Delta image sensor with digital pixel storage using different ramps for storage and comparison

A delta image sensor comprising an arrangement of pixels and a plurality of acquisition circuits corresponding to at least one pixel of the arrangement of pixels and formed as part of an integrated circuit, each acquisition circuit including:

• at least one sensor circuit comprising a photosensor configured to generate a sensor signal, VSIG, depending on a light signal illuminating the photosensor;
• at least one analogue to digital conversion, A/D, circuit configured to generate a digital representation corresponding to a current sensor signal VSIG, wherein the A/D circuit is configured to use one of a plurality of ramps to generate the digital representation;
• at least one digital storage circuit configured to store a representation of at least one digital signal generated using a storage ramp which constitutes one of the plurality of ramps, the representation corresponding to a previous sensor signal VSIG;
• at least one digital comparison circuit configured to compare a level of the stored digital representation with the digital representation of the current sensor signal VSIG, being generated using a comparison ramp which constitutes a different one of the plurality of ramps than the storage ramp, to detect whether a changed level is present;
• and
• at least one digital output circuit configured to generate an event output under a condition of the changed level.