Abstract: A method and apparatus for a personal identification card system includes a card having a plurality of lamina joined permanently together, with identification information written on the inner surfaces of the lamina. The information is not visible from the exterior of the card, and is written as analog and digital indicia and images adapted to be read by ultrasonic imaging means. An ultrasonic imaging card reading terminal may include either pulse-echo, through-transmission, or tomographic amplitude sensing devices, or may include acoustic holographic imaging sensors for appropriately formed indicia and images. The personal identifying data contained within the card may include a fingerprint image or an acoustic vocal spectrogram of the individual, as well as personal identifying numbers, signature, and the like.

Abstract: A method for control monitoring the phase, depth, and area polarization of a piezoelectric transducer element. A piezoelectric element is energized by electrical pulses of controlled amplitude, duration, and repetition rate, and the response of the element is recorded by an oscilloscope or other suitable device. By properly matching the configuration, duration, and repetition rate of the driving pulses, with respect to the desired depth and phase of individual element layers, controlled-phase controlled-volume transducers may be achieved with a single piezoelectric transducer element.

Abstract: A method for obtaining controlled depth, controlled area, and controlled phase polarization of a piezoelectric transducer element. A controlled phase bias voltage is applied to two generally opposing surfaces of the transducer element, and heat is then applied in a pulsed fashion to one of the two surfaces. By properly coordinating the phase of the bias voltage and the pulsed heating of the one surface, discrete layers of polarization may be created between the two surfaces, the phase, area and depth of the discrete layers being accurately controllable.