Vertico SMI

Vertico spatially modulated illumination (Vertico-SMI) is the fastestlight microscope for the 3D analysis of complete cells in the nanometer range. It is based on two technologies developed in 1996, SMI (spatially modulated illumination) and SPDM (spectral precision distance microscopy). The effective optical resolution of this optical nanoscope has reached the vicinity of 5 nm in 2D and 40 nm in 3D and surpasses the 200 nm resolution limit predicted by Abbe‘s law.Abbe postulated in 1873 the theoretical limit of resolution of optical microscopy.

The Vertico-SMI microscope was developed by a team led by Christoph Cremer, Professor of Applied Optics and Information Processing at Heidelberg University and is based on the combination of light optical techniques of localization microscopy (SPDM, spectral precision distance microscopy) and structured illumination (SMI, spatially modulated illumination).

Since March 2008 many standard fluorescent dyes like GFP and Alexa fluorescent dyes can be used with this so-called SPDMphymod (physically modifiable fluorophores) localization microscopy, for which only one single laser wavelength of suitable intensity is sufficient for nanoimaging.

SMI stands for a special type of laser optical illumination (spatially modulated illumination) and Vertico reflects the vertical arrangement of the microscope axis which renders possible the analysis of fixed cells but also of living cells with an optical resolution below 10 nanometers (1 nanometer = 1 nm = 1 × 10⁻⁹ m).

A particularity of this technology compared with focusing techniques such as 4Pi microscopy, is the wide field exposures which allow entire cells to be depicted at the nano scale. Such a 3D exposure of a whole cell with a typical object size of 20 µm × 20 µm require only 2 minutes. Wide field exposures signify that the entire object is illuminated and detected simultaneously.

SMI microscopy is a light optical process of the so-called point spread function-engineering. These are processes which modify the point spread function (PSF) of a microscope in a suitable manner to either increase the optical resolution, to maximize the precision of distance measurements of fluorescent objects that are small relative to the wavelength of the illuminating light, or to extract other structural parameters in the nanometer range.

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