 Lateral resolution

Lateral resolution describes distinguishable separation in a plane perpendicular to an imaging system's axis. For incoherent point objects imaged through a circular aperture, the Rayleigh criterion gives the specimen-space scale $d\simeq 0.61\lambda /\mathrm{NA}$, where $\lambda$ is the vacuum wavelength and $\mathrm{NA}$ the numerical aperture.^[ref]

For example, $\lambda =550\mathrm{nm}$ and $\mathrm{NA}=1.0$ give $d\simeq 336\mathrm{nm}$ under that criterion. Sampling the image with more pixels can represent this blur more accurately, but cannot by itself distinguish closer features. Comparisons between instruments must specify both the object and the criterion.