Apparatus of high dynamic-range CMOS image sensor and method thereof

Abstract

The present invention discloses an apparatus of high dynamic-range CMOS image sensor and method thereof. The present invention utilize a pixel circuit outputting an output signal, wherein the pixel circuit has a photodiode and a plurality of transistors; and utilize a current source as a charge supplement unit to supply current into one end of the photodiode, and providing charges to the parasitic capacitor of the photodiode to delay saturation in the pixel circuit. In addition, a feedback circuit can be further designed connecting the pixel circuit. The feedback circuit receives the output signal from the pixel circuit and then outputs a control signal according to the output signal of the pixel circuit to control status of the charge supplement unit, and thereby increasing the dynamic range of the CMOS image sensor.

1 . A method for increasing dynamic range of CMOS image sensor, comprising: outputting an output signal through a pixel circuit, wherein the pixel circuit comprises a photodiode and a plurality of transistors; and utilizing a current source as a charge supplement unit to supply current into one end of the photodiode, and providing charges to the parasitic capacitor of the photodiode to delay saturation in the pixel circuit. 
     
     
         2 . The method for enhancing dynamic range of CMOS image sensor of  claim 1 , wherein the output signal of the pixel circuit can be further received by a feedback circuit and the feedback circuit outputs a control signal according to the output signal of the pixel circuit to control status of the charge supplement unit. 
     
     
         3 . The method for increasing dynamic range of CMOS image sensor of  claim 1 , wherein the current source is a constant current source or a variable current source. 
     
     
         4 . The method for increasing dynamic range of CMOS image sensor of  claim 3 , wherein the constant current source provides charge supplement to delay saturation of the pixel circuit. 
     
     
         5 . The method for increasing dynamic range of CMOS image sensor of  claim 3 , wherein the variable current source can be further provided by a bias signal to control the amount of currents and supply applicable charges to delay saturation of the pixel circuit. 
     
     
         6 . The method for increasing dynamic range of CMOS image sensor of  claim 1 , wherein the pixel circuit is linear integration mode. 
     
     
         7 . The method for increasing dynamic range of CMOS image sensor of  claim 1 , wherein the charge supplement unit can supply charges to the parasitic capacitor of the photodiode during discharging to enhance dynamic range of the CMOS image sensor. 
     
     
         8 . The method for increasing dynamic range of CMOS image sensor of  claim 1 , wherein the charge supplement unit further comprises a control node, when the current source is a variable current source, the control node can determine whether turning on the charge supplement unit and amount of the charges supplied according to the control signal of the feedback circuit. 
     
     
         9 . The method for increasing dynamic range of CMOS image sensor of  claim 8 , wherein the control node can be provided by a bias signal and the feedback circuit receives the output signal of the pixel circuit and processes it to yield the output signal to address the control node of the charge supplement unit. 
     
     
         10 . The method for increasing dynamic range of CMOS image sensor of  claim 2 , wherein the feedback circuit can comprise an amplifier with variable active loading, controlled by the output signal of the pixel circuit. 
     
     
         11 . The method for increasing dynamic range of CMOS image sensor of  claim 2 , wherein the feedback circuit controls the charges of the charge supplement unit supplying into the photodiode by a voltage-level way.