Research On Design Of Wide Field Of View High Resolution Imaging Optical System

With the development of electro-optical imaging technology,to obtain wider spatial range and higher resolution objective image information,electro-optical imaging system are gradually developed towards wide field of view and high resolution.As far as single optical system is concerned,total information content is mainly determined by the number of effective pixels of image sensor.Once the total information content is determined,field of view and resolution becomes a pair of contradictory parameters,that is,it is impossible to increase field of view and resolution simultaneously.Generally speaking,the resolution of optical systems with wide field of view is low;the field of view of optical systems with high resolution is narrow.So,resolving the contradiction between field of view and resolution,achieving wide field of view and high resolution imaging is a research focus in the field of optics.Optical systems with wide field of view and high resolution have wide prospects of application in military and civilian areas like space remote sensing,aerial reconnaissance,security monitoring,astronomical observation,heritage conservation,and so on.This dissertation study the subject of wide field of view and high resolution imaging,focus on the design of off-axis three-mirror optical system,off-axis four-mirror optical system,monocentric multiscale optical system and optical system with curved Petzval image surface.Four main research contents of this dissertation are as follows:1)Research on the design of off-axis three-mirror optical system.Based on the law of reflection and sine condition,W-W differential equaitons for solving coaxial three-mirror optical system initial structure are derived.Profile data points of the secondary and tertiary mirros are obtained by solving the differential equations,fitting them into W-W surface by polynomial fitting,and the coaxial three-mirror initial structure with aspherical secondary and tertiary mirror is obtained.Take this initial structure as starting point,using even polynomial aspheric,a F/4 off-axis three-mirror optical system with 1.2m focal length and 18o ? 4ofield of view is designed.The Modulation Transfer Functions(MTFs)of entire fields of this system are above 0.5 at 50 lp/mm,the image quality is good.In addition,the conic primary mirror,aspherical second and tertiary mirror of the off-axis three-mirror system are not decentered or tilted,which can effectively reduce fabricate cost and alignment difficulty.2)Research on the design of off-axis four-mirror optical system.Vector aberration theory of off-axis optical system and the nodal behavior of aberrations are studied.Aberrations of coaxial four-mirror optical system are analysed,then objective function which is composed of weighted aberration coefficients and structural constraints is constructed.Parameters of initial structure are solved through optimizing objective function by genetic algorithm,and coaxial four-mirror initial structures with good image quality and specific optical structure are obtained.Select the intial structure with the smallest obstruction ratio as the starting point,the compact off-axis four-mirror optical system with 1.2m focal length,30o ? 4ofield of view and F/4 is designed by using Zernike polynomial freeform surface.The MTFs of entire fields are above 0.52 at 40lp/mm.3)Research on the design of monocentric multiscale optical system.Monocentric multiscale design can resolve the contradiction between field of view and resolution,and is the best strategy to achieve wide field of view and high resolution at present.The monocentric multiscale design theory is studied.The focal length,achromatic condition and aplanatic condition of two layer monocentric lens are derived,the image surface shift of the monocentric lens is analysed.Aberrations of relay microcamera are analysed,field overlap of two adjacent microcameras and the packing pattern of relay microcameras on a spherical surface are studied.Based on the theory of monocentric multiscale design,the F/2.8 gigapixel moncentric multiscale optical system with 35 mm focal length and 120o ? 60ofield of view is designed.The MTFs of entire fields are above 0.3 at 270 lp/mm.This system is composed of 104 microcameras which are close packing based on icosahedron,and the packing density is 76.6%.Finally,the tolerance analysis of this system is finished.4)Research on the design of optical systems with curved Petzval image surfaces.To accurately evaluate distortion relative to curved image surface,arc distortion is proposed.A F/2.8 curved Petzval lens with 100 mm focal length and 40ofield of view is designed by constraining image surface coincide with Petzval surface through building Code V macros.MTFs of entire fields are above 0.69 at 100 lp/mm,relative illumination is larger than 92.4%,and arc distortion is in 0.5%.Compared with traditional optical systems,optical systems with curved Petzval image surfaces have many optical advantages: comapt optical layout,less optical elements,strong aberration correction ability,uniform optical power distribution and good degree of lens symmetry.Optical systems with curved Petzval image surfaces provide a new developmental orientation for wide field of view and high resolution imaging.