TW341684B - Object position detector - Google Patents

Abstract

An object proximity sensor, including: a capacitive touch-sensitive transducer including row conductive lines disposed in a first direction insulated from column conductive lines disposed in a second direction generally perpendicular to the first direction to form a matrix, and an insulating layer disposed over the matrix and having a thickness selected to achieve significant capacitive coupling between an object placed on its surface and the matrix; means for first driving each of the row conductive lines to a fixed voltage and then for simultaneously injecting a known amount of charge onto each of the row conductive lines, and then sensing for each row conductive line a row-sense voltage created by the known amount of charge injected onto each of the row conductive lines, and, simultaneous with injecting the known amount of charge, changing the voltage on all of the column conductive lines in the same direction as the row-sense voltage of the each row conductive line by an amount no greater than about twice the difference between the fixed voltage and an average of all row-sense voltages in the transducer; means for first driving each of the column conductive lines to a fixed voltage and then for simultaneously injecting a known amount of charge onto each of the column conductive lines, and then sensing for each column conductive line a column-sense voltage created by the known amount of charge injected onto each of the column conductive lines, and, simultaneous with injecting the known amount of charge, changing the voltage on all of the row conductive lines in the same direction as the column-sense voltage of said each column conductive line by an amount no greater than about twice the difference between the fixed voltage and an average of all column-sense voltages in the transducer; and means for producing a set of object-sensed electrical signals related to all of the row-sense voltages and said all of the column-sense voltages.