A plate type (mirror-type) beamsplitter is an optical window with semi-transparent mirrored coating to break a beam into two or more separate beams. A beamsplitter will reflect a portion of the incident energy, absorb a relatively small portion, and transmit the remaining energy. Beamsplitter plates have very neutral color characteristics and are often referred to as beam-splitters plate.
Round beam-splitter, Plate beam-splitter