基于光学系统结构研究了硬性内窥镜光学系统内部杂散光的成因及抑制方法, 以提高其成像效果。通过Lighttools软件进行光线追迹, 分析了硬性内窥镜光机结构的杂散光; 通过杂光路径分析, 提出光线在中继系统和物镜组中发生全反射是硬性内窥镜存在杂散光的原因, 由此研究了相应的杂散光抑制方法: 即调整物镜组结构控制系统中光线传播的路径, 并在光学系统优化过程中加入相应的控制条件。最后, 采用提出的方法设计了视场角为70°, 透镜直径为2.7 mm的高成像性能消杂散光硬性关节镜。验证实验显示, 研制的硬性内窥镜光学系统在100 lp/mm 处各视场的调制传递函数(MTF)值均在0.4以上, 逼近衍射极限。光线追迹结果表明, 在物镜组中消除杂散光可避免光线在棒镜内壁全反射, 完全消除杂散光并保证良好的像质。

On the structure of optical system, the causes of stray light of a rigid endoscope and its suppression methods were explored to eliminate the stray light and to improve its imaging performance. Firstly, the stray light in the optical and mechanical system was simulated and analyzed by ray tracing in Lighttools. By analysis of the stray light path, it points out that the stray light of the optical system comes from the total reflection of a relay system and an objective system. Then, with the possible causes, the suppression methods for the stray light were proposed, including adjusting objective structure and controlling ray path. Finally, a rigid arthroscopy with a Field of View(FOV) of 70° and an outer diameter of 2.7 mm was designed to suppress the stray light. With proposed methods, the Modulation Transfer Function(MTF) reaches diffraction limit, the values of all fields are higher than 0.4 at 100 lp/mm, and the size of spot diagram is smaller than 4 μm. Besides the high-definition imaging, simulation demonstrates that the stray light has been moved out entirely in the optical system, and the system shows excellent imaging quality.