Real-Time registration of acoustic images

This paper proposes a technique for online three-dimensional reconstruction of underwater environments from multiple range views acquired by an acoustic camera. The final target of the work lies in improving the under- standing of a human operator guiding an underwater remotely operated vehicle (ROV) equipped with an acoustic camera, which provides a sequence of 3D images. Since the field of view is narrow, we devise a technique for the reconstruction of relevant information of the image sequence up to build a mosaic of the surrounding scene in real time. Due to the absence of control of the sensor position, no information is available about the degree of overlapping between the range images; further, speckle noise and low resolution make more difficult the registra- tion process. In order to allow the real time registration we introduce a method for speed up the Iterative Closest Point (ICP) basing on a reverse calibration approach. Examples on real images have been presented to show the promising performances of the proposed algorithm.