Direct Time-of-Flight Single-Photon Imaging

Abstract

This paper provides a tutorial introduction to the direct Time of Flight (dToF) signal chain and typical artifacts introduced due to detector and processing electronic limitations. We outline the memory requirements of embedded histograms related to desired precision and detectability which are often the limiting factor in the array resolution. A survey of integrated CMOS dToF arrays is provided highlighting future prospects to further scaling through process optimization or smart embedded processing. Index Terms-direct time-of-flight (dTOF), light detection and ranging (LiDAR), single photon avalanche diode (SPAD), silicon photo multiplier (SiPM), CMOS Image Sensor (CIS), SPAD array, 3D ranging

Towards a solid‐state light detection and ranging system using holographic illumination and time‐of‐flight image sensing

“…In use cases where saturation is a concern, sensors with alternative TDC architectures and techniques such as temporal photon windowing can be used that avoid TDC saturation, limit its effect, or compensate for it. 4,15,16 The distance measurements are based on the aforementioned TCSPC technique. We give a brief overview of relevant aspects here, while a detailed explanation can be found in relevant literature.…”

“…Our detector is the “QuantiCam” SPAD‐array image sensor that has 33‐ps temporal resolution, which equates to 0.5‐cm distance resolution, 12 based on Equation (). The precision of the distance measurements is affected by time jitter inherent to the sensor and is also affected by experimental parameters, such as the duration of the laser pulse, received photon rate from the reflected laser illumination, and ambient noise 4 . Precision can be improved by accumulating distance measurements over multiple laser cycles, based on a technique known as time correlated single‐photon counting (TCSPC), as we discuss further later in this section.…”

“…The precision of the distance measurements is affected by time jitter inherent to the sensor and is also affected by experimental parameters, such as the duration of the laser pulse, received photon rate from the reflected laser illumination, and ambient noise. 4 Precision can be improved by accumulating distance measurements over multiple laser cycles, based on a technique known as time correlated single-photon counting (TCSPC), as we discuss further later in this section. In this work, under optimum conditions, distance measurement precision is approximately 2 cm.…”

“…More advanced algorithms exist to locate the signal pulse that can tolerate more demanding conditions, at the expense of increased complexity. 4,19,20 Figure 4 shows a typical TCSPC histogram under more demanding conditions. The number of histogrammed events is low, and the signal pulse produces a peak that is close to the noise floor.…”

“…The detector may directly measure the propagation time of pulses of light (direct time of flight [D-ToF]) or may infer the time indirectly based on measurements of the phase delay between the transmission and reception of modulated waveforms (indirect time of flight [I-ToF]). 2,4 Various detector technologies are available, such as avalanche photodiodes (APD), SPADs, silicon photomultipliers (SiPM), and complementary metal oxide semiconductor (CMOS) active pixel sensors (APS). 1,5 The optimal approach is highly application dependent.…”