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Proceedings Paper

Telephoto axicon
Author(s): Anna Burvall; Alexander Goncharov; Chris Dainty
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Paper Abstract

The axicon is an optical element which creates a narrow focal line along the optical axis, unlike the single focal point produced by a lens. The long and precisely defined axicon focal line is used e.g. in alignment, or to extend the depth of focus of existing methods such as optical coherence tomography or light sectioning. Axicons are generally manufactured as refractive cones or diffractive circular gratings. They are also made as lens systems or doublet lenses, which are easier to produce. We present a design in the form of a reflective-refractive single-element device with annular aperture. This very compact system has only two surfaces, which can be spherical or aspheric depending on the quality required of the focal line. Both surfaces have reflective coatings at specific zones, providing an annular beam suitable for generating extended focal lines. One draw-back of a normal axicon is its sensitivity to the angle of illumination. Even for relatively small angles, astigmatism will broaden the focus and give it an asteroid shape. For our design, with spherical surfaces concentric about the center of the entrance pupil, the focal line remains unchanged in off-axis illumination.

Paper Details

Date Published: 14 October 2005
PDF: 8 pages
Proc. SPIE 5962, Optical Design and Engineering II, 596213 (14 October 2005); doi: 10.1117/12.625162
Show Author Affiliations
Anna Burvall, National Univ. of Ireland/Galway (Ireland)
Alexander Goncharov, National Univ. of Ireland/Galway (Ireland)
Chris Dainty, National Univ. of Ireland/Galway (Ireland)

Published in SPIE Proceedings Vol. 5962:
Optical Design and Engineering II
Laurent Mazuray; Rolf Wartmann, Editor(s)

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