Testing a new method for small-angle rotation measurements with the optical vortex interferometer

We present one of the applications of the Optical Vortex Interferometer (OVI). OVI is based on the regular net of optical vortices which are generated by the interference of three plane waves. Disturbing one of the interfering waves causes a change in the position of the vortex points in the vortex net. The measurement is based on tracking the vortex position change. This method can be used to determine small-angle rotation. OVI distinguishes two axis of rotation and the corresponding two rotation angles can be measured with sub-second resolution. The linear vibrations of the measured element are automatically subtracted. The single measurement provides hundreds of measurements points, so the statistical methods for data analysis and corrections can be effectively applied. In the paper we present the experimental testing of the method. To get the precise rotation of one of the interfering wave's the optical wedge is put into one of the interferometer's arm. The analysis shows that the amplitude`s decrease does not influence the measurement accuracy. From the vortex net shifting the rotation angle of one of the interfering waves is calculated and this rotation is also used to calculate the refracting angle of the applied optical wedge.