INTERFERENCE MICROSCOPY 



fiage plane- ^^q 



Polarizer-—^ 



L, - 



To eyepiece 



Specimen- 



-Anal 



alyzer 



q^Rotatable wedge 

 with central hole 



--Savart plate 



•Objective 



Condenser 



ource 



Mirror- 



Fig. 10. The NIFE interference microscope. Except for the slit, an ordinary microscope may be used 

 up to lens Lz . This lens coUimates the light for passage through the Savart plate, which is between 

 crossed polarizer and analyzer. The wedge and the specimen image are reimaged by lens L4 , the new 

 image being doubled because of the Savart plate. 



color matching technique and the advan- 

 tages of the sht source. 



Leitz Interference Microscope. A recent ad- 

 dition to the commercially available inter- 

 ference microscopes is the Leitz Interference 

 Microscope (29). See Fig. 11. In the con- 

 denser light is divided by means of a prism 

 system. Two identical objectives are used, 

 one to view the object, the other to receive 

 light transmitted through a reference slide. 

 Six tiltable compensator plates are used to 

 adjust the interference fringe pattern. An- 

 other prism system unites the two beams be- 

 fore the eyepiece. Measurements are made 

 either visually by means of a wedge com- 



pensator or by photographic photometry. 

 The accuracies obtained are 1/70 and 1/200 

 wavelength, respectively (29). 



A major advantage of this system is the 

 complete removal of the reference beam 

 from the specimen area. That is, there is no 

 error due to part of the reference beam pass- 

 ing through the object or through an un- 

 known area of the slide, and there is no out- 

 of-focus image in the field. In return for this 

 advantage it is necessary that objectives 

 be carefully matched by the manufacturer. 

 The user must compensate for the slide — 

 mounting medium— coverglass system by 

 proper adjustment of the tiltable compen- 



430 



