High-amplitude vibrations detection on rough surfaces using a photorefractive velocimeter

We present and characterize theoretically and experimentally a photorefractive velocimeter. This device, based on two-wave mixing in a rapid photorefractive crystal, measures the instantaneous velocity of a vibrating target. It is particularly adapted to the measurement of high-amplitude (as high as some mm) low-frequency (until some kHz) vibrations. Instantaneous velocity as high as 25 mm s⁻¹ are expected to be measured with common photorefractive semiconductors and CW lasers.