A device that projects images or video onto a screen or surface. Often used interchangeably with プロジェクター, though 投影機 can sound slightly more technical.
See also: プロジェクター
We installed a projector in the conference room.
This projector displays clearly even in a bright room.
planetarium projector
Compound of 投影 (projection) + 機 (machine, device). The exact historical derivation is uncertain, but the word follows a standard pattern for naming technical equipment.