CN113300204A - Near-infrared human eye safe coherent light ultrafast scanning device and method - Google Patents
Near-infrared human eye safe coherent light ultrafast scanning device and method Download PDFInfo
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
- H01S3/0071—Beam steering, e.g. whereby a mirror outside the cavity is present to change the beam direction
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/08—Devices involving relative movement between laser beam and workpiece
- B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/08—Devices involving relative movement between laser beam and workpiece
- B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
- B23K26/0821—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head using multifaceted mirrors, e.g. polygonal mirror
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
- H01S3/1022—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
Abstract
The invention provides a near-infrared human eye safe coherent light ultrafast scanning device and a method thereof, comprising the following steps: the laser processing system comprises a semiconductor laser pumping source, a coupling lens group, a resonant cavity input mirror, a laser gain crystal, an acousto-optic crystal modulator, a laser nonlinear KTP crystal, a resonant cavity output mirror, a plane reflector, a beam shaper, a scanning polygonal rotating mirror assembly, a scanning galvanometer assembly, an f-theta focusing lens group and a laser processing target surface; the ultra-fast scanning of the near-infrared human eye safe coherent light is realized, and the synchronous scanning of the laser pulse repetition frequency and the scanning speed can be realized by combining the control of an industrial personal computer editable logic gate array. Has important research significance for the fields of biological processing, laser radar, military laser countermeasure and the like, and provides important application value for the safe coherent light of the human eye with the diameter of 1.57 mu m in each practical application.
Description
Technical Field
The invention relates to the technical field of laser, in particular to a near-infrared human eye safe coherent light ultrafast scanning device and method.
Background
The laser eye safety wave band with the diameter of 1.5-1.8 mu m is a new technology developed by the fact that the military second-generation Nd: YAG laser distance measuring machine which is provided with a large amount of equipment is not safe to eyes, and the smoke and fog penetrating capability is poor at the end of seventies.
The allowable exposure amount of 1.57 mu m laser to human eyes is 1.06 mu m Nd, 20-40 ten thousand times of that of YAG laser, and 10.6 mu m CO2The laser is 100 times safer than the lasers in other wave bands. The main technique for generating 1.57 mu m laser at present mainly applies an optical parametric oscillator to generate 1.57 mu m human eye safe coherent light except for using a laser crystal doped with special rare earth ions. The optical parametric oscillator has the characteristics of low threshold value, high conversion efficiency, high repetition frequency and high output energy. The 1.57 mu m optical parametric oscillator mainly adopts a 1064nm all-solid-state laser as a pumping source to generate 1573nm near infrared and 3400nm middle infrared coherent light through second-order nonlinear frequency conversion of nonlinear crystals such as KTP and the like.
The OPO is taken as a technical means capable of effectively obtaining coherent light sources in mid-infrared and near-infrared bands, is favorable for realizing the update of military laser equipment of Nd: YAG lasers, and draws more and more attention. The near-infrared human eye safe waveband of 1.5-1.6 microns is positioned in an atmospheric transmission window, has stronger penetrating power to red phosphorus and white phosphorus, the absorptivity of the near-infrared human eye safe waveband is one fifth of 1064nm, in addition, the 1.57 micron laser has strong anti-electromagnetic interference capability, and simultaneously, when the near-infrared human eye safe waveband is used for laser ranging, the target reflectivity is higher, the target has higher contrast ratio compared with the background, and the background noise is low.
In summary, the 1.57 μm laser has important research significance in the fields of biology, human eye medical operation, environment, wind speed detection, military weapon confrontation, laser radar ranging and the like, which have wide application in the fields of industry, military, medical treatment and the like at present.
How to effectively exert the advantages of the method of large-area quick scanning by using 1.57 mu m human eye safe coherent light in the fields of biology, human eye medical operation, environment, wind speed detection, military weapons confrontation, laser radar ranging and the like.
Disclosure of Invention
The near-infrared human eye safe coherent light ultra-fast scanning device provided by the invention realizes the application of a large-area fast scanning mode of 1.57 mu m human eye safe coherent light to the fields of biology, human eye medical operation, environment, wind speed detection, war weapon confrontation, laser radar ranging and the like, and effectively exerts the advantages thereof.
The method specifically comprises the following steps: the laser processing system comprises a semiconductor laser pumping source, a coupling lens group, a resonant cavity input mirror, a laser gain crystal, an acousto-optic crystal modulator, a laser nonlinear KTP crystal, a resonant cavity output mirror, a plane reflector, a beam shaper, a scanning polygonal rotating mirror assembly, a scanning galvanometer assembly, an f-theta focusing lens group and a laser processing target surface;
the semiconductor laser pumping source and the coupling lens group are connected through optical fibers, and the coupling lens group, the resonant cavity input mirror, the laser gain crystal, the acousto-optic crystal modulator, the laser nonlinear KTP crystal and the resonant cavity output mirror are arranged in a collinear manner;
the output mirror of the resonant cavity and the plane mirror are arranged in a matching mode at a preset angle, the plane mirror is connected with the beam shaper in a matching mode, a beam light outlet hole of the beam shaper is arranged in a matching mode with the input end of the scanning polygonal rotating mirror assembly, the output end of the scanning polygonal rotating mirror assembly is horizontally collinear with the input end of the scanning galvanometer assembly, the output end of the scanning galvanometer assembly is vertically collinear with the input end of the f-theta focusing lens group, and the output end of the f-theta focusing lens group is arranged in a matching mode with the laser processing target surface.
It is further noted that 808nm of central radiation wavelength of the pumping source of the semiconductor laser is transmitted to the coupling lens group through the optical fiber with the fiber core diameter of 400 μm;
the focused 808nm spot is projected into the laser gain crystal through the resonator input mirror.
It is further noted that the maximum pump power of the semiconductor laser pump source is 50W; the maximum acousto-optic modulation frequency is 100 kHz; the conversion efficiency of the optical parametric oscillator is 38.2%;
the conversion efficiency is the light-light conversion efficiency of converting 1064nm fundamental frequency light into 1573nm signal light;
when the maximum acousto-optic Q-switched IOPO average output power obtained by the pump power of 30W is 1.08W, the single pulse energy is 0.108mJ under the pulse repetition frequency of 10kHz, the pulse width is 5.677ns, the peak power is 19kW, and the scanning speed is 10m/s-50 m/s.
It is further noted that the scanning polygon turning mirror assembly comprises: the polygon prism is provided with a plurality of reflecting surfaces and is arranged on a rotating shaft of the motor;
the scanning motor drives the polygon scanning rotating mirror to rotate, so that the polygon scanning rotating mirror rotates at a constant speed, and the rotating speed reaches 1000m/s at most;
the scanning polygon rotating mirror assembly is provided with a scanning motor and a polygon scanning rotating mirror connected with an output shaft of the scanning motor; the polygon scanning rotating mirror rotates around the output shaft of the scanning motor at a preset speed, and each surface of the polygon scanning rotating mirror scans an incident light beam along the same axis.
It should be further noted that the scanning galvanometer assembly is provided with a laser galvanometer, the laser galvanometer is connected with a connecting shaft, the connecting shaft is connected with an adjusting motor, and the adjusting motor adjusts the angle of the laser galvanometer so that the laser can adjust the angle direction in the scanning area.
It should be further noted that the beam shaper is used for expanding and shaping the emitted laser light so that the emitted laser light impinges on the surface of the polygon scanning mirror;
the beam shaper adopts a Galileo structure, the laser beam is a Gaussian beam, the diameter of an incident light spot is about 20mm, and the radius of the incident light spot is 40 mu M after the incident light spot is focused by a focusing lens21.2 and achieves a uniform distribution of laser energy.
The focal length of the f-theta focusing lens group is 420 mm.
The invention also provides a near-infrared human eye safe coherent light ultrafast scanning method, which comprises the following steps:
a pumping source of the semiconductor laser receives the control instruction and emits laser;
the emitted laser is transmitted to the coupling lens group through an optical fiber;
after being focused by the coupling lens group, the laser is transmitted to the plane reflector through the resonant cavity input mirror, the laser gain crystal, the acousto-optic crystal modulator, the laser nonlinear KTP crystal and the resonant cavity output mirror in sequence;
shaping the laser beam by a beam shaper after the laser beam is reflected by the plane mirror;
after shaping, a polygonal scanning rotating mirror of the polygonal rotating mirror assembly realizes two-dimensional plane scanning at a preset speed, each surface of the polygonal scanning rotating mirror scans an incident beam along the same axis at the preset speed, and a scanning vibrating mirror deflects laser scanned by the polygonal scanning rotating mirror to separate reproduction lines;
after the laser is deflected by the polygonal rotating mirror assembly and the reflecting vibrating mirror assembly, the laser is focused on a laser processing target surface through the f-theta focusing lens assembly to form a light spot with a preset radius, so that the laser reaches a preset spatial power density and the injection flux of the material.
It should be further noted that, the pumping source of the semiconductor laser radiates a laser beam with a wavelength of 808nm according to the control instruction, and the laser beam is transmitted to the coupling lens group through the optical fiber with a fiber core diameter of 400 μm;
the focused 808nm spot is projected into the laser gain crystal through the resonator input mirror.
It is further noted that the maximum pump power of the semiconductor laser pump source is 50W; the maximum frequency of acousto-optic modulation is 100 kHz; the conversion efficiency of the optical parametric oscillator is 38.2%;
converting the base frequency light with the wavelength of 1064nm into signal light with the wavelength of 1573 nm;
when the pumping power is 30W, the average output power of the maximum acousto-optic Q-switched IOPO is 1.08W, the single pulse energy is 0.108mJ under the pulse repetition frequency of 10kHz, the pulse width is 5.677ns, the peak power is 19kW, and the scanning speed is 10m/s-50 m/s.
According to the technical scheme, the invention has the following advantages:
in the near-infrared eye-safe coherent light ultrafast scanning device provided by the invention, the near-infrared eye-safe coherent light ultrafast scanning is realized, and the synchronous scanning of the laser pulse repetition frequency and the scanning speed can be realized by combining the control of an editable logic gate array of an industrial personal computer.
The invention can also respectively control the scanning polygon rotating mirror component, the scanning vibrating mirror component, the semiconductor laser pumping source and the acousto-optic crystal modulator through the industrial personal computer. Based on an industrial personal computer, scanning speed information of a polygonal rotating mirror assembly, average laser output power data of a laser generating device, pulse repetition frequency, deflection angle of a laser galvanometer and the like can be acquired; realizing phase-locked control of laser pulse signal phase shift through a programmable logic gate array to complete synchronous processing of signals; the laser pulse repetition frequency and the position information scanned by the rotating mirror can be controlled; the industrial personal computer can control laser generated by a pumping source of the semiconductor laser and irradiate the laser on the polygonal scanning rotating mirror rotating at a preset rotating speed at a preset angle through the light beam shaper, each surface of the polygonal scanning rotating mirror scans an incident light beam along the same optical axis at a preset speed, and the laser vibrating mirror deflects the laser scanned by the polygonal scanning rotating mirror to separate reproduction lines and complete synchronous scanning;
the invention realizes ultra-fast two-dimensional plane scanning by combining near-infrared human eye safe coherent light generated by KTP-IOPO with a polygonal scanning rotating mirror, a rotating mirror scanner rapidly rotates around a mechanical shaft at a constant speed, each surface scans an incident beam along one shaft at a very high speed, and after laser scanning, a vibrating mirror finishes deflection of laser and separates reproduction lines. The scanning speed of the rotating mirror can reach 1000m/s at most.
The device has wide application field, and provides important application value based on the practical application of the 1.57 mu m human eye safe coherent light.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings used in the description will be briefly introduced, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of an embodiment of a near-infrared eye-safe coherent light ultrafast scanning apparatus;
FIG. 2 is a schematic diagram of an optical parametric oscillator outputting a 1.57 μm human eye safe coherent optical pulse sequence;
FIG. 3 is a diagram of a single pulse of an optical parametric oscillator outputting 1.57 μm of eye-safe coherent light;
FIG. 4 is a flow chart of a near-infrared eye-safe coherent light ultrafast scanning method.
Description of reference numerals:
the laser processing system comprises a 1-semiconductor laser pumping source, a 2-optical fiber, a 3-coupling lens group, a 4-resonant cavity input mirror, a 5-laser gain crystal, a 6-acousto-optic crystal modulator, a 7-laser nonlinear KTP crystal, an 8-resonant cavity output mirror, a 9-plane reflector, a 10-beam shaper, an 11-scanning polygonal rotating mirror assembly, a 12-scanning galvanometer assembly, a 13-f-theta focusing lens group and a 14-laser processing target surface.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to fig. 1 in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The 1.57 micron near infrared laser is called as eye-safe waveband laser, can work in all weather, is positioned in an atmosphere transmission window, has strong penetrating power to white phosphorus and red phosphorus in smoke, is used for laser detection, has high material surface reflectivity, small background noise and good electromagnetic interference resistance, and has important research value in fields of laser radar, biological processing, laser weapons, environmental monitoring and the like. The invention applies 1.57 micron laser to the fields of biology, human eye medical operation, environment, wind speed detection, military weapons confrontation, laser radar ranging and the like.
Based on the development of the KTP-OPO technology, the KTP crystal is called as KTiOPO4The (potassium titanyl phosphate) has a large range of transmission spectrum region, has the advantages of non-linear coefficient, stable physicochemical property, difficult deliquescence and the like, and can be matched with more pumping wavelengths. Visible mid-infrared bands can be obtained.
The device can realize the near-infrared human eye safe coherent light ultra-fast scanning by combining the KTP-OPO and the ultra-fast rotating mirror scanning device, and realizes the control by combining the editable logic gate array of the industrial personal computer, thereby realizing the synchronous scanning of the laser pulse repetition frequency and the scanning speed. The 1.57 micron laser is applied to the fields of biology, human eye medical operation, environment, wind speed detection, military weapon confrontation, laser radar ranging and the like.
The invention provides a near-infrared human eye safe coherent light ultrafast scanning device, comprising: the laser processing system comprises a semiconductor laser pumping source 1, a coupling lens group 3, a resonant cavity input mirror 4, a laser gain crystal 5, an acousto-optic crystal modulator 6, a laser nonlinear KTP crystal 7, a resonant cavity output mirror 8, a plane reflecting mirror 9, a beam shaper 10, a scanning polygon rotating mirror assembly 11, a scanning galvanometer assembly 12, an f-theta focusing lens group 13 and a laser processing target surface 14;
the semiconductor laser pumping source 1 and the coupling lens group 3 are connected through an optical fiber 2, and the coupling lens group 3, the resonant cavity input mirror 4, the laser gain crystal 5, the acousto-optic crystal modulator 6, the laser nonlinear KTP crystal 7 and the resonant cavity output mirror 8 are arranged in a collinear way; the collinear arrangement can be understood as that the center of the coupling lens group 3, the center of the resonant cavity input mirror 4, the center of the laser gain crystal 5, the center of the acousto-optic crystal modulator 6, the center of the laser nonlinear KTP crystal 7 and the center of the resonant cavity output mirror 8 are on the same straight line, and the collinear arrangement can be better configured by utilizing collimated light beams, so that the center of the coupling lens group 3, the center of the resonant cavity input mirror 4, the center of the laser gain crystal 5, the center of the acousto-optic crystal modulator 6, the center of the laser nonlinear KTP crystal 7 and the center of the resonant cavity output mirror 8 are collinear.
Laser beams emitted by a semiconductor laser pumping source 1 pass through a coupling lens group 3, a resonant cavity input mirror 4, a laser gain crystal 5, an acousto-optic crystal modulator 6, a laser nonlinear KTP crystal 7 and a resonant cavity output mirror 8 in sequence after passing through an optical fiber 2.
The resonator output mirror 8 and the plane mirror 9 are arranged in a matching manner at a preset angle. The angle of the plane mirror 9 can be set according to actual needs, and can be 45 °, or 50 °, or 60 °, and the specific degree is not limited.
The plane reflector 9 is connected with the beam shaper 10 in a matching way, a beam light outlet hole of the beam shaper 10 is arranged in a matching way with an input end of the scanning polygon rotating mirror assembly 11, an output end of the scanning polygon rotating mirror assembly 11 is horizontally collinear with an input end of the scanning galvanometer assembly 12, an output end of the scanning galvanometer assembly 12 is vertically collinear with an input end of the f-theta focusing lens group 13, and an output end of the f-theta focusing lens group 13 is arranged in a matching way with the laser processing target surface 14.
Wherein, the semiconductor LD laser pumping source is produced by coherent U.S. A, the central radiation wavelength is 808nm, and the 1:1 coupling lens group 3 is connected by an optical fiber with the core diameter of 400 μm. Hitting 808nm focusing light spot to gain crystal Nd3+:GdVO4Nd of internal laser gain crystal 53+The ion doping concentration is 0.5 at.%, and the crystal length is 5 mm.
Based on the generated 1573nm laser, the scanning mode of the near-infrared human eye safe coherent light is solved by combining the technical characteristics in the device. The device can realize the ultrafast scanning of near-infrared laser, and the device can also realize the ultrafast near-infrared laser processing, or high-power, the high-energy laser processing, be applied to fields such as biology, people's eye medical treatment operation, environment, wind speed detection, war weapon confrontation, laser radar range finding.
An acousto-optic crystal with the length of 47mm is arranged in an acousto-optic crystal modulator 6 of the device, the tunable frequency range is 1kHz-100kHz, and the model number is MQC041-20DC-FPS-15V (Gooch & Housego, U.K.). The resonant cavity input mirror 4 is a plane mirror, the input surface of the resonant cavity input mirror is plated with a 808nm high-transmittance film, the transmittance is greater than 95%, the 1064nm high-reflectance film reflectivity is greater than 98%, and the other surface is plated with 808nm and 1064nm anti-reflection films, the reflectivities of which are less than 0.2%.
The two surfaces of the laser gain medium 5 and the acousto-optic crystal modulator 6 are both coated with 808nm and 1064nm antireflection films, the resonant cavity output mirror 8 is a plane mirror, and the transmittance of 1064nm laser is 25%. The laser resonant cavity is a critical cavity. The laser nonlinear KTP crystal 7 adopts II-type noncritical phase matching, and the maximum nonlinear coefficient can be effectively obtained along the X axis (theta is 90 degrees and theta is 0 degrees). The input surface of the laser nonlinear KTP crystal 7 is plated with a 1573nm high-reflection film and a 1064nm high-transmission film, the input surface and an output mirror form an OPO resonant cavity, the physical cavity length of the fundamental frequency optical resonant cavity is about 87.22mm, and all mirrors and crystals of the OPO resonant cavity which is about 28mm are placed in a 17MAX600 optical adjusting frame (Melles Griot, USA).
The maximum pump power of the semiconductor laser pump source (1) is 50W; the maximum frequency of acousto-optic modulation is 100 kHz; the conversion efficiency of the optical parametric oscillator is 38.2%; converting the base frequency light with the wavelength of 1064nm into signal light with the wavelength of 1573 nm; when the pumping power is 30W, the average output power of the maximum acousto-optic Q-switched IOPO is 1.08W, the single pulse energy is 0.108mJ under the pulse repetition frequency of 10kHz, the pulse width is 5.677ns, the peak power is 19kW, and the scanning speed is 10m/s-50 m/s.
Illustratively, for example, in the case where the average output power P-I curve is best obtained at 30w of the semiconductor laser pump source 1, the nonlinear crystal is not greatly affected by thermal effects, and at high pump power, the crystal thermal effects seriously decrease the output power, whereas at low pump power, the maximum average output power obtained is relatively low. The acousto-optic modulation frequency is 10kHz, so that synchronous scanning can be realized by better matching the scanning speed of the rotating mirror under the condition of obtaining larger single pulse energy.
The resonator input mirror 4 and the resonator output mirror 8 may both be in which the laser beam is reflected back and forth to provide optical energy feedback. The resonant cavity input mirror 4 and the resonant cavity output mirror 8 can be formed by two plane or concave spherical reflectors which are vertical to the axis of the active medium.
The resonant cavity 4 and the resonant cavity 8 are used as a 1064nm fundamental frequency light resonant cavity in an optical parametric oscillator, an input surface and an output mirror form an OPO resonant cavity, the physical cavity length of the fundamental frequency light resonant cavity is 87.22mm, the OPO resonant cavity is 28mm, and all mirrors and crystals are placed in a 17MAX600 optical adjusting rack (Melles Griot, USA).
The polygon scanning mirror assembly 11 involved in the apparatus employs a polygon scanning mirror from moewe, germany. The polygon rotating mirror assembly comprises a scanning motor and a polygon prism, wherein the polygon prism is provided with a plurality of reflecting surfaces and is arranged on a rotating shaft of the scanning motor. The polygon prism can realize high-speed rotation through the rotation of the scanning motor, thereby realizing large-angle and high-speed light beam scanning. The invention can control the rotation and vibration of the polygon rotating mirror and the vibrating mirror by setting the control computer to drive the polygon scanning rotating mirror to rotate at a constant speed, and the maximum rotating speed can reach 1000 m/s.
The scanning galvanometer component 12 involved in the device is provided with a laser galvanometer, the laser galvanometer is connected with a connecting shaft, the connecting shaft is connected with an adjusting motor, and the adjusting motor adjusts the angle of the laser galvanometer to enable laser to adjust the angle direction in a scanning area.
The beam shaper 10 of the present invention comprises: the beam lens and the beam reflecting mirror are used for expanding and shaping laser emitted by the laser source generating device, so that the emitted laser can be irradiated on the surface of the polygonal scanning mirror.
The focal length of the f-theta focusing lens group 13 related to the invention is 420 mm. The beam shaper 10 adopts a Galileo structure, the laser beam is a Gaussian beam, the diameter of an incident light spot is about 20mm, and the radius of the light spot is 40 mu M and M after the incident light spot is focused by a focusing lens21.2 and achieves a uniform distribution of laser energy. The F-theta focusing lens group is also called a flat field focusing lens, the image height of the F-theta focusing lens group is equal to F theta which is the focal length multiplied by the scanning angle y, notThe same as that of the common lens Y is Ftan theta. The f-theta focusing lens group is specially designed to enable the light beam incident angle and the light spot position on the image surface to meet the linear relation, so that the position of the light spot on the image surface can be controlled by controlling the scanning angle of the incident light beam to form a linear scanning speed, and finally the laser beam can form a uniform-size focusing light spot in the whole marking plane.
After the laser is deflected by the polygonal rotating mirror assembly and the reflecting vibrating mirror assembly, the laser is focused on a laser processing target material through the f-theta focusing lens assembly to form light spots with preset radiuses and two-dimensional array scanning lines.
Based on the above, the invention also relates to a near-infrared human eye safe coherent light ultrafast scanning method, as shown in fig. 2 to 4, the method comprises:
s1, the semiconductor laser pumping source receives the control instruction and emits laser;
s2, transmitting the emitted laser to the coupling lens group through an optical fiber;
s3, after being focused by the coupling lens group, the laser is transmitted to the plane reflector through the resonant cavity input mirror, the laser gain crystal, the acousto-optic crystal modulator, the laser nonlinear KTP crystal and the resonant cavity output mirror in sequence;
s4, shaping the laser beam by the beam shaper after the reflection of the plane mirror;
s5, after shaping, the polygon scanning rotating mirror of the polygon rotating mirror assembly realizes two-dimensional plane scanning at a preset speed, each surface of the polygon scanning rotating mirror scans an incident beam along the same axis at the preset speed, and the vibrating mirror deflects the laser scanned by the polygon scanning rotating mirror to separate reproduction lines;
the scanning rotating mirror can realize ultra-fast scanning, the scanning speed can reach 1000m/s at the fastest speed when scanning the same line on a scanning plane, the scanning of the same line is continued from the beginning of one line after the rotating mirror rotates for one circle after one line is scanned, and the vibrating mirror is used for separating the wiring beams of each scanning. Ultra-fast two-dimensional planar scanning can be achieved.
And S6, after the laser is deflected by the polygonal rotating mirror assembly and the reflecting vibrating mirror assembly, the laser is focused on the laser processing target surface through the f-theta focusing lens group to form a light spot with a preset radius, so that the laser reaches a preset spatial power density and the injection flux of the material.
In the method, the maximum pump power of the used semiconductor laser pump source is 50W; the maximum frequency of acousto-optic modulation is 100 kHz; the conversion efficiency of the optical parametric oscillator is 38.2%; the 1064nm fundamental frequency light is converted into 1573nm signal light; when the pumping power is 30W, the average output power of the maximum acousto-optic Q-switched IOPO is 1.08W, the single pulse energy is 0.108mJ under the pulse repetition frequency of 10kHz, the pulse width is 5.677ns, the peak power is 19kW, and the scanning speed is 10m/s-50 m/s. The user can make innovation according to own equipment and can reach dozens of watts for optical fiber OPO output power at present, and for the all-solid-state laser OPO, because the refrigeration requirement is strict, need strict control nonlinear crystal heat effect and the walk-off effect that arouses by the heat effect. It is clear that a better beam quality for higher pulse energies will have a better effect on practical applications.
The invention combines polygon rotating mirror scanning and galvanometer scanning to realize ultra-fast two-dimensional plane scanning, a rotating mirror scanner rotates around a mechanical shaft at a constant speed, each surface scans an incident beam along one shaft at a very high speed, deflection is completed in laser scanning, and a plurality of fast reproduction lines are separated. The scanning speed of the invention is dozens of times of the scanning speed of the galvanometer in the current market and can reach 1000m/s at most, but the invention only applies the scanning speed of 10m/s-50 m/s. Obviously, the device can be practical for higher near-infrared laser devices and has wide prospect.
The device can also provide a laser synchronous scanning method, the scanning device comprises a polygonal rotating mirror assembly, a polygonal vibrating mirror assembly, a motor control system, a laser source, an acousto-optic controller and the like, and the scanning device can be additionally controlled by an industrial personal computer, and the industrial personal computer can acquire information such as scanning speed information of the polygonal rotating mirror assembly, deflection angle of a laser vibrating mirror, laser average output power data of the laser generating device, pulse repetition frequency and the like; realizing phase-locking control of laser pulse signal phase shift through a programmable logic gate array to complete signal synchronization; the laser pulse repetition frequency and the position information scanned by the rotating mirror are controlled to realize synchronous scanning. The device and the method further realize the ultra-fast scanning of the near-infrared human eye safe coherent light, and simultaneously can realize the synchronous scanning of the laser pulse repetition frequency and the scanning speed by combining the control of the programmable logic gate array of the industrial personal computer. Has important research significance for the fields of biological processing, laser radar, military laser countermeasure and the like, and provides important application value for the safe coherent light of the human eye with the diameter of 1.57 mu m in each practical application.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A near-infrared eye-safe coherent light ultrafast scanning device, comprising: the laser processing system comprises a semiconductor laser pumping source (1), a coupling lens group (3), a resonant cavity input mirror (4), a laser gain crystal (5), an acousto-optic crystal modulator (6), a laser nonlinear KTP crystal (7), a resonant cavity output mirror (8), a plane mirror (9), a beam shaper (10), a scanning polygon rotating mirror assembly (11), a scanning galvanometer assembly (12), an f-theta focusing lens group (13) and a laser processing target surface (14);
the semiconductor laser pumping source (1) is connected with the coupling lens group (3) through the optical fiber (2), and the coupling lens group (3), the resonant cavity input mirror (4), the laser gain crystal (5), the acousto-optic crystal modulator (6), the laser nonlinear KTP crystal (7) and the resonant cavity output mirror (8) are arranged in a collinear way;
the resonant cavity output mirror (8) and the plane reflecting mirror (9) are arranged in a matched mode at a preset angle, the plane reflecting mirror (9) is connected with the beam shaper (10) in a matched mode, a beam light outlet of the beam shaper (10) is arranged in a matched mode with the input end of the scanning polygon rotating mirror assembly (11), the output end of the scanning polygon rotating mirror assembly (11) is horizontally collinear with the input end of the scanning galvanometer assembly (12), the output end of the scanning galvanometer assembly (12) is vertically collinear with the input end of the f-theta focusing lens assembly (13), and the output end of the f-theta focusing lens assembly (13) is arranged in a matched mode with the laser processing target surface (14).
2. The near-infrared eye-safe coherent light ultrafast scanning device of claim 1,
the center radiation wavelength 808nm of a semiconductor laser pumping source (1) is transmitted to a coupling lens group (3) through an optical fiber (2) with the fiber core diameter of 400 mu m;
the focused 808nm light spot is emitted into a laser gain crystal (5) through a resonant cavity input mirror (4).
3. The near-infrared eye-safe coherent light ultrafast scanning device of claim 1,
the maximum pumping power of the semiconductor laser pumping source (1) is 50W; the maximum acousto-optic modulation frequency is 100 kHz; the conversion efficiency of the optical parametric oscillator is 38.2%;
the conversion efficiency is the light-light conversion efficiency of converting 1064nm fundamental frequency light into 1573nm signal light;
when the maximum acousto-optic Q-switched IOPO average output power obtained by the pump power of 30W is 1.08W, the single pulse energy is 0.108mJ under the pulse repetition frequency of 10kHz, the pulse width is 5.677ns, the peak power is 19kW, and the scanning speed is 10m/s-50 m/s.
4. The near-infrared eye-safe coherent light ultrafast scanning device of claim 1,
the scanning polygon turning mirror assembly (11) comprises: the polygon prism is provided with a plurality of reflecting surfaces and is arranged on a rotating shaft of the motor;
the scanning motor drives the polygon scanning rotating mirror to rotate, so that the polygon scanning rotating mirror rotates at a constant speed, and the rotating speed reaches 1000m/s at most;
the scanning polygon rotating mirror assembly (11) is provided with a scanning motor and a polygon scanning rotating mirror connected with an output shaft of the scanning motor; the polygon scanning rotating mirror rotates around the output shaft of the scanning motor at a preset speed, and each surface of the polygon scanning rotating mirror scans an incident light beam along the same axis.
5. The near-infrared eye-safe coherent light ultrafast scanning device of claim 1,
the scanning galvanometer component (12) is provided with a laser galvanometer, the laser galvanometer is connected with a connecting shaft, the connecting shaft is connected with an adjusting motor, and the adjusting motor adjusts the angle of the laser galvanometer to enable laser to adjust the angle direction in a scanning area.
6. The near-infrared eye-safe coherent light ultrafast scanning device of claim 1,
the beam shaper (10) is used for expanding and shaping the emitted laser so that the emitted laser can be irradiated on the surface of the polygonal scanning mirror;
the beam shaper (10) adopts a Galileo structure, the laser beam is a Gaussian beam, the diameter of an incident light spot is about 20mm, and the radius of the light spot is 40 mu M and M after the incident light spot is focused by a focusing lens21.2 and achieves a uniform distribution of laser energy.
7. The near-infrared eye-safe coherent light ultrafast scanning device of claim 1,
the focal length of the f-theta focusing lens group (13) is 420 mm.
8. A near-infrared eye-safe coherent light ultra-fast scanning method is characterized by comprising the following steps:
the semiconductor laser pumping source (1) receives the control instruction and emits laser;
the emitted laser is transmitted to the coupling lens group (3) through the optical fiber (2);
after being focused by the coupling lens group (3), laser is transmitted to the plane reflector (9) through the resonant cavity input mirror (4), the laser gain crystal (5), the acousto-optic crystal modulator (6), the laser nonlinear KTP crystal (7) and the resonant cavity output mirror (8) in sequence;
shaping the laser beam by a beam shaper (10) after the laser beam is reflected by a plane reflector (9);
after shaping, a polygonal scanning rotating mirror of the polygonal rotating mirror assembly realizes two-dimensional plane scanning at a preset speed, each surface of the polygonal scanning rotating mirror scans an incident beam along the same axis at the preset speed, and a scanning vibrating mirror deflects laser scanned by the polygonal scanning rotating mirror to separate reproduction lines;
after the laser is deflected by the polygonal rotating mirror assembly and the reflecting vibrating mirror assembly, the laser is focused on a laser processing target surface (14) through an f-theta focusing lens assembly (13) to form a light spot with a preset radius, so that the laser reaches a preset space power density and the injection flux of materials.
9. The near-infrared eye-safe coherent light ultrafast scanning method of claim 8,
the semiconductor laser pumping source (1) radiates a laser beam with the wavelength of 808nm according to a control instruction, and the laser beam is transmitted to the coupling lens group (3) through an optical fiber (2) with the fiber core diameter of 400 mu m;
the focused 808nm light spot is emitted into a laser gain crystal (5) through a resonant cavity input mirror (4).
10. The near-infrared eye-safe coherent light ultrafast scanning method of claim 8,
in the method, the maximum pumping power of a semiconductor laser pumping source (1) is 50W; the maximum frequency of acousto-optic modulation is 100 kHz; the conversion efficiency of the optical parametric oscillator is 38.2%;
converting the base frequency light with the wavelength of 1064nm into signal light with the wavelength of 1573 nm;
when the pumping power is 30W, the average output power of the maximum acousto-optic Q-switched IOPO is 1.08W, the single pulse energy is 0.108mJ under the pulse repetition frequency of 10kHz, the pulse width is 5.677ns, the peak power is 19kW, and the scanning speed is 10m/s-50 m/s.
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