A Feedback Light-Amplifier Panel for Picture Storage

With a new type of light-amplifier panel, incorporating optical feedback, a transient input image can be stored for an indefinite time as a black-and-white or on-off picture. Using 420-cycle operation, an exposure of about 1 foot-candle-second is required for triggering an image on, with the excited elements having a brightness of 0.5 foot-lamberts. When desired, the stored image can be rapidly erased by electrical means without the delay normally required by the decay of the photoconductor. A panel construction of 40 elements per linear inch is used, with each element optically and electrically isolated from its neighbors. By means of separate phosphor layers for viewing and feedback, ambient light on the viewing side is prevented from exciting the panel. Calculated and measured curves are shown, indicating the effects of varying the feedback factor in general light amplifier operation. A relation is also derived, taking into account the build-up and decay properties of the amplifier, which specifies the conditions for bistable operation.