634 DISPLAY SYSTEM DESIGN PROBLEMS 



diameter front face. The length of such a tube using electrostatic deflection 

 is usually greater than 18 inches. Associated with the tube, and usually- 

 packaged in the same unit, is the high-voltage supply for the tube. The 

 combination makes for inefficient form factor. Developmental display 

 devices such as electroluminescence and the flat plate tube (these are 

 described in Paragraph 12-9) give hope of reducing the volume. 



Special Features. The requirements of certain applications may 

 necessitate certain display device characteristics not normally found in 

 the ordinary CRT — e.g., color, storage, and erase features and three- 

 dimensional representations. As will be described later in this chapter, such 

 features may be provided by special types of display devices. Generally 

 speaking, however, such characteristics are provided at the sacrifice of 

 some of the other important characteristics, such as resolution, contrast, 

 bandwidth, and tube size and complexity. Thus, the designer must 

 scrutinize all the important characteristics of a display device to ensure 

 that he has not purchased freedom from one problem at the price of 

 creating several new problems. 



Susceptibility to Influence of the Physical Environment. The 



displays discussed are subject to environmental conditions which have an 

 efi^ect on the presentation. The ambient light level on the open cockpit 

 indicators of fighter aircraft may vary from darkness to several thousand 

 foot-lamberts. In the latter case, the presentation of the CRT tends to be 

 washed and the phosphor exhibits practically no persistance. The tube 

 has to be driven to a maximum beam current; therefore, resolution and 

 gray scale are limited. The tubes are also subject to a wide temperature 

 range as well as vibration and shock and therefore must be ruggedly 

 constructed. For military application the requirements are given in the 

 MIL-E-1 specification. 



12-7 IMPORTANT CHARACTERISTICS OF THE HUMAN 

 OPERATOR 



When the human operator is an integral part of an airborne radar 

 system, the achievement of optimum performance depends upon how well 

 his characteristics are considered in the design of the system. The charac- 

 teristics of the human operator that can influence the system can be 

 divided into the following categories: (1) physical, (2) physiological, 

 (3) psychological, and (4) anthropometric. The anthropometric data, or 

 measurements of the parts of the body, will not be considered in this 

 discussion since these data have been adequately presented elsewhere®; 



^C. W. Bessemer, Missile En<!,ineerin'i Handbook, pp. 378-380, D. Van Nostrand, Princeton, 

 N. J., 1958. 



