Small angular displacement measurement based on an autocollimator and a common-path compensation principle.

A novel method for small angular displacement measurement based on an autocollimator and a common-path compensation principle by using single CCD detector was proposed. The principles of the angular displacement measurement and the common-path compensation were analyzed. The feasibility of measurement method was verified and the experimental results revealed that the linear correlativity between the relative displacement of the measuring beam spot and the angular displacement is 0.99996. And the measurement resolution is about 0.03 arcsec. To test the compensation's effect, a series of experiments introducing three different interferences from system and external environment were performed. The experimental results indicated that the standard deviations of the measuring beam spot's angular drift were improved by at least 25.0% to at most 80.0% in x direction while by at least 28.2% to at most 95.6% in y direction. Thus, the stability of the system and the measurement resolution were improved.