{HEAD ~ a second step}, in which the third sensing electrode switches are turned off not to interconnect the pixel groups, the first sensing electrode switches are turned off to block the first voltage source, and a voltage V2 is applied to the second voltage source, such that a mean capacitance value for each pixel group is calculated in association with each of {TAIL ~ the pixel groups}; and 
{ HEAD ~ a second step } , in which the third sensing electrode switches are turned off not to interconnect the pixel groups , the first sensing electrode switches are turned off to block the first voltage source , and a voltage V2 is applied to the second voltage source , such that a mean capacitance value for each pixel group is calculated in association with each of { TAIL ~ the pixel groups } ; and
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH