Abstract:
In this paper, an image reconstruction method for relatively moving targets with acoustical holography or a synthetic aperture focusing technique is proposed. A high-speed imaging system using transmitting pulses modulated with a system of Walsh functions was proposed by the authors. The method, which utilizes multiplex transmission, is called encoded wavefront transmission. Moving targets are simultaneously observed with a multiple transmission of pulses modulated by the Walsh functions. For each repetition period, a 3-D image is reconstructed. From a sequence of the reconstructed images, the relative velocity is estimated. Then the images are combined to a single motion compensated image. In the paper, the influence of the quantization of delay on the quality of reconstructed images is discussed. Allowable errors of velocity estimation are evaluated using computer simulations. Also discussed are the velocity vector estimation algorithms and the feasibility of this method to a ``Holographic Doppler Velocimetry,'' which visualizes the spatial distribution of the velocity vector. The experimental results demonstrate the ability of the method for a simple moving object.