为满足海洋浮游生物的观测，设计了大相对孔径、水下浮游生物观测专用变焦显微光学系统。该系统利用Zemax软件实现，物距模拟海水介质，采用平面水密隔窗，设计像面尺寸为8.8 mm×6.6 mm CCD感光板，显微成像系统倍率变化范围为1.0~4.0。变倍过程中数值孔径为0.15，物方线视场范围为8 mm×6 mm~2 mm×1.5 mm。最大视场下，奈奎斯特频率50 lp/mm处近轴视场和1视场的光学传递函数值均大于0.4；成像系统的畸变控制在3%以内。该显微成像系统结构简单，可以满足较小尺寸的浮游生物成像，为浮游生物的分析及浮游生物种群的研究提供技术支持。

Marine plankton imaging technology plays an important role in the study of Marine ecosystem, and has great significance to fishery production and basic research of Marine science. In order to adapt to the observation of Marine plankton, a zoom micro-optical system with large relative aperture made for underwater plankton observation was designed. The imaging environment simulated seawater medium and this system was designed by Zemax software. The system used a 8.8 mm×6.6 mm CCD camera, and the imaging system multiplier were 1, 2, 4, respectively. The numerical aperture remains 0.15 during the process of changing times. The field of view was 8 mm×6 mm~2 mm×1.5 mm. At the maximum field of view, the optical transfer function (MTF) of near-axial field of view and 1 field of view at Nyquist frequency 50 lp/mm was both greater than 0.4, and the distortion of the imaging system was controlled within 3%. The microscopic imaging system structure is simple, and can satisfy the plankton imaging of small size, providing the analysis of the plankton and phytoplankton population research with technical support.