Small-angle measurement of laser beam steering based on total internal-reflection effect

A precision small-angle measurement system is introduced based on optical total internal reflection effect. When the incident angle of a polarized beam is larger than the critical angle, and the beam has a small steering angle in the vicinity of the critical angle, the total internal reflection will take place and a relative phased shift between the s- and the p-polarized components is produced. By utilizing the characteristics we could measure the small angle displacement of the incident beam. A differential optical system including four right-angle prisms is set up based on above, and we take the difference of the interference intensity of sand p- components divided by their sum as the output signal. A good linearity between the output signal and the angular displacement is proved by the theoretical simulation. The system result and error analysis are given as well. The experiment shows that the measurement range of this system is +/- 2 degrees, and a resolution of 10" is achieved. This method has many advantages, such as simple configuration, high sensitivity, good linearity and high antinoise ability.