Optical design of a transmissive ultra-widefield non-mydriatic confocal fundus imaging system.

A fully transmissive ultra-wide-field non-mydriatic confocal fundus imaging system design is proposed for retinal imaging under pupil diameters smaller than 3 mm. Real-ray tracing and conjugate relationship analyses are employed, providing a theoretical basis for the optical design and optimization of the system. Based on this analysis, a fully transmissive coaxial architecture integrating ultra-wide-field imaging and multispectral compatibility is designed. An internal focusing mechanism is further introduced to compensate for refractive errors through axial translation of a focusing lens without changing the overall system length. The proposed design achieves a simulated retinal field angle of 189.06° with a working distance of 15 mm and supports multispectral imaging at 488 nm, 520 nm, 635 nm, and 785 nm. Optical simulation results indicate near diffraction-limited imaging performance across the full field. The retinal resolution remains better than 15 μm over a refractive compensation range from -15 D to +15 D. To the best of our knowledge, the proposed design achieves the largest single-frame field of view for transmissive confocal fundus imaging systems while maintaining non-mydriatic operation.