Abstract: Disclosed is a piezoelectric loudspeaker.According to the present invention, a piezoelectric loudspeaker comprises: a flat compound piezoelectric sheet in which multiple piezoelectric devices are arranged in an organic material; electrodes which are provided on respective surfaces of the compound piezoelectric sheet; an acoustic impedance matching support layer for maintaining the flat compound piezoelectric sheet in a curved shape and for matching an acoustic impedance; and a support frame for supporting the compound piezoelectric sheet at its circumference. Thus, sound reproduction with a desirable frequency properties that have little distortion can be performed.

Abstract: In an image reconstruction method in a nuclear magnetic resonance imaging apparatus, the method comprises first and second steps to get detected data S.sub.I for at least about half of region inclusive of an origin and data S.sub.IV in a region symmetric with respect to a line passing through an origin on one of axes from the detected region in the acquired data space and parallel to the other axis, respectively, third and fourth steps to perform inverse Fourier transform on the data S.sub.I and S.sub.

Abstract: An ultrasonic measuring system including a transducer having a plurality of row electrodes on one surface thereof and a plurality of column electrodes crossing the plurality of row electrodes on the other surface thereof and made of an electrostrictive material in which piezoelectricity is induced by a bias electric field applied thereto to thereby obtain sectional images sequentially. A row position selector is connected to the row electrodes to select several row electrodes and apply a direct current bias voltage to the selected electrode and to shift the position of the selection sequentially. An electronic B-mode image scanner is connected to the column electrodes to shift the directivity of the transmission/reception ultrasound beams sequentially widthwise of the column electrodes (in the direction of row extension) to obtain echo signals indicative of an acoustic reflective response.

Abstract: In an ultrasonic probe produced by forming stripe electrodes on a piezoelectric composite material consisting of a plurality of piezoelectric ceramic rods buried in an organic material, the gaps between the stripe electrodes in the direction of disposition are expanded as much as possible while the gaps of the piezoelectric ceramic rods or their width in the direction of disposition is reduced as much as possible. When the width of the piezoelectric ceramic rod is reduced in the manner described above, the width of the piezoelectric ceramic rod is expanded in a direction orthogonal to the direction of disposition or the gaps of the piezoelectric ceramic rods in that direction is reduced in order to reduce crosstalk and to improve flexibility and sensitivity.

Abstract: An input device such as a keyboard or a tablet for input of pattern employing a piezoelectric material/polymer 1-3 composite of the structure in which a number of rods of piezoelectric material are buried in a polymer.

Abstract: Disclosed is an ultrasonic probe which is capable of externally and selectively controlling the conversion efficiency of an electroacoustic conversion portion. For the electroacoustic conversion portion is used a material which does not exhibit or exhibit the piezoelectricity depending on the absence or the presence of bias electric field, for example, a certain kind of ferroelectric material which is maintained at a temperature in the vicinity of the phase transition temperature thereof or a material having high electrostrictive effect. The electroacoustic conversion efficiency is controlled by applying bias electric field to such a material.

Abstract: A ultrasonic transducer using such a piezoelectric composite that a number of piezoelectric poles made of piezoelectric ceramics are arranged in a plate-like polymer matrix perpendicular to the plate surface. The volume ratio of the piezoelectric poles is set in a range of 0.15-0.75 and a spacing between every adjacent piezoelectric poles is set smaller than the thickness of the polymer plate, thereby resulting in a transducer which has higher sensitivity than the conventional one using a homogeneous piezoelectric ceramic plate.

Abstract: A monolithic array ultrasonic transducer has a plurality of transducer elements formed thereon by isolating metallized areas on a piezoelectric plate without cutting the piezoelectric plate apart for each transducer element, and an acoustic matching layer having a longitudinal wave velocity within .+-.25% of a longitudinal wave velocity of the piezoelectric plate and a thickness equal to one half of that of the piezoelectric plate. The acoustic matching layer suppresses the radiation to an object of a partial wave in a direction of 60.degree. to a normal line to the plane of the piezoelectric plate.

Abstract: An ultrasonic transducer using a piezoelectric composite in which a plurality of piezoelectric poles are arranged in matrix maintaining a gap and a polymer is charged into the gap. The piezoelectric poles are arranged maintaining a pitch which is shorter than a wavelength of a sound wave at a fundamental resonance frequency of the transducer in a medium. Further the pitch may be changed in a direction in which the piezoelectric poles are arranged, in order to restrain the grating lobe from generating.

Abstract: A high-sensitivity ultrasonic probe comprising a plate of a composite material having the regions of a piezoelectric ceramic polarized uniformly in the direction of thickness and the regions of polymer, both regions existing dispersed alternately in the direction parallel to the plate surface, electrodes formed on both sides of the composite material, and a connecting layer formed on at least one side of the composite material and composed of a material harder than said polymer.

Abstract: An acoustic microscope wherein an ultrasonic beam is projected on a sample through a propagating medium by an ultrasonic transducer having a short focus, reflected acoustic waves from the sample are detected by the transducer, and a microscopic image of the sample is obtained by scanning the sample mechanically in two dimensions, comprises a cover member which is interposed between the sample and the propagating medium and which has an acoustic impedance higher than those of the two. The intensity of a reflection signal depends upon multipath reflection within the cover member, and an intense reflection signal is obtained even for a sample which differs slightly in the acoustic impedance from the propagating medium.

Abstract: A probe which is inserted into a lumen to obtain an ultrasonic tomogram using mechanical scanning is disclosed. A cylindrical acoustic case is filled with a liquid medium which transmits sound waves, and an elliptical ultrasonic transducer is immersed therein in such a manner that it can be rotated by a motor. The diameter of the transducer parallel to its axis of rotation is greater than that perpendicular to the axis of rotation, so that the lateral resolution parallel to the axis of rotation is improved, as well as the sensitivity.

Abstract: A tomographic imaging system is disclosed in which the quantity of absorption or transmittance of a transmissive radiation by or through a certain tomographic cross-section of an object under consideration is detected and the distribution of radiation absorption or transmittance in the cross-section is reconstructed through a convolution operation. A weighting function used in the convolution operation is prepared with a predetermined one of its positive orders the value of which is an integration of the weighting function from the predetermined positive order to positive infinity and a predetermined one of its negative orders the value of which is in integration of the weighting function from the predetermined negative order to negative infinity.

Abstract: In a system in which the tomographic image of an object under investigation is produced on the basis of the amount of absorption of radiation by the object when a source of radiation and a plurality of radiation sensitive detectors with the object interposed therebetween are rotated around the object, the output signal from at least one of the plural detectors is used to correct the radiation absorption amount. Another selected one of the plural detectors may be used for checking whether the object is positioned within a useful detection view.