LIGHT SOURCES AND DETECTORS 



To detect radiant energy beyond 3 /n a. Mullard 61RV lead-selenide 

 uncooled cell may be used (Figure 28.45); alternatively, the 63TV lead- 



100 



30 

 at 



c 

 o 



S- 10 



a: 



123 45 678 



Figure 28.45 Spectral sensitivity curve of a 61 R V Mullard lead-selenide cell 



100 



30 



10 



01 



c 



O. 3 

 (U 



0-3 



0-1 



1 



Figure 28.46 Spectral response curve of a Mullard 63TV 

 cooled lead-telluride cell 



telluride cell is available, which requires liquid O^ or Ng for its operation 

 {Figure 28.46). The 61RV has a time constant of 15 /isec, and the 63TV, 10 

 to 100 //sec. 



376 



