Abstract
Here we present the design of telecentric model eyes for measuring image distortion in adaptive optics ophthalmoscopes, using pairs of achromatic or near-achromatic commercial off-the-shelf (COTS) and/or custom doublet lenses. The proposed model eyes can operate over visible or visible plus near infrared wavelength ranges, across a 15-diopter focus range, with an 8 mm entrance pupil diameter. COTS lens selection was implemented as a systematic evaluation of catalog lenses after optimization of axial distances. Custom lens optimization was initially guided by wavefront aberration constraints derived from object-shift 3(rd) order aberration theory, before traditional variation of surfaces and distances to minimize a performance metric. When a wavefront corrector compensates for field-constant aberrations, the model eyes achieve nominal wavefront RMS below λ/20 across a ∼6.9° circular full field of view for COTS and hybrid lens pairs, limited by vignetting from a self-imposed 27.9 mm clear aperture. For custom lens pairs, the field of view is about 10.2°, limited by aberrations. A tolerance study indicates that a COTS lens pair for 450-1100 nm can achieve as-built diffraction-limited wavefront error of 0.044 λ @450 nm at 95% production yield. Model eyes with this lens pair yielded telecentricity quantified as image size changed per diopter of 0.1%/D when assembled with a camera and 0.01%/D when assembled with a power meter. The model eye was tested with an optical setup that emulates a fundus camera with Badal focus correction.