Optimization design of rigid endoscope with high definition and large depth of field

A rigid endoscope with high definition is designed. In order to ensure the effective field of view and normal transmission path in the limited lenses with diameters of 2.7 mm, the incident height and exit angle on the relay lens of feature rays are controlled during the optimization. As a result, an entrance pupil of 0.3 mm is achieved, with a resolution of higher than 21 lp/mm and an angular resolution of 8.45 C/(°) in the object space. Stray light caused by total reflection on the inner wall of the rod lens is avoided at the same time. The modulation transfer function (MTF) reaches diffraction limit and the values of all fields are higher than 0.3 at 120 lp/mm. By taking consideration of large depth of field (DOF), a system with multiple object distance configurations is set up before the optimization. After optimization with an eyepiece added, the MTF values of all fields are 0.1 at 3 lp/mrad, close to the resolution limit of human eye. Test results show that the resolution of fabricated system reaches theoretical design values.