Design Of Large-Caliber Long-Focus Airborne Ultraviolet Imaging Optical System Based On Free-Form Surface

In order to realize the functions of imaging,detecting,identifying,alarming,and detecting long-range ultraviolet targets,the airborne imaging system should adopt a large-caliber,long-focus ultraviolet optical system.Due to its compact optical structure,light weight,no color difference,and wide spectral range,it has important applications in airborne UV imaging optical systems.However,as the field of view expands,the off-axis aberration of the reflective optical system increases rapidly.By introducing optical free-form surfaces,using the non-rotational symmetry of the free-form surface and the powerful surface representation ability,different surface representations are used for each local sub-surface,which makes the free-form surface have good aberrations in the full field of view.Balance ability can significantly improve image quality.Therefore,we carry out related research and design work.The paper studies the free-form surface,optical system structure type and selection,initial structure calculation,optimization design,etc.The main contents are as follows:1)In the research of free-form surface theory,the characterization patterns ofpolynomial,radial basis function and NURBS surface are described.Theindirect and direct design method of free-form surface are analyzed.TheRayleigh,criterion method,point graph method and MTF curve in theevaluation method of optical system is discussed.2)In many optical system structural types,the optical structure types related tothis thesis are analyzed and compared,and useful technical suggestions areobtained,which provides structural selection basis for subsequent design research.3)For the three optical system structures of Cassegrain,RC and coaxial three-reverse,based on the same technical indicators,the corresponding initialparameters are obtained,and then the optical surface image of the free-formsurface is verified by design comparison.The qualitative influence,select theoptimal structure type,and briefly analyze the setting of the optimization function in the design.4)The calculation method of the initial structure of the coaxial three-reversestructure is studied.The coaxial triple-reflex optical system based on free-formsurface is optimized by Zemax software.A 250mm-diameter,1000 mm focallength large-caliber,long-focus airborne UV imaging optical system was designed.The results show that the designed airborne UV imaging system meets the requirements of technical specifications,has a simple structure and a relatively large field of view.Through tolerance analysis,it has the feasibility of manufacturing and assembly.This paper has its guiding role and significance for the in-depth study and technical design of large-caliber long focal length airborne UV imaging system.