# US 7,746,325 B2 · Method for improving positioned accuracy for a determined touch input > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,746,325 B2 - Document ID: US7746325B2 - Status: Granted - Kind: B2 - Application number: 10/140,209 - Filed: 2002-05-06 - Published: 2003-11-06 - Granted: 2010-06-29 - Earliest claimed: 2002-05-06 - Assignees: 3M Innovative Properties Company - Inventors: Jerry B. Roberts - Web page: https://patentgrep.com/patent/US7746325B2 ## CPC - G06F 3/04142: {the force sensing means being located peripherally, e.g. disposed at the corners or at the side of a touch sensing plate} - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract An approach for accurately determining touch location on a touch screen is provided. According to one aspect, a touch signal shape may be correlated with a level of touch-induced touch signal error present in the touch signal. The touch signal shape is associated with a preferred time for obtaining touch signal information to determine the touch location. Touch signal location information is acquired in response to detecting the touch signal shape in the touch signal. The location of the touch is determined from the acquired touch signal information. ## Claims ### Claim 1 A method for determining a touch location on a touch screen, comprising; acquiring a touch signal corresponding to a touch on the touch screen; detecting the first occurrence of a predetermined shape in the touch signal, the predetermined shape being associated with low signal error and based on a slope or a rate of change of the touch signal; determining touch location using touch signal information obtained in response to detecting the predetermined shape. ### Claim 2 (depends on 1) The method of claim 1, wherein acquiring the touch signal further comprises acquiring a signal indicative of a touch force. ### Claim 3 (depends on 1) The method of claim 1, wherein detecting the first occurrence of the predetermined shape comprises detecting a preferred time for obtaining touch signal information to determine touch location. ### Claim 4 (depends on 3) The method of claim 3, wherein detecting the preferred time comprises detecting a time when touch signal errors in the touch signal are minimal. ### Claim 5 (depends on 3) The method of claim 3, wherein detecting the preferred time comprises detecting a time when damping effect errors in the touch signal are minimal. ### Claim 6 (depends on 3) The method of claim 3, wherein detecting the preferred time comprises detecting a time when inertial effect errors in the touch signal are minimal. ### Claim 7 (depends on 1) The method of claim 1, wherein detecting the first occurrence of the predetermined shape comprises detecting a predetermined relative slope of the touch signal. ### Claim 8 (depends on 7) The method of claim 7, wherein detecting the predetermined relative slope comprises dividing a slope of the touch signal at a particular time by a magnitude of the touch signal at the particular time. ### Claim 9 (depends on 7) The method of claim 7, wherein detecting the first occurrence of the predetermined shape comprises detecting the first occurrence of the relative slope falling below a predetermined value. ### Claim 10 (depends on 7) The method of claim 7, wherein detecting the first occurrence of the predetermined shape comprises detecting the first occurrence that the relative slope changes sign. ### Claim 11 (depends on 7) The method of claim 7, wherein detecting the first occurrence of the predetermined shape comprises detecting the first occurrence of a touch signal point halfway through an interval of the touch signal for which the relative slope is less than a predetermined value. ### Claim 12 (depends on 8) The method of claim 8, wherein detecting the first occurrence of the predetermined shape comprises detecting the first occurrence of a touch signal point following a predetermined delay interval after the relative slope falls below a predetermined value. ### Claim 13 (depends on 1) The method of claim 1, wherein using a fixed threshold to determine that the touch signal represents a valid touch input further comprises determining that the touch signal exceeds a predetermined magnitude before detecting the first occurrence of a predetermined shape in the touch signal. ### Claim 14 (depends on 1) The method of claim 1, wherein using a fixed threshold to determine that the touch signal represents a valid touch input further comprises examining the touch signal to detect a rise of the touch signal above a predetermined magnitude after detecting the first occurrence of the predetermined shape in the touch signal. ### Claim 15 (depends on 3) The method of claim 3, further comprising obtaining touch location information if the preferred time is not detected after a predetermined interval and if the touch is deliberately slow. ### Claim 16 (depends on 3) The method of claim 3, further comprising masking a touch signal output until a current touch condition is removed if the preferred time is not detected after a predetermined interval and if the touch is not deliberately slow. ### Claim 17 (depends on 16) The method of claim 16, wherein the current touch condition is removed when the touch signal magnitude falls below a predetermined magnitude. ### Claim 18 (depends on 3) The method of claim 3, further comprising determining a series of touch locations after the preferred time is detected if the touch is a continuing touch. ### Claim 19 (depends on 18) The method of claim 18, wherein the further step of determining a series of touch locations after the preferred time is detected if the touch is a continuing touch comprises masking a touch location output when the relative slope falls below a predetermined range around zero. ### Claim 20 (depends on 18) The method of claim 18, further comprising reporting as a touch location output a first touch location in the series of touch locations until a predetermined time interval has elapsed. ### Claim 21 (depends on 18) The method of claim 18, further comprising reporting as a touch location output a first touch location in the series of touch locations until the touch location is calculated to be a predetermined distance from the first touch location. ### Claim 22 A method for determining a touch location on a touch screen, comprising: associating a predetermined touch signal shape with a low touch signal error and based on a slope or a rate of change of the touch signal; acquiring a touch signal corresponding to a touch on the touch screen; detecting the first occurrence of the predetermined touch signal shape in the touch signal; and determining touch location using touch signal information obtained in response to detecting the predetermined touch signal shape. ### Claim 23 (depends on 22) The method of claim 22, wherein acquiring the touch signal corresponding to the touch on the touch screen further comprises acquiring a signal indicative of a touch force. ### Claim 24 (depends on 22) The method of claim 22, wherein detecting the first occurrence of a touch signal shape comprises detecting a predetermined relative slope of the touch signal. ### Claim 25 (depends on 22) The method of claim 22, wherein associating the touch signal shape with the level of touch signal error comprises associating the touch signal shape with a reduced level of touch signal error in comparison to a maximum touch signal error. ### Claim 26 (depends on 22) The method of claim 22, wherein associating the touch signal shape with the level of touch signal error comprises detecting a time when damping effect errors in the touch signal are minimal. ### Claim 27 (depends on 22) The method of claim 22, wherein associating the touch signal shape with the level of touch signal error comprises detecting a time when inertial effect errors in the touch signal are minimal. ### Claim 28 (depends on 21) The method of claim 21, wherein detecting the first occurrence of the touch signal shape comprises detecting a preferred time for obtaining touch signal information to determine touch location. ### Claim 29 A method for determining a touch location on a touch screen, comprising; associating a touch signal shape with a local minimum in touch-induced error; acquiring a touch signal arising from a touch on the touch screen; determining a particular time at which the touch signal shape is present in the touch signal by analyzing a slope or rate of change in the touch signal; and determining touch location using touch signal information obtained at the particular time. ### Claim 30 (depends on 29) The method of claim 29, wherein the acquiring a touch signal arising from a touch comprises acquiring a signal indicative of a touch force. ### Claim 31 (depends on 29) The method of claim 29, wherein determining the particular time at which the touch signal shape is present in the touch signal comprises determining a preferred time for obtaining touch signal information to determine touch location. ### Claim 32 (depends on 29) The method of claim 29, wherein associating the touch signal shape with the local minimum in touch-induced error present in the touch signal comprises associating the touch signal shape to a time during the touch signal that damping effect errors are minimal. ### Claim 33 (depends on 29) The method of claim 29, wherein associating the touch signal shape with the local minimum in touch-induced error present in the touch signal comprises associating the touch signal shape to a time during the touch signal that inertial effect errors are minimal. ### Claim 34 (depends on 29) The method of claim 29, wherein associating the touch signal shape with the local minimum in touch-induced error present in the touch signal further comprises associating a predetermined relative slope of the touch signal with the local minimum in touch-induced error present in the touch signal. ### Claim 35 A method for determining a touch location on a touch screen, comprising: acquiring a touch signal indicative of a force due to a touch on the touch screen; detecting a touch signal shape within an interval of the touch signal associated with maximum touch force, the touch signal shape being associated with low signal error and determined using slope or a rate of change of the touch signal; and determining touch location using touch signal information obtained in response to detecting the touch signal shape. ### Claim 36 (depends on 35) The method of claim 35, wherein detecting the touch signal shape within the interval of the touch signal associated with maximum touch force comprises detecting the touch signal shape within an interval beginning with the application of a touch and ending when a slope of the touch signal falls below a predetermined value. ### Claim 37 (depends on 35) The method of claim 35, wherein detecting the touch signal shape within the interval of the touch signal associated with maximum touch force comprises detecting the touch signal shape within an interval beginning with the application of a touch and ending when a magnitude of the touch signal falls below a predetermined value. ### Claim 38 (depends on 35) The method of claim 35, wherein detecting a touch signal shape within the interval of the touch signal associated with maximum touch force comprises detecting a preferred time for obtaining touch signal information to determine touch location. ### Claim 39 (depends on 38) The method of claim 38, wherein detecting the preferred time comprises detecting a time when touch signal errors in the touch signal are minimal. ### Claim 40 (depends on 38) The method of claim 38, wherein detecting the preferred time comprises detecting a time when damping effect errors in the touch signal are minimal. ### Claim 41 (depends on 34) The method of claim 34, wherein detecting the preferred time comprises detecting a time when inertial effect errors in the touch signal are minimal. ### Claim 42 (depends on 35) The method of claim 35, wherein detecting the touch signal shape within the interval of the touch signal associated with maximum touch force comprises detecting a predetermined relative slope of the touch signal. ### Claim 43 A method for determining touch location on a touch screen comprising; acquiring a touch signal representative of a touch on the touch screen, the touch signal having an error related to the rate of change of the touch signal; detecting a particular time for obtaining touch signal information for determining touch location based on a slope or the rate of change of the touch signal that relates to a low signal error; and determining the touch location using touch signal information obtained at the particular time. ### Claim 44 A touch screen system, comprising; a touch surface; a plurality of touch sensors, each of the touch sensors physically coupled to the touch surface and producing a sensor signal in response to a touch applied to the touch surface; and a control system, coupled to the touch sensors and receiving the sensor signals, the control system acquiring a touch signal corresponding to a touch on the touch screen, detecting a first occurrence of a touch signal shape in the touch signal, the touch signal shape being associated with low signal error and based on a slope or a rate of change of the touch signal; and determining touch location using touch signal information obtained in response to detecting the touch signal shape. ### Claim 45 (depends on 44) The system of claim 44, wherein the touch sensors comprise force sensors. ### Claim 46 (depends on 44) The system of claim 44, wherein the touch sensors comprise capacitive force sensors. ### Claim 47 (depends on 44) The system of claim 44, wherein the touch surface is substantially rectangular with one of the plurality of touch sensors located at each corner of the touch screen. ### Claim 48 (depends on 47) The system of claim 47, wherein each touch sensor produces a sensor signal indicative of a force of a touch sensed at a location of the touch sensor. ### Claim 49 (depends on 44) The system of claim 44, wherein the control system derives one or more touch signals by combining one or more sensor signals. ### Claim 50 (depends on 44) The system of claim 44, wherein the control system comprises a filter for filtering touch signals produced by the touch sensors. ### Claim 51 (depends on 50) The system of claim 50, wherein the filter comprises a digital filter. ### Claim 52 (depends on 51) The system of claim 51, wherein the digital filter comprises a finite impulse response filter or an infinite impulse filter. ### Claim 53 (depends on 44) The system of claim 44, wherein the touch signal shape used to determine the touch location comprises a slope of the touch signal calculated by the processor. ### Claim 54 (depends on 44) The system of claim 44, wherein the processor calculates a relative slope of the touch signal as the slope of the touch signal at a particular time divided by a magnitude of the touch signal at the particular time. ### Claim 55 A touch screen display system, comprising; a force sensitive touch screen system including a touch surface and a plurality of touch sensors, each of the touch sensors physically coupled to the touch surface and producing a touch signal in response to a touch force applied from a touch to the touch surface; a control system coupled to the touch sensors and receiving the sensor signals, the control system detecting a first occurrence of a touch signal shape in the touch signal by at least using a slope or a rate of change of the touch signal, the touch signal shape being associated with low signal error; and determining touch location using touch signal information a display for displaying information through the touch screen system. ### Claim 56 (depends on 55) The system of claim 55, wherein the display is a liquid crystal display, a light emitting diode display, a plasma display, an organic electroluminescent display, or a cathode ray tube display. ### Claim 57 (depends on 55) The system of claim 55, wherein the touch sensors comprise force sensors. ### Claim 58 (depends on 55) The system of claim 55, wherein each touch sensor produces a sensor signal indicative of a force of a touch sensed at a location of the touch sensor. ### Claim 59 (depends on 55) The system of claim 55, wherein the control system derives one or more touch signals by combining one or more sensor signals. ### Claim 60 A display system, comprising: a force sensitive touch screen system including a touch surface and a plurality of touch sensors, each of the touch sensors physically coupled to the touch surface and producing a touch signal in response to a touch force applied from a touch to the touch surface; a control system, coupled to the touch sensors and receiving the sensor signals, the control system detecting a first occurrence of a touch signal shape in the touch signal, the touch signal shape being associated with low signal error and determined with reference to a slope of rate of change of the touch signal; and determining touch location using touch signal information obtained in response to detecting the touch signal shape; a display for displaying information; and a processor coupled to the display and the touch screen system for processing data to be displayed on the display and information received from the touch screen system. ### Claim 61 (depends on 60) The system of claim 60, wherein the display displays information through the touch screen. ### Claim 62 (depends on 60) The system of claim 60, wherein the display is a liquid crystal display, a light emitting diode display, a plasma display, an organic electroluminescent display, or a cathode ray tube display. ### Claim 63 (depends on 60) The system of claim 60, wherein the processor receives information regarding a touch made on the touch screen relative to information displayed on the display. ### Claim 64 (depends on 60) The system of claim 60, wherein the touch sensors comprise force sensors. ### Claim 65 (depends on 60) The system of claim 60, wherein each touch sensor produces a sensor signal indicative of a force of a touch sensed at a location of the touch sensor. ### Claim 66 (depends on 60) The system of claim 60, wherein the control system derives one or more touch signals by combining one or more sensor signals. ### Claim 67 (depends on 60) The system of claim 60, further comprising: one or more data storage devices coupled to the processor for storing data; one or more input devices for transferring information to the processor; and one or more output devices for transferring information from the processor. ### Claim 68 (depends on 60) The system of claim 60, further comprising one or more interfaces for coupling the system to one or more networks. ### Claim 69 A system for determining the location of a touch on a touch screen, comprising: means for acquiring a touch signal indicative of a force due to a touch on the touch screen; means for detecting a first occurrence of a predetermined shape in the touch signal, the predetermined shape being associated with low signal error and detected with reference to a slope or rate of change of the touch signal; and means for determining touch location using touch signal information obtained in response to detecting the predetermined touch signal shape. ### Claim 70 (depends on 69) The method of claim 69, wherein means for acquiring the touch signal further comprises means for acquiring a signal indicative of a touch force. ### Claim 71 (depends on 69) The method of claim 69, wherein means for detecting the first occurrence of the touch signal shape comprises means for detecting a preferred time for obtaining touch signal information to determine touch location. ### Claim 72 (depends on 71) The method of claim 71, wherein means for detecting the preferred time comprises means for detecting a time when touch signal errors in the touch signal are minimal. ### Claim 73 (depends on 69) The method of claim 69, wherein means for detecting the first occurrence of the touch signal shape comprises means for detecting a predetermined relative slope of the touch signal. ### Claim 74 A system for determining the location of a touch on a touch screen, comprising: means for associating a predetermined touch signal shape with a low level of touch signal error and detected with reference to a slope or rate of change of the touch signal; means for acquiring a touch signal corresponding to a touch on the touch screen; means for detecting a first occurrence of the predetermined signal shape in the touch signal; and means for determining touch location using touch signal information obtained in response to detecting the predetermined touch signal shape. ### Claim 75 A system for determining a touch location on a touch screen, comprising: means for acquiring a touch signal indicative of a force due to a touch on the touch screen; means for detecting a touch signal shape within an interval of the touch signal associated with maximum touch force, the touch signal shape associated with low signal error and detected with reference to a slope or rate of change of the touch signal; and means for determining touch location using touch signal information obtained in response to detecting the touch signal shape. ### Claim 76 A non transient computer readable medium configured with executable instructions for causing one or more computers to perform a method of determining the location of a touch on a touch screen, the method comprising: acquiring a touch signal indicative of a force due to a touch on the touch screen; detecting a first occurrence of a predetermined shape in the touch signal, the predetermined shape associated with low signal error and calculated with reference to a slope or a rate of change of the touch signal; and determining touch location using touch signal information obtained in response to detecting the touch signal shape.