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Proceedings Paper

Micromirror-based sending and detection optical assembly for time-of-flight laser scanners
Author(s): Britta Satzer; Claudia Baulig; Thilo Sandner; Stefan Schwarzer
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Paper Abstract

We design the optical unit for an imaging time-of-flight scanner camera based on partially steerable micro mirrors. This new class of 3D cameras enables video frame rates and-in conjunction with the accompanying user software-online real-time selection of regions of interest. The challenges for the optical design comprise (i) sufficient light collection from close-up objects, (ii) maximizing optical efficiency for objects at large distances, (iii) reduction of the dynamical range of signal returns and (iv) minimization of parasitic scattering. We present a solution based on coaxial beam guidance, where the emitted beam first passes a beam splitter, is then deflected by a dedicated emission mirror in the center of a point-symmetrical, synchronized arrangement of five micro mirrors and finally passes a protective spherical glass cover. The mirror assembly is slightly displaced from the center of the dome in order to establish a secondary focus for parasitic reflections at the inside of the cover. The light scattered at the target surface which reaches the mirror array is directed towards an assembly of rhomboid prisms. These prisms reshape the distributed mirror array aperture such that a small lens with high numerical aperture suffices to focus the light onto a fast, small-area avalanche photo diode, thus maximizing the acceptance angle of the detector and permissible misalignments of the element mirrors.

Paper Details

Date Published: 9 May 2012
PDF: 10 pages
Proc. SPIE 8439, Optical Sensing and Detection II, 84390Z (9 May 2012); doi: 10.1117/12.922764
Show Author Affiliations
Britta Satzer, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
Claudia Baulig, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
Thilo Sandner, Fraunhofer-Institut für Photonische Mikrosysteme (Germany)
Stefan Schwarzer, Fraunhofer-Institut für Physikalische Messtechnik (Germany)

Published in SPIE Proceedings Vol. 8439:
Optical Sensing and Detection II
Francis Berghmans; Anna Grazia Mignani; Piet De Moor, Editor(s)

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