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21 November 1977 Virometer-An Instrument For The Measurement Of The Size Of Viruses Using An Optical Microscope
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Viruses are too small to resolve in an optical microscope so their sizes have generally been measured using electron microscopes. The problem we have addressed is this: there is a solution containing on the order of 1012 viruses per ml. They are all the same size; somewhere between 200A and 3000A in diameter. How does one accurately measure their size using only an optical microscope to view them? The problem is compounded by the fact that even using a focused 100 mwatt laser beam, the amount of light scattered by a small virus is too small to conveniently detect. A further complication: virus-sized particles, in the solutions in which they naturally occur and in which we would like to observe them, are in constant Brownian motion. Our solution to this problem has been embodied in an instru-ment called a Virometer and involves evanescent waves, noise spectra, and fluorescent stains. This paper describes the design and operation of the Virometer, and gives examples of its use. Using a 1 μl sample and a 60 sec observation time, viruses less than 300A in diameter have been accurately sized at concentrations as low as 108 viruses per ml.
© (1977) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael Hercher "Virometer-An Instrument For The Measurement Of The Size Of Viruses Using An Optical Microscope", Proc. SPIE 0126, Clever Optics: Innovative Applications of Optics, (21 November 1977);

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