noun
An optical instrument for viewing two slightly different images simultaneously to create a three-dimensional effect. Used in fields such as photogrammetry, surveying, and early 3D imaging.
実体鏡を使って航空写真を立体視する。
Use a stereoscope to view aerial photographs in 3D.
Compound of 実体 (じったい, 'solid body; substance') and 鏡 (きょう, 'mirror; lens'), likely a calque from Western terminology for stereoscope.