Application of near-field beam-forming in large-aperture optical towed linear array

Far-field beam-forming is applied in the detection system of large-aperture optical towed linear arrays to estimate the direction of targets. Actually, for a large-aperture line array, multiple targets are located in near-field. In these circumstances, if we still use far-field beam-forming for approximate processing, it will cause bearing-amplitude distortion which seriously influences the precision of the target direction estimate. For such targets, this paper compares the performance of near-field focused beam-forming and far-field beam-forming through simulation and towed trials data. The results show that, when detecting targets which can't be considered to be located in far-field, near-field focused beam-forming can achieve the narrowest beam width and the strongest focused energy. It can also effectively improve the precision of target direction finding and estimate target distance. The value of applying near-field focused beam-forming in the detection system of large-aperture optical towed linear arrays is confirmed.