Instrument used to measure the distance from the instrument to a selected point or object.
The optical range finder, used chiefly in lenses and prisms set at each end of a tube. The object's range is determined by measuring the angles formed by a line of sight at each end of the tube; the smaller the angles, the greater the distance, and vice versa. Since the mid-1940s, radar has replaced optical range finders for most military targeting, and the laser range finder, developed in 1965, has largely replaced optical range finders for {{link=surveying">surveying and radar in certain military applications.