REFLECTED-LIGHT MICROSCOPY 



143 



two rays, one reflected, IR, one transmitted, IT. The ray IR is re- 

 flected by the object A, passes through the separator and enters the 

 microscope's objective O, . The transmitted ray IT is reflected on the 

 silvered side MM' of the prism Po , then on the gap //' and enters the 

 objective Oi. The wave, deformed by the unevennesses of the object A. 



Fig. 4.22. Sagnac interference microscope. 



interferes with the reference plane-wave reflected by MM\ The 

 unevennesses of the object A are thus evinced. Linnik's, Krug's and 

 Lau's rnicroscopes are also based on the principle of the Michelson 

 interferometer. 



Liunik^s interference microscope (Fig. 4.23.) 



The incident light-beam from the vertical illuminator, schematized 

 in Fig. 4.23, is spht in two by the 45°, slanted separator G. Some of 

 the light is reflected in the lower part of the figure, passes through 

 the objective O^ and illuminates the object P. It is then reflected back, 

 passes again through O^ and the separator G, and travels towards 

 the eyepiece 0^. The light, transmitted by G, passes through the 

 objective 0[ (which is identical with Oi), is reflected back by the 

 mirror M, passes through 0[ again and is reflected back by G to the 

 eyepiece O2. Both images of the source S, F^ and F[, are formed 

 in the focal plane of the two objectives O^ and 0[. 



The wave 27^, deformed by the surface unevennesses of the object P, 

 and the reference plane- wave E[ , interfere in the image P', seen through 

 the eyepiece Oo. If the image of the mirror M, through reflection 

 on G, is parallel with P, the field is uniform. Thickness unevennesses 

 show up as fight-intensity changes. Tilting M sfightly causes the 



