Scanning ultra fast distance sensor based on acousto-optic deflection

We present distance measurement technique to any rough surface based on spatial filtering of a speckle pattern generated when the object surface is scanned by a laser beam deflected from an acousto-optic device. Scanning velocity of 150 m/s allows to complete single measurement within as short time as 50 ns. However stochastic nature of the speckle effect caused rather high inaccuracy. The data averaging is easily implemented within a single scan and allows us to achieve the accuracy of 110 mum within the time window of 2.5 mus. We analysed the factors affecting the performance of the proposed technique and showed that the response time can be diminished by an order of value using an acousto-optic crystal with higher acoustic speed. The proposed technique may be useful for monitoring of the geometrical parameters of fast moving or rotating surfaces in various industrial applications.