Fig. 3.

Location estimation via fitting a Gaussian-shaped intensity profile to an image of a diffraction-limited spot. (A) An image of a diffraction-limited spot as acquired from a camera provides inadequate resolution to determine the location of a fluorescent molecule with high precision. Pixel size: 200 nm. (B) A 2-D Gaussian intensity profile closely approximates the theoretical intensity pattern produced by point-source of light. By selecting a Gaussian intensity profile that best-fits the image, an accurate approximation can be made about the location of the point-source of light (i.e., at the peak intensity of the Gaussian profile).