Controller for an acoustic wave touch panel
AssigneeCarroll Touch Inc.
InventorsTerrence J. Knowles, Del Ogren
Life of this patent
Estimating the term…
Abstract
A controller for an acoustic wave touch panel includes a signal conditioning circuit that can receive and process X axis and Y axis sense signals from the touch panel where the touch panel can be configured with either one or two transducers per sense axis. The signal conditioning circuit includes a differential amplifier to which simultaneously received X axis and Y axis sense signals are applied to provide common mode rejection. The controller also includes a touch position detector that accurately determines the position and pressure of a touch without jitter, the touch position detector including a software low pass filter and peak detector for analyzing the output of the signal conditioning circuit.
Claims65
A controller for an acoustic wave touch panel having a substrate, X axis transducer means for imparting acoustic waves into said substrate for propagation therein relative to an associated X axis, said X axis transducer means receiving acoustic waves incident thereto to generate an X axis signal representing sensed acoustic waves from which the position of a touch relative to said X axis can be determined and a Y axis transducer means for imparting acoustic waves into said substrate for propagation therein relative to an associated Y axis, said Y axis transducer means receiving acoustic waves incident thereto to generate a Y axis signal representing sensed acoustic waves from which the position of a touch relative to said Y axis can be determined, said controller comprising:
- a signal conditioning circuit responsive to an X axis signal and a Y axis signal simultaneously received by said circuit for rejecting common modes from said signals to provide conditioned X axis and Y axis signals;
- means for converting said conditioned X axis signal to a plurality of discrete X axis magnitude values, each value being associated with a position along said X axis, said converting means converting said conditioned Y axis signal to a plurality of discrete Y axis magnitude values, each value being associated with a position along said Y axis;
- means for comparing each of a plurality of said X axis magnitude values to a reference X axis value associated with the same position with respect to said X axis as the position of said X axis magnitude value to provide an X-axis difference value representing the difference between said compared X axis values, said comparing means comparing each of a plurality of said Y axis magnitude values to a reference Y axis value associated with the same position with respect to said Y axis as the position of said Y axis magnitude value to provide a Y axis difference value representing the difference between said compared Y axis values;
- and
- means for determining the position of a touch from a plurality of X axis difference values associated with X axis positions within a given range of the X axis position along the X axis associated with a maximum X axis difference value and from a plurality of Y axis difference values associated with X axis positions within a given range of the X axis position associated with a maximum Y axis difference value.
A controller for an acoustic wave touch panel having a substrate, X axis transducer means for imparting acoustic waves into said substrate for propagation therein relative to an associated X axis, said X axis transducer means receiving acoustic waves incident thereto to generate an X axis signal representing sensed acoustic waves from which the position of a touch relative to said X axis can be determined and a Y axis transducer means for imparting acoustic waves into said substrate for propagation therein relative to an associated Y axis, said Y axis transducer means receiving acoustic waves incident thereto to generate a Y axis signal representing sensed acoustic waves from which the position of a touch relative to said Y axis can be determined, said controller comprising:
- a signal conditioning circuit responsive to an X axis signal and a Y axis signal simultaneously received by said circuit for rejecting common modes from said signals to provide a conditioned X axis and Y axis signals, said circuit including an amplifier with an adjustable gain;
- means for detecting the presence or absence of a touch from said conditioned X axis and Y axis signals;
- means responsive to the detection of a touch for determining the position of said touch relative to said X and Y axes;
- means operable in the absence of a recognized touch for determining from said conditioned X axis and Y axis signals whether the gain of said amplifier needs adjustment;
- and
- means for automatically adjusting the gain of said amplifier if needed.
A touch position detector for an acoustic touch panel having a substrate and at least one transducer for imparting an acoustic wave into said substrate for propagation along a plurality of paths, each path representing a position along a first axis and for receiving an acoustic wave incident thereto to provide a signal representative of said wave, a touch on said substrate intersecting one of said paths forming a perturbation in said acoustic wave propagating along said path, comprising:
- means for converting said signal to a plurality of discrete magnitude values each value being associated with a position with respect to said first axis;
- means for comparing each of a plurality of said magnitude values to a reference value associated with the same position with respect to said first axis as the position of said magnitude value to provide a value representing the difference between said magnitude and reference values;
- and
- means for comparing a maximum difference value to a touch threshold to detect a touch on said substrate when said maximum difference is greater than said threshold;
- and
- means for determining the position of a touch from a plurality of difference values associated with positions with respect to said first axis within a given range of the first axis position associated with said maximum difference value.
A touch position detector for an acoustic touch panel having a substrate and at least one transducer for imparting an acoustic wave into said substrate for propagation along a plurality of paths, each path representing a position along a first axis and for receiving an acoustic wave incident thereto to provide a signal representative of said wave, a touch on said substrate intersecting one of said paths forming a perturbation in the acoustic wave propagating along said path comprising:
- a comparator for comparing said received acoustic wave signal to a reference signal to provide a signal representing the difference therebetween;
- a software low pass filter for filtering said difference signal to provide a filtered difference signal;
- and
- a software peak detector for detecting a peak of said filtered difference signal, said peak representing the position of said touch relative to said axis.
A surface acoustic wave touch panel system comprising:
- a touch panel substrate;
- X axis transducer means for imparting surface acoustic waves into said substrate for propagation therein relative to an associated X axis, said X axis transducer means receiving acoustic waves incident thereto to generate an X axis signal representing sensed surface acoustic waves from which the position of a touch relative to said X axis can be determined;
- Y axis transducer means for imparting surface acoustic waves into said substrate for propagation therein relative to an associated Y axis, said Y axis transducer means receiving surface acoustic waves incident thereto to generate a Y axis signal representing sensed surface acoustic waves from which the position of a touch relative to said Y axis can be determined;
- means for applying a drive signal to one of said X-axis or Y-axis transducer means to impart a surface acoustic wave in said substrate with respect to the axis associated with the driven transducer, said drive signal having a frequency sufficiently low so as to allow said touch panel substrate to be hermetically sealed;
- and
- differential means coupled to said X axis and Y axis transducer means for providing a signal representing the difference between simultaneously received X axis and Y axis signals, said difference signal corresponding to said sensed surface acoustic waves propagating relative to the axis associated with said one driven transducer.
A surface acoustic wave touch panel comprising:
- a touch panel substrate;
- X axis transducer means for imparting surface acoustic waves into said substrate for propagation therein relative to an associated X axis, said X axis transducer means receiving surface acoustic waves incident thereto to generate an X axis signal representing sensed surface acoustic waves from which the position of a touch relative to said X axis can be determined;
- Y axis transducer means for imparting surface acoustic waves into said substrate for propagation therein relative to an associated Y axis, said Y axis transducer means receiving surface acoustic waves incident thereto to generate a Y axis signal representing sensed acoustic waves from which the position of a touch relative to said Y axis can be determined, said controller comprising:
- means for applying a drive signal to one of said X-axis or Y-axis transducer means to impart a surface acoustic wave in said substrate with respect to the axis associated with the driven transducer, said drive signal having a frequency sufficiently low so as to allow said touch panel substrate to be hermetically sealed;
- a signal conditioning circuit responsive to an X axis signal and a Y axis signal simultaneously received by said circuit for rejecting common modes from said signals to provide conditioned X axis and Y axis signals;
- means for converting said conditioned X axis signal to a plurality of discrete X axis magnitude values, each value being associated with a position with respect to said X axis, said converting means converting said conditioned Y axis signal to a plurality of discrete Y axis magnitude values, each value being associated with a position with respect to said Y axis;
- means for comparing each of a plurality of said X axis magnitude values to a reference X axis value associated with the same position with respect to said X axis as the position of said X axis magnitude value to provide an X-axis difference value representing the difference between said compared X axis values, said comparing means comparing each of a plurality of said Y axis magnitude values to a reference Y axis value associated with the same position with respect to said Y axis as the position of said Y axis magnitude value to provide a Y axis difference value representing the difference between said compared Y axis values;
- and
- means for determining the position of a touch from a plurality of X axis difference values and from a plurality of Y axis difference values.
A surface acoustic wave touch panel comprising:
- a touch panel substrate;
- X axis transducer means for imparting surface acoustic waves into said substrate for propagation therein relative to an associated X axis, said X axis transducer means receiving surface acoustic waves incident thereto to generate an X axis signal representing sensed surface acoustic waves from which the position of a touch relative to said X axis can be determined;
- Y axis transducer means for imparting surface acoustic waves into said substrate for propagation therein relative to an associated Y axis, said Y axis transducer means receiving surface acoustic waves incident thereto to generate a Y axis signal representing sensed acoustic waves from which the position of a touch relative to said Y axis can be determined, said controller comprising:
- means for applying a drive signal to one of said X-axis or Y-axis transducer means to impart a surface acoustic wave in said substrate with respect to the axis associated with the driven transducer, said drive signal having a frequency sufficiently low so as to allow said touch panel substrate to be hermetically sealed;
- a signal conditioning circuit responsive to an X axis signal and a Y axis signal simultaneously received by said circuit for rejecting common modes from said signals to provide conditioned X axis and Y axis signals;
- means for detecting the presence or absence of a touch from said conditioned X axis and Y axis signals;
- means responsive to the detection of a touch for determining the position of said touch relative to said X and Y axes;
- means operable in the absence of a touch for determining from said conditioned X axis and Y axis signals whether the gain of said amplifier needs adjustment;
- and
- means for automatically adjusting the gain of said amplifier if needed.
Dependencies are inferred from the claim text.