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

Abstract

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.

Statistical Modelling of SPADs for Time-of-Flight LiDAR

“…In stationary conditions, where the probability of having a detection is constant, this equation can be rewritten as P ( DET ( k )) = P ( DET ): The equivalent rate in the continuous-time domain is P(DET)/T step for T step → 0, hence: The result converges to others reported in literature [ 18 , 19 ] and is shown also in Figure 1 , which compares this model with a Monte Carlo simulation, in case of 80 background photons within the simulation time (500 ns) and 20 signal photons within a 5 ns FWHM gaussian shape pulse, centred at a 300 ns. All simulations were performed with T step = 100 ps quantization step and 100,000 repetitions.…”

Controlled biodegradation of magnesium alloy in physiological environment by metal organic framework nanocomposite coatings

“…It was shown that the MOF particles decorated the surface of the nanofibers and slightly decreased their diameters. The reduced sizes can be attributed to the increase in the size of the Taylor cone and decrease in the jet velocity due to a change in the viscosity of the solution 58 , 59 . Since ZIF MOFs are hydrophilic 39 , the particles tend to be pushed toward the outer layer and collected on the surface.…”

Review of lens-assisted beam steering methods

“…Instead, the entire field is illuminated at once and a detector provides both spatial resolution and timing resolution. This done in either direct time-of-flight systems (where a fast counter is used to directly measure the time-of-flight of the light 4 ) or indirect time-of-flight systems (where the outgoing light and the detector efficiency are modulated, and the phase between these modulations is measured 5 ). Flash systems offer low cost and small size.…”