Microscopic investigations parallel light

At its simplest, the collection optics will contain no lenses but will simply define an approximately parallel beam by means of apertures. If small areas of the sample are to be investigated a microscope system may be used, but in that case consideration must be given to the effect of the large collection angle on the polarisation of the detected light. The detection system will usually be a photomultiplier and amplifier whose output is observed either on an electrometer or a chart recorder, although an oscilloscope has been used for dynamic recording. ... 

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