RESOLVING POWER OF PHASE MICROSCOPES 



73 



G(r/rj/7r^~pJ 



2.50B±X/4 diffraction plate 

 P>.= 0.5455 

 P>.= 0.7727 



-^r r^ 



■A 



Fig. 11.23. Comparison of the primary diffraction images produced by a 0.14A ± x/20 

 and by a 2.50B±x/-l diffraction plate. Whereas the first minimum occurs near 

 r/r a = 1, that is, near the Airy Umit of resolution, the B-type diffraction plate pro- 

 duces a lower central maximum in the energy density, G(0), and a greater relative 

 amount of energy density in the diffraction rings, h^ = 0.14 in A; h"^ = 2.50 in B. 



play only a secondary role in modifying the shape of the primary 

 diffraction curve and hence in modifying the contrast or resolution in the 

 image. 



The relative energy content in the diffraction rings is less with the 

 Airy-type objective than with any of the illustrated objectives, but the 



