| With the development of satellite-based imaging telescope,the high-resolution demand requires the aperture and focal length of the optical system larger and larger.The high-resolution telescope is easily affected by the space microgravity and thermal environment,and vibration of the launch process,which leads to the degradation of imaging performance.At present,the passive compensation methods are often applied at space cameras,but these ways show the limited ability to correct wavefront aberrations such as spherical,astigmatism and coma aberration caused by the space environment.So,a new method using the active deformable mirror is used to correct the wavefront aberration.The thin flat deformation mirror is deformed by the high number of actuators on the satellite and the actuators configuration is complex and consumes the large resources of satellite.The thesis proposes a method of using a deformation mirror with variable thickness distribution which can be applied to the space camera,in order to simplify the actuation design of the deformable mirror.Two actuators are used to compensate the spherical aberration and astigmatism.This method can effectively improve the wavefront quality of the system,relax the thermal control requirements,and reduce the difficulty of the development of the spaceborne optical-mechanical system.The main contents of the thesis include:(a)The mathematical calculation and modeling design of the deformation mirror with variable thickness distribution.The theoretical relationship between the wavefront aberration expression and the thickness distribution of the deformable mirror is established based on the theory of elasticity.The calculation ways of the thickness distribution corresponding to various aberration modes are obtained.The variable thickness relative to three different loading and force boundary conditions is calculated and designed to correct spherical aberration and astigmatic.The mathematical modeling of the deformed mirror is verified by simulation and comparison of the mirror surface shape.(b)The optical-structural simulation and analysis of the deformation mirror with variable thickness distribution.The process of optical-structural simulation combines the finite element analysis with optical surface fitting calculation and evaluation.After the model is loaded at stresses,its simulation and evaluation of the aberration compensation effect are carried out.The simulation results show that the deformable mirror can greatly reduce the stress concentration effect and the print-through effect,and produce the well-matched spherical and astigmatism aberration.The amounts of spherical aberration and astigmatism are respectively proportional to the loaded force.The deformable mirror can effectively compensate the spherical aberration of the optical system with Zernike polynomial Z9 becoming zero.The remaining wavefront error RMS of the optical system is reduced by 80% and the PV value error is reduced by 66% after compensation of the whole wavefront.(c)The actuation scheme and structure design of adopting dual actuators to compensate spherical aberration and astigmatism.A feasible optical structure of the deformable mirror with variable thickness based on the mathematical model with the edge-driven method is used as the driving method of the deformable mirror.The simulation analysis is carried out on the model.The simulation result is similar to that of the mathematical model,and the dual compensation of spherical aberration and astigmatism can be realized.(d)Experimental verification of the compensation effect of the deformable mirror.A deformable mirror test device is built and applied to an afocal optical system.The results show that the deformable mirror with variable thickness distribution designed can produce the spherical and astigmatism aberration.The deformable mirror can compensate the spherical aberration and astigmatism produced by its own manufacture error,and the wavefront error of the afocal optical system.The residual aberration RMS error of the system is reduced by 36.8%,and the PV value error is reduced by 16 %after compensation.This thesis focuses on the key technology of the deformable mirror in order to compensate the wavefront distortion error of the space camera.The method of calculating the variable thickness distribution of the active mirror is derived.The integrated simulation analysis of the optical-mechanical of deformation mirrors with variable thickness distribution is carried out.The deformable mirror is designed and driven by two actuators which greatly simplify the number of actuators and decrease the driving difficulty.The spherical aberration and astigmatism are effectively compensated,and the wavefront quality of the system is improved.The designconfigurations,methods,prototype and experimental results of the deformable mirror with variable thickness distribution applied to the satellite-based camera are introduced in detail. |
