In an extremely compact imaging system, the far-field-based algorithm still exhibited a better resolution than the point-like-transducer-based algorithm did. However, it suffers from severe patterned artifacts (near-field artifacts). The patch-based algorithm (m = 2) mitigated the artifacts. (a) The original phantom in the z = 0 plane. The reconstruction results for (b) the point-like transducer approximation, (c) the far-field approximation, and (d) the patch approximation (m = 2), respectively.