- a small telescope with crosshairs at its focus, fixed to another telescope, surveying instrument, etc. for adjusting the line of sight
- a device that causes a beam of radiation, as light, to move as parallel rays
Origin of collimatorsee collimate
- (physics) An optical device that generates a parallel beam of light. Often used to compensate for laser beam divergence.
- (physics) A similar device that produces a parallel beam of particles such as neutrons.
- (astronomy) A small telescope attached to a larger one, used to point it in the correct general direction