Design of uniform illumination system of fundus camera and its stray light shield

A new design of illuminating system used in fundus cameras was proposed. The design was a improved system based upon Kohler illumination, and it used the near infrared light which could not be felt by human eye to deal with the problem of iris shrinking effect when illuminating light flashed. The design had only four lenses and the illuminated area could be adjust continuously, meanwhile the energy of the illumination light could be used efficiently. By inserting black dot boards and a ring stop in the light, the design could shield almost 99% stray light, and the Ratio of Signal to Noise(S/N) of the system could be up to 20 dB. The Gullstrand_Le standard eye model was used in the system, and a uniform illuminated area with the uniformity of 95% could be achieved.