超短焦水下广角监控镜头的设计与分析

Design and Analysis of Ultra-Short Focal Underwater Wide Angle Monitoring Lens

目前市面上的水下镜头以视场角小、光学总长大的镜头为主。利用超短焦距的方案,从6片玻璃镜片的初始结构出发,结合水下成像镜头的特点,设计了一款500万像素的超短焦水下广角监控镜头。其全视场为95°,焦距仅为3.1 mm,系统光学总长为32.8 mm,后工作距为5.3 mm。该镜头由隔水窗以及由4片球面镜片和2片非球面镜片(包含滤光片和光阑)所构成的透镜组组成。在水下工作时,该镜头在全视场范围内的调制传递函数在250 lp/mm频率处都在0.3以上,同时中心视场系统的光学性能接近衍射极限,配合IMX675传感器能实现良好的成像效果。通过温度和公差分析,证明该镜头能适应水温变化,满足实际生产和装配的要求。

Currently,commercial underwater lenses are mainly those that have small field angles and large optical lengths.Based on the initial structures of six glass lenses and the characteristics of underwater imaging lenses,this study designs a 5-megapixel ultra-short focal underwater wide-angle monitoring lens using an ultra-short focal length scheme.Its full field of view is 95°,the focal length is only 3.1 mm,the total optical length of the system is 32.8 mm,and the rear working distance is 5.3 mm.The lens is composed of a waterproof window and a lens group consisting of four spherical and two aspherical lenses(including a filter and an aperture stop).When the lens operates underwater,the modulation transfer function is greater than 0.3 at a frequency of 250 lp/mm in the entire field of view,and the optical performance of the central field-of-view system is close to the diffraction limit.With an IMX675 sensor,the lens achieves a good imaging effect.An analysis of temperature and tolerance shows that the lens can adapt to changes in water temperature and meet the requirements of practical production and assembly.