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. Author manuscript; available in PMC: 2012 Feb 5.
Published in final edited form as: Cell. 2010 Dec 23;143(7):1047–1058. doi: 10.1016/j.cell.2010.12.002

Figure 1.

Figure 1

Diffraction-Limited Resolution of Conventional Light Microscopy

(A) The focal spot of a typical objective with high numerical aperture, depicted by the cyan ellipsoid, has a width of ~250 nm in the lateral directions and ~550 nm in the axial direction. The image of a point emitter imaged through the objective, namely the point spread function, also has similar widths. These widths define the diffraction-limited resolution. Two objects separated by a distance larger than this resolution limit appear as two separate entities in the image. Otherwise, they appear as a single entity (i.e., unresolvable). These two cases are exemplified by the two cross sections of the microtubule image, cyan curves A and B in the right panel, at the corresponding positions indicated by the white lines in the middle panel.

(B) The size scale of various biological structures in comparison with the diffraction-limited resolution. (Left to right) A mammalian cell, a bacterial cell, a mitochondrion, an influenza virus, a ribosome, the green fluorescent protein, and a small molecule (thymine).