Study On Design Method Of Modern Large-aperture Long-focus Full-frame Zoom Optical System

Imaging is the main theme of optical design.With the rapid development of modernization,the demand and requirements for imaging lenses in various industries are gradually increasing.For example,in the fields of photography,security,scientific research,medical treatment,industry,and etc.,put forward higher requirements for the field of view,the aperture,the target image size of the lens,and the zoom ratio.At present,high-quality lenses such as medium format and full-frame are occupying the mainstream of the industry,but the domestic related technology level is at the primary stage of development and the lens in the high-end field are still monopolized by foreign countries.The Gaussian structure calculation method of the traditional continuous zoom system is difficult to meet the requirements of large aperture,long focal length and fullframe zoom lens.This thesis proposed three optimization algorithms for continuous zoom Gaussian structure optimization based on generalized Lagrangian multiplier method,interior point method and modified sequence quadratic programming.The zoom Gaussian structure optimization algorithm combined the given system parameters with the primary aberration theory to construct a custom target optimization function,and adopted a positive – negative – positive – negative-positive five-group structure with reasonable aberration distribution.The universal parameters were optimized by three algorithms to obtain focal length of 30.356-100.243 mm,F/# 2.8(constant),fullframe continuous zoom system Gaussian structure with five moving groups,and the advantages and disadvantages of the Gaussian structure of the zoom lens calculated by the three optimization algorithms were compared and analyzed.In view of the robustness of the interior point method and its advantages in high-magnification ratio optimization calculation,this thesis uses the interior point method to optimize the structure to obtain the focal length of 21.421-109.835 mm,F/# 2.8(constant),fullframe continuous zoom system Gaussian structure with six moving groups.The actual lens group was used to replace the Gaussian structure of five moving groups obtained by Generalized Lagrangian Multiplier,and the initial structure of focal length of 33-100 mm,F/# 3.0(constant),full-frame continuous zoom system with five groups was obtained.By controlling the consistency of the principal plane of the actual system and the Gaussian structure,the cam curves have good linearity.In addition,the Gaussian structure of six moving groups obtained by interior point method were subjected to the actual group replacement,the principal plane of the actual zoom system was controlled to be consistent with the Gaussian structure,and the focal length of 24.67-107.00 mm,F/# 4.0(constant)was obtained,which is a reasonable initial structure for a full-frame continuous zoom optical system.Using the initial structure obtained from the above design,by reducing the constraint on the cam curve(increasing the optimization design freedom),and advanced aberration correction of aspherical surface was introduced.The focal length of 33-100 mm,F/# 3.0(constant),full field of view 24.42°-66.51°,full-frame continuous zoom system with five moving groups and focal length of 22.183-109.808 mm,F/# 3.0(constant),full field of view 22.28°-88.58°,full-flame continuous zoom system with six moving groups was finally obtained.The full field of view modulation transfer function of the final design zoom system have greater than 0.2 at 50 lp/mm and greater than 0.5 at 30 lp/mm,meeting the full-frame high-quality imaging requirements.