Friday, October 08, 2021

Old ToF Presentations

IEEE Sensors keeps publishing old videos from its archives. Here is a recent bunch of such publications:

"Introduction to Time-of-Flight Imaging" by Edoardo Charbon from Technische Universiteit Delft, Netherlands

"In this paper, the most important architectures used in time-of-flight (TOF) imaging will be described, starting with global shutter image sensors, ultra-fast CCDs with 100ns frames, on to TOF-specific architectures, such as direct, or pulse-based TOF and indirect, or phase-based TOF, implemented both in CCD and CMOS processes with optimized optical stacks."

"A Fast Global Shutter Image Sensor Based on the VOD Mechanism" by Erez Tadmor, Idan Bakish, Shlomo Felzenshtein, Eli Larry, Giora Yahav, David Cohen from Microsoft

"In this paper the physical principles that allow a fast (ns scale) global shutter operation using the vertical overflow drain mechanism are explained and characterized. Several new measurement methodologies are developed in order to quantify the fast shutter temporal and spatial behaviour. Measurement results that highlight different physical properties of the shutter mechanism are surveyed, and the results are studied and analyzed. Process and device simulations of a pinned photodiode with a VOD mechanism are presented in order to give insights regarding the physical origins of the measured phenomena."

"Resolving Multipath Interference in Kinect: an Inverse Problem Approach" by Ayush Bhandari, Micha Feigin, Shahram Izadi, Christoph Rhemann, Mirko Schmidt, Ramesh Raskar from MIT and Microsoft

"Multipath interference (MPI) is one of the major sources of both depth and amplitude measurement errors in Time"of"Flight (ToF) cameras. This problem has received a lot of attention in the recent past. In this work, we discuss the MPI problem within the framework of inverse problems based on the Fredholm integral and multi"frequency measurements. As compared to previous approaches that consider up to two interfering paths, our model considers the general case of K"interfering paths. In the theoretical setting, we show that for the case of K"interfering paths of light, 2K + 1 frequency measurements suffice to compute the depth and amplitude images corresponding to each of the K optical paths. Our algorithm is practical, by providing a deterministic solution. Also, for the first time, we demonstrate the effectivity of our model on an off-the-shelf Microsoft Kinect. Theoretical findings and practical demonstration warrants future research and further experimentation."

"Depth-Range Extension with Folding Technique for SPAD-Based TOF LIDAR Systems" by Daniele Perenzoni, Leonardo Gasparini, Nicola Massari, David Stoppa from Fondazione Bruno Kessler, Italy

"Direct Time-of-Flight cameras can be implemented combining Single-Photon Avalanche Diodes (SPAD) with Time-to-Digital Converters (TDCs). Such a technology exhibits an intrinsic distance range limitation due to the TDC range, which is fixed by the TDC resolution and number of bits. Up to now it was not possible to extend this range without redesigning the TDC. In this work we propose a method to overcome this limitation thanks to a folding measuring technique. In our implementation the TDC is based on a ring-oscillator; the TDC starts when a photon is detected and stops when an external Stop signal is provided. As the number of bits is limited, the TDC restarts from 0 after reaching the final value (folding). In this paper, we show that it is possible to arbitrary extend the maximum detectable distance through repeated measurements by modifying the timing of the “stop” signal in multiples of the TDC’s maximum range."

"A Low-Power Pixel-Level Circuit for High Dynamic Range Time-of-Flight Camera" by Nicola Massari, David Stoppa, Lucio Pancheri from Fondazione Bruno Kessler, and Università degli Studi di Trento, Italy.

"Design of a low-power pixel-level circuit for extending the dynamic range of a ToF camera."

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