Signal generator and method for generating signals for reducing noise in signals

Abstract

A CMOS image sensor may include an active pixel sensor array and a noise canceller array corresponding to the active pixel sensor array. A method of operating such an CMOS image sensor may involve generating a varying reference signal that mirrors noise external to the active pixel sensor array, outputting the varying reference signal to the noise canceller array, and using the varying reference signal in the noise canceller array to cancel noise both internal to and external to the active pixel sensor array.

1 . A method for operating a CMOS image sensor including an active pixel sensor array and a noise canceller array corresponding to the active pixel sensor array, the method comprising: 
 generating a varying reference signal that mirrors noise external to the active pixel sensor array;    outputting the varying reference signal to the noise canceller array; and    using the varying reference signal in the noise canceller array to cancel noise both internal to and external to the active pixel sensor array.    
     
     
         2 . The method as claimed in  claim 1 , wherein generating the varying reference signal comprises mirroring noise in a power supply supplying power to the active pixel sensor array.  
     
     
         3 . The method as claimed in  claim 2 , wherein mirroring noise in the power supply comprises creating a replicated signal in accordance with pixel functioning of a pixel in the active pixel sensor array and power from the power supply.  
     
     
         4 . The method as claimed in  claim 3 , wherein generating the varying reference signal further comprises adding the replicated signal to a constant reference signal.  
     
     
         5 . The method as claimed in  claim 3 , wherein creating the replicated signal comprises providing an optical black pixel having a pixel structure equivalent to that of the pixel in the active pixel sensor array and supplying power from the power supply to the optical black pixel.  
     
     
         6 . The method as claimed in  claim 3 , wherein creating the replicated signal comprises providing an equivalent circuit having a response to input power equal to that of the pixel in the active pixel sensor array and supplying power from the power supply to the equivalent circuit.  
     
     
         7 . The method as claimed in  claim 3 , wherein generating the varying reference signal further comprises mirroring switching offset noise within the noise canceller array.  
     
     
         8 . The method as claimed in  claim 7 , wherein generating the varying reference signal further comprises supplying the replicated signal to a dummy noise canceller having an equivalent structure to that of a noise canceller of the noise canceller array.  
     
     
         9 . The method as claimed in  claim 1 , wherein generating the varying reference signal comprises mirroring switching offset noise within the noise canceller array.  
     
     
         10 . The method as claimed in  claim 9 , wherein generating the varying reference signal further comprises supplying a constant reference signal to a dummy noise canceller having an equivalent structure to that of a noise canceller of the noise canceller array.  
     
     
         11 . An apparatus for use with a CMOS image sensor including an active pixel sensor array and a noise canceller array corresponding to the active pixel sensor array, the apparatus comprising: 
 a varying reference signal generator to generate a varying reference signal that mirrors noise external to the active pixel sensor array and to output the varying reference signal to the noise canceller array.    
     
     
         12 . The apparatus as claimed in  claim 11 , wherein the varying reference signal mirrors noise in a power supply supplying power to the active pixel sensor array.  
     
     
         13 . The apparatus as claimed in  claim 12 , further comprising a replication unit for creating a replicated signal in accordance with pixel function of a pixel in the active pixel sensor array and power from the power supply.  
     
     
         14 . The apparatus as claimed in  claim 13 , wherein the varying reference signal generator comprises a comparator for adding the replicated signal and a constant reference signal.  
     
     
         15 . The apparatus as claimed in  claim 13 , wherein the replication unit comprises an optical black pixel having a pixel structure equivalent to that of the pixel in the active pixel sensor array, the optical black pixel receiving power from the power supply.  
     
     
         16 . The apparatus as claimed in  claim 13 , wherein the replication unit comprises an equivalent circuit having a response to input power equal to that of the pixel in the active pixel sensor array, the equivalent circuit receiving power from the power supply.  
     
     
         17 . The apparatus as claimed in  claim 13 , wherein the varying reference signal further mirrors switching offset noise within the noise canceller array.  
     
     
         18 . The apparatus as claimed in  claim 17 , wherein the varying reference signal generator comprises a dummy noise canceller having an equivalent structure to that of a noise canceller of the noise canceller array, the dummy noise canceller receiving the replicated signal.  
     
     
         19 . The apparatus as claimed in  claim 11 , wherein the varying reference signal mirrors switching offset noise within the noise canceller array.  
     
     
         20 . The apparatus as claimed in  claim 19 , wherein the varying reference signal generator comprises a dummy noise canceller having an equivalent structure to that of a noise canceller of the noise canceller array.  
     
     
         21 . The apparatus as claimed in  claim 20 , wherein the varying reference signal generator comprises a plurality of dummy noise cancellers.