Study On Collimating System For Space Solar Telescope

Since there are compelling advantages observing solar activities from space over ground-based observations,space solar exploration has drawn more and more attention and concentration among many countries all over the world in recent years.Following the world’s pace,Chinese scientists plan to self-design our own solar observing probe: Deep-space Solar Observatory,which will promote breakthroughs of space exploration and solar physics research and lift our country to a world-leading level at solar exploration.Magnetic Field Telescope onboard Deep-space Solar Observatory adopts reflector-refractor system,which have the advantages of small central obscuration,high resolution,compact structure and so on.To achieve resolution of 0.1aresec to 0.15 arcsec and image quality of diffraction limit,optical design of collimating lenses is an essential segment.Because of special working environment and diffraction limiting image quality requirement,optical design of collimator is much harder than normal telescopic objectives.In addition,correction of secondary order spectrum is a key and difficult point owing to big relative aperture and long focal length.So research on optical design of collimating lenses system is of great significance to the whole telescope.Applying the method of confocal optimization,a scheme collimator system is given in this paper.Firstly,a brief introduction to optical system of Magnetic Field Telescope onboard Deep-space Solar Observatory is made and the influence of temperature change on optical system is deduced.Then basic theories of optical system design consist of primary aberration theory and athermalization design theory are illustrated,based on which athermalization equations and chart are established.Thirdly,the parameters of collimator are calculated according to the overall technical requirements of Magnetic Field Telescope system.Cooke Triplet is chosen as an initial structure after summarizing the properties of general telescopic objectives.The parameters of initial structure is acquired using Wave-deviation Method.The collimating lenses of MFT is well designed,satisfying the specifications of spectral region from 393 nm to 656 nm,focal length of 155.6mm,relative aperture 1/3.5,full field of view of 1.485°.After optimized and re-optimized,collimator system of high image quality is eventually achieved.Finally,image quality evaluation methods,based on which the image quality of well-designed collimator is evaluated,are simply illustrated.The results show that the resolution is reaching diffraction limit at full field of view,meeting performance goal of telescope.