64 



AN ELEMENTARY THEORY OF PHASE MICROSCOPY 



ness of the B-type diffraction plate in observing stained and other 

 biological or industrial particles was appreciated after the utility of the 

 A-type diffraction plate had been well established. Since h" = 1.81 



5.5 



5.0 



4.5 



4.0 



3.5 



3.0 



2.5 



2.0 



1.5 



1.0 



0.5 



0.5 



1.0 



1.5 2.0 



2.5 3.0 



Fig. 11.18. The energy densities Gs and Gp as functions of h at the indicated fixed 

 values of 5 with a particle for which A = +x/4 and g = 0.9. 



and since —42° = —0.1166 X, the best B-type diffraction plate for use 

 with a particle for which A = +X/4 and g = 0.9 will be the 1.8B — 0.117X 

 diffraction plate. 



The curve of Fig. 11.19 for the contrast value K has been plotted as a 

 function oi g for a diffraction plate whose In, and 5 values are fixed at 

 1p? = 1.81 and 5 = —42°. The optical path difference of the particle 

 is fixed at A = +X/4, but the g value extends over the entire range from 



