noun
lens barrel; lens tube
Refers to the cylindrical housing that holds lenses in optical devices such as telescopes, microscopes, and cameras.
望遠鏡の鏡筒をのぞいて星を観察した。
I observed the stars by looking through the telescope's lens tube.
このカメラの鏡筒は金属製でとても頑丈だ。
This camera's lens barrel is made of metal and is very sturdy.