We present numerical calculations on the field distribution in the focus of an optical system with high numerical aperture. The diffraction integrals which are based on the Debye approximation are derived and evaluated for a radially polarized input field with a doughnut-shaped intensity distribution. It is shown that this mode focusses down to a spot size significantly smaller as compared to the case of linear polarization. An experimental setup to measure the three-dimensional intensity distribution in the focal region is presented, which is based on the knife-edge method and on tomographic reconstruction.
Multiple-wavelength interferometry for absolute distance measurement and three-dimensional imaging
J. Trautner,
K. Walcher,
Gerd Leuchs,
B. Bodermann,
H. R. Telle
With an absolutely measuring interferometric distance sensor the three-dimensional shape of objects with rough surfaces is recorded from a large distance. The measuring principle of the sensor is multiple-wavelength interferometry. For the measurement of the interferometric phases the heterodyne detection is used. The distance resolution of the sensor is limited only by the roughness of the surface. The operation of the 3D-image sensor is demonstrated for objects with heights of a few millimeters up to several centimeters measured from a distance of about one meter. With an integration time of 60 ms a distance resolution of a few 10 Pm is achieved.
Investigation of phase singularities in the vicinity of small structures using a Linnik Interference microscope
Ralf Dorn,
M Eberler,
M Piringer,
Susanne Quabis,
Gerd Leuchs
We present studies of the electric field that is reflected by sub-A structures. The occurrence of singularities in the phase distribution of the field is investigated theoretically and experimentally with regard to the possibility to achieve lateral superresolution. A theoretical model for the calculation of the electric field is discussed that is based on the Green function formalism. Measurements on two-dimensional objects were performed using a Linnik interference microscope.
Focusing light to a tighter spot
Susanne Quabis,
Ralf Dorn,
M. Eberler,
O. Glöckl,
Gerd Leuchs
The smallest spot sizes are reached by focusing an annular shaped light beam with a high aperture lens, We show theoretically that the focal area is further reduced when using a novel radially polarized instead of a linearly polarized light annulus. In the vicinity of the focus there is a large longitudinally polarized field component [1] which is still narrower and has no pronounced side lobes. A special photosensitive layer prepared to be sensitive only to this longitudinal field component may be used to reach an even smaller focal area, 0.1 lambda(2), which is determined by the contour of the intensity distribution at half the maximum value. The radially polarized doughnut mode may also be used to build improved near field sensors having a substantially increased brightness. (C) 2000 Elsevier Science B.V. All rights reserved.
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