Picture intensifier tube with memorization

Claim 1

A picture intensifier tube comprising a vacuum enclosure enclosing at opposite ends an input screen which is adapted to be irradiated with radiation corresponding to the image to be intensified and incorporates a photocathode for emitting electrons corresponding to the image, simultaneously over its entire emitting surface, and an output screen separated by space from the input screen and positioned to be bombarded by the emitted electrons for providing the intensified image, characterized in that the output screen comprises an electroluminescent cell which has a pair of opposed surfaces, is adapted for emitting visible light rays when an alternating voltage of amplitude larger than that of a characteristic threshold voltage is applied between its surfaces, has hysteresis such that so long as the applied voltage is maintained above an erasure voltage light emission is maintained even though the applied voltage drops below the characteristic threshold voltage, and has the property that electron bombardment effectively augments the applied voltage so that even an applied voltage lower than the characteristic threshold voltage permits emission of visible light.