Classical optics has a well defined limit of resolution that is given by 2. In the past this quantity was considered as a firm barrier that one could not overcome. Hence the solution to get higher resolutions was to use the particle-wave duality to get shorter wavelengths, for example the electron microscope. However, in 1952 Toraldo di Francia foresaw that the classical limit was in reality not as formidable as its looked at that time. He suggested ways to achieve higher resolutions (the multiple corona approach). Furthermore, he saw the connection between super resolution and evanescent light fields. He performed the first experiments showing the existence of evanescent fields in the range of visible optics. In recent times a variety of experimental set ups have been utilized to go beyond the classical optics limit, the more effective ones based on the use of optical fibers tips to sense near fields (near field microscopy). In this paper, it is shown for the first time that full field near field observation is possible. Further by combining the optical advantages gained with the use of evanescent fields with numerical techniques of super resolution one can go well beyond the classical limit getting to the region of /8 by optical means and reaching the /20 with super resolution numerical techniques. Examples are shown of the observation of the shapes of small particles including some nanocrystals geometries.
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|Titolo:||Determination of the shape of objects in the range of 1/20 of the wavelength of light|
|Data di pubblicazione:||2007|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|