12-9 



SPECIAL DISPLAY DEVICES 



659 



Vertical Deflection 

 Plates 



Transparent 



Horizontal Deflection 

 Plates 



Fig. 12-37 The Aiken Tube. 



to the right. This is true since the electrons closer to the deflection plates 

 have a sharper radius of curvature than the electrons farther removed from 

 the plate. The coarsely focused beam can now be considered as a ribbon 

 beam when it travels upward. This process is repeated in the other plane 

 when acted on by the second set of deflection plates as shown in Fig. 12-38. 

 This double focused beam is brought to bear on the phosphor. 



One of the limitations of the tube is the need for multiple plates to 

 deflect the beam. Present experimental tubes use ten deflection plates 

 for horizontal deflection and ten more plates for vertical deflection; it is 

 necessary to provide separate and sequential sweep voltages to each plate. 

 Various deflection mechanization schemes have been used, including the 

 use of a separate amplifier for each plate, delay lines, radial switch tubes, 

 and other special devices. 



Although this tube still has sealing and stress problems and deflection 

 mechanization problems, the excellent form factor and special features such 

 as transparency, multiple color display, and high resolution make it very 

 attractive for radar system display use. 



Transparent Phosphor Films. Research work is being done on the 



development of thin transparent phosphors to improve the CRT resolution 

 by negating the optical scattering properties of conventional powders used 

 to make the phosphor screen and to overcome the reflectivity problem at 

 high ambient light levels. The transparency of the film limits reflectivity 

 and allows viewing the backside of the screen. The thinness and homoge- 



