Figure 6.

Compressed images for three diameters of Polystyrene nanospheres (70, 100, and 150 nm) imaged in water are generated by collecting the maximum and minimum normalized intensities present over a sequence of sequentially defocused images on a per-pixel basis. Solid lines denote compressed signatures from nanospheres on 30nm oxide, and dashed lines denote signatures from a 40nm oxide. The underlying Z-stacks are composed of 61 images simulated for a .9 NA imaging system in water at 200 nm increments over a 6 μm range centered on the oxide surface.

A) Largest positive normalized intensity values per pixel. B) Largest negative normalized intensity per pixel. C) Total differential intensity generated from the subtraction of plots in B from A. Differential intensity measurements demonstrate strong agreement between conditions despite significant variation in single – plane appearance and defocus behavior.