| 摘要 |
PROBLEM TO BE SOLVED: To improve the distance resolution and azimuth resolution of an ultrasonography.SOLUTION: In a circuit 14 for processing received ultrasonic signals, a component of the same basic frequency f1 as the transmission pulse is extracted with a correlation part F1 composed of a matched filter, and components of harmonic waves f2, f3, ... generated from non-linear distortion of a subject are extracted by one or a plurality of band pass filters F2, F3, .... The extracted components are added after multiplying prescribed coefficients k1, k2, ... by coefficient multipliers K1, K2, ... to be used for the image processing. Accordingly, the signal-to-noise ratio can be improved by subjecting the basic frequency component to the correlation process, and the capability of detecting signals can be improved by the pulse compression effect. At the same time, the penetration (the distance resolution in the depth) can be improved and the contrast to noise can be also improved. Only the basic frequency component permitting use of the transmission signal itself as a reference signal is subjected to the correlation processing, while conventional band pass filters which can be easily prepared are used for harmonic waves, so that the azimuth resolution can be also improved. |
