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25 April 2008 Analysis of non-ideal behavior of CAPD based time-of-flight pixels
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An overview is given of the output of two main pixels based on a Current Assistant Photonic Demodulator (CAPD) and their usability in a ranging camera based on the Time-Of-Flight (TOF) principle. The first structure is based on an active pixel with an integrating capacitor, while the second structure is based on a transimpedance amplifier. A measurement system capable of interfacing with a one-dimensional array of CAPD pixels has been designed and is briefly discussed. The linearity of both CAPD pixels is measured, compared to each other and discussed. Several sources of non-idealities present in the CAPD output have been investigated, including differences between rise and fall time and duty cycle imperfections of the high frequency binary correlating signal, as well as CAPD bandwidth. The possible influences of such non-idealities of the correlating wave on the measurements as well as on the calculated distance are discussed. Resulting non-idealities in the raw CAPD output values include clipping and non-linearity, yielding offsets and non-linearities in the calculated phase difference between the original and the reflected signal. Theoretic values are shown and compared against measurements. Finally, inter-pixel properties of a one-dimensional array of CAPD structures are presented, as well as a sample range image acquired by scanning.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Riemer Grootjans, Ward van der Tempel, Daniël Van Nieuwenhove, and Maarten Kuijk "Analysis of non-ideal behavior of CAPD based time-of-flight pixels", Proc. SPIE 7000, Optical and Digital Image Processing, 70001E (25 April 2008);

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