Research On Optical Design Of Space Deep Ultraviolet Camera System

Space deep ultraviolet detection technology is an emerging method of space exploration which mainly receives the strong absorption lines and emission lines of various elements of various celestial bodies in the deep ultraviolet band,and is used in the research of space exploration such as data observation in ultraviolet astronomy and celestial model construction.As the core part of the space deep ultraviolet detection device,the deep UV optical system directly determines the performance of the detection system.In order to meet the requirements of large field of view,high precision,thermal stability and low emission cost of space detection system,transmission photographic system plays an important role in the detection application.However,due to the limitation of available materials in the deep ultraviolet band,so normally the achromatism is difficult to correct,and the athermalization is hard to guarantee and the structure is more complicated.In this dissertation,based on the analysis of the design process of deep UV optical system,considering the limitation of available materials in the deep UV radiation band and the large dispersion of materials,an initial structure athermal design method of splitting and regrouping is proposed.Firstly,the dispersive and thermal residuals of the system are calculated according to the athermal and achromatic equations.Then,the number of system groups is determined according to the design parameters.Secondly,the optimal dispersive and thermal residuals are selected according to the boundary conditions,and combined according to the principle of pupil connection.Finally,the initial structure of the space deep ultraviolet photography optical system is built by simple adjustment.Based on the initial structure of splitting and regrouping design,the performance of the system is improved by adding a special surface without affecting the system transmittance.Although aspheric surface can improve the optical performance of the system,the final design structure is still complicated and special materials are used.In contrast,the refractive diffractive hybrid system uses the imaging characteristics of diffractive optical elements to remove the special materials in the system,reduces the number of lenses,and improves the optical performance of the system.Finally,the athermal design process of the deep UV photographic optical system is realized and the structure is simplified.The imaging characteristics of single-layer diffractive optical element in the deep UV band are analyzed.According to the practical application,based on the method of combining the design of splitting and regrouping athermalization and single-layer diffractive optical element,this dissertation realizes the athermalization design of space deep UV photography optical system which focal length is 110 mm,the F number is 3.5 and the field of view is 20 ° in the range of-60 ? ?+100 ?.The average MTF is greater than 0.68 at the Nyquist frequency of 18.5lp/mm.The maximum value of the bandwidth integral diffraction efficiency is 98.99% when the design wavelength of single-layer diffractive optical element is 248.7nm in the range of230nm?270nm,and the impact of temperature is small.The results show that this method can provide a reference idea for solving the problems of thermal defocusing,complicated design process and structure of deep UV transmission optical system in a wide temperature range.