Surface reflectance validation and resolution. (A) SLRM images of fluid layers (volumes, 5, 10, and 20 µl) sandwiched between cover glasses. (Right) Schematic showing origin of the reflections. (B; left) Corresponding intensity versus distance profiles measured at dashed white lines in A. (Middle) Distance-expanded view of second reflections. (Right) Fluid thickness computed from fluid volume added (Thickness_calc) as a function of fluid thickness measured by SLRM (Distance_meas). Mean ± SEM of five measurements per cover glass with linear regression (r² = 0.99). (C; left) Intensity versus distance profiles for reflections from a cover glass, with 2-µm displacements in the z-direction. (Right) Corresponding computed displacements (Distance_meas) against actual z-displacement. Mean ± SEM of five measurements. (D) Measured width in pixels (8× magnification) between reflections for a 100-µm-thick cover glass as a function of incident light angle versus theoretical width calculated from incident light angle, and cover glass thickness (78 pixels) and refractive index. Mean ± SEM of three measurements.