Small roll angle measurement based on auto-collimation and moire fringe

摘要

A novel method for small roll angle measurement based on auto-collimation and moire fringe is presented. A right-angle prism is used as an indicator of small roll angle around the optical axis, and a CCD is used to collect moire fringes that are generated by scale grating image which is reflected by prism and index grating. Any small roll angle of the prism will change the include angle of the grating pair and meanwhile induce a change in the moire fringe period. The relationship between roll angle and period of moire fringes is established. The period data is obtained by image processing. The experimental result certifies that the principle of small angle measurement method based on auto-collimation and moire fringe is correct and feasible. The measuring error is smaller than 0.2" within 7' range compared with 0.2" autocollimator.