120 



PROGRESS IN MICROSCOPY 



11. AXIAL IMAGE DUPLICATION INTERFERENCE MICROSCOPES 



Smith investigated an instrument, based on microscopes of the 

 type c, described in § 5, which was buiU by Messrs. C. Balcer Ltd. 

 This instrument is shown in Fig. 3.21: it is convertible and either 

 the full sidewise-duphcation or the method now described can be 

 applied to it. 



Reference to Fig. 3.31 shows the spar plate ^o- only a few tenths 

 of a millimeter thick, cemented against the frontal lens of the mic- 



.1 . 



Z) 



=1 p 



Fig. 3.31. Smith inlerferencc microscope. 



roscope objective Oy and cut parallel to its axis. It is well known 

 that the surface-wave of a single-axis crystal such as spar comprises 

 two portions: the ordinary and the extraordinary wave surfaces 

 (a sphere and an ellipsoid, respectively). When a beam of ordinary 

 rays passes through the objective O^. the latter images the specimen P 

 at Pn. The effect on these rays is that obtaining had a mere glass 



o 



plale been cemented to the front lens. The effect is quite different 



