A measuring instrument for angle based on invariant optical path and autocollimation principle

A measuring instrument for angle based on invariant optical path and autocollimation principle is proposed in the paper. The measuring principle and optical structure of the instrument are analyzed. By using analyse software, many experiments comparison between the measuring instrument for angle and commercial photoelectric autocollimator ELCOMAT3000.. The instrument has many advantages such as small structure, high-precision and cheap cost.