144 



PROGRESS IN MICROSCOPY 



image of M to be no longer parallel with P and straight fringes are 

 developed. The greater the space between these fringes the wider the 



r 



Fig. 4.23. Linnik interference microscope. 



angle formed by the image of M and P. Now, thickness uneven- 

 nesses can be measured by shifting the fringes. This microscope is 

 built in the U.S.S.R. 



L,c:i=3 



0, 



p '/////./-■ '/^ 



Fjg. 4.24. Zeiss interference microscope. 



Zeiss (K. Raentsch) has also designed a microscope based on this 

 principle (Fig. 4.24). In this instrument, the direction and spacing of the 

 fringes are adjusted by the two plates L^ and Lo set in the pupils of the 



