REFLECTED-LIGHT MICROSCOPY 



137 



of the observation microscope objective O, is at right angles to the 

 optical system C. The observed surface P is, therefore, illuminated 

 at a 45^ angle. Let us assume that, in some area of the field of view, 

 the sample surface is at P. In this area, the slit is imaged at A. If, in 



Wo, 



Fig. 4.11. Schmaltz's method. 



another area, the surface is at P^, the image slit is visible at A-^. The 

 difference in level h is shown by the lateral motion d = h ] 2 of the 

 imaged sHt. The unevenness shown in Fig. 4.12 is the strip-shaped 

 extra thickness A^, the remainder of the object (A) being flat. 



Owing to the instrument's layout, the space between the objectives 

 and the object P is always large. This fact makes the use of 



Fig. 4.12. Image aspect in Schmaltz's method. 



objectives, whose focal length is less than 16 mm, hardly feasible. 

 Only low magnifying powers are usable. Schmaltz's layout was im- 

 proved by Busch and Tolansky who designed the microscope ob- 

 jective Oi so as to illuminate and be used for observation at the same 

 time (Fig. 4.13). The source S is imaged by the lens L in the sHt F. 

 The rays originated from F are reflected by the mirror M, pass through 

 the objective Oi and after being reflected in the object P, form the 



