Spatial resolution of images reconstructed from a bulk-detection scanning-laser microscope

We present theory and experimental data on the minimum detectable feature size and spatial resolution for a scanning-laser microscope system that uses bulk photodetection. In the analysis, interactions of laser photons with an object are given a probability function that varies with the position within an object. Typical interactions that can be measured with such a scanning device include photon absorption (densitometry), scattering, and photofluorescence. Because bulk photodetection is used, image resolution is a function of laser-probe spot size and recording precision. We present data from simulations that predict a minimum separation between feature centers of approximately 1.56 times the half-width of the laser spot. Experimental verification by scans of U.S. Air Force test targets confirms this theory.