System and method for sensing touches in capacitative panels
AssigneeKapik Inc.
InventorWilliam Martin SNELGROVE
Life of this patent
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Abstract
A multi-touch sensing system and a method for estimating a location of at least one touch point are provided. The multi-touch sensing system includes a panel, a grid of conductor disposed on the panel, a driver array connected to the grid, a receiver array connected to the grid, a signal processing system, and a controller. The method involves transmitting drive signals to the grid, receiving signals from the grid, estimating a capacitance, and transforming the capacitance into touch coordinates.
Claims20
A multi-touch sensing system for estimating a location of at least one touch point, the multi-touch sensing system comprising:
- a panel;
- a grid of conductor disposed on the panel, the grid of conductor configured to provide capacitances between rows and columns of the grid;
- a driver array connected to the grid, the driver array configured to transmit a set of overlapping and independent row drive signals to the grid;
- a receiver array connected to the grid for receiving column signals from the grid via a plurality of inputs, the receiver array configured to:
- sense a pre-charge voltage on a differential pair of inputs selected from the plurality of inputs;
- pre-charge the plurality of inputs to increase a voltage detection accuracy;
- pre-charge the plurality of inputs between sampling times to substantially equalize a common-mode input to a differential input;
- equalize a differential mode for the differential pair of inputs by returning the differential pair of inputs to the pre-charge voltage and reducing slow drifting due to slowly changing offsets;
- and
- produce digital estimates of the column signals;
- a signal processing system in communication with the driver array and the receiver array, the signal processing system configured to estimate a coupling capacitance between the columns and the rows by correlating the digital estimates of the column signals with the independent row drive signals;
- and
- a controller for transforming the coupling capacitance into touch co-ordinates by detecting and extracting potential touches from raw differential data collected from the panel.
A method of estimating a location of at least one touch point on a multi-touch sensing system, the method comprising:
- transmitting a set of overlapping and independent row drive signals to a grid using a driver array, wherein the grid comprises conductor disposed on a panel, the grid configured to provide capacitances between rows and columns of the grid;
- receiving column signals from the grid via a plurality of inputs using a receiver array, wherein receiving column signals comprises:
- sensing a pre-charge voltage on a differential pair of inputs selected from the plurality of inputs;
- pre-charging the plurality of inputs to increase a voltage detection accuracy;
- pre-charging the plurality of inputs between sampling times to substantially equalize a common-mode input to a differential input;
- equalizing a differential mode for the differential pair of inputs by returning the differential pair of inputs to the pre-charge voltage and reducing slow drifting due to slowly changing offsets;
- and
- producing digital estimates of the column signals;
- estimating a coupling capacitance between the columns and the rows by correlating the digital estimates of the column signals with the independent row drive signals using a signal processing system;
- and
- transforming the coupling capacitance into touch co-ordinates by detecting and extracting potential touches from raw differential data collected from the panel.
Dependencies are inferred from the claim text.