40.4 Experiment 40.4.1 Displacement Measurement An experiment of displacement measurement using the optical setup of the prototype shown in Fig. 40.2. A He-Ne laser with 5 mW is used as a light source. An aluminum plate placed on a 3-axes PZT stage is used as a specimen as shown in Fig. 40.3a. Figure 40.3b shows a photograph of the specimen. The size of the analysis area is 5 mm 5 mm. The outside area of the analysis area is covered with a piece of black flocked paper. The movable area can be shifted into the any direction with the 3-axes PZT stage. In this experiment, the amount of moving is 200, 400 and 100 nm for the x, y and z-direction, respectively. Figure 40.4 shows phase difference distributions before and after moving the specimen obtained with a windowed PSDHI [13] with 64 windows. Figure 40.5 shows displacement distributions obtained from the phase difference distributions with Eq. (40.7). The sensitivity matrix is obtained using a movable plate attached on the 3-axes PZT stage in advance. Table 40.1 shows the result of displacement measurement. The measured displacements are given as the difference between the fixed part and the movable part. The errors for thex, yandz directions are -10 nm, 25 nm and 6 nm, respectively. Fig. 40.3 Experimental setup (a) Prototype of strain measurement system and specimen (b) Photograph of specimen Fig. 40.4 Phase difference distributions (a) Sensor 1 (b) Sensor 2 (c) Sensor 3 Fig. 40.5 Displacement distributions (a) x-direction (b) y-direction (c) z-direction 346 M. Fujigaki et al.
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