Medium focal length flange video lens

The invention discloses a medium-focal-length flange video lens which sequentially comprises a first lens group, an iris diaphragm and a second lens group in the light incidence direction, the first lens group and the second lens group are both positive focal power, the first lens group is a fixed group, and the second lens group is a focusing group capable of moving along an optical axis. The first lens group and the second lens group satisfy the following relationships: 2.8 lt; f1/f2lt; 3.8); f1 represents the focal length value of the first lens group, and f2 represents the focal length value of the second lens group. The camera module is large in clear aperture, high in MTF resolution, capable of reducing achromatism, small in distortion and capable of being matched with a long flange back focus. 本发明公开了一种中焦长法兰视频镜头，沿光线入射方向依次包括第一透镜组、可变光阑以及第二透镜组，所述第一透镜组和第二透镜组均为正光焦度，第一透镜组为固定组，第二透镜组可沿光轴移动的调焦组，第一透镜组和第二透镜组满足以下关系：2.8