Z-Axis Displacement Sensor Based on Total-Internal Reflection and Surface Plasmon Resonance in Heterodyne Interferometry

In this paper, a z-axis displacement sensor based on Total-Internal Reflection and Surface Plasmon Resonance in heterodyne interferometry is proposed. The sensing unit is composed of a parallelogram prism, i.e. elongated prism, and a displacement probe. One side surface of the elongated prism was coated with a 2 nm Ti-film and a 45.5 nm Au-film, but the other side surface of that were not coated with metal films. The z-axis displacement sensor is with high sensitivity and resolution due to multiple attenuated total reflections and total internal reflections effects. Besides, we can obtain the results of the experiment in a distant place by uses of the USB data acquisition card (DAQ card) and a ZigBee module. In fact, the displacement resolution of the z-axis displacement meter can reach sub-nanometer by numerical simulation. The small-displacement sensor has some merits, e.g., in real-time test, easy operation, high measurement accuracy, high resolution, etc.