Research On Stray Radiation Suppression Of Space Optical System

Stray radiation suppression, combined with optical system design, mechanical structure design, surface material, radiation transfer, orbit simulation, is a crossing field and runs through the whole process of design, fabrication, testing, alignment and integration. The space optical system is susceptible to the influence of sun, earth, moon, and the radiance of these strong stray light sources are always higher than target with several oders of magnitude. If stray radiation is not suppressed successfully, the image quality and target resolution would degrade dramatically. To the visibal waveband optical system, the external stray radiation is the predominant issue. To the middle and long infrared waveband optical system, the internal and external stray radiations dominate together.In recent years, as the detection requirements of long distance, faint target, super wide field of view and multi-spectrum increase dramatically, the performance of stray radiation suppression limits the development of optical detection system. The traditional method is not able to meet these requirements, and a noval stray radiation suppression method is an urgent need. To concentrate on different requirements of space telescope with large aperture and long focal length, camera with wide field of view, infrared system with compact structure and low self radiation, this dissertation proposes a method which combined the optical design and stray light suppression design, and executes the stray light suppression during all the optomechanical design processes. On the premise of image quality, the stray radiation suppression ability is improved significantly by the way of mirrors spatial arrangement, infrared materials selection and extinction trap optimization.On the basis of a large number of articles, the detection make an comprehensive review the development situation at home and abroad, then illustrates the important position of stray radiation suppression. The main research work and results are shown as follows:1. A series theories and methods of baffle design are summarized, and a parameters caculation formula of wide FOV off-axis system is deduced. The input parameters of stray light analysis software are improved. A series optical forms applicable to space telescope are designed, and their stray light suppression behavior are analyzed and compared. A variety of stray light sources suppression budget and quantitative analysis are given.2. A rapid construction method of the initial spherical optical form based on analogy optical power distribution theory of retrofocus system is proposed. The bright stray light side due to vignetting is solved. A stray light suppression design of small avoiding angle and high suppression ratio is achieved and the stray light of optical and mechanical system is measured in the vacuum. The angle conversion formula between stray light source and optical axis of off-axis system is deduced, which is based on transformation matrix of homogeneous coordinate. The imaging area is sheared effectively, and the veiling glare index of off-axis system is resolved.3. A compact catadioptric LWIR system is presented as an example. The structures including baffle vanes, housing, field stop, Lyot stop, dewar vanes, nosecone and golden dot were optimized to achieve a further attenuation of self-emitting stray radiation. The radiance of internal and external stray radiation is reduced significantly under the premise of image quality.