Design of the relay lens for infrared system coupled with imaging fiber bundle

Relay lens is an important element for infrared system coupled with imaging fiber bundle. According to the basic composition and structural characteristics of infrared system coupled with imaging fiber bundle, this paper put forward the general principle and method of its relay lens design, then a material relay lens has been designed by ZEMAX with definite performance index. It has a working spectral coverage from 3.7 mu m to 4.8 mu m, focal length of 33.5mm, magnification of -0.6, linear field of view of 12mm, objective numerical aperture of 0.15. It is objective telecentric and is adapted to the relay of infrared detector and imaging fiber bundle. The total lens has two aspheric surfaces and only four pieces of singlet. Its MTF value is 0.7@17 lp/mm, and distortion is -0.19%. After necessary tolerance analysis and structural design, this relay lens has been fabricated. The optical performances fulfill the design requirements and clear images have been got by this lens. These prove the validity and rationality of the design method. It gives a foundational guidance for such relay lens design.