Small angle measurement method based on the total internal multi-reflection

A small angle measurement method based on total internal multi-reflection (TIMR) effect has been presented. In the proposed configuration, the semiconductor laser with single-mode fiber affords the stable illumination beam, and the beam expander induces a gain factor enlarging the small angular displacement, thus improving the angle measurement sensitivity and stability simultaneously. The experimental results show that our method has better sensitivity and higher stability than the conventional method. These results in association with the theoretical analysis, demonstrates the potential applicability of the presented method in high precision on-line measurement of small angle.

► We set up a new small angular measurement configuration.
► A beam expander is used to induce a gain factor enlarging the small angular displacement.
► Measurement error can be decreased, thus obtaining higher sensitivity and stability.
► Signal to noise ratio can be increased to obtain higher stability.