Cambridge Touch Technologies Ltd.

Babak Bastani

Arokia Nathan

Paul Richard Routley

Riccardo Micci

Michael Robert Astley

Xiang Cheng

Jiahao Li

Matteo Vit

Mojtaba Bagheri

Silviu Toma

An apparatus () for processing signals from a touch panel () is described. The touch panel () includes a layer of piezoelectric material () disposed between a number of sensing electrodes () and at least one common electrode (). The apparatus () includes a capacitive touch controller () for connection to the sensing electrodes (). The apparatus () also includes a switch network () including a number of inputs for connection to some or all of the sensing electrodes (), and an output connected to system ground or a common mode voltage (V). The apparatus () also includes a second circuit () for connection to the at least one common electrode () and configured to generate, based on signals received from the at least one common electrode, a second pressure signal () indicative of a total pressure applied to the touch panel (). The apparatus () also includes a controller () configured to control the switch network () to couple any connected sensing electrodes () to system ground or the common mode voltage (V) during a pressure measurement period, and to determine an estimate of the total pressure based on the second pressure signal during the pressure measurement period.

Pressure sensing apparatus and method

An apparatus for processing signals from a touch panel. The touch panel includes a layer of piezoelectric material disposed between a number of sensing electrodes and one or more common electrodes. The apparatus includes a capacitive touch controller for connection to the sensing electrodes and a switch network including inputs for connection to the sensing electrodes and an output connected to system ground or a common mode voltage. The apparatus includes a circuit for connection to the common electrodes and to generate, for each common electrode, a corresponding pressure signal indicative of a pressure applied to the touch panel proximate to that common electrode. The apparatus includes a controller to control the switch network to couple any connected sensing electrodes to system ground or the common mode voltage during a pressure measurement period, and to sample the one or more second pressure signals during the pressure measurement period.

Touch panel system with piezoelectric pressure sensing

A method includes receiving (S), from a touch panel (), force values () corresponding to a plurality of piezoelectric sensors (), Each piezoelectric sensor corresponds to a physical location (xm, yn) on the touch panel. The method also includes receiving (S) one or more user touch locations corresponding to user touches, The method also includes excluding (S) all force values () corresponding to physical locations within a distance of a user touch location, and setting the remaining force values () as valid force values (S). The method also includes interpolating and/or extrapolating (S), based on the valid force values, one or more reconstructed force values () corresponding to same physical locations (xm, yn) as the respective excluded force values ().

Pressure signal processing

An apparatus () for processing signals from a touch panel () is described. The touch panel () includes a layer of piezoelectric material () disposed between a plurality of sensing electrodes () and at least one common electrode (). The apparatus () includes a first circuit () for connection to the plurality of sensing electrodes (). The first circuit () is configured to generate a plurality of first pressure signals (). Each first pressure signal () corresponds to one or more sensing electrodes () and is indicative of a pressure acting on the touch panel () proximate to the corresponding one or more sensing electrodes (). The apparatus also includes a second circuit () for connection to the at least one common electrode (). The second circuit () is configured to generate a second pressure signal () indicative of a total pressure applied to the touch panel (). The apparatus also includes a controller () configured to determine an estimate of the total pressure based on a weighted difference of the second pressure signal () and a sum over the plurality of first pressure signals ().

Mitigation of external fields in piezoelectric sensors

An apparatus () for processing signals from a touch panel () is described. The touch panel () includes a layer of piezoelectric material () disposed between a plurality of sensing electrodes () and at least one common electrode (). The apparatus () includes a first circuit () for connection to the plurality of sensing electrodes (). The first circuit () is configured to generate one or more first pressure signals (). Each first pressure signal () corresponds to one or more sensing electrodes () and is indicative of a pressure acting on the touch panel () proximate to the corresponding one or more sensing electrodes (). The apparatus also includes a second circuit () for connection to the at least one common electrode (). The second circuit () is configured to generate a second pressure signal () indicative of a total pressure applied to the touch panel (). The apparatus also includes a controller () configured to determine an estimate of the total pressure based on a weighted difference of the second pressure signal () and a sum over the one or more first pressure signals ().

A device () for processing signals from a projected capacitance touch panel () is described. The projected capacitance touch panel () includes a layer of piezoelectric material () disposed between a number of sensing electrodes () and at least one counter electrode (). The device () includes a capacitive touch controller () having a number of measurement ports (). The device () also includes a number of charge amplifiers (). The device () also includes a number of terminals (C, . . . , C, D, . . . , D) for connection to the sensing electrodes () of the projected capacitance touch panel (). Each terminal (C, . . . , C, D, . . . , D) is connected to one of the measurement ports (). Each terminal (C, . . . , C, D, . . . , D) is also connected to an input of one of the charge amplifiers () via a corresponding switch (SW) of a number of switches (). The device () also includes a controller () configured to synchronise the capacitive touch controller () and the number of switches (SW,) so that during a first portion ([t, t]) of a cycle the capacitive touch controller () outputs a capacitance measurement signal () to one or more of the terminals (C, . . . , C, D, . . . , D), and the plurality of charge amplifiers () are disconnected from the terminals (C, . . . , C, D, . . . , D) by the respective switches (SW,). The controller () is also configured to synchronise the capacitive touch controller () and the number of switches (SW,) so that during a second portion ([t, t]) of the cycle the capacitive touch controller () does not output the capacitance measurement signal (), and one or more of the charge amplifiers () are connected to the corresponding terminals (C, . . . , C, D, . . . , D) by the respective switches (SW,).

Device for processing signals from a pressure-sensing touch panel

A method includes receiving (S), from a touch panel (), force values () corresponding to a plurality of piezoelectric sensors (). Each piezoelectric sensor corresponds to a physical location (x, y) on the touch panel. The method also includes receiving (S) an identification of which, if any, of the force values () are influenced by coupling to external electric fields. The method also includes, in response to one or more force values () being identified as influenced by coupling to external electric fields (S), setting the corresponding force values () as excluded force values (S), and setting the remaining force values () as valid force values (S). The method also includes interpolating and/or extrapolating (S), based on the valid force values, one or more reconstructed force values () corresponding to same physical locations (x, y) as the respective excluded force values ().

Apparatus () for processing signals from a touch panel () is described. The touch panel () includes a layer of piezoelectric material () disposed between a plurality of sensing electrodes () and at least one common electrode (). The apparatus () includes a first circuit () for connection to the plurality of sensing electrodes (). The first circuit () is configured to generate a plurality of first pressure signals (). Each first pressure signal () corresponds to one or more sensing electrodes () and is indicative of a pressure acting on the touch panel () proximate to the corresponding one or more sensing electrodes (). The apparatus () also includes a second circuit () for connection to the at least one common electrode (). The second circuit () is configured to generate a second pressure signal () indicative of a total pressure applied to the touch panel (). The apparatus () also includes a controller () configured to determine an external interference signal () based on a weighted sum over the second pressure signal () and the plurality of first pressure signals (). The controller () is also configured to compare the external interference signal () against a pre-calibrated threshold (V). The controller is also configured, in response to the external interference signal () being greater than or equal to the pre-calibrated threshold (V), to output an interference flag (Int) indicating that the first and second pressure signals () are influenced by coupling to one or more external electrical fields.

A device () is provided for processing signals () from a projected capacitance touch panel (), the touch panel () including a layer of piezoelectric material () disposed between a plurality of first electrodes () and at least one second electrode (). The device is configured, in response to receiving input signals () from a given first electrode (), to generate a pressure signal () indicative of a pressure applied to the touch panel () proximate to the given first electrode () and a capacitance signal () indicative of a capacitance of the given first electrode (). The device () includes an amplifier () configured to generate an amplified signal () based on the input signals (). The device () also includes an analog-to-digital converter () configured to be synchronised () with the capacitance signal (), and to generate the pressure signal () by sampling the amplified signal () at times corresponding to the amplitude of the capacitance signal () being substantially equal to a ground, common mode or minimum value.

A touchscreen system for generating localised haptic excitations includes a touchscreen panel for measuring force and/or capacitance. The touchscreen system includes one or more first piezoelectric transducers arranged to generate excitations in the touchscreen panel along a first line. The touchscreen system includes one or more second piezoelectric transducers arranged to generate excitations in the touchscreen panel along a second line which is inclined to the first line at an angle. The touchscreen system includes a pressure and/or capacitance sensing module connected to the touchscreen panel and configured to measure a force and/or capacitance from the touchscreen panel. The touchscreen system includes a haptic driving module connected to the first and second piezoelectric transducers and configured to generate user perceptible haptic excitation by driving the first piezoelectric transducers at a first frequency, and driving the second piezoelectric transducers at a second frequency, wherein the difference of the first and second frequencies is a beating frequency, and the beating frequency is a frequency perceptible by human skin, or by driving the first and second piezoelectric transducers at a carrier frequency which is modulated at a modulation frequency which is a frequency perceptible by human skin. The angle is selected to cause Moir&#xe9; fringes between excitations generated along the first line and the second line.

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Palo Alto, CA, United States of America

Babak Bastani