Research On Infrared Dual-band Athermal Detection Imaging System With Long Focal Length And Wide Spectrum

With the fast development of modern science technologies and detector fabrication technologies,the common aperture infrared dual band athermal imaging technology has been widely employed in the space and national defense industries.The technology considers the demand for target detection by using dual band and the demand for athermal design.It can not only improve the target detection and recognition ability effectively,but also work under severe temperature environment.Meanwhile,the cost,the size and weight of the system can be reduced,which is of great significance for space optical instruments.Based on the common aperture optical structure,the dissertation proposes three solutions for the infrared dual band athermal imaging system.The system initial structure analytical expressions are deduced.At last the common aperture catadioptric infrared dual band athermal optical structure are adopted considering the engineering feasibility.A catadioptric common aperture infrared dual band optical system with long focal length and wide spectrum is fabricated.The main research contents and contributions are summarized as follows:(1)The background and significance of infrared dual band athermal imaging technology are introduced.The influence of temperature on the infrared optical system are analyzed,such as curvature radius,thickness of optical lens,refractive index,distance between the neighboring two optical lenses,aspheric coefficients and diffractive surface parameters.And the corresponding mathematical models are established.For the influence of temperature on the infrared optical system,the dissertation studies the mechanical athermalization,passively mechanical athermalization,actively optical athermalization methods.The implementation,performance,reliability,weight,cost,environmental stability and maintainability of these three methods and comapared.(2)The characteristics of modern infrared athermal optical system are analyzed.The design types of infrared dual band athermal optical system are proposed.A reflective common aperture optical structure with long focal length and wide spectrum is proposed.The analytical expressions of initial structure for coaxial reflective system with four mirrors is deduced.And a design example is given.As the design requirements for higher image quality,the dissertation proposes a catadioptric common aperture infrared dual band optical structure,in which the common optical elements are composed by both reflective mirrors and refractive lenses.The analytical expressions of initial structure for the system is deduced.In order to solve the aspheres inflection in the system,this dissertation proposes an effective aspheres inflection removal method by solving the first derivative and the second derivative of the sagittal height at different radii.This mothod has been applied in the catadioptric common aperture infrared dual band optical system with long focal length and wide spectrum as verification example.(3)In the dissertation,the aberration characteristics of diffractive optical element are analyzed,and the diffractive efficiency of diffractive optical element is explored.The dispersion and temperature characteristics of diffractive optical element are studied.For the aberrations induced by the spectroscope in the refractive optical system,the dissertation proposes an effective aberration correction method based on diffractive optical elements which has the arbitrary phase modulation characteristics.Compared with the existing methods correcting by using spheres or ashpheres,the proposed method shows superiority in the designed example.Based on the special dispersion and temperature characteristics of diffractive optical element,this dissertation proposes a hybrid common aperture infrared dual band optical structure with long focal length and wide spectrum,which achieves good performance.(4)The dissertation analyzes the influence of ghost on optical system and proposes a method that can analyze the ghost quickly.As the verification example,the dissertation analyzes the ghost in the designed catadioptric common aperture infrared dual band optical system with the proposed ghost analysis method.(5)The three athermal optical structures are compared and analyzed.As a result,the common aperture catadioptric infrared dual band athermal optical structure are adopted considering the engineering feasibility.A catadioptric common aperture infrared dual band optical system with long focal length and wide spectrum is fabricated.The image quality of the optical system is evaluated according to the encircled energy,and the experiment verifies the validity of the proposed scheme.