The first, more common usage, refers to a microscopy technique that uses intense illumination to generate sufficient scattering on particles with a diameter below the wavelength of light. Dark field microscopy is more familiar term to describe the same principle. At least that's how I learned it.

Surprisingly, LaVision BioTech uses the term Ultramicroscopy to name their Light-Sheet Microscope. This is a bit confusing, as contrast in Light-Sheet Microscopy is produced by fluorescence, not by scattering. Personally, I wouldn't use the term UM to refer to Light-Sheet Microscopy. 

Thank you for your opinion, Tobias

One idea:

Ultramicroscopy (UM):

Standard system (UM): Slit aperture+ Cylindrical lens => Thin Laser Lightsheet & Transparent Specimen=>3D reconstruction

Please discuss with me  ;-)

Best wishes,

Nina