Cathode ray tube

Claim 1

A STORAGE TUBE COMPRISING A STORAGE SCREEN INCLUDING A CONDUCTIVE SUBSTRATE, A UNIFORMLY THIN LAYER OF CUBIC ZINC SULFIDE DISPOSED OVER AT LEAST A PORTION OF SAID CONDUCTIVE SUBSTRATE TO PROVIDE STORAGE SURFACE; MEANS FOR PRODUCING A NEGATIVE VOLTAGE DROP ACROSS SAID LAYER OF CUBIC ZINC SULFIDE; MEANS FOR COLLECTING SECONDARY ELECTRONS EJECTED FROM SAID STORAGE SURFACE THEREBY TO CAUSE ELECTRONS OF A PREDETERMINED ENERGY LEVEL TO CHARGE SAID STORAGE SURFACE BY SECONDARY ELECTRON EMISSION AND TO DISCHARGE SAID STORAGE SURFACE BY BOMBARDMENT INDUCED CONDUCTIVITY AT THE SAME RATES; MEANS FOR PRODUCING AN ELECTRON BEAM HAVING A FIRST ENERGY LEVEL, SAID FIRST ENERGY LEVEL BEING LESS THAN SAID PREDETERMINED ENERGY LEVEL AND WITHIN THE RANGE OF POTENTIAL LEVEL WHEREIN THE SECONDARY ELECTRON EMISSION RATIO OF SAID LAYER OF CUBIC ZINC SULFIDE IS GREATER THAN UNITY; MEANS FOR SCANNING SAID ELECTRON BEAM OF SAID FIRST ENERGY LEVEL OVER SAID STORAGE SCREEN THEREBY TO CHARGE ELEMENTAL AREAS OF SAID STORAGE SURFACE IN POSITIVE DIRECTIONS IN PROPORTION TO THE INTENSITY OF SAID ELECTRON BEAM OF SAID FIRST ENERGY LEVEL INCIDENT THEREON TO PRODUCE A CHARGE PATTERN; MEANS FOR PRODUCING AN ELECTRON BEAM OF A SECOND ENERGY LEVEL, SAID SECOND ENERGY LEVEL BEING GREATER THAN SAID PREDETERMINED ENERGY LEVEL AND WITHIN THE RANGE OF POTENTIAL LEVELS WHEREIN THE SECONDARY ELECTRON EMISSION RATIO OF SAID LAYER OF CUBIC ZINC SULFIDE IS GREATER THAN UNITY; AND MEANS FOR SCANNING SAID STORAGE SCREEN WITH SAID ELECTRON BEAM OF SAID SECOND ENERGY LEVEL THEREBY TO INDUCE CONDUCTIVITY THROUGH SAID LAYER OF CUBIC ZINC SULFIDE TO SAID CONDUCTIVE SUBSTRATE THEREBY TO DISCHARGE SAID STORAGE SURFACE TO A DETERMINABLE REFERENCE POTENTIAL LEVEL.