We report the detection of moiré displacement signals using the photoacoustic effect. By using the transmission and reflection (absorption) gratings with a 25-μm pitch, the lateral displacement of the grating is detected from the photoacoustic signals. The probe-beam deflecton method and the microphone method are used for detecting the acoustic vibration and the acoustic pressure, respectively. The signals vary periodically as the pitch of the grating for the lateral displacement. The characteristics of the displacement signal are also examined by using the Fresnel diffraction theory.
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