Pressure sensitive film display having multiple gray levels

摘要

A pressure sensitive film display is disclosed having a piezoelectric substrate and a thin film of pressure sensitive phase change material disposed thereon. A film of pressure sensitive material such as samarium sulfide is deposited on a piezoelectric substrate and exhibits a marked increase in reflectance at a region thereof subjected to a pressure in excess of a selected threshold pressure. Three interdigital surface acoustic wave transducers are provided along three edges of the display and are utilized to produce selective surface acoustic wave pulses in the surface of the film. Each surface acoustic wave pulse generates an area of pressure such that an external pressure greater than the selected threshold pressure is generated only at each point where three surface acoustic wave pulses intersect. Circuitry is provided for ensuring that all three surface acoustic wave pulses can intersect at any selected region of the film and the pulsewidth of at least one surface acoustic wave pulse is selectively varied to allow only a selected portion of any selected region to exhibit the increase in reflectance. In this manner the gray level of each selected region may be altered accordingly.