Detectivity limit of very small objects by video-enhanced microscopy.

Video-enhanced optical microscope imaging has recently achieved considerable improvements in the detectivity of very small objects, even exceeding Rayleigh's resolution criterion. Improvements in the signal-tonoise ratio have been attained utilizing digital image processing by reducing background and fixed pattern noise. Thus the video-enhanced optical microscope is a modern version of a traditional dark-field ultramicroscope for detecting scattered light. Theoretical calculations presented in this paper predict that the ultimate detectable size is several nanometers, 1/100 of the wavelength. This is in agreement with recent experimental reports. Effects of microscope structure factors are discussed.