Collimator

A collimator is an optical tool that projects an illuminated test chart (reticle) to infinity. The emerging beam leaves the autocollimator as a narrow parallel beam of light which is called a collimated beam. The collimator is often used as a test chart projector for the inspection of infinity corrected objective lenses, e.g. photography lenses. In combination with a telescope, the collimator can also be used for aligning machine elements along the line of sight.