17 January 2005 Novel pixel architecture with inherent background suppression for 3D time-of-flight imaging
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Proceedings Volume 5665, Videometrics VIII; 566501 (2005) https://doi.org/10.1117/12.586933
Event: Electronic Imaging 2005, 2005, San Jose, California, United States
Abstract
The time-of-flight (TOF) principle is a well known principle to acquire a scene in all three dimensions. The advantages of the knowledge of the third dimension are obvious for many kinds of applications. The distance information within the scene renders automatic systems more robust and much less complex or even enables completely new solutions. A solid-state image sensor containing 124 x 160 pixels and the corresponding 3D-camera, the so-called SwissRanger camera, has already been presented in detail in [1]. It has been shown that the SwissRanger camera achieves depth resolutions in the sub-centimeter range, corresponding to a measured time resolution of a few tens of picoseconds with respect to the speed of light (c~3•108 m/s). However, one main drawback of these so-called lock-in TOF pixels is their limited capacity to handle background illumination. Keeping in mind that in outdoor applications the optical power on the sensor originating from background illumination (e.g., sun light) may be up to a few 100 times higher than the power of the modulated illumination, the sensor requires new pixel structures eliminating or at least reducing the currently experienced restrictions in terms of background illumination. Based on a 0.6 µm CMOS/CCD technology, four new pixel architectures suppressing background illumination and/or improving the ratio of modulated signal to background signal at the pixel-output level were developed and will be presented in this paper. The theoretical principle of operation and the expected performance are described in detail, together with a sketch of the implementation of the different pixel designs at silicon level. Furthermore, test results obtained in a laboratory environment are published. The sensor structures are characterized in a high background-light environment with up to sun light conditions. The distance linearity over a range of a few meters with the mentioned light conditions is measured. At the same time, the distance resolution is plotted as a function of the target distance, the integration time and the background illumination power. This in-depth evaluation leads to a comparison of the various background suppression approaches; it also includes a comparison with the traditional pixel structure in order to highlight the benefits of the new approaches. The paper concludes by providing parameter estimations which enables the outlook to build a sensor with a high lateral resolution containing the most promising pixel.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Thierry Oggier, Rolf Kaufmann, Michael Lehmann, Bernhard Buttgen, Simon Neukom, Michael Richter, Matthias Schweizer, Peter Metzler, Felix Lustenberger, Nicolas Blanc, "Novel pixel architecture with inherent background suppression for 3D time-of-flight imaging", Proc. SPIE 5665, Videometrics VIII, 566501 (17 January 2005); doi: 10.1117/12.586933; https://doi.org/10.1117/12.586933
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