INFRA-RED AND ULTRA-VIOLET MICROSCOPY 



239 



Fig. 9.15. Bausch and Lomb ultra-violet microscope with an R.C.A. image converter. 



Reference must be made to receivers of the television camera type. 

 They can function below 2300 A and, owing to their sensitivity, it is 

 possible to use faint radiations and to irradiate certain objects for 

 some length of time. Television camera tubes have also been used 

 in Brumberg's colour transposition process. 



3. FLUORESCENCE 



Under the effect of ultra-violet radiation, a fluorescent body has 

 the property of emitting visible radiation. This phenomenon enables 

 detection of substances not visible in a standard microscope. In primary 

 fluorescence the substance radiates light which is visible under the 

 effects of ultra-violet radiation only, without any further processing. 

 In secondary fluorescence, the substance is impregnated with a fluo- 

 rescent solution. 



In order to examine the fluorescent image without the objectionable 

 exciting radiation, stop-filters are provided which eliminate the ultra- 



