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Characterization of dim light response in DVS pixel: Discontinuity of event triggering time

Xiao Jiang, Fei Zhou

TL;DR

The paper addresses non-first-order behaviors of dynamic vision sensors (DVS) in dim-light conditions, focusing on a discontinuity in the event-triggering time. By analyzing a typical DVS pixel, it derives that a charge/discharge process of the photodiode's parasitic capacitor $C_J$ creates a time delay $\Delta t_e = \Delta Q_e / \Delta I_{pd}$ between consecutive events, which scales inversely with the changing speed of light intensity $\mu$ and is largely independent of the instantaneous light level $L$. Experimental validation on public DAVIS data confirms the existence of $\Delta t_e$ and the discontinuity, showing shorter delays at higher $\mu$ and a near-constant $\Delta t_e \cdot \mu$ across $L$. The results reveal a non-first-order behavior in DVS under dim illumination and offer guidance for improving DVS design and the realism of event-level simulators.

Abstract

Dynamic Vision Sensors (DVS) have recently generated great interest because of the advantages of wide dynamic range and low latency compared with conventional frame-based cameras. However, the complicated behaviors in dim light conditions are still not clear, restricting the applications of DVS. In this paper, we analyze the typical DVS circuit, and find that there exists discontinuity of event triggering time. In dim light conditions, the discontinuity becomes prominent. We point out that the discontinuity depends exclusively on the changing speed of light intensity. Experimental results on real event data validate the analysis and the existence of discontinuity that reveals the non-first-order behaviors of DVS in dim light conditions.

Characterization of dim light response in DVS pixel: Discontinuity of event triggering time

TL;DR

The paper addresses non-first-order behaviors of dynamic vision sensors (DVS) in dim-light conditions, focusing on a discontinuity in the event-triggering time. By analyzing a typical DVS pixel, it derives that a charge/discharge process of the photodiode's parasitic capacitor creates a time delay between consecutive events, which scales inversely with the changing speed of light intensity and is largely independent of the instantaneous light level . Experimental validation on public DAVIS data confirms the existence of and the discontinuity, showing shorter delays at higher and a near-constant across . The results reveal a non-first-order behavior in DVS under dim illumination and offer guidance for improving DVS design and the realism of event-level simulators.

Abstract

Dynamic Vision Sensors (DVS) have recently generated great interest because of the advantages of wide dynamic range and low latency compared with conventional frame-based cameras. However, the complicated behaviors in dim light conditions are still not clear, restricting the applications of DVS. In this paper, we analyze the typical DVS circuit, and find that there exists discontinuity of event triggering time. In dim light conditions, the discontinuity becomes prominent. We point out that the discontinuity depends exclusively on the changing speed of light intensity. Experimental results on real event data validate the analysis and the existence of discontinuity that reveals the non-first-order behaviors of DVS in dim light conditions.
Paper Structure (9 sections, 7 equations, 4 figures, 2 tables)

This paper contains 9 sections, 7 equations, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Discontinuity of event triggering time
  3. DVS circuit and operation principle
  4. parasitic capacitor of photodiode
  5. time delay and discontinuity
  6. EXPERIMENTS
  7. experimental datasets and settings
  8. results
  9. CONCLUSIONS

Figures (4)

  • Figure 1: DVS pixel circuit.
  • Figure 2: distributed diagram of photodiode PD.
  • Figure 3: distributions of event triggering time. Blue lines indicate the histograms of event triggering time and red dashed lines are the fitting curves. For different $L$, the lengths of discontinuity remain stable, demonstrating that the time delay $\Delta t_e$ is not related to current light intensity. Different from that, the changing speed $\mu$ decreases the length of discontinuity.
  • Figure 4: exemplified discontinuity of event triggering time. (Here $\mu=50$, $L=10$)