Research On The Optical System Of Catadioptric Ultra-short Throw Projection Display

With the increasing demand for display size,it is difficult for traditional liquid crystal displays to balance price and performance at the same time.Therefore,projection display technology has gradually become the mainstream of market research and has developed rapidly.As one of the cutting-edge products,ultra-short-throw projection display technology plays an indispensable role in the display field due to its large screen size,ultra-short focal length,large field of view,high brightness,clear image quality,and small space occupancy rate.The dissertation gives an overview of modern display technology,analyzes the existing main projection technology and product parameters,and calculates the relevant parameters of the ultra-short throw projection display optical system required in this dissertation.The advantages and disadvantages of the three existing ultra-short-focus projection structures are analyzed,the catadioptric structure is determined as the structure of this design,and the main image quality evaluation methods of ultra-short-focus projection are discussed.In order to establish the initial structure of the catadioptric ultra-short-focus projection system,the focus is on the construction and calculation of the mirror surface.Taking the vertex of the rotating paraboloid as the coordinate origin and the symmetry axis of the rotating paraboloid as the z(4)axis,a three-dimensional Cartesian coordinate system is established.According to the principle of spatial geometrical optics,the coordinate expressions of 9 representative image points of chief ray,meridian ray,and sagittal ray under different fields of view are deduced on the ideal image plane.According to the functional requirements and the principle of geometric optics,the constraint equation is established,and the initial surface shape of the parabolic mirror is obtained by solving.Based on the modeling of the reflector,the system parameters of the refraction part are allocated and specifically designed,and the two are combined and optimized as a whole.The system finally consists of 13 lenses in 9 groups and a parabolic mirror.The focal length is 4.37 mm,the full field of view is 140°,and the throw ratio is 0.3.It can project a60-inch image ultrashort projection objective at a projection distance of 420 mm,all fields of view The MTF values are all greater than 0.6@66lp/mm,the RMS value of the system is less than the size of a single pixel of the DMD chip,the TV distortion meets human vision requirements,and the remaining residual aberrations are all less than the focal depth of the system.The tolerance analysis of the system shows that the system has Good tolerance performance.