6S6 



DISPLAY SYSTEM DESIGN PROBLEMS 



described above, in that they have higher brightnesses, controlled persist- 

 ence, or good form factor. 



Storage Tubes. The ideal display device is capable of (1) accepting 

 a picture with many bits of information, (2) displaying this for a full frame 

 time as a uniformly illuminated display, and (3) removing the past infor- 

 mation for rewrite in a new frame. The newest display systems approach 

 these goals by using storage tube principles. A storage tube is a device 

 capable of producing a charge pattern on an insulator surface corresponding 

 to input video signals. The charge pattern is developed by secondary 

 emission techniques. Reading of this information by either visual obser- 

 vation or electrical scanning of the storage information is incorporated in 

 the storage tube. The classification of tubes into electrical-to-electrical or 

 direct viewing is determined by the method of reading. The direct-view 

 storage tube, which is finding application in the fixed fire-control system 

 where high ambient light level is a problem, has the capability of displaying 

 a high light level, uniformly illuminated radar presentation. Whereas the 

 light output of a target integrated over the frame time in a conventional 

 CRT is a few foot lamberts, it can be made higher than 1000 foot lamberts 

 in the direct-view storage tube. A typical direct view storage tube usually 

 has two guns. One gun (for writing) produces a fine beam which deposits 

 a pattern of electric charges on an insulating mesh surface located just under 

 the phosphor screen. The other gun produces a highly divergent beam 

 which uniformly floods the whole tube screen. The purpose of developing 

 a wide coUimated beam is to illuminate the phosphor continuously so as to 

 obtain a high level of brightness and a uniformly illuminated picture. The 

 electrons of this beam are, however, able to penetrate the insulating mesh 

 surface only in accordance with the charge pattern produced by the write 



-2500V 



Storage 

 Video Insulator^ 



Signal Writing Gun Collector. 



Flood Gun 



Flood Beam 



150V +10V +10KV 



Glass Envelope 

 Fig. 12-36 Direct-View Storage Tube 



