CN-121978876-A - Three-dimensional diffraction master model high-speed direct writing system based on dynamic focusing

CN121978876ACN 121978876 ACN121978876 ACN 121978876ACN-121978876-A

Abstract

The invention discloses a three-dimensional diffraction master model high-speed direct writing system based on dynamic focusing, which relates to the technical field of laser direct writing and comprises a data processing module, a focusing control module, an energy modulation module, a scanning execution module, an error sensing module and an error compensation module. The data processing module receives three-dimensional point cloud data, calculates an optimal focusing position by the local curvature of the current scanning point, the focusing control module drives the piezoelectric ceramic micro-displacement platform to enable a focus to accurately fall on the surface of the scanning point, the error sensing module synchronously acquires the center coordinates of an actual light spot when each laser pulse is transmitted, and the error compensation module corrects driving voltage through closed loop control after comparison, so that focus drift is eliminated. All modules of the system work cooperatively to realize precise matching of the contours of the focus and the scanning point, avoid error accumulation, give consideration to direct writing speed and precision, achieve high-speed precise alignment writing of the three-dimensional diffraction master model, promote direct writing spatial resolution and contour re-engraving precision, and guarantee focus stability.

Inventors

Mo Tuba
LI JIAYI
SUN YUE
CAI XIAOGU
Di Make
WANG WEN
GONG SHIJIE
ZHAO ERSHUAI
LONG TAN
ZHANG CHI
ZHU ZHILIN

Assignees

南通诺瞳奕目医疗科技有限公司
北京诺瞳奕目医疗科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260408

Claims (10)

1. The utility model provides a three-dimensional diffraction master model high-speed direct writing system based on dynamic focus which characterized in that includes: the data processing module is used for receiving the diffraction master model three-dimensional point cloud data to be directly written and calculating an optimal focusing position of the laser beam in a scanning plane, wherein the optimal focusing position is determined by the local curvature of the current scanning point; The focusing control module drives the piezoelectric ceramic micro-displacement table to perform axial displacement according to the optimal focusing position, so that the focus of the laser beam is positioned on the surface of the current scanning point; The energy modulation module activates the acousto-optic modulator after the focus of the laser beam is adjusted in place, and controls the laser pulse energy to modulate according to the gray value of the corresponding point in the three-dimensional point cloud data of the diffraction master model; the scanning execution module starts a two-dimensional galvanometer scanning system to drive a laser beam to scan the current scanning area line by line, and the line by line scanning path is determined by the slice contour of the three-dimensional point cloud data of the diffraction master model; the error sensing module is used for collecting the actual spot center coordinates fed back by the photoelectric position detector when each laser pulse is emitted; The error compensation module is used for comparing the acquired actual light spot center coordinates with the ideal light spot center coordinates calculated in theory, calculating a current focusing error, and inverting and correcting the driving voltage of the piezoelectric ceramic micro-displacement platform through a closed-loop control algorithm according to the focusing error so as to eliminate focus drift; the modules work cooperatively, and the process from calculating the optimal focusing position to inverting and correcting the focusing error is repeatedly executed until the direct writing task of the whole three-dimensional point cloud data is completed.
2. The dynamic focus-based three-dimensional diffraction master model high-speed direct writing system as claimed in claim 1, wherein calculating an optimal focus position of the laser beam in the scanning plane based on the diffraction master model three-dimensional point cloud data comprises: The diffraction master model three-dimensional point cloud data comprises a space coordinate and a normal vector of a target structure; Extracting a grid model of a contour boundary and an internal filling area of a current processing layer from the diffraction master model three-dimensional point cloud data; Performing surface fitting on the grid model, and calculating a unit normal vector at each grid vertex; setting the optical axis direction of the laser beam as a reference direction, and calculating an included angle between a normal vector at each grid vertex and the reference direction; According to the size of the included angle, calculating the axial offset of the laser beam required to be adjusted for vertically entering the grid vertex by utilizing a geometric projection relation; Gaussian smoothing filtering is carried out on the axial offset required by all grid vertexes, so that jitter caused by local noise is eliminated; and mapping the filtered axial offset into a target displacement of the piezoelectric ceramic micro-displacement table, and taking the target displacement as the optimal focusing position.
3. The dynamic focus-based three-dimensional diffraction master model high-speed direct writing system as claimed in claim 2, wherein driving the piezo-ceramic micro displacement stage to perform axial displacement according to the optimal focus position comprises: Reading a current actual displacement value of the piezoelectric ceramic micro-displacement table, wherein the current actual displacement value is obtained by monitoring a capacitance sensor in real time; Comparing the calculated target displacement corresponding to the optimal focusing position with the read current actual displacement value to obtain displacement deviation; Invoking a displacement transfer function calibrated in advance, and converting the displacement deviation into a driving voltage increment; The driving voltage increment is added to the current working voltage of the piezoelectric ceramic micro-displacement table to generate a new control voltage; applying the generated new control voltage to the piezoelectric ceramic micro-displacement table to enable the piezoelectric ceramic micro-displacement table to generate corresponding axial expansion deformation; And after the piezoelectric ceramic micro-displacement platform enters a steady state, reading the actual displacement value again, and verifying whether the optimal focusing position is reached.
4. The high-speed direct writing system of a three-dimensional diffraction master model based on dynamic focusing as claimed in claim 3, wherein activating the acousto-optic modulator after the focus of the laser beam is adjusted in place, controlling the laser pulse energy to modulate according to the gray value of the corresponding point in the three-dimensional point cloud data of the diffraction master model comprises: analyzing the gray value of the current point to be processed in the diffraction master model three-dimensional point cloud data, wherein the gray value represents the depth-to-width ratio or the duty ratio of the microstructure at the current point; linearly mapping the analyzed gray value into a driving current value of the acousto-optic modulator, wherein the higher the gray value is, the larger the driving current is, and the higher the laser transmissivity is; loading the converted driving current value to the acousto-optic modulator, and controlling diffraction efficiency of the acousto-optic modulator so as to change the power of emergent laser; Maintaining the stable driving current of the acousto-optic modulator during the laser pulse duration period, and ensuring the consistency of laser energy output; and when switching to the next point to be processed, recalculating and updating the driving current value according to the gray value of the new point.
5. The high-speed direct writing system of a three-dimensional diffraction master model based on dynamic focusing as set forth in claim 4, wherein the starting the two-dimensional galvanometer scanning system to drive the laser beam to scan the current scanning area line by line comprises: projecting the three-dimensional point cloud data of the current processing layer onto a horizontal plane to generate a two-dimensional bitmap mask; Planning a path of the two-dimensional bitmap mask, generating a scanning path consisting of continuous straight line segments, and avoiding a non-processing area; Converting the generated scanning path into a position instruction sequence which can be identified by the two-dimensional galvanometer scanning system, wherein the position instruction sequence comprises deflection angles of an X axis and a Y axis; transmitting the position instruction sequence to the two-dimensional galvanometer scanning system at a set scanning speed, and controlling the swinging frequency of the reflecting mirror; and synchronously triggering the acousto-optic modulator while sending the position command, so that the emitting time of the laser pulse is strictly synchronous with the time when the vibrating mirror reaches the target position.
6. The dynamic focus-based three-dimensional diffraction master model high-speed direct writing system as claimed in claim 5, wherein the collecting the actual spot center coordinates fed back by the photoelectric position detector at the same time of each laser pulse emission comprises: an auxiliary detection beam coaxial with the main laser beam is arranged in a laser path, and is separated by a spectroscope and then irradiates the photoelectric position detector; capturing the position change of the auxiliary light spot caused by thermal effect or scattering by utilizing the photoelectric position detector when the main laser beam ablates the material; Performing differential operation on four-way quadrant signals output by the photoelectric position detector, and calculating the sub-pixel level position of the actual light spot center coordinate; And correlating the calculated actual light spot center coordinates with the theoretical deflection angle of the current vibrating mirror, and establishing a real-time light path pointing model.
7. The dynamic focus-based three-dimensional diffraction master model high-speed direct writing system as claimed in claim 6, wherein the comparing the collected actual spot center coordinates with the theoretically calculated ideal spot center coordinates to calculate the current focus error comprises: the coordinate position of the current scanning point and the calibration parameters of the two-dimensional galvanometer scanning system are called, and the ideal light spot center coordinate under the condition of no aberration is calculated; reading the center coordinates of the actual light spots fed back by the photoelectric position detector in real time; calculating the difference value between the actual light spot center coordinate and the ideal light spot center coordinate in the X-axis and Y-axis directions, and respectively recording the difference value as a transverse offset and a longitudinal offset; inputting the transverse offset and the longitudinal offset into a pre-trained aberration identification model as input vectors, and identifying the main aberration type and the main aberration size which cause the light spot deviation; the primary aberration type and magnitude are converted to an equivalent axial defocus amount as the focus error.
8. The dynamic focus-based three-dimensional diffraction master model high-speed direct writing system as claimed in claim 7, wherein said inverting the driving voltage of the correction piezoelectric ceramic micro-displacement stage by a closed-loop control algorithm according to the focus error comprises: Acquiring a hysteresis characteristic curve of the piezoelectric ceramic micro-displacement platform at the current temperature, wherein the hysteresis characteristic curve is obtained by a data index provided by a temperature sensor; Multiplying the calculated focusing error by the current system running speed to predict the defocusing trend at the next moment; introducing a feedforward compensation term on the basis of traditional proportional integral control according to the predicted defocus tendency to generate comprehensive control quantity; Performing predistortion treatment on the comprehensive control quantity by using an inverse model of the hysteresis characteristic curve to obtain a hysteresis-compensated driving voltage correction value; and directly writing the obtained driving voltage correction value into a driving circuit of the piezoelectric ceramic micro-displacement table to finish dynamic compensation of the focal position.
9. The dynamic focus-based three-dimensional diffraction master model high-speed direct writing system as claimed in claim 8, wherein the repeatedly performing the steps from calculating the optimal focus position to inverting the corrected focus error until the direct writing task of the whole three-dimensional point cloud data is completed comprises: Establishing a global counter, and recording the number of scanning lines or points cloud mass which are successfully processed; after finishing the processing of one scanning line at a time, checking whether the numerical value of the global counter reaches the preset total line number; if not, automatically loading the point cloud data of the next scanning line, and re-executing the cycle from the curve fitting to the focus compensation; When the layers are in transition, suspending laser output, and adjusting the height of the piezoelectric ceramic micro-displacement table in advance by one step according to the thickness data of the next slice layer so as to realize interlayer seamless connection; And stopping the two-dimensional galvanometer scanning system and the acousto-optic modulator when the numerical value of the global counter reaches the preset total line number.
10. The high-speed direct-writing system of a three-dimensional diffraction master model based on dynamic focusing as claimed in claim 9, further comprising a data recording module for recording a focal position change curve and a laser energy modulation sequence in the whole direct-writing process, wherein the data recording module is specifically as follows: In the direct writing process, reading focus position data from the piezoelectric ceramic micro-displacement table controller at a fixed sampling frequency to form a time sequence; simultaneously, reading an energy setting value corresponding to each laser pulse from the acousto-optic modulator driver to form an energy sequence; aligning and combining the focus position data sequence and the energy setting value sequence according to a time stamp; removing abnormal points from the combined data sequences, and reserving data characteristics in a normal processing state; and storing the processed data in the form of a binary file, and attaching a processing time stamp, a material type and a system configuration parameter to a file header to generate the direct writing process log.

Description

Three-dimensional diffraction master model high-speed direct writing system based on dynamic focusing Technical Field The invention belongs to the technical field of laser direct writing, and particularly relates to a three-dimensional diffraction master model high-speed direct writing system based on dynamic focusing. Background The high-speed precise alignment writing of the three-dimensional diffraction master model is a key link in the preparation of a diffraction optical element, in the prior art, a three-dimensional diffraction master model direct writing system generally adopts fixed focusing parameters or determines the focusing position of a laser beam according to the height information of an integral scanning area, and drives the laser beam to scan line by line through a two-dimensional galvanometer, and the energy modulation module is matched to realize the regulation and control of laser pulse energy so as to complete the master model direct writing task. In the aspect of error control, the existing system mostly adopts a spaced error acquisition mode, namely, spot position information is acquired once every certain scanning period, and then the focusing position is corrected according to the acquired information. In the prior art, the local contour characteristics of a single scanning point are not considered in the determination of the focusing position, and when the scanning point has local curvature change, the fixed focusing parameters or the focusing mode based on the whole height cannot enable the laser beam focus to accurately fall on the surface of the current scanning point, so that focusing deviation is easy to generate, and direct writing precision is influenced. Meanwhile, the interval type error acquisition and correction mode cannot timely capture focus drift during each laser pulse emission, hysteresis exists in error correction, focus errors are easy to accumulate, focus stability is insufficient in the direct writing process, direct writing speed and accuracy are difficult to achieve, and the requirements of high-accuracy and high-speed direct writing of the three-dimensional diffraction master model cannot be met. Disclosure of Invention The present invention aims to solve at least one of the technical problems existing in the prior art; Therefore, the invention provides a three-dimensional diffraction master model high-speed direct writing system based on dynamic focusing, which comprises the following steps: the data processing module is used for receiving the diffraction master model three-dimensional point cloud data to be directly written and calculating an optimal focusing position of the laser beam in a scanning plane, wherein the optimal focusing position is determined by the local curvature of the current scanning point; The focusing control module drives the piezoelectric ceramic micro-displacement table to perform axial displacement according to the optimal focusing position, so that the focus of the laser beam is positioned on the surface of the current scanning point; The energy modulation module activates the acousto-optic modulator after the focus of the laser beam is adjusted in place, and controls the laser pulse energy to modulate according to the gray value of the corresponding point in the three-dimensional point cloud data of the diffraction master model; the scanning execution module starts a two-dimensional galvanometer scanning system to drive a laser beam to scan the current scanning area line by line, and the line by line scanning path is determined by the slice contour of the three-dimensional point cloud data of the diffraction master model; the error sensing module is used for collecting the actual spot center coordinates fed back by the photoelectric position detector when each laser pulse is emitted; The error compensation module is used for comparing the acquired actual light spot center coordinates with the ideal light spot center coordinates calculated in theory, calculating a current focusing error, and inverting and correcting the driving voltage of the piezoelectric ceramic micro-displacement platform through a closed-loop control algorithm according to the focusing error so as to eliminate focus drift; the modules work cooperatively, and the process from calculating the optimal focusing position to inverting and correcting the focusing error is repeatedly executed until the direct writing task of the whole three-dimensional point cloud data is completed. Further, calculating an optimal focusing position of the laser beam in the scanning plane based on the diffraction master model three-dimensional point cloud data comprises: The diffraction master model three-dimensional point cloud data comprises a space coordinate and a normal vector of a target structure; Extracting a grid model of a contour boundary and an internal filling area of a current processing layer from the diffraction master model three-dimensional point cloud data; Performi