RESEARCH ON VISIBILITY: INTENSITY-MODULATED SCOPES 



115 



♦ 05 



1 I 



2 



I I f 5 '° 



PULSE LENGTH (MICROSEC ) I I 



5 10 50 100 



VISUAL ANGLE (MINUTES) 



50 



Fig. 5. Visibility as a function of pulse length 

 Data are shown only for two beamwidths (1° and 60°) and for three bias levels. Dim is the visual 

 reference bias and is, effectively, about 0.0001 ft.-L; optimal is 5.5 volts less, about 0.1 ft.-L; bright is|10 

 volts less than the reference, about 2 ft.-L. No video noise. Otherwise conditions are same^aslin Fig. 

 2. Reprinted from Bartlett, Williams and Hanes (6). 



KEY 



O 0.5 MICROSECONDS 

 A 30 MICROSECONDS 



OPTIMAL 



BRIGHT 



BEAM WIDTH 

 ' (DEGREES) 



10 I 50 I 



50 100 VISUAL ANGLE 500 



(MINUTES) 



Fig. 6. Visibility as a function of beamwidth 

 Conditions same as for Fig. 5; reprinted from Bartlett, Williams and Hanes (5). 



dimension are exposed simultaneously, sizes, then, correspond more to those in 

 whereas points on the angular dimension optical presentations; angular sizes, above 

 (azimuth) are exposed successively. Radial a few degrees, are more of a gradual "un- 



