Long focal length large-aperture switch-zoom system design

摘要

Compared with continuous zoom system, switch-zoom system has many advantages, such as simple structure, perfect imaging quality and easy fixing. A set of long focal length large-aperture visible switch-zoom system is designed in this paper. The system is composed of two parts: the front R-C object lens and the back switch-zoom system. When the back system is reversed, 1500～3000mm switch-zoom can be realized. In order to match the front R-C object lens' exit pupil with the back switch-zoom lens' entrance pupil, the front R-C object lens is controlled to be telecentric and the back switch-zoom system is telecentric at both image and object. The back switch-zoom system's object NA at short focal position is controlled to be equal to the front R-C object lens' image NA. Thus, the two parts can match with each other properly and the whole long focal length large-aperture visible switch-zoom system is designed. When the spatial frequency is 501p/mm, the MTF of the R-C system and the back switch-zoom system are reaching to the diffraction limit to ensure the MTF of the whole system at both long focal position and short focal position. The RMS at each focal position is less than 10μm. From the first surface to image plane, the overall length is 1100mm. The designed result shows that this zoom system has the advantages of simple structure, high image quality and easy fixing.