Large Aperture Fast Steering Mirror Profile Test System Based On Wavefront Measurement

To achieve the purpose of controlling the output beam pointing and suppressing jitter in the high-energy laser system,the technology of the output beam deflected by controlling the external posture change or internal attribute change of the light guide medium is called light beam pointing control.With the development of modern technology,the requirement of light beam pointing control technology is getting higher and higher.The fast steering mirror(FSM)is one of the most important core components in realizing fast and high precision beam pointing control system.The large aperture fast steering mirror surface figure test system based on wavefront measurement with an effective aperture of 400 mm has a working wavelength of 633nm.The system is mainly composed of an off-axis shrink-beam system and a focal plane system to achieve real-time detection of the mirror surface figure error when the large aperture fast steering mirror is working.The paper describes the design parameters of the test system and the selection of optical element.The optical system is modeled and simulated.At 0.05° field of view of the optical system,the PV is 0.008λ(RMS,λ=633nm)and the RMS is 0.006λ(RMS,λ=633nm)The design scheme of the mechanical system of the large aperture fast steering mirror surface figure test system based on wavefront measurement is finished,and the effect of temperature variation on the test system is obtained based on the integrated optical-mechanical-thermal analysis.The thermal analysis of the fast steering mirror surface figure test system is completed using finite element software.The primary and secondary mirror shape are fitted with Zernike polynomials.The aberrations are analyzed using Zemax software,proving that the test system has temperature stability.The machining method of the primary and secondary mirrors of the large aperture fast steering mirror surface figure test system based on wavefront measurement is described.The surface shape accuracy for mirrors meet the design requirement using interferometer.The off-axis shrink-beam system of the surface figure test system is adjusted and tested.The wavefront error of the system is 0.046λ(RMS,λ=633nm),proving that the test system has high stability.To achieve high precision and rapid quantitative analysis of wavefront aberrations,a wavefront analysis method of irregular aperture shape and a single interferogram based on deep learning are proposed.The wavefront image with irregular aperture shape is used as the input image,and the corresponding wavefront image with circular aperture is output.The corresponding Zernike coefficient are obtained by fitting the wavefront image with circular aperture through MATLAB to obtain wavefront aberration information.A single interferogram is used as the input image,the Zernike coefficient are output,and the wave aberration information can be obtained.