Fig. 4.15 — Focusing near an interface

Schematic representation of the focusing near a planar interface at z = z_i between glass (n_t = 1.55) and water (n_t = 1.33) using (a) a 1.30 NA oil-immersion objective and (b) a 1.45 NA total internal reflection objective. The dashed lines represent the light ray directions without interface. The presence of the interface produces spherical aberrations in (a) and evanescent waves in (b).