Design of ultra-short throw ratio lens using annularly stitched aspheric surface

Stitched surfaces have the advantages of high degrees of freedom and flexibility, which can improve the performance of imaging optical system while reducing volume and weight. In this paper, a new type of surface, called annularly stitched aspheric surface (ASAS), is demonstrated. Firstly, the definition of ASAS is given, and it meets the C1 continuity condition. Then, a high-precision conversion method from traditional aspherical surface to ASAS is proposed to establish the initial system with this novel surface. The optimization strategy and implementation method are explained. Special constraints that are needed when optimize the system with ASAS is also mentioned. Finally, the ASAS is applied to the design and an ultra-short throw (UST) ratio projector objective lens is optimized. The total length of the optimized system is only 155mm, the maximum distortion value is only 1.36%, and MTF value of full field of view at 66lp/mm is higher than 0.3. The result shows that this new surface type can increase the degrees of freedom and flexibility to optical system, verifying the feasibility of ASAS.