Fig. 1. Simulation flow chart of measuring micro-displacement based on the theory of vortex beams and spherical wave interference

Fig. 2. Interference intensity of vortex beams and spherical wave before and after micro-displacement in the simulation

Fig. 3. Subtractive intensity distribution of the interferogram before and after the micro-displacement of the object in the simulation

Fig. 4. Tangent line of the spiral fringe before and after micro-displacement of object in the simulation

Fig. 5. Experimental set up for measuring micro-displacement of objects based on vortex beams and spherical wave interferometry

Fig. 6. Interference fringes of vortex and spherical waves in the experiment. (a) Interference pattern before the displacement of the piezoelectric ceramics , (b) Interference pattern after the displacement of the piezoelectric ceramics

Fig. 7. MATLAB processing results of experimental image. (a) Subtractive intensity distribution of the interferogram before and after the micro-displacement, (b) Tangent of the spiral fringe before the micro-displacement, (c) Tangent of the spiral fringe after the micro-displacement