| Atmospheric turbulence distorts the optical wavefront,affecting the image quality of astronomical telescopes.With the invention and application of adaptive optics system,the distorted wavefront is actively corrected to improve the resolution of astronomical telescopes.The development of electronic,mechanical and material technologies has driven the application of adaptive optics in high-power lasers,free-space laser communications and retinal imaging,and the variety of deformation mirrors used in adaptive optics to correct aberrated wavefronts is increasing according to the needs of different application situations.Compared with piezoelectric ceramic deformation mirrors,thin film deformation mirrors and microelectromechanical system deformation mirrors,voice coil deformation mirrors have the adavantage of large modulation,fast response,no hysteresis and high linearity.The objective of this paper is to design an efficient small-aperture voice coil deformation mirror for laboratory use and to simulate the performance of the deformation mirror numerically by means of finite element simulation.The details of the study are as follows:(1)A dynamic magnetic voice coil actuator for deformable mirror is designed and its structural parameters are optimized through equation derivation and finite element simulation.The innovative dual-coil structure greatly improves the output force reaches 0.43 N and has a good linear relationship with the control current,and the actuator constant reaches0.9,which is 50% higher than the actuator constant of the ESO's voice coil actuator for the Multiple Mirror Telescope adaptive optics system.The design also takes into account the heat generated by the coil and reduces the imapact of heat on the mirror.(2)A 37-unit voice coil deformation mirror was designed with a positive hexagonal arrangement of the actuator array,and the centrosymmetric arrangement simplifies the process of extracting the driver influence function.The deformation capabilities of K4 glass,K9 glass and ZERODUR microcrystalline glass materials were compared through finite element simulation,and the choice of K4 glass was determined for the mirror material.A Zernike polynomial fitting method was used to fit the mirrors,and the ability of the mirrors to fit low-order aberrations was analysed.The modal simulation of the mirror surface was carried out to obtain the intrinsic frequency of the mirror to provide the necessary parameters to avoid resonance phenomena during operation.(3)In order to investigate the influence of the voice coil actuator heat on the performance of the deformed mirror under operating conditions,the heat generation of the voice coil and the change of the deformation capability of the mirror under the corresponding temperature conditions are simulated by multi physical fields coupled finite element analysis.The results show that the steady state temperature of the coil will reach 40°C at 0.5A input control current,and the mirror deformation capacity will increase by 11% at 40°C compared to20°C.The large difference in mirror deformation capability at different temperatures affects the control accuracy of the voice coil actuator's control of the mirror shape,leading to a reduction in the ability to correct for distortion wavefonts and new requirements for the optimization of the influence function and control algorithm.This work has completed the design and simulation verification of the high-efficiency voice coil driver and the 37-actuator voice coil deformable mirror,and obtained the optimized design method of the voice coil deformable mirror,which lays a good foundation for the design of the voice coil deformable mirror with a large number of actuators;At the same time,the design methods and ideas proposed in this work will be valuable for voice coil actuators used in tilt mirrors and active optics.This is of great significance for reducing the cost of deformable mirrors,promoting the application of adaptive optics technology in more fields,and promoting technology progress in astronomical observation,laser atmospheric transmission,and human eye retinal imaging. |
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