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Analysis of non-ideal behavior of CAPD based time-of-flight pixels Host Publication: Finds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet Authors: R. Grootjans, W. van der Tempel, D. Van Nieuwenhove and M. Kuijk Publisher: SPIE Publication Date: Apr. 2008 ISBN: 978-0-8194-7198-7
Abstract: 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.
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