CN114563870B - Laser galvanometer scanning device - Google Patents
Laser galvanometer scanning device Download PDFInfo
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- CN114563870B CN114563870B CN202210189911.8A CN202210189911A CN114563870B CN 114563870 B CN114563870 B CN 114563870B CN 202210189911 A CN202210189911 A CN 202210189911A CN 114563870 B CN114563870 B CN 114563870B
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- laser
- galvanometer
- light
- vibrating mirror
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/105—Scanning systems with one or more pivoting mirrors or galvano-mirrors
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
- G02B1/11—Anti-reflection coatings
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/08—Mirrors
- G02B5/0816—Multilayer mirrors, i.e. having two or more reflecting layers
- G02B5/0825—Multilayer mirrors, i.e. having two or more reflecting layers the reflecting layers comprising dielectric materials only
- G02B5/0833—Multilayer mirrors, i.e. having two or more reflecting layers the reflecting layers comprising dielectric materials only comprising inorganic materials only
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- Laser Beam Processing (AREA)
Abstract
The invention discloses a laser galvanometer scanning device, and belongs to the field of laser processing. The device comprises: the focusing mirror group, the beam splitting type vibrating mirror and the transmitted light absorption module. Incident light is converged by the focusing mirror group, laser irradiated on the beam splitting type galvanometer is transmitted and reflected to generate transmitted light and reflected light, the transmitted light is absorbed by the transmitted light absorption module, and the reflected light is used for laser processing. The incident surface of the light splitting type vibrating mirror is plated with a reflection increasing film, the back surface of the light splitting type vibrating mirror is plated with an anti-reflection film, the vibrating mirror substrate is made of a low-absorption material, the number of layers of the front medium reflection increasing film is reduced, reflection of transmitted light on the rear surface of the vibrating mirror is reduced, laser energy absorbed by a vibrating mirror film layer and a base material is effectively reduced, laser power borne by the vibrating mirror is greatly improved, and meanwhile a high damage threshold value of the film layer is guaranteed. The invention has wide application in high-power laser processing and other vibrating mirror scanning energy transmission processes.
Description
Technical Field
The invention belongs to the technical field of laser processing, and particularly relates to a laser galvanometer scanning device.
Background
The laser scanning galvanometer system is a system which utilizes a plurality of rotatable reflecting mirrors controlled by servo motors to control the propagation direction of light beams, and a computer controls the action of the motors to realize the formation of focusing on different positions on the surface or inside a workpiece. The galvanometer lens is a direct core device which acts mechanical motion on a light track, and inevitably absorbs part of light energy and converts the light energy into heat energy while reflecting laser light.
Under the working state, the temperature rise caused by the energy absorption of the vibrating mirror lens cannot be ignored. In order to obtain high reflectivity at each angle during the operation of the galvanometer, a working surface of the galvanometer lens is generally plated with a multilayer dielectric film and an Al film, and the interface between the dielectric film material and the film layer and a lens substrate can absorb part of light energy; in addition, the galvanometer back is typically textured. These factors all contribute to the high overall absorption of the galvanometer lens. In the production practice, the requirement on the movement speed of the galvanometer is very high, and the rotational inertia of the galvanometer needs to be very small, so that a complex liquid cooling heat sink device is difficult to add on the high-speed galvanometer body.
The maximum output power of the fiber laser is already in the ten thousand watt and hundred thousand watt level, and the vibrating mirror system has damage risk in the power above 5000 watt due to insufficient heat bearing capacity, and can not be applied to high-power laser processing in a matching way. The heat accumulation of galvanometer lenses is the biggest bottleneck in the development of galvanometer processing equipment towards higher power processing.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a laser galvanometer scanning device, aiming at solving the problem of heat accumulation of a galvanometer lens.
In order to achieve the above object, the present invention provides a laser galvanometer scanning device, which comprises a focusing lens group, a beam splitting galvanometer and a transmission light absorption module; incident laser is converged by the focusing lens group, most of the laser irradiated on the beam splitting type galvanometer is reflected, a small part of the laser penetrates through the galvanometer, transmitted light is absorbed by the transmitted light absorption module, and the reflected light is used for laser processing;
the incidence surface of the beam splitting type galvanometer is coated with medium reflection increasing films with high refractive index and low refractive index alternated, which are not more than 17 layers, except for the outer protective film, and a metal film is not used for bottoming, so that the effects of most reflection, less transmission and ultralow absorption are realized. The reflection increasing film with fewer layers can reduce the absorption of light by the interface between the film layer material and the film layer. High refractive index materials in the dielectric film layer include but are not limited to HfO 2 Low index materials including, but not limited to, siO 2 . The back of the emergent surface is plated with an anti-reflection film to obtain ultrahigh transmissivity. The design improves the damage threshold and the yield of the reflection increasing film of the incident surface by exposing the reflection film with fewer layers to high-power laser. Meanwhile, the specially designed film layer and the vibrating mirror substrate with low absorption rate reduce the back-and-forth reflection of light in the vibrating mirror lens substrate, thereby reducing the light energy absorbed by the vibrating mirror and the film layer and enabling the vibrating mirror and the film layer to be matched with a laser source with higher power.
Wherein, the reflectivity of the reflection increasing film on the incidence surface of the galvanometer is 90-99%, and the transmissivity of the reflection increasing film on the emergence surface is more than 99%.
The galvanometer substrate material is a material with extremely low absorption at the operating wavelength, and includes but is not limited to high-purity SiO 2 。
Further, the rear surface of the spectroscopic mirror is formed into an inclined surface or a zigzag shape, and the inclination angle is an angle favorable for a small incident angle when the laser light enters the rear surface. The zigzag shape is adapted to the case where a galvanometer is used under large angle incidence. When the incident angle exceeds 70 degrees, the reflectivity of the rear surface of the galvanometer is far higher than 50 percent and is close to the total reflection condition, which is not beneficial to designing an antireflection film system. The scheme designs a sawtooth structure on the back of the vibrating mirror, the direction and the angle of the sawtooth are determined by the angle of incident light, the incident angle when the incident light passing through the vibrating mirror reaches the rear surface of the vibrating mirror is minimized as much as possible, the number of coating layers can be greatly reduced by the method, and the manufacturing efficiency and the durability are improved. Meanwhile, the zigzag structure can change the surface type of the rear surface of the galvanometer and control the rotational inertia of the lens, and the problems that the mass distribution of the galvanometer is uneven due to the introduction of an asymmetric surface type, the working load of a galvanometer motor is increased, and the response is insensitive are avoided.
Preferably, the base material of the galvanometer mirror is a material with low absorptivity in the laser band to minimize the absorption of the laser light as it propagates in the lens medium. The reflectivity of the reflection increasing film on the front surface of the vibrating mirror is designed to be in a range of 90% -99%, and compared with the reflection increasing film with the reflectivity of more than 99.5% used in high-power laser processing, the reflectivity is reduced, the number and thickness of the film layers are greatly reduced, and the absorption of the film layers is reduced. The transmittance of the anti-reflection film layer on the reverse side is controlled to be more than 99%, so that the reflection of transmitted light passing through the lens substrate to the rear surface of the lens once is greatly reduced, and most of light is transmitted from the rear surface, so that the energy ratio of the light reflected back to the lens is reduced. The design aims are to reduce the temperature rise of the vibrating mirror under laser irradiation as much as possible, so that the vibrating mirror can be matched with the application scene of high-power laser processing, and the laser absorption in the film layer of the lens and the lens matrix is controlled to be at the lowest level by controlling the number of layers and the process of optical coating.
Preferably, the transmitted light absorbing structure will be disposed behind the galvanometer. Such as a roughened surface light absorbing structure with water cooling disposed in the transmission light path through the galvanometer.
The device also comprises software and hardware used for connection and control, such as a motor and a clamp, and a driver, software and the like used for controlling the movement of the galvanometer, wherein the motor is used for controlling the movement of the beam splitting type galvanometer through the clamp and adjusting the deflection angle of light rays so as to focus laser on the surface of a workpiece.
Through the technical scheme, compared with the prior art, the invention can obtain the following advantages
Has the advantages that:
1. the invention realizes the purpose of greatly reducing the temperature rise of the galvanometer caused by light absorption on the premise of not increasing the rotational inertia of the galvanometer by the design of front and rear film layers of the light splitting galvanometer and the selection of a substrate of the galvanometer, so that the galvanometer, which is a classical laser processing device, can be applied to the fields of laser processing and laser cleaning with high power of ten-thousand watts.
2. The laser galvanometer scanning device provided by the invention properly reduces the number of layers of the reflection film on the front surface of the galvanometer, and reduces the process difficulty and cost of film coating.
Drawings
Fig. 1 is a schematic structural view of a spectroscopic galvanometer according to the present invention.
Fig. 2 is a schematic structural diagram of a laser galvanometer scanning apparatus according to an embodiment of the present disclosure.
Fig. 3 is a schematic structural diagram of a laser galvanometer scanning device according to a second embodiment of the present disclosure.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1. the device comprises a focusing lens group, 2 a light splitting type vibrating mirror, 3 a transmitted light absorption module, 4 a workpiece, 5 a vibrating mirror motion control related component, 2-1 a multilayer reflection increasing film, 2-2 a vibrating mirror substrate, 2-3 a multilayer reflection increasing film.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
First, the principle of the reflection increasing film and the antireflection film according to the present invention will be explained. Light is reflected and refracted at the interface of two media, where the refracted light enters another medium than the incident light, referred to herein as transmitted light. According to the fresnel formula, some energy is reflected and some energy is transmitted in both s-light and p-light at different angles. In order to reflect or transmit more light at different working interfaces, it is necessary to coat the substrate of the optical lens. The multilayer dielectric film can obtain high reflectivity or high transmissivity by utilizing the interference of light among various layers of films. Generally, the more the number of the film layers, the stronger the reflection increasing or anti-reflection capability is, but as the film layers become thicker, the effect of increasing reflection and anti-reflection shows obvious marginal effect, meanwhile, the film layer material has a certain absorption effect on light, and impurities introduced into the film layer material in the film coating process are very easy to cause film layer damage when irradiated by high-power laser.
When light is incident normally, the reflection increasing film is a high refractive index-low refractive index alternate structure with 2s +1 layers, and the thickness of each layer is
Wherein both the layers near the air and near the substrate are high refractive index layers. Then according to the relevant physical optical formula and the refractive indexes of the film layer and the substrate, the reflectivity R is:
wherein n is 0 Is the refractive index of air, n h Refractive index of high refractive index film material, n l Is the refractive index of the low refractive index film material, n g Is the refractive index of the lens substrate material.
Fig. 1 is a schematic structural view of a spectroscopic galvanometer according to the present invention. The front surface is plated with a plurality of reflection increasing films, the reflectivity (reflection light intensity/input light intensity) of the front surface after film plating is controlled to be 90-99%, the back surface is plated with a plurality of reflection increasing films, and the transmissivity (emergent light intensity/light intensity before entering the reflection increasing films from the vibrating mirror substrate) of the back surface is controlled to be more than 99%. The base material of the galvanometer can be selected from quartz glass and other materials with relatively weak light absorption effect. After the coating is arranged, the reflectivity of the front surface is 97%, the transmissivity of the back surface is 99.5%, compared with the traditional process, the reflectivity of the front surface is coated with the reflection increasing film of 99.8%, the extreme condition (the rear surface of the lens is completely reflected or absorbed) is considered, and the reflection increasing film is coated behind the lensThe light reflected by the surface can be reflected back and forth in the lens base material until the light is completely absorbed, and at an incidence angle of 65 ℃,10000 watts of polarized random light can be absorbed by the base body under the condition of the vibrating mirror lens of the traditional method, and the energy absorbed by the base body of the vibrating mirror lens provided by the invention is about 3.3 watts. Assuming that the high and low refractive index materials adopted by the coating film are respectively TiO with the refractive index of 2.4 2 MgF of refractive index 1.38 2 Then the conventional method needs to plate at least 12 complete high and low refractive index structures, while only 7 can be plated using the method of the present invention. If the single-layer absorption of the two film layers is about 0.01%, the film layer can absorb about 25 watts by the traditional method, and the film layer absorption provided by the invention is less than 15 watts. Therefore, the method provided by the invention reduces the loss on the galvanometer lens by 42%. Meanwhile, the embodiment provides a form of the back surface of the sawtooth-shaped galvanometer lens, and the sawtooth-shaped inclination angle of the back surface is designed according to the principle that light can be incident at the incident angle as small as possible, so that the number of layers of the antireflection film can be reduced.
Fig. 2 is a schematic diagram of a laser galvanometer scanning apparatus according to an embodiment of the present disclosure. Incident light is firstly focused by the focusing lens group, when passing through the vibrating mirror, most energy is reflected, a small part of energy passes through the vibrating mirror substrate and is transmitted by the antireflection film, and a small part of energy is absorbed by the vibrating mirror. The transmission light is refracted by the sawtooth-shaped inclined rear surface, is absorbed by the absorption structure of the roughened surface after being transmitted for a certain distance, and is cooled by water in the transmission light heat treatment structure. The reflected light forms a focus at a specific position of the processing material due to the regulation and control of the galvanometer system.
Fig. 3 is a schematic diagram of a laser galvanometer scanning apparatus according to a second embodiment of the present disclosure. The principle of laser regulation and the design method of the galvanometer lens are the same as those of the first embodiment. In order to realize the regulation and control of reflected light with two degrees of freedom on a processing plane by a galvanometer system, a focus is formed at a specific position of a processing material.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. A laser galvanometer scanning device is characterized by comprising a focusing lens group, a beam splitting galvanometer and a transmitted light absorption module; the laser irradiated on the beam splitting type galvanometer is transmitted and reflected to generate transmitted light and reflected light, the transmitted light is absorbed by the transmitted light absorption module, and the reflected light is used for laser processing;
the incident surface of the beam splitting type galvanometer is plated with an antireflection film, and the back surface of the incident surface is plated with an antireflection film; the back surface of the beam splitting type vibrating mirror is set to be an inclined surface or a sawtooth shape, and the inclined angle is an angle which is favorable for the incident angle of the laser to be small when the laser enters the back surface of the vibrating mirror.
2. The apparatus according to claim 1, wherein the reflection reducing film has a reflectivity of 90% to 99% and a transmittance of >99%.
3. The laser galvanometer scanning device of claim 2, wherein the reflection increasing film is a structure of high-low refractive index alternating dielectric film layers, and the number of layers is not more than 17.
4. The apparatus according to claim 1, wherein the focusing mirror is disposed in front of the galvanometer, and the focal length is an average total optical length of the laser light reflected by the galvanometer to the working surface after passing through the focusing mirror.
5. The apparatus according to claim 1, wherein the transmissive light absorbing module is a roughened surface light absorbing structure with water cooling.
6. The apparatus according to claim 1, further comprising a motor and a fixture, wherein the motor is used for controlling the movement of the beam splitter via the fixture, and adjusting the deflection angle of the beam to focus the laser on the surface of the workpiece.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210189911.8A CN114563870B (en) | 2022-02-28 | 2022-02-28 | Laser galvanometer scanning device |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210189911.8A CN114563870B (en) | 2022-02-28 | 2022-02-28 | Laser galvanometer scanning device |
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| CN114563870A CN114563870A (en) | 2022-05-31 |
| CN114563870B true CN114563870B (en) | 2023-04-11 |
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| DE20306411U1 (en) * | 2003-04-24 | 2003-07-03 | Trumpf Laser Marking Systems A | Arrangement of an optical element in the beam path of a laser beam |
| CN101375474A (en) * | 2005-07-12 | 2009-02-25 | 杰斯集团公司 | System and method for high power laser processing |
| CN105762632B (en) * | 2016-05-06 | 2019-06-07 | 中国人民解放军国防科学技术大学 | High power laser high brightness spectrum synthesis system |
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