Evaluating the performance of fluorescence microscopes.

A simple means of evaluating the performance of fluorescence microscopes is described. The proposed test gives an overall figure of merit that takes into account all of the important instrumental parameters that determine image quality. The essence of the test is to use a specimen whose photobleaching rate is a measure of the illumination time-intensity integral. When this time-intensity integral is controlled, the signal-to-noise ratio in the image of small subresolution objects becomes a system-independent measure of light throughput, resolution and intrinsic noise.