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18 June 2007 Time-of-flight based pixel architecture with integrated double-cathode photodetector
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For various industrial applications contact-less optical 3D distance measurement systems with active illumination are suitable. A new approach for a pixel of such a 3D-camera chip for applications in displacement and 3D-shape measurement is presented here. The distance information is gained by measuring the Time-of-Flight (TOF) of photons transmitted by a modulated light source to a diffuse reflecting object and back to the receiver IC. The receiver is implemented as an opto-electronic integrated circuit (OEIC). It consists of a double-cathode photodetector performing an opto-electronic correlation, a decoupling network and an output low-pass filter on a single silicon chip. The correlation of the received optical signal and the electronic modulation signal enables the determination of the phase-shift between them. The phase-shift is directly proportional to the distance of the object. The measurement time for a single distance measurement is 20 ms for a range up to 6.2 m. The standard deviation up to 3.4 m is better than 1cm for a transmitted optical power of 1.2 mW at a wavelength of 650 nm. The OEIC was fabricated in a slightly modified 0.6 &mgr;m BiCMOS technology with a PIN-photodetector. The photosensitive area of the integrated PIN-photodetector is 120x115 &mgr;m2. A fill factor of ~67% is reached.
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Klaus Oberhauser, Gerald Zach, Alexander Nemecek, and Horst Zimmermann "Time-of-flight based pixel architecture with integrated double-cathode photodetector", Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 66160C (18 June 2007);

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