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Proceedings Paper

Range imaging behind semi-transparent surfaces by high-speed modulated light
Author(s): D. Geerardyn; H. Ingelberts; R. Deleener; M. Kuijk
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Paper Abstract

Range-imaging is a measurement technique able to generate an image which contains the distance information from the camera to all the points of a scene. This distance information can be captured by, amongst others, the Time-of-Flight principle which measures the time a light pulse needs to travel back and forth from the camera to the scene and converts this time into a depth value. For a good operation of the Time-of-Flight principle, a high-power, fast-modulated light source is required. Currently, most 3D cameras use laser diodes or LEDs. Moreover, most systems use square-wave modulation of the light source, requiring high bandwidths of the optical driver. To enhance both bandwidth and optical power, we developed a light source consisting of 16 high-power (50 mW) laser diodes using GHz laser drivers, combined with GHz buffers. Moreover, this light source can be integrated in a Time-of-Flight camera. Specifically, we designed and experimentally validated this new light source, based on ultra-fast laser diodes, allowing an increased performance of the current Time-of-Flight cameras. In this paper, we first discuss the development of a high-power illumination board, with a large beam divergence and suitable for high-speed square-wave modulation with a chosen duty-cycle. Our light source can be modulated faster than 1 GHz, which corresponds to optical pulses shorter than 500 ps. Moreover, the pulses can be shifted in time with sub-nanosecond precision. Secondly, we integrated this light source into a Time-of-Flight setup, able to measure the distances of objects behind a semi-transparent surface. The resulting images are compared with the image quality of commercially available Time-of-Flight cameras. From these results, we can conclude that our light source is suitable for Time-of-Flight measurements and gives a low-cost alternative for imaging purposes. Moreover, it can handle both pulsed as continuous-wave Time-of-Flight, to allow a broader range of applications.

Paper Details

Date Published: 22 June 2015
PDF: 7 pages
Proc. SPIE 9530, Automated Visual Inspection and Machine Vision, 95300D (22 June 2015); doi: 10.1117/12.2184737
Show Author Affiliations
D. Geerardyn, Vrije Univ. Brussel (Belgium)
H. Ingelberts, Vrije Univ. Brussel (Belgium)
R. Deleener, Vrije Univ. Brussel (Belgium)
M. Kuijk, Vrije Univ. Brussel (Belgium)

Published in SPIE Proceedings Vol. 9530:
Automated Visual Inspection and Machine Vision
Jürgen Beyerer; Fernando Puente León, Editor(s)

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