collimator

名词 collimator:

1. a small telescope attached to a large telescope to use in setting the line of the larger one
2. optical device consisting of a tube containing a convex achromatic lens at one end and a slit at the other with the slit at the focus of the lens; light rays leave the slit as a parallel beam

col.li.ma.tor

n.（名词）
A device capable of collimating radiation, as a long narrow tube in which strongly absorbing or reflecting walls permit only radiation traveling parallel to the tube axis to traverse the entire length.
准直仪，平行光管：一种能使射线成平行状的仪器，如一个狭长试管的强烈吸收或反射的内壁，使得射线只有在和试管轴线相平行时才能穿过整个试管