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Modeling of CMOS image sensors for time-of-flight applications

 
: Driewer, Adrian; Hosticka, Bedrich J.; Spickermann, Andreas; Vogt, Holger

:

Baldini, Francesco (Hrsg.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optical Sensors 2015 : Prague, Czech Republic, 13 - 16 April 2015
Bellingham, WA: SPIE, 2015 (Proceedings of SPIE 9506)
ISBN: 978-1-62841-627-5
Paper 950603, 9 S.
Conference "Optical Sensors" <2015, Prague>
Englisch
Konferenzbeitrag
Fraunhofer IMS ()
CMOS image sensor; Time-of-Flight (ToF); charge transfer modeling; LDPD; analytic modeling

Abstract
This contribution describes the modeling of CMOS image sensors employed in time-of-flight (ToF) sensor systems for 3D ranging applications. Our model relies on the theoretical description of photo-generation, charge transfer including diffusion, fringing field, and self-induced drift (SID). This method makes it possible to calculate the time-dependent charge carrier generation, transfer, and distribution. The employed approach allows elimination not only of irradiance-dependent charge transfer, but also of undesired reflectance effects, and the influence of ambient light through an in-pixel background measurement. Since the sensor is operated with very short integration times it is crucial to accomplish a fast transfer of the generated charge from the photodetector to the sense node, and speedy conversion into an electrical signal at its output. In our case, we employed a lateral drift field photodetector (LDPD), which is basically a pinned photodiode with a built-in drift field formed by a doping gradient. A novel pixel structure is presented which is optimized for a fast charge transfer by the appliance of the shown model. Numerical calculations predict a two times faster charge collection.

: http://publica.fraunhofer.de/dokumente/N-341403.html