ULTRASONIC DIAGNOSTIC EQUIPMENT

摘要

PURPOSE:To improve the frequency characteristic of a reception signal from a shallow part by performing focusing based on a delay characteristic which gives a fixed and maximum delay time to the reception signal from the center of simultaneously used ultrasonic oscillators. CONSTITUTION:Reception signals from plural ultrasonic oscillators 3 arranged one- dimensionally are amplified by a receiving circuit 7 and are given to a picture display part 6 through a delay circuit 8 and a dynamic filter 5. The delay circuit 8 consists of a fixed delay circuit 9 showing the delay characteristic expressed by a prescribed formula and a variable delay circuit 10 showing the delay characteristic expressed by another prescribed formula. That is, the circuit 9 shows the fixed delay characteristic independent of the depth of a reception focal length. The delay characteristic of the circuit 10 is a positive square-law characteristic but is determined by a control voltage corresponding to the reception focal length. Thus, the curvature of the delay characteristic of the circuit 8 is changed in accordance with the reception focal length, and it shows the approximately parabolic characteristic where the curvature is maximum when the signal is received from the shallow part, and this characteristic gives the fixed and maximum delay time to the reception signal from the center of simultaneously used ultrasonic oscillators 3.