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Proceedings Paper

Modeling and calibration of pulse-modulation based ToF imaging systems
Author(s): Andreas Süss; Gabor Varga; Michael Marx; Peter Fürst; Stefan Gläsener; Wolfram Tiedke; Melanie Jung; Andreas Spickermann; Bedrich J. Hosticka
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Paper Abstract

Conversely to the continuous wave indirect time-of-flight (CW-iToF) imaging scheme, pulsed modulation ToF (PM-iToF) imaging is a promising depth measurement technique for operation at high ambient illumination. It is known that non-linearity and finite charge-transfer speed impact trueness and precision of ToF systems.1–3 As pulses are no Eigenfunctions to the shutter system, this issue is especially pronounced in pulsed modulation.2, 3 Despite these effects, it is possible to find analytical expressions founded on physical observations that map scenery parameters such as depth information, reflectance and ambient light level to sensor output.3, 4 In the application, the inverse of this map has to be evaluated. In PM-iToF, an inverse function cannot be yielded in a direct manner, as models proposed in the literature were transcendental.3, 4 For a limited range an approximating linearization can be performed to yield depth information.5 To extend the usable range, recently, an alternative approach that indirectly approximates the inverse function was presented.6 This method was founded on 1D doping concentration profiles, which, however, are typically not made available to end users. Also, limitations of the 1D approximation as well as stability are yet to be explored. This work presents a calibration methodology that copes with detector insufficiencies such as finite charge transfer speed. Contrarily to the state of the art, no prior knowledge on details of the underlying devices is required. The work covers measurement setup, a benchmark of various calibration schemes and deals with issues such as overfitting or defect pixels.

Paper Details

Date Published: 3 March 2016
PDF: 9 pages
Proc. SPIE 9751, Smart Photonic and Optoelectronic Integrated Circuits XVIII, 975117 (3 March 2016); doi: 10.1117/12.2213156
Show Author Affiliations
Andreas Süss, IMEC (Belgium)
Fraunhofer IMS (Germany)
Gabor Varga, RWTH Aachen Univ. (Germany)
Fraunhofer IMS (Germany)
Michael Marx, Fraunhofer IMS (Germany)
Peter Fürst, Fraunhofer IMS (Germany)
Stefan Gläsener, Fraunhofer IMS (Germany)
Wolfram Tiedke, TriDiCam (Germany)
Melanie Jung, Fraunhofer IMS (Germany)
Andreas Spickermann, Fraunhofer IMS (Germany)
Bedrich J. Hosticka, Fraunhofer IMS (Germany)


Published in SPIE Proceedings Vol. 9751:
Smart Photonic and Optoelectronic Integrated Circuits XVIII
Sailing He; El-Hang Lee; Louay A. Eldada, Editor(s)

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