Regular papers

Increasing the lateral resolution of scanning microscopes by a factor of two using 2-Image microscopy

¹ Université Pierre et Marie Curie - Paris VI, BioMoCeTi - UMR CNRS 7033, Case Courrier 138 4 Place Jussieu 75252 Paris Cedex 05, France
² CPGE Lycée Paul Valéry, Paris, France
³ Institut Fresnel, CNRS, Aix-Marseille Université, École Centrale de Marseille, Campus de Saint-Jérôme, 13013 Marseille, France

^* nicolas.sandeau@upmc.fr

Received: 4 March 2009

Abstract

Increasing the resolution of optical microscopes is a challenging task for studying the cell machinery at the molecular level. 4Pi or Total internal-reflection fluorescent microscopy (TIRF) microscopies permit one to reduce the axial dimension of the detection volume. To reduce its lateral dimension, we have proposed a solution in which the scanning head of a 4Pi microscope or of a confocal microscope is coupled to an interferometer. With this technique two beams coming from the source produce two images that are superimposed coherently. For this reason, one can call this technique 2-Image microscopy. It has been shown that with 2-Image microscopy, the complete use of the spatial frequencies collected by the objective allows to reach a 1.22λ/4NA lateral resolution as defined by Rayleigh. This improvement is independent of the excitation mode and is effective with incoherent light such as fluorescent or chemiluminescent (i.e. without optical excitation) samples. In this paper, we present an interferometric set-up and a modulation technique that make benefit fully from the advantages of 2-Image microscopy.