Recent advances in photographic sensing technologies have made it possible to achieve light detection in terms of a single photon. Photon counting sensors are being increasingly used in many diverse applications. We address the problem of jointly recovering spatial and temporal scene radiance from very few photon counts. Our ConvNet-based scheme effectively combines spatial and temporal information present in measurements to reduce noise. We demonstrate that using our method one can acquire videos at a high frame rate and still achieve good quality signal-to-noise ratio. Experiments show that the proposed scheme performs quite well in different challenging scenarios while the existing approaches are unable to handle them.
SPAD sensors are photodetectors in which photon radiation can be detected from the resulting large avalanche currents. SPAD sensor arrays are capable of photon counting at a high speed with high timing resolution and are useful in a variety of applications such as fluorescence lifetime imaging microscopy (FLIM), positron emission tomography (PET), time-of-flight imaging etc. @cite_30 @cite_24 @cite_14 . Recently, developed a SPAD array known as SwissSPAD @cite_25 . The SwissSPAD is fabricated in a high-voltage CMOS process and features a large 512 @math 128 array with global gating. In this paper, we use data from different SwissSPAD sensor arrays for demonstrating our high speed video recovery scheme.
@cite_30 @cite_14 @cite_25 @cite_24
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Avalanche photodiodes, which operate above the breakdown voltage in Geiger mode connected with avalanche-quenching circuits, can be used to detect single photons and are therefore called single-photon avalanche diodes SPAD’s. Circuit configurations suitable for this operation mode are critically analyzed and their relative merits in photon counting and timing applications are assessed. Simple passive-quenching circuits (PQC’s), which are useful for SPAD device testing and selection, have fairly limited application. Suitably designed active-quenching circuits (AQC’s) make it possible to exploit the best performance of SPAD’s. Thick silicon SPAD’s that operate at high voltages (250–450 V) have photon detection efficiency higher than 50 from 540- to 850-nm wavelength and still 3 at 1064 nm. Thin silicon SPAD’s that operate at low voltages (10–50 V) have 45 efficiency at 500 nm, declining to 10 at 830 nm and to as little as 0.1 at 1064 nm. The time resolution achieved in photon timing is 20 ps FWHM with thin SPAD’s; it ranges from 350 to 150 ps FWHM with thick SPAD’s. The achieved minimum counting dead time and maximum counting rate are 40 ns and 10 Mcps with thick silicon SPAD’s, 10 ns and 40 Mcps with thin SPAD’s. Germanium and III–V compound semiconductor SPAD’s extend the range of photon-counting techniques in the near-infrared region to at least 1600-nm wavelength. Single-photon avalanche diode (SPAD) based transient imaging suffers from an aberration called pile-up. When multiple photons arrive within a single repetition period of the illuminating laser, the SPAD records only the arrival of the first photon; this leads to a bias in the recorded light transient wherein the transient response at later time-instants are under-estimated. An unfortunate consequence of this is the need to operate the illumination at low-power levels to reduce the probability of multiple photons returning in a single period. Operating the laser at low power results in either low signal-to-noise ratio (SNR) in the measured transients or reduced frame rate due to longer exposure durations to achieve a high SNR. In this paper, we propose a signal processing-based approach to compensate pile-up in post-processing, thereby enabling high power operation of the illuminating laser. While increasing illumination does cause a fundamental information loss in the data captured by SPAD, we quantify this information loss using Cramer-Rao bound and show that the errors in our framework are only limited to this information loss. We experimentally validate our hypotheses using real data from a lab prototype. Time-of-flight depth imaging and transient imaging are two imaging modalities that have recently received a lot of interest. Despite much research, existing hardware systems are limited either in terms of temporal resolution or are prohibitively expensive. Arrays of Single Photon Avalanche Diodes (SPADs) promise to fill this gap by providing higher temporal resolution at an affordable cost. Unfortunately SPAD arrays are to date only available in relatively small resolutions. In this work we aim to overcome the spatial resolution limit of SPAD arrays by employing a compressive sensing camera design. Using a DMD and custom optics, we achieve an image resolution of up to 800A—400 on SPAD Arrays of resolution 64A—32. Using our new data fitting model for the time histograms, we suppress the noise while abstracting the phase and amplitude information, so as to realize a temporal resolution of a few tens of picoseconds. The recent availability of miniaturized photon-counting pixels in standard CMOS processes has paved the way to the introduction of photon counting in low-cost time-of-flight cameras, robotics vision, mobile phones, and consumer electronics. In this paper we describe the technology at the core of this revolution: single-photon avalanche diodes (SPADs) and the architectures enabling SPAD based image sensors. We discuss tradeoffs and design trends, often referring to specific sensor chips and applications.