Image sensor sampled at non-uniform intervals

An image sensor comprising:

• a plurality of pixel circuits disposed in rows and columns, each of the plurality of pixel circuits having a first light-detecting element operable to integrate photocharge, output circuitry operable to selectively output a signal indicative of photocharge integrated by the first light-detecting element, and reset circuitry operable to remove photocharge integrated by the first light-detecting element since the prior operation of the reset circuitry;
• control circuitry operable to select subgroups of the pixel circuits to output the respective signals indicative of integrated photocharge, and operable such that each pixel circuit in the plurality is selected at least four times during a frame period, wherein the at least four selections of a given pixel circuit are spaced to define a set of sampling intervals within the frame period, including a longest sampling interval at least four times the duration of a shortest sampling interval;
• a plurality of comparators, operable such that each pixel circuit in a given subgroup selected by the control circuitry is switchably paired with a respective one of the comparators in response to each of the at least four selections of the pixel circuit to enable generation of a comparison result that indicates whether a threshold is exceeded by the photocharge integrated within the light-detecting element of the pixel circuit during a corresponding one of the sampling intervals;
• a plurality of reset signal generators each coupled to receive the output of a respective one of the comparators and operable such that, when the comparison result generated by the respective comparator indicates a threshold exceedance, the reset signal generator asserts a reset signal to cause the reset circuitry within the currently paired pixel circuit to reset the state of the light-detecting element;
• and
• counter logic to generate count values corresponding to respective logical collections of the pixel circuits, each logical collection of the pixel circuits including at least two of the pixel circuits and each of the count values indicating a collective number of threshold exceedances with respect to the constituent pixel circuits of the corresponding logical collection during the frame period.