136 



PROGRESS IN MICROSCOPE' 



The Bendford and Seidenberg layout ( Baiisch and Lomh) 



The instrument is shown diagramniatically in Fig. 4.10. The 

 source S is projected on the annular diaphragm D^ which is imaged 

 at F\ after being reflected in the prism /?i. passing through the lens C 

 and the 45'-slanted plate G. The focus of the objective O^ coincides 

 with F' so that, for every point of the source, the light-emerging 



Fig. 4.10. Bendford and Seidenberg device. 



from the objective O^, forms a parallel beam. The rays are re- 

 flected by the reflective object /*, pass through the objective O^ and are 

 reflected on G. The retractable prism R.. reflects the light into the 

 eyepiece O., designed to observe the image without phase-contrast. 

 The prism R-i, being removed, the light passes through the optical sys- 

 tem Lo which images F\ i.e. the diaphragm D^. on the phase-plate Q. 

 Next, the light passes into the cube R^ which splits it in two equal 

 parts: the first passes through the eyepiece O;,, the other proceeds 

 to the photographic plate E. The image, observed in the eyepiece O3, 

 and the photographic-plate image, are both phase-contrasted. The 

 device is so adjusted that the object P, imaged by the objective O^. 

 is focused simultaneously on the photographic plate and in the 

 eyepiece O^. 



I 



3. OBLIQUE ILLUMINATION AND DARK GROUND IN REFLECTED LIGHT. 



SCHMALTZ'S SLIT 



In reflecting microscopes, oblique illumination enables one to detect 

 surface unevennesses. In Schmaltz's method, a slit is imaged by the 

 optical system C (Fig. 4. 11) on the surface to be studied P. The axis 



