A collimator is a device that narrows a beam of particles or waves and is used in many applications involving lasers, LEDs, and other light sources. In optics, a collimator may consist of a curved mirror or lens with a type of light source and/or image at its focus. This is used to replicate a target focused at infinity with little or no displacement. Collimator systems can be used to calibrate other optical devices, check if all elements are aligned on an optical axis, set elements at a proper focus, or align two or more devices such as in binoculars or gun sights.