Background Light Rejection in SPAD-Based LiDAR Sensors by Adaptive Photon Coincidence Detection

Beer, Maik; Haase, Joachim; Ruskowski, Jennifer; Kokozinski, Rainer

doi:10.3390/s18124338

Cited by 57 publications

(43 citation statements)

References 28 publications

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“…Mitigating challenges from high background noise have been addressed by coincidence detection (or similar technique) on the sensor [7,11,12,16]. Coincidence detection is a well-known technique which utilizes spatio-temporal correlation of photons within a laser pulse to filter out background noise photons which are uniformly distributed in time.…”

Section: Dtof Sensor Adapted For Coincidence Detectionmentioning

confidence: 99%

“…At the sensor-level, ambient light suppression has been addressed by coincidence detection on chip [11,12,16], a well-known technique utilizing spatio-temporal closeness of photons within a laser pulse to filter out background noise photons. While TCSPC with coincidence detection have shown effective noise-filtering properties, imaging in a wide dynamic range scenario is an ongoing challenge.…”

Section: Introductionmentioning

confidence: 99%

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Modeling and Analysis of a Direct Time-of-Flight Sensor Architecture for LiDAR Applications

Zhang

Charbon

2019

Sensors

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Tel.: +41-216-954-413 † This paper is an extended version of our paper published in: Padmanabhan, P.; Zhang, C.; Charbon, E.Analysis of a modular SPAD-based direct time-of-flight depth sensor architecture for wide dynamic range scenes in a LiDAR system. Abstract:Direct time-of-flight (DTOF) is a prominent depth sensing method in light detection and ranging (LiDAR) applications. Single-photon avalanche diode (SPAD) arrays integrated in DTOF sensors have demonstrated excellent ranging and 3D imaging capabilities, making them promising candidates for LiDARs. However, high background noise due to solar exposure limits their performance and degrades the signal-to-background noise ratio (SBR). Noise-filtering techniques based on coincidence detection and time-gating have been implemented to mitigate this challenge but 3D imaging of a wide dynamic range scene is an ongoing issue. In this paper, we propose a coincidence-based DTOF sensor architecture to address the aforementioned challenges. The architecture is analyzed using a probabilistic model and simulation. A flash LiDAR setup is simulated with typical operating conditions of a wide angle field-of-view (FOV = 40 • ) in a 50 klux ambient light assumption. Single-point ranging simulations are obtained for distances up to 150 m using the DTOF model. An activity-dependent coincidence is proposed as a way to improve imaging of wide dynamic range targets. An example scene with targets ranging between 8-60% reflectivity is used to simulate the proposed method. The model predicts that a single threshold cannot yield an accurate reconstruction and a higher (lower) reflective target requires a higher (lower) coincidence threshold. Further, a pixel-clustering scheme is introduced, capable of providing multiple simultaneous timing information as a means to enhance throughput and reduce timing uncertainty. Example scenes are reconstructed to distinguish up to 4 distinct target peaks simulated with a resolution of 500 ps. Alternatively, a time-gating mode is simulated where in the DTOF sensor performs target-selective ranging. Simulation results show reconstruction of a 10% reflective target at 20 m in the presence of a retro-reflective equivalent with a 60% reflectivity at 5 m within the same FOV.

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Section: Dtof Sensor Adapted For Coincidence Detectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling and Analysis of a Direct Time-of-Flight Sensor Architecture for LiDAR Applications

Zhang

Charbon

2019

Sensors

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“…the lower DCR level allows the laser peak to be seen and is then entirely suppressed by the correlator. A study of the degree of rejection of uncorrelated noise sources is given in [14] versus the coincidence level setting.…”

Section: Fig 14 Shows Distance Accuracy In Multi-eventmentioning

confidence: 99%

A Reconfigurable 3-D-Stacked SPAD Imager With In-Pixel Histogramming for Flash LIDAR or High-Speed Time-of-Flight Imaging

Hutchings

Johnston

Gyöngy

et al. 2019

IEEE J. Solid-State Circuits

155

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A 256 x 256 single photon avalanche diode (SPAD) sensor integrated in a 3D-stacked 90nm 1P4M/40nm 1P8M process is reported for flash light detection and ranging (LIDAR) or high speed direct time of flight (ToF) 3D imaging. The sensor bottom tier is composed of a 64x64 matrix of 36.72 m pitch modular photon processing units which operate from shared 4x4 SPADs at 9.18 m pitch and 51% fill-factor. A 16 x 14-bit counter array integrates photon counts or events to compress data to 31.4 Mbps at 30 fps readout over 8 I/O operating at 100 MHz. The pixel-parallel multi-event TDC approach employs a programmable internal or external clock for 0.56 ns to 560 ns time bin resolution. In conjunction with a perpixel correlator, the power is reduced to less than 100 mW in practical daylight ranging scenarios. Examples of ranging and high speed 3D TOF applications are given. Index Terms-3-D imaging, CMOS, direct time of flight (dTOF), histogramming, image sensor, light detection and ranging (LiDAR), single photon avalanche diodes (SPADs), time-to-digital converter (TDC), TDC sharing architecture, TOF.

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“…Far better results could be reached with a time of flight (ToF) distance sensor, which is typically used as a scanning device [12][13][14][15] rang finder [16][17][18] and gesture detection sensor [19]. The used VL53L0X module is capable of capturing distances up to a maximum range of 2 m with a very high accuracy.…”

Section: Combination Of the Sensorsmentioning

confidence: 99%

Development of a Sensor to Measure Physician Consultation Times

Gabl

Stummer

2019

Sensors

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The duration of patient–physician contact is an important factor for the optimisation of treatment processes in healthcare systems. Available methods can be labour-intensive and the quality is, in many cases, poor. A part of this research project is to develop a sensor system, which allows the detection of people passing through a door, including the direction. For this purpose, two time of flight sensors are combined with a door sensor and a motion detection sensor (for redundancy) on one single side of the door frame. The period between two single measurements could be reduced to 50 ms, which allows the measurement of walking speed up to 2 ms − 1 . The accuracy of the time stamp for each event is less than one second and ensures a precise documentation of the consultation time. This paper presents the development of the sensor system, the miniaturisation of the installation and first measurement results, as well as the measurement’s concept of quality analysis, including multiple door applications. In future steps, the sensor system will be deployed at different medical practices to determine the exact duration of the patient–physician interaction over a longer time period.

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Background Light Rejection in SPAD-Based LiDAR Sensors by Adaptive Photon Coincidence Detection

Cited by 57 publications

References 28 publications

Modeling and Analysis of a Direct Time-of-Flight Sensor Architecture for LiDAR Applications

Modeling and Analysis of a Direct Time-of-Flight Sensor Architecture for LiDAR Applications

A Reconfigurable 3-D-Stacked SPAD Imager With In-Pixel Histogramming for Flash LIDAR or High-Speed Time-of-Flight Imaging

Development of a Sensor to Measure Physician Consultation Times

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