Refractive adaptive optics scanning light ophthalmoscope with fast 2D MEMS scanner

We describe a refractive adaptive optics scanning light ophthalmoscope designed for small animal imaging through a 1.8 mm diameter pupil. The optical setup, based on a search of achromatic doublets through multiple lens catalogs, consists of a sequence of modified afocal relays that deliver diffraction-limited imaging in pupil and retina conjugates. Real ray tracing is used to compare imaging performance when correcting large focus errors using a pupil conjugate wavefront corrector, a traditional Badal optometer, and a modified Badal optometer. Polarization control, focal length selection, and systematic lens tilting are explored for mitigating reflections with minimal imaging performance degradation. A 2-dimensional optical scanner with a 29.2 kHz resonant frequency around one axis and low dynamic surface distortion allows doubling the frame rate of prior instruments and simplifies the optical setup. Scanner orientation and trigger electrical signals are used to correct sinusoidal image warping and line sampling jitter. The instrument is demonstrated by imaging mice under 800 nm illumination with two reflectance detection modalities: confocal and quadrant non-confocal.