Hugh F. Frohbach

Electrostatic electrographic printing

This paper describes the empirically observed characteristics of electrographic printing in which electrostatic charge patterns are deposited onto a dielectric surface via a contacting electrode and subsequently made visible by toning. The process exhibits a threshold effect that may be used in simplifying the addressing circuitry. An equivalent circuit of the electrode and dielectric coated-paper combination that incorporates the threshold effect is presented. Typical printers using this electrographic process are described, and some requirements of the drive circuitry necessary for such printers are discussed.

An Ultrasonic Camera System for Medical Diagnosis

An ultrasonic camera system for throughtransmission as well as reflection imaging has been developed for diagnostic use. The ultrasonic camera produces real-time focused, orthographic images of a 15- x-15 cm field. A specially designed linear array of 19 2 piezoelectric detectors provides both high resolution and high sensitivity. The camera incorporates a unique wavefield deflection system which scans the focused image past the transducer array, producing 15 image-fields per second on a television display. The principles of operation of this camera system are described and demonstrated.