Research On Non-similar Imaging Technology In The Quadric Screen Projection System

Along with booming development of culture industry,the image engineering based on digital image technology have entered a rapid developing period in cultural tourism,entertainment,science and education area.As an imaging technology that could resolve the curve screen mapping problem effectively,non-similar imaging technology has been applied increasingly.In a projection system applying non-similar imaging technology,one usually uses a non-symmetrical projector layout,curve screen,fisheye lens and projection lens with ultra-field characteristic.Such system sacrifices similar imaging to acquire special visual effect and an easier projection allocating plan and a rational audience position distribution,which leads a complicated “object-image” optical conjugate relationship.However,conventional system design plan and conventional lens mapping regulation usually cannot resolve engineering problem or cannot realize maximum utilization of pixel.Here,we aim at the study of non-similar imaging technology,including optical system parameters obtaining of projection system,fisheye lens design of special performance and specific mapping regulation,relative illumination analysis of lens image surface,and so on.To quickly calculate all parameters of multichannel complicated curve screen projection system,a method to rapidly get optimum system parameters—two-dimensional scan method is proposed,that is,first,the function of different relationship between sorts of system parameters in system is discussed,the precise expressions of important parameters are presented.Then based on the result expressions,simulation or calculation software is used to create programs,2-D data is scanned assuming projector position as variable,and then combining optimum parameter judging principle,to find the optimum system parameter solution.To solve the universality problem of matching mainly used projectors screen of different types and specifications,a basic method of designing universal zoom fisheye lens is presented,with the simplest structure to achieve universal purpose.Based on the characteristic and universal features of projection fisheye lens,the determination of optical structure in target system is made.Through selecting optimum collocation of two-component zoom unit initial condition parameters,to linearly reform the position moving curve of compensation unit,and to synchronously build the two cam curves into standard helix;through rationally controlling spherical aberration of front fixed unit and focal distance of rear fixed unit,to make image surface position stable during zoom process.To improve the pixel utilization rate of dome screen projection system with single projector,the design concept of bi-direction anisotropic digital fisheye projection lens is proposed,to gain same largest field acquiring confirmed image height ratio in two perpendicular dimensions.By analyzing the characteristics of cylindrical lens,the function relationship of astigmatism and the focal length of cylindrical lens is given,and the focal length distribution relationship in sagittal direction and meridian direction are reported.The structure of bi-direction digital fisheye projection lens is analyzed the gradual changing focal lengths along dimensions are produced by introducing cylindrical lens structure,to achieve image height difference in sagittal dimension and meridional dimension,and to form a mapping regular of bi-direction anisotropy.To improve the pixel utilization rate of circular screen projection system with single projector,the method of building the structure of bi-direction anisotropic digital fisheye projection lens is proposed,to make different largest field acquiring confirmed image height ratio of at two perpendicular dimensions,and to form a mapping regular of bi-direction anisotropy,the basic steps and processes of constructing a bi-direction anisotropic fisheye lens for a circular screen are presented.In order to analyze the distribution law of illumination of image plane in a wide-angle lens system quantitively,the limitation of the existing calculation method is analyzed,a method to calculate luminous flux by ray tracing based on aperture stop constraint mode is introduced,the expression of feature points and the illuminated area of first optical surface from extra-axial ray under the control of aperture stop is presented,through vector analysis and derivations.According to and the condition and the law of Lambert reflector,from object space of lens,two kinds of lens image illumination analysis modes under conjugated condition are built.For similar imaging system and non-similar imaging system with large field,the expression of image illumination and relative illumination are derived respectively,and the basic scheme to increase relative illumination during optical designing is proposed.