title: Measuring large numerical apertures by imaging the angular distribution of radiation of fluorescing molecules.
abstract: Exact knowledge of the numerical aperture is crucial in many applications using high-aperture objectives such as confocal microscopy, optical trapping, or advanced sub-wavelength imaging methods. We propose and apply a precise and straightforward method for measuring this fundamental parameter of microscope objectives with numerical apertures above unity. Our method exploits the peculiarities of the fluorescence emission of molecules at a glass/air interface.
authors.forename: Luru
authors.initials: L
authors.lastname: Dai
authors.forename: Ingo
authors.initials: I
authors.lastname: Gregor
authors.forename: Iris
authors.initials: I
authors.lastname: von der Hocht
authors.forename: Thomas
authors.initials: T
authors.lastname: Ruckstuhl
authors.forename: Jörg
authors.initials: J
authors.lastname: Enderlein