Dynamic vision sensor (DVS) event camera output is affected by noise,
particularly in dim lighting conditions. A theory explaining how photon and
electron noise affect DVS output events has so far not been developed.
Moreover, there is no clear understanding of how DVS parameters and operating
conditions affect noise. There is an apparent paradox between the real noise
data observed from the DVS output and the reported noise measurements of the
logarithmic photoreceptor. While measurements of the logarithmic photoreceptor
predict that the photoreceptor is approximately a first-order system with RMS
noise voltage independent of the photocurrent, DVS output shows higher noise
event rates at low light intensity. This paper unravels this paradox by showing
how the DVS photoreceptor is a second-order system, and the assumption that it
is first-order is generally not reasonable. As we show, at higher
photocurrents, the photoreceptor amplifier dominates the frequency response,
causing a drop in RMS noise voltage and noise event rate. We bring light to the
noise performance of the DVS photoreceptor by presenting a theoretical
explanation supported by both transistor-level simulation results and chip
measurements.Comment: Presented in 2021 International Image Sensor Workshop (IISW