Fig. 1. Schematic of micro-displacement measurement apparatus based on transmissive laser air-wedge interference

Fig. 2. Micro-displacement measuring instrument. (a) Schematic of measurement and test apparatus; (b) schematic of interferometric micro-displacement measuring instrument; (c) optical interferometer structure

Fig. 3. Displacement of the piezo-type nanometer translation stage as a function of applied voltage

Fig. 4. Experimental image and image after image processing. (a) Raw measured image; (b) image obtained by intensity subtraction and normalization

Fig. 5. Measured and fitted laser interference fringes in micro-displacement measurements

Fig. 6. Variation of interference fringes with the elongation of piezoelectric ceramics

Fig. 7. Displacement obtained by calculating the spatial period of interference fringes for scanned elongations of piezoelectric ceramics