collimator

UK: /ˈkɒlɪˌmeɪtə/ US: (kol′ə mā′tər)

WordReference Random House Unabridged Dictionary of American English © 2025

col•li•ma•tor  (kol′ə mā′tər), n. 

1. Optics
   • a fixed telescope for use in collimating other instruments.
   • an optical system that transmits parallel rays of light, as the receiving lens or telescope of a spectroscope.
2. Physics a device for producing a beam of particles in which the paths of all the particles are parallel.

• collimate + -or² 1815–25

Collins Concise English Dictionary © HarperCollins Publishers::

collimator / ˈkɒlɪˌmeɪtə/ noun

1. a small telescope attached to a larger optical instrument as an aid in fixing its line of sight
2. an optical system of lenses and slits producing a nondivergent beam of light, usually for use in spectroscopes
3. any device for limiting the size and angle of spread of a beam of radiation or particles