128 



RADAR SCOPES 



emphasizes the contribution of operator skill 

 to the overall efficiency of the radar system. 

 Operators really become trained in pipology, 

 of course, and a fair amount of psychological 

 research has already been expended on the 

 problems of training methods. Training 

 will no doubt change with the years, particu- 

 larly with respect to training models and 

 devices. For research on training methods 

 carried out during the war, the reader is re- 

 ferred to the reports of Project SC-70, NS- 

 146 of the Apphed Psychology Panel, NDRC 

 (32), and to Report No. 12 of the Army 

 Air Forces, Aviation Psychology Program 

 (9). Both references also deal with tests 

 for selecting the best operators. 



Summary 



The general design of cathode-ray tubes is 

 discussed in relation to the visual require- 

 ments of a human observer, with the chief 

 emphasis on intensity modulated scopes of 

 the type used in search radar. Radar scopes 

 are rather poor as viewing screens, because 

 they flicker and fluctuate in such a way as to 

 make them difficult to maintain at optimal 

 brightness. Even when they are operated 

 optimally, they fall short of ideal visual 

 requirements. Improvements to date have 

 been notable but they have not been suffi- 

 cient for two reasons: (1) there is a genuine 

 lack of properly coordinated knowledge of 

 the visual requirements themselves, and (2) 

 the luminous output of electronic excita- 

 tion of phosphor screens is not accurately 

 predictable. Nevertheless, workers in both 

 visual science and radar engineering have 

 recently made significant advances as a re- 

 sult of direct visibility tests of various scopes. 

 A major Hne of research is the investigation 

 of the radar parameters which significantly 

 determine visibihty. Most of the research 

 work in this field has been reviewed with the 

 aim of highlighting the major problems and 

 disclosing areas of ignorance. The major 

 variables in visual detection are : the bright- 

 ness and uniformity of the viewing screen; 

 the contrast, shape and size of the pip to be 



seen; and the methods of visual search used 

 by the observer. Many of these depend on 

 the electrical parameters of the radar pulsing 

 and receiving system. The functions relat- 

 ing the visual to the electrical variables are 

 only partly known today, but those that are 

 known are briefly described. 



References 



1. AsHBT, R. M., JosEPHsoN, V. & Sydoriak, S. 



Signal threshold studies. Naval Research 

 Laboratory Rep. No. R-3007, 1 Dec. 1946. 

 Pp. 38. 



2. Bachman,C.H. Image contrast in television. 



General Electric Rev., 1945, 48, 13-19. 



3. Bartlett, N. R. The relation between criti- 



cal flicker frequency and flash duration. 

 Amer. Psychologist, 1947, 2, 295. (Abstract) 



4. Bartlett, N. R., & Williams, S. B. Signal 



mark size and visibility of radar signals on a 

 plan position indicator. Systems Research 

 Laboratory, The Johns Hopkins University. 

 Rep. No. 166-1-30. 20 Sept. 1947. Pp. 16. 



5. Bartlett, N. R., Williams, S. B., & Hanes, 



R. M. Visibility on cathode-ray tube screens: 

 The effect of size and shape of pip. Systems 

 Research Laboratory, The Johns Hopkins 

 University. (In preparation) 



6. Blackwell, H. R. Contrast thresholds of the 



human eye. /. opt. Soc. Amer., 1946, 36, 

 624-643. 



7. Bramley, a. Aluminum backed phosphor 



screen in cathode ray tubes. Electrochem. 

 Soc, preprint No. 91-30 for meeting Apr. 

 9-12, 1947, 463-466. 



8. Brill, E. R. The improvement in minimum 



detectable signal in noise through the use of the 

 long after-glow CR tube, and through photo- 

 graphic integration. Harvard University 

 Radio Res. Lab. Rep. No. 411-84, 8 Feb. 

 1944. Publ. Bd. No. 14158, U. S. Dept. of 

 Commerce. Pp. 27. 



9. Cook, S. W. (Ed.) Psychological research on 



radar observer training. AAF Aviation 

 Psychology Program Reports. U. S. Gov. 

 Printing Office, No. 12. 1947. Pp. 331. 



10. Craik, K. J. W., & Macpherson, S. J. The 



effect of certain operating conditions on the 

 visibility of P.P.I, radar echoes. 1945. 

 Med. Res. Council, APRU, Psychol. Lab., 

 Downing St., Cambridge. APU 16. 



11. Crouch, C. L. The relation between illumi- 



nation and vision. Ilium. Engng., 1945, 40, 

 747-784. 



12. Epstein, D. W., & Pensak, L. Improved 



