MICROSPECTROSCOPY AND MICROSPECTROPHOTOMETRY 



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When photographic layouts are involved, a double beam arrange- 

 ment may be used (Fig. 10.6). The light from the monochromator 

 (not shown in Fig. 10.6) may follow alternatively two different paths: 

 the normal path through the microscope and the comparison path, 

 ending direct on to the photomultipher R. The mirror m^ moves 

 to and fro, thus alternating the beams corresponding with both paths. 



Fig. 10.5. Diagram of a basic system for microspectrophotometry with photo-cell. 



The objective Oi images the specimen P on the diaphragm Ti, set 

 close to the lens l^. The lens I^ images O^ on the photomultipher. 

 The lens 4, athwart the comparison beam, ensures uniform illumination 

 of the photomultipher R. The adjustable diaphragm Tg is set against 4 

 while the continuous adjustment of the intensity of the reference beam 

 is provided by the neutral wedge W. The photomuhiplier-suppHed 

 signal is amplified in the amplifier AM and eventually fed to the 

 oscillograph U. 



The measurement consists in equalizing the signals generated by 

 the two beams, this being accomplished by merely shifting JV whose 

 positions are shown by a graduated scale. Since the image A' of the 

 detail A is formed on T^, the signals are equalized when the neutral 

 wedge W is in the position W^'. 



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