Optical Design Of Large Zoom Ratio Security Surveillance Lens

The overall imaging effect of the video surveillance system was directly determined by the security surveillance lens as the core component of the video surveillance system.With the advancement of "China Skynet",although the security zoom surveillance lens has been widely used in the market,the zoom surveillance system was proposed in terms of large zoom ratio,large relative aperture,wide spectrum,miniaturization and high image quality.In order to achieve higher requirements,it has become a hot and difficult point of current design.Mainly based on market demand and corporate index requirements,the optical design of a day and night security zoom surveillance lens with a total length of less than 166mm,an F number ranging from 1.6 to 4.5,a zoom ratio of 22 times and a pixel of up to 2 million has been completed.Firstly,based on the analysis of different zoom forms,2-4 groups of mechanically compensated zoom forms were selected,and the feasibility and advantages of this zoom form in realizing the design of a large zoom ratio of the system were demonstrated by Gaussian optical analysis.Secondly,the initial structure of the zoom system was constructed through Gaussian parameter calculation,ideal optical simulation,component design and component recombination,and its rationality was verified by the distribution of optical power and deflection angle.According to the characteristics of system aberrations,a comprehensive plan for aberration correction has been formulated.The system aberration was corrected by Zemax,and the system image quality has been comprehensively evaluated by using a variety of image quality evaluation methods.Based on the current processing technology and assembly level,the system tolerances were analyzed,and the sensitivity of each tolerance was optimized to make the system have good machinability and high yield rate.Then,the zoom curve fitting was completed by the method of renormalization design,which not only ensures the smoothness of the zoom curve,but also ensures good image quality at each focal length.The temperature compensation design of the system was carried out by adopting electromechanical active compensation technology to ensure good imaging of the system in the high and low temperature environment of-40??+60?.Finally,with 12 standard spherical and 3 aspheric lens elements,the zoom lens not only guarantees the good image quality of the lens,but also takes into account the requirements of miniaturized design.At a Nyquist frequency of 125/mm,the MTF values of the on-axis points were all greater than 0.4,and the MTF values of the off-axis points were all greater than 0.3,and the image quality was good,with a total of 2 million pixels.The total length of the lens was only 165.75mm and the maximum clear aperture was less than 60mm,contributing to a compact structure.The continuous and smooth zoom curve of the lens not only ensures the smoothness and image quality of the zoom process,but also the lens tolerance meets the processing technology and has good adaptability to a wide range of temperatures.