Patent ID: 7652706

Claim:
An image sensor comprising: (a) a photosensitive region that accumulates charge corresponding to received incident light; (b) a voltage supply having a ramped voltage over time that is applied to a transfer gate; (c) a charge-to-voltage conversion region for receiving at least a portion of the charge from the photosensitive region in response to the ramped voltage applied to the transfer gate, wherein the charge-to-voltage conversion region converts the charge to a voltage; (d) an amplifier for receiving and amplifying the voltage received from the charge-to-voltage conversion region; (e) a comparator for comparing the voltage received from the amplifier to a reference voltage; and (f) a counter for counting clock cycles between an initial application of the ramped voltage to the transfer gate and the receipt of a signal from the comparator, wherein the signal from the comparator indicates a voltage change at the charge-to-voltage conversion region indicating an initiation of charge transfer from the photosensitive region to the charge-to-voltage conversion region.