Touch input device

Abstract

A touch sensor input device includes a first and second array of electrodes, the electrodes in the first array being orthogonal to the electrodes in the second array. A capacitor sensing arrangement senses an electrode capacitance signal which varies in the presence of a touch input. The capacitance signals for groups of electrodes in each array are combined in order to derive respective individual sense signals. This arrangement has electrodes with a finer resolution than the sensing resolution, and this gives improved ability to sense accurately the position of the touch input.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 125,917, filed on Apr. 30, 2008, and U.S. Provisional Application No. 61 / 125,963, filed on Apr. 30, 2008, the entirety of which are incorporated by reference herein.[0002]This application claims priority of EP Patent Application No. 09152695.4, filed on Feb. 12, 2009, the entirety of which is incorporated by reference herein.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]This invention relates to touch input devices, for example for use in display devices with touch screens.[0005]2. Description of the Related Art[0006]Touch screens are becoming increasingly common in consumer electronics applications where an LCD display is present in a device e.g. mobile phone, PDA or camera. User interaction via a touch screen saves the space required for key inputs and therefore allows a larger display area for a given size of device. The touch screen provides a...

AI Technical Summary

Benefits of technology

[0025]In one example, each group of electrodes comprises an adjacent group of electrodes. This means that each sense electrode is effectively an arrangement of electrodes spread over an area using a higher resolution array of electrodes. The high resolution electrodes can thus be considered to be sub-electrodes. Because these sense sub-electrodes have a finer resolution than the resolution being sensed (for example finer than size of the object being detected), there is a more gradual shift in capacitance change from one sense electrode arrangement to the next as the input moves. However, the sense electrode arrangements can still occupy a small area and therefore the effect of the touch sensor device on the output of an underlying display device can be minimised. The touch sensor capacitance signal is stronger when the input position is between sense electrode arrangement positions.

Problems solved by technology

The presence of the sense electrodes may therefore degrade the quality of the displayed images particularly when moving images are being viewed.

A further concern is that when the object to be sensed is significantly smaller than the sense electrode pitch, this will affect the way in which the capacitance values change with the position of the object, making it difficult to uniquely locate the position of the object when it is centred on one of the sense electrodes.

This may make it difficult to detect the location of the stylus on one set of electrodes, for example the A electrodes, when the stylus is centred over one of the other set of electrodes, for example the B electrodes.

This will make it difficult to detect which of the A electrodes the object is closest to.

However, the electrode shape required to produce the desired sensor characteristics may not be consistent with the pattern required to minimize the visibility of the sense electrodes.

Images