Patent ID: 7164114

Claim:
A pixel sensor comprising: a first switch coupled between a first voltage source and a first node, turned on or off by a reset signal, thereby providing a first voltage from the first voltage source to the first node when turned on; a light sensing unit coupled to the first node generating a transformation current responsive to an incident light source and transforming the transformation current to the first node; and a decision device coupled to the first node and a reference signal, generating an intensity reference signal comprising a plurality of pulses with pulse numbers corresponding to the intensity of the incident light source when the voltage at the first node is lower than that of the reference signal, wherein the decision device comprises: a comparison device for comparing the voltage at the first node with that of the reference signal and outputting an enable signal when the voltage at the first node is less than that of the reference signal; and a transformation device coupled with the comparison device, transforming the intensity of the incident light source into the intensity reference signal after receiving the enable signal, wherein the transformation device comprises: a second switch coupled to a second voltage source and the output terminal of the pixel sensor, turning on or off according to the enable signal, allowing the second voltage source to provide the output terminal with a second voltage when turned on; and a third switch coupled between the output terminal and a voltage reference node, turning on or off according to a first clock signal, transforming the second voltage into the intensity reference signal.