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Proceedings Paper

Illumination waveform optimization for time-of-flight range imaging cameras
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Paper Abstract

Time-of-flight range imaging sensors acquire an image of a scene, where in addition to standard intensity information, the range (or distance) is also measured concurrently by each pixel. Range is measured using a correlation technique, where an amplitude modulated light source illuminates the scene and the reflected light is sampled by a gain modulated image sensor. Typically the illumination source and image sensor are amplitude modulated with square waves, leading to a range measurement linearity error caused by aliased harmonic components within the correlation waveform. A simple method to improve measurement linearity by reducing the duty cycle of the illumination waveform to suppress problematic aliased harmonic components is demonstrated. If the total optical power is kept constant, the measured correlation waveform amplitude also increases at these reduced illumination duty cycles. Measurement performance is evaluated over a range of illumination duty cycles, both for a standard range imaging camera configuration, and also using a more complicated phase encoding method that is designed to cancel aliased harmonics during the sampling process. The standard configuration benefits from improved measurement linearity for illumination duty cycles around 30%, while the measured amplitude, hence range precision, is increased for both methods as the duty cycle is reduced below 50% (while maintaining constant optical power).

Paper Details

Date Published: 21 June 2011
PDF: 13 pages
Proc. SPIE 8085, Videometrics, Range Imaging, and Applications XI, 80850D (21 June 2011); doi: 10.1117/12.889399
Show Author Affiliations
A. D. Payne, The Univ. of Waikato (New Zealand)
A. A. Dorrington, The Univ. of Waikato (New Zealand)
M. J. Cree, The Univ. of Waikato (New Zealand)

Published in SPIE Proceedings Vol. 8085:
Videometrics, Range Imaging, and Applications XI
Fabio Remondino; Mark R. Shortis, Editor(s)

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