折反式眼底相机光学系统设计

Abstract

To eliminate the scatter light and central ghost in a classical fundus camera,the optical system of a catadioptric fundus camera with a field of view 40° and a working distance of 48 mm was designed.An off-axial reflecting ophthalmic lens with free form surfaces was designed to correct the off-axial aberrations.Two free-form-surfaces were introduced in the imaging objective system to correct the residual off-axial aberrations of the reflective ophthalmic lens.In the optimization of the imaging system,an eye model with varying defocuses was proposed to eliminate the negative effect of eye aberrations as well as to accommodate the eye with different refractive errors.Three adjacent illumination rings were introduced in the illumination part to avoid the undesirable light reflected by the eye optical system.Experiments show that the accommodation range of the system is between-10 m-1 and 10 m-1,the resolution at the object plane is 33 lp/mm across the entire field of view,and the maximum distortion is less than 8.5%.Furthermore,the illumination non-uniformity is less than 15% in the conditions without scatter light and central ghost.The designed catadioptric fundus camera with a free-form-surfaces show a satisfactory large field of view and a large working distance,and removes the undesirable scatter light and central ghost greatly.