Abstract: An acoustic lens system is constructed so that at least one surface of acoustic lenses constituting the acoustic lens system is an aspherical surface, which has such a shape that curvature moderates progressively in separating from the axis of the acoustic lens system, and an acoustic beam stop is provided therein. As a result, aberrations can be favorably corrected even when the angle of view and the numerical aperture are increased and this brings about the acoustic lens system suitable for an objective lens of an acoustic system for securing an image of an object having a two-dimensional size in particular.

Abstract: The acoustic lens system is used for ultrasonic imaging in an ultrasonic system which displays an image of an object while transmitting ultrasonic waves and receiving the ultrasonic waves reflected from the object, and has a half field angle .omega. expressed as follows: ##EQU1## wherein the reference symbol v.sub.0 represents the velocity of sound in the medium located on the incidence side of the first lens surface and the reference symbol v.sub.1 designates the velocity of sound in the medium located on the emergence side of the first lens surface. Accordingly, the acoustic lens system according to the present invention is remarkably excellent in the performance thereof in respect of field angles, aberrations, aperture angles, attenuation, etc., and has an advantage to permits further reducing acoustic attenuation and preventing spurious images from being formed due to multiple reflections by arranging antireflection films on the lens surfaces.

Abstract: An acoustic lens system is constructed so that at least one surface of acoustic lenses constituting the acoustic lens system is an aspherical surface, which has such a shape that curvature moderates progressively in separating from the axis of the acoustic lens system, and an acoustic beam stop is provided therein. As a result, aberrations can be favorable corrected even when the angle of view and the numerical aperture are increased and this brings about the acoustic lens system suitable for an objective lens of an acoustic system for securing an image of an object having a two-dimensional size in particular.

Abstract: A ferroelectric memory includes a ferroelectric thin film having first and second surfaces opposite to each other, a first electrode assembly having a plurality of stripe electrodes arranged in parallel on the first surface side of the ferroelectric thin film, a second electrode assembly having a plurality of stripe electrodes arranged in parallel on the second surface side of the ferroelectric thin film to intersect the stripe electrodes of said first electrode assembly, first and second common electrodes arranged separately from the end portions of the respective first and second electrode assemblies to extend in respective directions in which the stripe electrodes of the first and second electrode assemblies are arranged, and selecting sections for respectively connecting the first and second electrode assemblies to the first and second common electrodes and selectively activating at least one of the stripe electrodes of each of the first and second electrode assemblies.