| 摘要 |
Ultrasonic imaging apparatus and method are shown which include electronic correction of focus defects produced by acoustic refractive index inhomogeneities within an object (14) being imaged. The region of interest (38) within which focus correction takes place is selected by the operator using control (42 or 84). The imaging system includes adjustable time delays (28-l through 28-c) through which return signals from transducers (10-l through 10-n) pass. Outputs from the delays are summed (30) and the resultant signal is envelope detected (32). The envelope detector output is prepared for display at display (36) by scan converter (34). The output from a focus correction delay control circuit (64) is used to control delay times of individual delays (28-l through 28-c) to provide for a delay profile across operative elements of transducer array (10), which delay profile includes delay profile components that correspond to low order terms of a series expansion, such as a Fourier series (FIG. 4). The adjustable signal delays (28-l through 28-c) are simultaneously adjusted by the focus correction delay control (64) during selection of delay profile component amplitudes which reduce focus defects within the region of interest 38. Either manual (FIG. 1) or automatic (FIG. 5) focus correction is provided.
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