collimate

Collimate is a verb meaning to make rays travel in parallel, or to align the axes of optical or other systems so that they share a common direction. The noun form is collimation. The word is derived from Latin collimare.

In optics and photonics, collimation seeks to produce a beam with minimal angular spread. A perfectly collimated laser beam, for example, remains roughly the same diameter over long distances. Collimation is typically achieved with lenses, mirrors, or specifically designed collimators, and is essential for interferometry, laser projection, and precision measurements.

In astronomy, telescope collimation refers to aligning the primary and secondary mirrors or lenses so that light converges accurately at the focal plane. Improper collimation degrades image quality and can mimic other optical faults. Techniques include adjusting collimation screws, using a Cheshire eyepiece, a laser collimator, or star testing to refine alignment.

In firearms, collimation describes aligning the sights with the bore so that the point of aim matches the point of impact at the intended range. Sighting-in and bore sighting are common procedures, often assisted by bore sighting devices or laser bore sights.

In physics and engineering, collimation also applies to particle, neutron, or X-ray beams, where collimators restrict angular divergence to improve resolution or safety. Collimation is evaluated by the beam’s width and angular spread, and is a standard step in beamline setup and imaging.