SciDVS: A Scientific Event Camera with 1.7% Temporal Contrast Sensitivity at 0.7 Lux

This paper reports a Dynamic Vision Sensor (DVS) event camera that is $6 x$ more sensitive at $14 x$ lower illumination than existing commercial and prototype cameras. Event cameras output a sparse stream of brightness change events. Their high dynamic range (HDR), quick response, and high temporal resolution provide key advantages for scientific applications that involve low lighting conditions and sparse visual events. However, current DVS are hindered by low sensitivity, resulting from shot noise and pixel-to-pixel mismatch. Commercial DVS have a minimum brightness change threshold of $\gt \mathbf{1 0 \%}$. Sensitive prototypes achieved as low as $1 \%$, but required kilo-lux illumination. Our SciDVS prototype fabricated in a 180 nm CMOS image sensor process achieves $1.7 \%$ sensitivity at chip illumination of 0.7 lx and 18 Hz bandwidth. Novel features of SciDVS are (1) an autocentering in-pixel preamplifier providing intrascene HDR and increased sensitivity, (2) improved control of bandwidth to limit shot noise, and (3) optional pixel binning, allowing the user to trade spatial resolution for sensitivity.