Design of a novel wide view-field angle and anti-stray-light fundus camera

A novel portable free-dilated fundus cameras with large field of view (FOV) is designed. By taking consideration of human eye's aberration and vergence, as well as the sharing of the eye-piece objective lens between the illumination system and the imaging system, a lens system with 16 configurations is set up for optimization. As a result, an FOV of 60° and 2 mega pixels resolution have been achieved. The camera can be adapted to eyes in which vergence ranges from -8 D to +10 D; the modulation transfer function (MTF) values of all fields are higher than 0.2 at 120 lp/mm with distortion less than 5%. In order to eliminate the stray light reflected by cornea, ring-shaped LED light source is used to replace traditional Kohler illumination system. The method not only ensures illumination uniformity on fundus, but also greatly improves illumination efficiency and dramatically simplifies the system. A polarizing beam splitter (PBS) and a quarter-wave retarder are used to replace the traditional beam splitter and the black dot board for the first time to shield the stray light. 99.5% of the stray light caused by the eye-piece objective lenses is eliminated.