反光镜

reflector (typically concave, as in a torch) / mirror (typically plane or convex)

contrary / in reverse / inside out or upside down / to reverse / to return / to oppose / opposite / against / anti- / to rebel / to use analogy / instead / abbr. for 反切[fan3 qie4] phonetic system

to reflect light

light / ray / CL:道[dao4] / bright / only / merely / to use up

mirror / lens