Fig. 1. Schematic of cornea alignment optical path

Fig. 2. Schematics of cornea alignment method based on two-light-spot vision marker. (a) d=D₀; (b) d>D₀; (c) d₀

Fig. 3. Cornea alignment optical path. (a) Path for light incident on cornea surface through two-aperture diaphragm; (b) path for two light beams reflected from cornea convergent through objective lens ( solid line indicates that cornea is at correct working position, and dashed line indicates that cornea is away from correct working position)

Fig. 4. Alignment range and precision of two-light-spot vision marker. (a) Schematic diagram of out-of-alignment-range; (b) ZEMAX simulation of out-of-alignment-range; (c) ZEMAX simulation of alignment precision

Fig. 5. Relationships of aperture distance in two-aperture diaphragm with alignment range and precision. (a) Aperture distance and alignment range; (b) aperture distance and alignment precision

Fig. 6. Alignment optical path with two-light-spot vision marker

Fig. 7. Images of two spots on CMOS under different Δ. (a) Δ=4.6 mm; (b) Δ=-3.6 mm; (c) Δ=0.25 mm; (d) Δ=-0.25 mm;

Fig. 8. Effect of d on positions of two light spots. (a) Relationship between distance of two separated light spots and d; (b) distance from light spot to focus point versus d

Fig. 9. Fundus images for two light spots with different states. (a)-(e) Fundus color photos; (f)-(j) near infrared images of fundus; (k)-(o) locally enlarged image