CN114185168B - Aberration-free laser scanning method and system - Google Patents
Aberration-free laser scanning method and system Download PDFInfo
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- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
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Abstract
The invention discloses an aberration-free laser scanning method and system, and belongs to the field of optics. The method comprises the following steps: a preprocessing stage, namely slicing a scanning track into N concentric circular tracks, wherein N is a positive integer; taking any point on each circular track as a scanning starting point; obtaining aberration correction data corresponding to each scanning starting point; a scanning stage, step S1, generating a laser beam; step S2, selecting an unscanned circular track as the circular track to be scanned, controlling the deflection angle of the laser beam to focus on the scanning starting point of the circular track to be scanned, and setting the aberration correction data corresponding to the scanning starting point to make the laser beam rotate for a circle along the circular track from the scanning starting point, wherein the angular speed of the self-rotation of the light beam is consistent with the angular speed of the annular scanning in the scanning process; and step S3, repeating the step S3 until the scanning of all the N circular tracks is completed. The invention realizes high-speed large-range aberration-free scanning on the basis of shortening aberration correction time.
Description
Technical Field
The invention belongs to the field of optics, and particularly relates to an aberration-free laser scanning method and system.
Background
In an optical system, aberrations inevitably exist, and the existence of the aberrations deteriorates optical performance parameters of the system, such as an increase in the beam waist radius of a focused spot, a decrease in energy density, and the like. In some fields, such as laser eye surgery and laser processing, this situation often results in reduced processing precision, increased laser power to be injected, and the like. In particular, in the scanning system, the magnitude and direction of the aberration are different at different scanning positions, so that the machining precision is different at different positions of the machined surface, and the machining quality is reduced.
The current methods for solving the aberration problem of the optical system are mainly divided into two methods, one is to add fixed aberration compensation to the system, and the other is to add dynamic aberration compensation to the system. The fixed aberration compensation method is to measure the system aberration according to the built optical system, design a fixed aberration compensation device, such as a phase plate, and compensate the system aberration by adding the designed aberration compensation device into the system. The limitation of this approach is that only aberrations at points on the system axis can be compensated. The dynamic aberration compensation method is to add a variable aberration compensation device, such as a liquid crystal Spatial Light Modulator (SLM), a Digital Micromirror Device (DMD), a Deformable Mirror (DM), etc., to the optical system, and calculate the sequence of the patterns or arrangements to be displayed by the compensation device through a specific algorithm or formula to calibrate the system aberration. Compared with the former method, the method can theoretically perform aberration correction on the full scanning field of the system, the method is to perform independent aberration correction on each scanning point, and when the current scanning point is scanned, corresponding aberration compensation patterns or the sequence of arrangement are loaded in the dynamic aberration compensation device. However, this is complicated and troublesome, takes a lot of time, and requires a high refresh rate for the aberration compensating device in the case of high-speed wide-range scanning, and the conventional device cannot meet the requirement.
Disclosure of Invention
In view of the defects and the improvement requirements of the prior art, the invention provides an aberration-free laser scanning method and system, and aims to shorten the aberration correction time on the premise of not increasing the performance of an aberration compensation device.
To achieve the above object, according to an aspect of the present invention, there is provided an aberration-free laser scanning method, including:
a pre-treatment stage comprising:
slicing the scanning track into N concentric circular tracks, wherein N is a positive integer; taking any point on each circular track as a scanning starting point to obtain N scanning starting points;
obtaining aberration correction data corresponding to each scanning starting point in the N scanning starting points to obtain N groups of scanning starting point data and aberration correction data which correspond one to one;
a scanning phase comprising the steps of:
step S1, generating a laser beam;
step S2, selecting an unscanned circular track as a circular track to be scanned, controlling the deflection angle of the laser beam to focus on the scanning starting point of the circular track to be scanned, setting aberration correction data corresponding to the scanning starting point, and rotating the laser beam for a circle along the circular track from the scanning starting point, wherein the rotation angular velocity of the light beam is consistent with the annular scanning angular velocity in the scanning process to correct each point on the circular track to be scanned;
and step S3, repeating the step S3 until the scanning of all the N circular tracks is completed.
Further, in the scanning stage, the laser beam is a pulse laser beam, and the scanning point intervals on all the circular tracks are the same.
Further, the laser frequency division N of the pulse laser beam on the current circular track L Comprises the following steps:
N L ＝floor(f L /f L′ +0.5)，
wherein f is L′ Is the repetition frequency, f, of a pulsed laser beam L Is the fundamental frequency of the pulsed laser beam, an
d P The distance between scanning points on the circular tracks corresponding to different radiuses is defined, R is the radius of the current circular track, omega is the rotation angular velocity of the pulse laser beam, and floor () is a downward integral function.
Further, the angular velocity ω of rotation of the pulsed laser beam is:
further, in the preprocessing stage, the aberration at the scanning start point is corrected by a zernike polynomial.
According to another aspect of the present invention, there is provided an aberration-free laser scanning system, comprising:
a laser light source for generating a laser beam;
the aberration correction unit is used for carrying out wavefront aberration precompensation on the laser beam to ensure that a light spot focused by the laser beam has no aberration;
a beam deflection unit for making the laser beam have a certain deflection angle;
the beam rotating unit is used for carrying out annular scanning on the laser beam with a certain deflection angle and enabling the laser beam to rotate in the scanning process, and the angular speeds of the annular scanning at the rotation angular speeds are consistent;
the control unit is used for slicing the scanning track into N concentric circular tracks, wherein N is a positive integer; taking any point on each circular track as a scanning starting point to obtain N scanning starting points; controlling an aberration correction unit to obtain aberration correction data corresponding to each scanning starting point in the N scanning starting points; controlling the deflection angle of the beam deflection unit and the rotation angular velocity of the beam rotation unit to focus the laser beam on a scanning starting point of an unscanned circular track, and setting aberration correction data corresponding to the scanning starting point to rotate the laser beam for a circle along the circular track from the scanning starting point; and controlling the aberration correction unit to replace the aberration correction data of different unscanned circular tracks until the scanning of all the N circular tracks is completed.
Further, the beam deflection unit is a galvanometer, an acousto-optic deflector, an optical wedge, a turning mirror or a movable micromirror.
Further, the aberration correcting unit is a spatial light modulator, a digital micromirror device, or a deformable mirror.
Further, the light beam rotating unit is a dove prism or an Abbe-Koniy prism or three reflectors arranged in a K shape and driven by a motor.
Further, still include: a relay unit between the beam deflection unit and the beam rotation unit for pupil matching of the beam deflection unit and the beam rotation unit.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the aberration-free rapid laser scanning system and the method of the invention utilize the characteristic that the aberration in the laser scanning light path is rotationally symmetrical about the optical axis, only one scanning starting point is corrected for each scanning circular track to obtain the corresponding aberration correction data, and the aberration on the circular track is set into the aberration correction data corresponding to the scanning starting point through annular scanning, so that the rotating angular speed of the light beam is consistent with the angular speed of the annular scanning, the effect of correcting the aberration on all the circular tracks is realized, the number of scanning points needing to be corrected is greatly reduced, and the aberration correction time is shortened. Meanwhile, one aberration correction data is required to be switched once for one circular track, the requirements on the updating speed and the storage space of the aberration correction unit are greatly reduced, and high-speed large-range (full-field) aberration-free scanning is realized.
(2) Preferably, for the pulse laser, the laser fundamental frequency division is calculated to reversely calculate the scanning angular velocity of the light beam corresponding to the scanning point interval under different radiuses, so as to obtain a data set in which the scanning point interval, the scanning angular velocity of the light beam, the radius of each circular track and the laser frequency division coefficient on the circular tracks corresponding to different radiuses are in one-to-one correspondence.
(3) Preferably, the aberration-free fast laser scanning system of the invention further comprises a relay unit, so that the pupils of the light beam deflection unit and the light beam rotation unit can be matched, and the scanning imaging quality is improved.
In summary, the aberration-free fast laser scanning system and method of the present invention realizes high-speed large-range (full field) aberration-free scanning on the basis of shortening the aberration correction time.
Drawings
Fig. 1 is a schematic structural diagram of an aberration-free laser scanning system provided by the present invention.
FIG. 2 is a diagram of aberration distribution in a conventional laser scanning system.
Fig. 3 is a schematic diagram of the image of the dove prism at 0 °.
Fig. 4 is a schematic diagram of the dove prism imaging at 45 °.
Fig. 5 is a schematic diagram of the imaging change of the dove prism during the 180 ° rotation.
Fig. 6 is a schematic structural diagram of implementing aberration-free laser scanning in the embodiment of the present invention.
FIG. 7 is a flowchart of an embodiment of an aberration-free annular scanning method.
FIG. 8 is a flowchart illustrating aberration correction according to an embodiment of the present invention.
FIG. 9 is a schematic diagram of the distribution of the spot pitch of the pulsed laser beam when the scanning angular velocity and the laser repetition frequency are unchanged.
FIG. 10 is a flow chart of calculation of trajectory control data to achieve the same spot spacing across the scan plane.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-a laser light source; 2-an aberration correction unit; 3-a beam deflection unit; 4-a beam rotation unit; 5-a beam focusing unit; 6-processing the platform; 8-a control unit; 71-system optical axis; 72, 74 are scanning tracks; 9-substance; 9' -like; 41-dove prism; 411-the axis of rotation; 21-a liquid crystal spatial light modulator; 211-a pattern; 31-a galvanometer; 32, 33 are lens groups; 10-optical axis.
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.
As shown in fig. 1, the present embodiment provides an aberration-free laser scanning system, which includes: a laser light source 1, an aberration correction unit 2, a beam deflection unit 3, a beam rotation unit 4, a beam focusing unit 5, and a control unit 8.
The laser light source 1 generates a laser beam which interacts with a processing substance, such as photodisruption, photoablation, photocrosslinking, photothermal, photochemical reaction, and the like, and can be a continuous laser or a pulse laser. When the laser light source generates pulse laser, the exposure time or repetition frequency and laser energy of the laser light source can be regulated and controlled. The laser beam preferably has a wavelength of 800nm to 1500nm, a fundamental frequency of 10kHz to 10MHz, and a laser power of 0.1W to 1000W.
And the aberration correction unit 2 is used for carrying out aberration correction on a certain position of the laser beam under different deflection angles, realizing dynamic aberration correction on the laser beam, and carrying out wavefront aberration precompensation on the laser beam so that a final laser beam focused light spot has no aberration. The aberration correcting unit may be a dynamic aberration compensating device. The dynamic aberration compensation device may be a dynamic diffractive device, such as a spatial light modulator, a digital micromirror device, or the like, or may be a deformable mirror.
The beam deflection unit 3 generates a controllable and variable deflection angle for the laser beam. The beam deflection unit 3 may be a galvanometer, acousto-optic deflector, optical wedge, turning mirror, movable micro-mirror, etc. In other embodiments, the aberration correction unit and the beam deflection unit may be implemented by the same device, such as a dynamic diffraction device, which may implement both aberration correction and beam deflection.
And the light beam rotating unit 4 is used for performing annular scanning on the laser light beams with a certain deflection angle, and in the annular scanning process, the light beams close to the scanning center are the same side of the light beams, namely the light beam rotating unit enables the rotation angular speed of the light beams to be consistent with the annular scanning angular speed. The light beam rotating unit 4 can be a dove prism or an Abbe-Koniy prism driven by a motor or three reflectors arranged in a K shape.
The beam focusing unit 5 focuses the scanning beam in the beam rotating unit 4 to form different circular tracks on the target position (the processing platform 6). The beam focusing unit 5 may be a field lens or an objective lens or the like. The diameter of the focused spot is preferably 1um to 1cm in size.
And the control unit 8 coordinates and controls the aberration correction and light beam deflection unit and the light beam rotation unit to enable the system to realize aberration-free annular scanning. Specifically, the method comprises the steps of slicing a scanning track into N concentric circular tracks, wherein N is a positive integer; taking any point on each circular track as a scanning starting point to obtain N scanning starting points; controlling an aberration correction unit to obtain aberration correction data corresponding to each scanning starting point in the N scanning starting points; controlling the deflection angle of the beam deflection unit and the rotation angular velocity of the beam rotation unit to focus the laser beam on a scanning starting point of an unscanned circular track, and setting aberration correction data corresponding to the scanning starting point to rotate the laser beam for a circle along the circular track from the scanning starting point; and controlling the aberration correction unit to replace the aberration correction data of different unscanned circular tracks until the scanning of all the N circular tracks is completed.
The method specifically comprises the steps of controlling the exposure time or repetition frequency and laser energy of a laser light source, and controlling the line spacing, the point spacing and the laser pulse energy density of a scanning track by matching with annular scanning control.
Since the sources of the aberrations are mainly lenses in the system, the lenses used in the conventional laser scanning optical path are all rotationally symmetric, which means that when the incident angle of the laser beam is constant, the magnitudes of the aberrations are substantially consistent, and the directions of the aberrations are rotated, i.e. the aberrations are also rotationally symmetric about the optical axis. Fig. 2 is a schematic diagram showing the distribution of aberration in a conventional laser scanning system. The aberration distribution of the system is rotationally symmetric about the system optical axis 71. The aberration sizes of the scanning spots at the same scanning radius are substantially the same and the directions are symmetrical about the system optical axis 71, as are the aberration patterns 73a, 73b, 73c of the scanning spots on the scanning track 72. The aberration differs in magnitude at different scanning radii, as shown by aberration pattern 73a on scan track 72 and aberration pattern 75a on scan track 74.
Therefore, if the annular scanning method is adopted and the aberration pattern can rotate along with the annular scanning method, only one scanning point can be corrected in each scanning circular track, and the effect of correcting all the scanning points on the circular tracks is achieved.
In this example, the beam rotator is a dove prism 41. As shown in fig. 3, the object 9 is imaged 9 'after passing through the dove prism 41, and the image 9' is obtained by rotating the object 9 by 180 ° and then mirroring the image. The dove prism 41 rotates by an angle of 2 ω after rotating by an angle of ω. As shown in fig. 4, the dove prism 41 is rotated by 45 ° about the dove prism rotation axis 411, and the image 9' is rotated by 90 ° about the rotation axis 411. Fig. 5 illustrates the image change process after the dove prism 41 rotates 180 °, and it can be seen that the patterns on the aberration correction device, i.e. the images 9a, 9b, 9c, are rotationally symmetric about the dove prism rotation axis 411, which is consistent with the aberration distribution rule of the optical system, so that each scanning circle track only needs to correct one scanning point to realize the correction of all the scanning points on the circle track. In other embodiments, in addition to dove prisms, any beam rotation device that satisfies this imaging law may be suitable for use in the system, such as abbe-konii prisms and K-shaped triple mirrors.
Fig. 6 is a schematic diagram of implementing aberration-free annular scanning in an embodiment of the present invention, in which the aberration correction unit 2 in fig. 1 is a liquid crystal spatial light modulator 21, and dynamic system aberration correction can be implemented by changing a loaded pattern 211 of the liquid crystal spatial light modulator. The beam deflection unit 3 is a galvanometer 31, can realize the deflection angle of the laser beam, the lens group 32 and the lens group 33 form a relay unit, and the pattern 211 on the liquid crystal spatial light modulator 21 is relayed to the surface of the dove prism 41 close to one side of the galvanometer 31, namely the liquid crystal spatial light modulator is matched with the pupil of the dove prism. The beam rotator 4 in fig. 1 adopts a dove prism, and the dove prism can realize aberration-free annular scanning by matching with a liquid crystal spatial light modulator and a galvanometer. All devices are centered on an optical axis 10.
As shown in fig. 7, the process of implementing aberration-free annular scanning in this example is:
step one, setting scanning track parameters. The scanning track parameters include: scanning radius range, scanning z-direction data, dot spacing, line spacing, single pulse energy, etc. These parameters may be imported to the control unit by parameter inputs, formula inputs or models.
And step two, scanning track slices. And slicing the scanning track into N circular tracks according to the scanning track parameters input into the control unit, wherein N is a positive integer. Each circular trajectory has the attributes: radius R, axial height Z. The value of N is determined from the scan radius and the line spacing.
And step three, aberration correction and track control data generation are carried out. Taking any point on each circular track as a scanning starting point of the circular track, and carrying out aberration correction on each scanning starting point by the aberration correction unit to obtain a data set consisting of N track control data (namely scanning starting point data) and aberration correction data which correspond to each other one by one; the data set in this example is N pieces of pattern data that can be loaded to the liquid crystal spatial light modulator, the pattern data carrying scanning start point data and aberration correction data (i.e., data that is aberration-corrected for the N scanning start point data). The trajectory control data (scan start point data) mainly includes a beam deflection angle and a rotational angular velocity of the beam rotator. When the laser beam is a pulse laser beam, the frequency division coefficient of the laser light source is also included.
And fourthly, starting scanning, and loading the aberration correction data and the light beam deflection angle data of the current circular track by the aberration correction unit and the light beam deflection unit. At the same time, the beam rotation unit loads rotational angular velocity data. After the light beam rotating unit rotates the light beam for one circle, the aberration correcting unit, the light beam deflecting unit and the light beam rotating unit are switched to the control data of the next circular track for continuous scanning. The scanning process is performed continuously. When the liquid crystal spatial light modulator loads one piece of pattern data, the dove prism rotates 180 degrees, and then one round track scanning is completed; after one round track scanning is finished, the liquid crystal spatial light modulator loads the next pattern data, and the process is repeated until all the N patterns are loaded, so that N round track scanning is finished.
Although the aberration correction is performed for only one point on each circular track in the above-described procedure, the rotation of the dove prism rotates the pattern 211, and the aberration rotation angle and direction on the pattern 211 and the circular track are both identical. Therefore, it is possible to correct aberrations for all scanning points on the circular track.
Fig. 8 is a flowchart of aberration correction, that is, aberration correction data is obtained by:
and calculating to obtain a data set consisting of N light beam deflection angles corresponding to each circular track according to the scanning track parameters. And loading the aberration correction data corresponding to the scanning starting point into the aberration correction unit by Zernike polynomial calculation when the light beam is positioned at a certain light beam deflection angle in the data set, wherein the aberration correction data corresponding to the scanning starting point and the scanning starting point form the pattern data of the circular track. And performing aberration evaluation on the focusing light spot captured by an aberration detection unit in the aberration correction unit by using a common mode, if an iteration condition is met or the maximum iteration number is reached, completing iteration to obtain aberration data of the circular track, and otherwise, circularly executing the operation. The loop is executed in sequence until the aberrations at the N beam deflection angles in the data set are corrected.
As shown in fig. 9, in the circular scanning process, for the pulse laser, the scanning point pitch d of the circular tracks with different radii is constant under the condition that the laser repetition frequency and the scanning angular velocity are not changed P All different, which is not allowed in many cases, such as laser eye surgery. Therefore, in this example, a method for controlling the scanning dot pitch is proposed, which is used to realize that the scanning dot pitches of the circular tracks with different radii are all the same, and as shown in fig. 10, the required scanning dot pitch of the circular tracks with different radii is set to d P The radius of the current circular track is R, and the fundamental frequency of the laser source is f L The beam rotation angular velocity is ω. The method specifically comprises the following steps:
calculating repetition frequency of a pulse laser beam;
in particular, the repetition frequency f of the pulsed laser beam L ' can be calculated as:
wherein, d P The distance between scanning points on the circular tracks corresponding to different radiuses is obtained, R is the radius of the current circular track, and the rotation angular speed of the light beam is omega;
step two, calculating a laser fundamental frequency division coefficient corresponding to the repetition frequency;
specifically, the laser light source cannot realize rapid frequency modulation, and only the high-speed optical switch can perform rapid frequency division on the fundamental frequency of the laser light source, so that the repetition frequency of the laser light source cannot realize stepless frequency modulation. The repetition frequency obtained by the calculation cannot be realized, and only the repetition frequency closest to the calculation result can be obtained, wherein the laser frequency division N of the current circular track L Comprises the following steps:
N L ＝floor(f L /f L′ +0.5)
wherein, floor () is a downward rounding operation to obtain a corresponding laser frequency division coefficient.
And step three, reversely calculating the error-free light beam scanning angular velocity of the point spacing under each radius based on the laser fundamental frequency division coefficient to obtain a data set corresponding to each circular track radius, the laser frequency division and the light beam scanning angular velocity.
Specifically, since the repetition frequency actual value of the laser light source is deviated from the theoretical value, the accuracy of the dot pitch can be ensured only by changing the beam rotation angular velocity, and finally the beam rotation angular velocity ω of the current circular trajectory can be obtained as:
the pulse laser beam has one or several fixed optional basic frequencies, and in the second step, high-speed frequency division can be realized through a built-in or external high-speed optical shutter. The high speed optical shutter may be an acousto-optic modulator (AOM) or electro-optic modulator (EOM), or the like.
According to another aspect of the present invention, the present embodiment provides an aberration-free laser scanning method, including the steps of:
a pre-treatment stage comprising:
slicing the scanning track into N concentric circular tracks, wherein N is a positive integer; taking any point on each circular track as a scanning starting point to obtain N scanning starting points;
obtaining aberration correction data corresponding to each scanning starting point in the N scanning starting points to obtain N groups of scanning starting point data and aberration correction data which correspond one to one;
a scanning phase comprising the steps of:
step S1, generating a laser beam;
step S2, selecting an unscanned circular track as a circular track to be scanned, controlling the deflection angle of the laser beam to focus on the scanning starting point of the circular track to be scanned, setting aberration correction data corresponding to the scanning starting point, and rotating the laser beam for a circle along the circular track from the scanning starting point, wherein the rotation angular velocity of the light beam is consistent with the annular scanning angular velocity in the scanning process to correct each point on the circular track to be scanned;
and step S3, repeating the step S3 until the scanning of all the N circular tracks is completed.
Specifically, in the preprocessing stage, the aberration at the scanning start point position is corrected by a zernike polynomial.
Preferably, the scanning spot pitch is the same on all circular tracks.
The invention can be well applied to the condition that the scanning track is in a rotation symmetrical structure, in particular to the laser eye surgery field and the laser processing field, for example, the scanning surface is a spherical surface, a cylindrical surface, a circular surface, a conical surface and the like in the femtosecond eye surgery and the laser processing, and the quality of the processing surface, such as the flatness and the like, can be improved. When the laser eye surgery instrument is applied to laser eye surgery, the flatness of a surgical incision can be improved, and the laser energy injected into eyes is reduced, namely after aberration correction, the energy of light spots is more concentrated, the energy density is improved, so that cutting can be performed by reducing single pulse energy, and the surgery safety is improved. The injection of reduced energy also provides the possibility of increasing the surgical scanning speed. Meanwhile, the system can realize full-field aberration-free high-speed annular scanning, the realization method is simple and convenient, and the performance requirement on an aberration compensation device is not high.
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 (10)
1. An aberration-free laser scanning method, comprising:
a pre-treatment stage comprising:
slicing the scanning track into N concentric circular tracks, wherein N is a positive integer; taking any point on each circular track as a scanning starting point to obtain N scanning starting points;
obtaining aberration correction data corresponding to each scanning starting point in the N scanning starting points to obtain N groups of scanning starting point data and aberration correction data which correspond one to one;
a scanning phase comprising the steps of:
step S1, generating a laser beam;
step S2, selecting an unscanned circular track as a circular track to be scanned, controlling the deflection angle of the laser beam to focus on the scanning starting point of the circular track to be scanned, setting aberration correction data corresponding to the scanning starting point, and rotating the laser beam for a circle along the circular track from the scanning starting point, wherein the rotation angular velocity of the light beam is consistent with the annular scanning angular velocity in the scanning process to correct each point on the circular track to be scanned;
and step S3, repeating the step S2 until the scanning of all the N circular tracks is completed.
2. The aberration-free laser scanning method according to claim 1, wherein in the scanning stage, the laser beam is a pulsed laser beam, and the scanning spot pitch is the same on all circular tracks.
3. The aberration-free laser scanning method according to claim 2, wherein the laser frequency division N of the pulsed laser beam at the current circular track L Comprises the following steps:
N L ＝floor(f L /f L′ +0.5)，
wherein f is L′ Is the repetition frequency, f, of a pulsed laser beam L Is the fundamental frequency of the pulsed laser beam, and
d P the distance between scanning points on the circular tracks corresponding to different radiuses is defined, R is the radius of the current circular track, omega is the rotation angular velocity of the pulse laser beam, and floor () is a downward integral function.
4. The aberration-free laser scanning method according to claim 3, wherein a rotation angular velocity ω of the pulsed laser beam is:
5. the aberration-free laser scanning method according to claim 1, wherein in the preprocessing stage, the aberration at the scanning start point is corrected by a zernike polynomial.
6. An aberration-free laser scanning system, comprising:
a laser light source (1) for generating a laser beam;
the aberration correction unit (2) is used for carrying out wavefront aberration precompensation on the laser beam to ensure that a light spot focused by the laser beam has no aberration;
a beam deflection unit (3) for causing the laser beam to have a certain deflection angle;
the beam rotating unit (4) is used for carrying out annular scanning on the laser beam with a certain deflection angle and enabling the laser beam to rotate in the scanning process, and the angular speeds of the annular scanning at the rotation angular speeds are consistent;
a control unit (8) for slicing the scanning track into N concentric circular tracks, wherein N is a positive integer; taking any point on each circular track as a scanning starting point to obtain N scanning starting points; controlling an aberration correction unit (2) to obtain aberration correction data corresponding to each scanning starting point in the N scanning starting points; controlling the deflection angle of the beam deflection unit (3) and the rotation angular velocity of the beam rotation unit (4) to focus the laser beam on a scanning start point of an unscanned circular track, and setting aberration correction data corresponding to the scanning start point to rotate the laser beam by one circle along the circular track from the scanning start point; and controlling the aberration correction unit (2) to replace the aberration correction data for different unscanned circular tracks until the scanning of all the N circular tracks is completed.
7. The aberration-free laser scanning system according to claim 6, wherein the beam deflection unit is a galvanometer, an acousto-optic deflector, an optical wedge, a turning mirror or a movable micro mirror.
8. The aberration-free laser scanning system according to claim 7, wherein the aberration correcting unit is a spatial light modulator, a digital micromirror device, or a deformable mirror.
9. The aberration-free laser scanning system according to claim 8, wherein the beam rotation unit is a dove prism or an abbe-cuny prism driven by a motor or a K-shaped arrangement of three mirrors.
10. An aberration-free laser scanning system according to any of claims 6-9, further comprising: a relay unit between the beam deflection unit (3) and the beam rotation unit (4) for pupil matching of the beam deflection unit (3) and the beam rotation unit (4).
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| EP3281598A1 (en) * | 2016-08-09 | 2018-02-14 | Koninklijke Philips N.V. | Light based skin treatment device and method |
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