Results and Discussions In this paper, we propose a method for direct observation of nasal mucosa cilia by a rigid microendoscope, which can avoid the damage of cilia functions and the pain of subjects caused by sampling and greatly improve the clinical diagnostic ability of cilia-related diseases. The numerical aperture of the system is 0.15, which greatly improves the resolution ability of the system. The relay system changes the HOPKINS structure to make a negative lens separated into a thick lens to effectively correct the field curvature. The system is designed as a variable-magnification structure, which can magnify objects as required. In this paper, the integrated design of the eyepiece system and the variable-magnification adapter system, as well as that of the whole system are proposed to simplify the structure, correct the aberration to the maximum extent, and achieve the imaging quality to the diffraction limit.

Motile cilia of nasal mucosa are widely distributed on the mucosal surface of the human respiratory tract. The defense function of removing mucus and pathogenic particles from the mucosal surface can be realized by swinging regularly in a specific direction. The normal operation of this function is important for maintaining respiratory tract health and human health. The dysfunction of cilia will lead to a series of pathological manifestations, which will seriously affect the health and quality of life of patients. The traditional ciliary motion assessment methods are invasive and cannot reflect the actual motion state of the body. In order to perform direct microscopic imaging of the nasal mucosal surface through the anterior nostril for non-invasive observation and measurement of nasal ciliary movement in vivo, we design a variable-magnification rigid microendoscope with a viewing angle of 30°. The nasal mucosal ciliary microendoscope will avoid the damage to ciliary function and the pain of subjects caused by material extraction, which thus greatly improves the clinical diagnosis ability of cilia-related diseases and becomes an important breakthrough in the scientific research and clinical work in the field of cilia.

optical system design, image quality analysis, and tolerance analysis. The optical system mainly includes an objective lens system, relay system, eyepiece system, and variational adapter system. Firstly, a prism structure is determined so that it has a viewing angle of 30°. On the premise of ensuring the object resolution, we reduce the circumscribed circle diameter of the prism as much as possible and then reduce the object diameter of the entire endoscope. According to the structure of the cilia, we determine the numerical aperture of the objective lens system to provide a sufficient margin to avoid machining errors in the actual processing. According to the principle of pupil matching, the object image side, the object image side of the relay system, and the object side of the eyepiece all adopt a telecentric optical path. The relay system adopts the HOPKINS lens whose fully symmetrical structure can realize equal-proportion image transmission, and the vertical axis aberration can be automatically reduced. A piece of the negative lens can be separated to make it a thick lens, so as to solve the problem of excessive field curvature. The whole endoscope system has no visual requirement. An integrated design method of eyepiece and variable-magnification adapter systems is proposed, which can simplify the structure, reduce the cost, and better correct the aberration. In order to obtain a complete rigid endoscope optical system, it is necessary to connect all parts of the structure. Each part is connected in the order of objective lens system, relay system, eyepiece system, and variable-magnification adapter system. During the connection process, we make a simple optimization to ensure that the positions of each image plane are in the air. In addition, in order to avoid the loss of light energy, operands are still used to control the telecentricity of each image plane, and the system magnification of the connected endoscope is controlled by the image plane height. Finally, we further optimize the connected optical system and use operands to reduce field curvature and distortion, control glass thickness and air spacing, and make it machinable and assembling. MTF curve, spot diagram, and field curve distortion diagram are selected as the image quality evaluation criteria of the system to determine the optimized image quality. Tolerance analysis is carried out according to the given tolerance value to meet the performance requirements and minimize the production cost.

Aiming at the invasiveness and inaccuracy of the existing methods for evaluating nasal ciliary motion, we propose a method of direct microscopic imaging of the nasal mucosal surface through the anterior nostril for non-invasive observation and measurement of nasal ciliary movement in vivo. We use an integrated design method to design a microendoscope system with a viewing angle of 30°, high resolution, and variable magnification. The system achieves the goal of a viewing angle of 30° by secondary reflection on the viewing prism. The working wavelength is the visible light band. The working distance of the system is 3 mm, and the resolution is 272 lp/mm. The object's surface height is 0.4 mm, and the object's square aperture is 4.65 mm. In addition, the magnification is 6×-10×. We evaluate the image quality and find that the defocused spots of the three structures are smaller than the Airy disk, and the MTF curve reaches the diffraction limit. We analyze the tolerance, and the results show that it meets the processing conditions. The endoscope system is of great significance for non-invasive observation and study of nasal mucosal cilia in vivo.