform light intensity distribution.
8. The laser scanning device capable of changing the spot size and shape of the laser focus position according to any one of claims 1 to 6, wherein the micro lens array is a Diffractive (DOE) micro lens array, and comprises N DOE micro lens optical units, the expanded light beam is subdivided and diffracted on the focal plane, and uniform output is realized by interference between the fine spots on the focal plane, so as to form uniform light intensity distribution.
9. The apparatus according to claim 1, wherein the galvanometer is an f-theta galvanometer or a rotating galvanometer.
10. The apparatus according to claim 1, wherein the field lens is located at the exit end of the scanning galvanometer and configured to focus the light beam scanned and output by the galvanometer; and the emergent end of the field lens is also provided with a protective lens.
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| CN112630984A (en) * | 2020-12-30 | 2021-04-09 | 南京理工大学 | Laser scanning device and scanning method capable of changing size and shape of laser focus position light spot |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112630984A (en) * | 2020-12-30 | 2021-04-09 | 南京理工大学 | Laser scanning device and scanning method capable of changing size and shape of laser focus position light spot |
| CN113977089A (en) * | 2021-10-28 | 2022-01-28 | 华南师范大学 | Laser head device and system for removing soldering tin of integrated circuit board |
| CN113977089B (en) * | 2021-10-28 | 2024-01-23 | 华南师范大学 | Laser head device and system for removing soldering tin on integrated circuit board |
| CN115351301A (en) * | 2022-08-18 | 2022-11-18 | 湖南华曙高科技股份有限公司 | Optical path system of additive manufacturing equipment and optical path adjusting method |
| CN115351301B (en) * | 2022-08-18 | 2023-09-29 | 湖南华曙高科技股份有限公司 | Optical path system and optical path adjusting method of additive manufacturing equipment |
| CN115791756A (en) * | 2022-11-24 | 2023-03-14 | 北京杏林睿光科技有限公司 | Laser-induced breakdown spectroscopy device for measuring full spectrum at one time |
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