1. A method comprising: receiving a same variable reference signal at a plurality of sensor pixels, wherein the variable reference signal changes monotonically within a plurality of reference levels, and wherein a same reference level is received at the plurality of sensor pixels at a given time; and at each reference level of the plurality of reference levels: converting, by each sensor pixel of the plurality of sensor pixels, an optical signal on each sensor pixel of the plurality of sensor pixels into an electrical signal; generating an event at each sensor pixel on which a condition based on a comparison between the electrical signal and the reference level is met; encoding an address of each sensor pixel that generates the event; and creating a binary image for the reference level based on the address of each sensor pixel that generates the event.