Optical configuration of fundus camera based on inner focusing manner

The fundus camera used in imaging retina includes two parts:fundus imaging path with a positive focusing lens and annular Kohler illuminating path.We present a pupil joint equation and a focus equation based on the internal focusing manner to analyze its configuration.Using these equations,the configuration of the camera is given in detail.The design result of the fundus imaging path shows compact initial configuration at a total length of about 123 mm.The focusing range is-10-10 diopter,and the movement of the focusing lens is nearly linear at displacement of more than a sub-millimeter per diopter.