Pressure-sensitive touch panel

Abstract

Pressure-sensitive touch panel. An apparatus for combined capacitance and pressure sensing is described. The apparatus includes a multiplexer (75) having a plurality of inputs (76) and an output (F), a touch panel (29), and a front end module (3). The touch panel includes a layer structure (5; Fig.15) comprising one or more layers, each extending perpendicularly to a thickness direction, the one or more layers including a layer of piezoelectric material (10; Fig.15), the layer structure having first (6) and second (7; Fig.15) opposite faces, and the layer(s) arranged between the first and second faces such that the thickness direction of each layer is perpendicular to the first and second faces. The touch panel also includes a plurality of first electrodes (8) disposed on the first face, each first electrode connected to a respective input of the multiplexer. The touch panel also includes at least one second electrode (9) disposed on the second face. The front end module is configured to receive an input signal (11) from the multiplexer output. The front end module includes a first stage (12) configured to provide an amplified signal based on the input signal, and a second stage comprising first (13) and second (14) frequency-dependent filters configured to receive the amplified signal and to provide respective first (16) and second (17) filtered signals. The first filtered signal has a first frequency bandwidth, and the second filtered signal has a second frequency bandwidth which has a relatively higher start-frequency than the first frequency bandwidth.

Description

technical field [0001] The present 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 type of capacitive touch panel, projected capacitive touch panels are often used in mobile devices because the outer layer can be made of glass, providing 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 the electric field caused by the proximity of conductive objects. Where a projected capacitive touch panel is touched is typically determined using an array or grid of capacitive sensors. Although projected capacitive touch panels can generally distinguish between single-touch events and multi-touch events, projected capacitive touch panels have the disadvantage of not being a...

AI Technical Summary

Problems solved by technology

However, a system that uses separate electronics to sense changes in capacitance and pressure would make the touch panel bulkier and more expensive

Systems where electrodes are applied or patterned directly onto the piezoelectric film are more complex and expensive to manufacture

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