长焦距变焦镜头的温度分析及补偿

Thermal analysis and compensation of long zoom lens

为了提高长焦距变焦镜头的温度稳定性,分析了温度对光学系统的影响。在CODE V里对长焦距变焦镜头光学系统进行温度仿真分析,发现温度对光学系统的像质影响很大。采用无热化技术成熟的主动调焦式补偿方式对光学系统的温度效应进行补偿,发现采取补偿后像质有很大改善,但在相机的最大空间频率处的MTF还是较低,且变焦系统各焦距时的最佳像面并不能齐焦。采用机械被动式补偿和主动调焦式补偿混合的方式进行温度补偿,使得变焦系统在要求的全温度范围内有良好的像质,短焦时MTF大于0.5,长焦时的MTF大于0.25,并且焦距也得到补偿,各焦距时的最佳像面齐焦并与CCD的像面位置重合。

In order to improve the temperature stability of long focal length zoom lens,the influence of temperature on the optical system was analyzed.By the simulation analysis of long zoom lens optical system for temperature in CODE V,it is found that the temperature has a great effect on the image quality of optical system.At first the initiative focusing compensation mode was adopted to compensate the temperature effect of the optical system.Although the image quality improved after compensation,the CCD's max frequency of modulation transfer function(MTF)is low,and the best image plane of every focal length of zoom system cannot parfocalize.By adopting the mechanical passive compensation and active focusing compensation to get the compensation of temperature,the optical system can realize good image quality within the required full temperature range,and the MTF is greater than 0.5in short focus while greater than 0.25 in long focus.The focus length can be compensated,and the best image plane of each focal length can parfocalize and overlap with the CCD image plane.