内窥镜是用来观察人体内部体腔的，通过它能直接观察到内腔器官的组成形态。现在内窥镜已成为医疗诊断和微创手术必不可缺的可靠工具。
Endoscope is used to observe the internal body cavity of human body. Through it, the composition and morphology of internal organs can be directly observed. Now endoscope has become an indispensable and reliable tool for medical diagnosis and minimally invasive surgery.
硬管内窥镜虽然品种繁多,但基本结构是一致的,内部的光学系统是由一系列透镜组成，其作用是把观察到的物体通过光学系统成像在观察者的视网膜上。
Although there are many kinds of rigid tube endoscopes, the basic structure is consistent. The internal optical system is composed of a series of lenses, which is used to image the observed objects on the observer's retina through the optical system.
硬管内窥镜的光学系统通常由物镜(含棱镜)、棒镜、目镜三部分组成。
The optical system of rigid tube endoscope is usually composed of objective lens (including prism), rod lens and eyepiece.

物镜系统：
Objective lens system:
物镜通常是由2～4片镜片（胶合镜片）组合而成。物镜的主要作用是把物体成像到镜头前。如果视向角不是0°(直视式)的话，如斜视、侧视式内窥镜，需要在物镜组内放置转像的棱镜。
The objective lens is usually composed of 2 ~ 4 lenses (glued lenses). The main function of objective lens is to image the object in front of the lens. If the viewing angle is not 0 ° (direct viewing type), such as strabismus and side looking endoscope, the image conversion prism needs to be placed in the objective lens group.
由多组同样尺寸的转像透镜组成。棒镜的主要作用是把物镜上成的像传输到光阑位置。根据内窥镜的工作长度不同,棒镜有1、3、5、7组转像透镜组成，通常转像系统棒镜的数量为奇数。
It is composed of multiple sets of image conversion lenses of the same size. The main function of the rod lens is to transmit the image formed on the objective lens to the position of the diaphragm. According to the working length of the endoscope, the rod mirror is composed of 1, 3, 5 and 7 groups of image conversion lenses. Generally, the number of rod mirrors in the image conversion system is odd.
目镜系统：
Eyepiece system:
目镜位于内窥镜后方镜体内。目镜的主要作用是把光阑位置成的像放大，目镜的放大倍数一般在15～30之间。放大倍数不能过大，否则物像将无法看清。<在硬管内窥镜插入管部分，又外管、内管和照明光纤组成。照明光纤位于内管和外管之间，作用是照亮整个视场范围。
The eyepiece is located in the body behind the endoscope. The main function of the eyepiece is to enlarge the image formed by the diaphragm. The magnification of the eyepiece is generally between 15 and 30. The magnification should not be too large, otherwise the object image will not be able to see clearly< The hard tube endoscope is inserted into the tube part, which is composed of an outer tube, an inner tube and a lighting optical fiber. The lighting fiber is located between the inner tube and the outer tube, and its function is to illuminate the whole field of view.