The scanistor—A solid-state image scanner

Scanistors form a new class of semiconducting devices which perform image scanning or dissection by reason of a novel electronic method of commutating a single output terminal to any preselected illuminated portion of the device. The selection is uniquely determined by a voltage applied across two terminals of the device. The present investigation is concerned with a strip-shaped unit called the multijunction scanistor which is comprised of a linear, integrated-circuit array of photodiodes. This device provides an output either as a sequence of pulses which represent spatial sampling of a line image at a discrete number of points, or as an analog wave-form which is a linear transformation of the line image. A theory appropriate to scanners of this type is developed and applied to the multijunction scanistor for purposes of design and analysis. A time-dependent circuit analysis of a model of the scanistor is carried out and tested experimentally. It provides an understanding of the upper limits to the scanning rate set by junction capacitance. Experimental units designed according to theory are tested for their sine-wave response, uniformity of output, sensitivity, and scanning linearity. These units are shown to give good results when used to scan a typewritten document for facsimile display on an oscilloscope.