Pressure-sensitive touch panel

Abstract

A device (48) for combined capacitance and pressure measurements includes a plurality of first input / output terminals (13) for a projected capacitance touch panel (36, 53, 58, 80), the touch panel (36, 53, 58, 80) including a layer of piezoelectric material (12) disposed between a plurality of sensing electrodes (10, 31) and a common electrode (11). The device (48) includes a plurality of second input / output terminals (14) for a capacitive touch controller (5). The device (48) includes a plurality of separation stages (2, 70, 76), each separation stage (2, 70, 76) connecting one first input / output terminal (13) to a corresponding second input / output terminal (14), and including a first frequency-dependent filter (15; Fig.1) for filtering signals (21, 33, 34) between respective first and second input / output terminals (13, 14). The device (48) includes at least one amplification stage (3, 71, 77), each amplification stage input is connected to one or more of the first input / output terminals (13) through the respective separation stage(s) (2, 70, 76). Each amplification stage (3, 71, 77) or each separation stage (2, 70, 76) includes a second frequency-dependent filter (16; Fig. 1) forfiltering signals between the respective first input / output terminal (13) and an amplification stage input. Each first frequency-dependent filter (16; Fig.1) is configured to pass signals (21, 33, 34) from the capacitive touch controller (5) and each second frequency-dependent filter (16; Fig.1 ) is configured to attenuate signals (21, 33, 34) from the capacitive touch controller (5).

Description

technical field [0001] The invention relates to a touch panel for combined capacitive and pressure sensing. Background technique [0002] Resistive touch panels and capacitive touch panels are used as input devices for computers and mobile devices. One class of capacitive touch panels, projected capacitive touch panels, is often used in mobile devices because the outer layers can be made of glass that provides a scratch-resistant hard surface. An example of a projected capacitive touch panel is described in US 2010 / 0079384 A1. [0003] Projected capacitive touch panels work by detecting changes in electric fields caused by the proximity of conductive objects. An array or grid of capacitive sensors is often used to determine where a projected capacitive touch panel is touched. While projected capacitive touch panels can generally distinguish between single and multiple touch events, they suffer from the inability to sense pressure. As a result, projected capacitive touch ...

AI Technical Summary

Problems solved by technology

However, systems that use separate electrodes and / or separate electronics to sense changes in capacitance and / or changes in pressure can make the touch panel bulkier and more expensive

Systems where electrodes are applied or patterned directly onto the piezoelectric film can be more complex and costly to produce

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