mi·cro·den·si·tom·e·ter 
(mī′krō-dĕn′sĭ-tŏmĭ-tər)
(mī′krō-dĕn′sĭ-tŏmĭ-tər)n.
An extremely sensitive densitometer used to measure optical densities of photographic plates or film to detect small details, such as spectral lines invisible to the human eye.