epi-illumination; incident-light illumination
Technical term in microscopy and optics: illumination that comes from the same side as the observation, typically through the objective lens.
This microscope is equipped with epi-illumination.
Epi-illumination is suitable for observing opaque specimens.
透過照明 is transmitted illumination (light passes through the sample), while 落射照明 is incident-light illumination (light comes from the viewing side).
Compound of 落射 (incident light, from 落 'drop/fall' and 射 'shine/irradiate') and 照明 (illumination). The exact historical derivation is uncertain; the term is a modern technical coinage.