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Proceedings Paper

Single-chip optoelectronic rangefinder using PIN-photodiode and correlated active integration
Author(s): Alexander Nemecek; Klaus Oberhauser; Horst Zimmermann
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Paper Abstract

Integrated optical distance measurement systems based on the Time-of-Flight (TOF) principle open up 3D vision for various applications like e.g. inspection systems. The introduced single pixel consists of both, a PIN photodiode and a signal-processing circuit on chip. Due to eye-safety reasons, the optical illumination power is limited (Popt<2mW). For diffuse reflecting objects in distances up to several meters, signal attenuation of about -50dB occurs with 1-inch optics. Therefore high responsivity of the photodiode is required: R=0.36A/W at 660nm. Resolutions of centimeters matter TOF far below 1ns, i.e. the photodiode has to feature high bandwidth (f3dB=1.35GHz). Distance information is gained by correlation between the modulated transmission signal and the run- ime delayed, attenuated received signal. The readout circuit consists of three stages: the first stage is a broadband current amplifier, realised with current mirrors. The correlation is performed in the second stage by a switching mixer. Amplification and smoothing is performed in the third, active integrator stage. The distance information is derived from the output signal by external sampling and simple data processing. A standard deviation of better than 1% (2%) for distances up to 2m (3.7m) is achieved for measurement durations of 10ms. The primary linearity error of less than 6cm is educed by error correction. The pixel has a fill factor of ~10%, including the overall pixel area of ~460µm×170µm and the photodiode with a diameter of 100µm. The chip was realised in a 0.6µm BiCMOS ASIC process.

Paper Details

Date Published: 23 September 2005
PDF: 10 pages
Proc. SPIE 5954, Optical Security Systems, 59540D (23 September 2005); doi: 10.1117/12.622855
Show Author Affiliations
Alexander Nemecek, Vienna Univ. of Technology (Austria)
Klaus Oberhauser, Vienna Univ. of Technology (Austria)
Horst Zimmermann, Vienna Univ. of Technology (Austria)

Published in SPIE Proceedings Vol. 5954:
Optical Security Systems
Zbigniew Jaroszewicz; Sergei Y. Popov; Frank Wyrowski, Editor(s)

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