Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
  • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
  • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
  • G06F3/0444—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means using a single conductive element covering the whole sensing surface, e.g. by sensing the electrical current flowing at the corners

Definitions

• This invention relates generally to touchpads using surface capacitance technology. More specifically, the present invention is a new method of determining the position of a pointing object or objects on a surface capacitance touch panel . ⁇
• Capacitive touch screens are readily available for use in diverse applications. As touch sensitive screens become more popular and more useful, the technologies to implement them are also evolving.
• Projected capacitance methods are currently required to implement gestures that utilize more than one finger or pointing object on the surface at the same time .
• figure 1 is a top view of an array of orthogonal electrodes 6, such as a plurality of X (2) and Y (4) electrodes, which are often used in touchpad and touch screen technologies such as those produced by Cirque Corporation ® .
• projected capacitance methods generally cost more to implement than surface capacitance methods because of the more intricate processes required to etch electrode patterns into a conductive surface.
• FIG. 2 An example of surface capacitance technology is shown in figure 2.
• a surface cap panel 10 is a solid sheet of a conductive material 16 disposed on an insulating substrate 18 such as glass, with sensors 12 disposed at the corners.
• the traditional method of measuring the position of a pointing object 14 or the "touch position" on the surface capacitance touch panel 10 is to apply an AC signal on all four corners of the touch panel's conductive layer 16.
• the conductive layer 16 can be made, for example, of Indium Tin Oxide (ITO) .
• ITO Indium Tin Oxide
• the surface of the glass substrate 18 is flooded or covered with a substantially even layer of a resistive ITO material which forms a sheet resistance.
• a dielectric is then applied to cover the ITO conductive material.
• the next step is to triangulate the touch position using the current flowing through each corner. It is common to apply either a sine wave or a square wave .
• Multi- finger gestures can also be accomplished using an "area gesture", such as in the method taught by Cirque Corporation ® , wherein multiple contacts are not tracked but instead the area gesture is accomplished by seeing the multiple contacts as only a single large object, where the multiple contacts only define the outer boundaries of the large object.
• the multiple points of contact can therefore be considered to have a height and a width.
• Operating system software and Human Interface Device (HIG) standards are being modified to include these new gestures and methods of reporting multi- finger contact with a touch sensitive surface.
• surface cap panels to support multi -finger gestures or area gestures because there has not been a suitable method available for tracking more than one point of contact or for determining the outer boundaries of a large object as defined by area gesture method of Cirque Corporation ® for multiple points of contact. In other words, it has not been possible to determine height and width of a large object.
• the present invention is a surface capacitance touch sensitive surface (or "surface cap panel") suitable for use in a touch screen or touchpad, wherein the surface cap panel has a substantially even coating of a conductive material on a non-conductive substrate and then covering the conductive material with a dielectric material, wherein a novel current measuring circuit reduces the effect of stray capacitance on the accuracy of a current measurement so that the relative X and Y position of an object on the surface cap panel can be determined using simple ratio equations, and wherein measuring the charge transfer rate in a measuring circuit, in addition to the total charge transfer for each toggle event, enables the location of two objects to be identified on the surface cap panel, wherein the charge transfer rate is used to determine the distance between two points of contact on the surface cap panel, and wherein height and width information related to the distance between the two points of contact can now be determined by doubling the number of electrodes at the corners of the surface cap panel.
• Figure 1 is a perspective view of a X and Y electrode grid touchpad as found in the prior art .
• Figure 2 is a perspective view of a surface cap panel as found in the prior art .
• Figure 3 is a perspective view of a surface cap panel 10 that is made in accordance with the principles of the present invention.
• Figure 4 is a circuit diagram showing how a current measuring circuit comprised of a capacitor and a current measuring sensor is applied to the surface cap panel when a single object is present.
• Figure 5 is a top view of a surface cap panel in the first embodiment for use with the 8 Wire Method that can detect a plurality of objects.
• Figure 6 is a circuit diagram showing how a current measuring circuit comprised of two capacitors and two current measuring sensors are applied to the surface cap panel to detect a plurality of objects.
• Figure 7 is a graph showing the measurements made during different time apertures.
• Figure 8 is a top view of a surface cap panel that shows in which corners the electrodes of the current measuring circuit are p [laced for the 8 different measurements that must be made in order to detect a plurality of objects.
• Figure 9 is an alternative embodiment of a surface cap panel that can be used in the present invention.
• FIG. 3 is a perspective view of a surface cap panel 10 that is made in accordance with the principles of the present invention.
• a new and novel approach to determining the position of an object on the touch panel is to charge a large capacitor and then apply this "flying capacitor" to two opposite ends of the touch panel 10.
• this method measures the instantaneous and total current induced in a contact on a surface of the surface cap panel 20 when a constant voltage gradient is produced across the surface in a single axis.
• a sensitive current measuring circuit 32 as shown in figure 4 is applied to the surface cap panel 10 to make this current measurement.
• the flying capacitor 30 is used to charge the surface cap panel 10. Any charge that is removed from the surface cap panel 10 is measured with the current measuring circuit 32. Linearity of a voltage gradient can improve accuracy of the surface cap panel 10 in figure 3. Therefore, in a first step, it is desirable but not essential that a lower resistance material be added around the edges of the touch panel 10 on the surface.
• the voltage gradient lines 20 become closer and more linear from a top edge 26 to a bottom edge 28.
• the present invention extends the capability of the "flying cap” method of position determination by using what is referred to as the "8 Wire Method” .
• the surface cap panel 40 used for the 8 Wire Method is shown in figure 5.
• a gap 42 is created in each corner so that individual electrodes can be connected to the low resistance material at each end of the low resistance path.
• electrodes are coupled at 50, 52, 54, 56, 58, 60, 62 and 64, which are the 8 wires of the 8 Wire Method.
• the low resistance paths are separated but are sufficiently close to each other so as to form the constant voltage gradient as in the 4 Wire Method of the co-pending application.
• the 8 Wire Method is performed by measuring the charge transfer rate in addition to the total charge transfer for each event.
• An event is defined as when a measurement is taken.
• the charge transfer rate is used to determine the distance between two points of contact on the surface cap panel 40. Height and width information related to the distance between the two points of contact .is thus determined by doubling the number of electrodes at the corners of the surface cap panel 40.
• Figure 6 shows a modified current measurement circuit 70 that is used in the 8 Wire Method.
• two flying capacitors 72 and 74 are applied simultaneously to the surface cap panel 40. Simultaneous application of the flying capacitors 72 and 74 enables relative measurement of the aggregate resistance between contacts and horizontal and vertical low resistance paths on the surface cap panel 40.
• the position of the contacts on the surface cap panel 40 is determined by measuring the current through the multiple fingers and determining the effective Norton resistances for each parallel axis to the contacts.
• the Norton resistance is derived by two (2) successive integrations of the current in each axis.
• the two (2) measurements integrated over a long and short aperture of time allow for the RC time constant to be determined.
• the position or proximity of a contact to an edge is then derived from the computed resistance between the contact and the edge.
• the total integrated current (area under the curve below) is proportional to the finger capacitance.
• the pinch gesture in one axis shown in figure 7 illustrates the changes in the time constant of the current as contacts are moved apart. 2/1 are before and after measurements as the fingers are first close together (2 and 4) and then farther apart (1 and 3) .
• a larger "short measurement" of 1 versus 2 indicates a larger pinch in that axis.
• the present invention also extends the capability of the previous 4 Wire "flying cap” method by measuring rapid changes in capacitance to detect a second point of contact. Holding the first point of contact position fixed and moving the second point of contact provides midpoint location information that can now be used, for example, to provide information for a "rotate" gesture.
• the 8 Wire Method operates on the same principle as the 4 Wire Method of the co-pending application because individual electrodes are connected to the low resistance material at each end of the electrodes.
• FIG 8 is a block diagram of a surface cap panel 40 of the present invention.
• the corners of the surface cap panel are labeled A, B, C and D.
• Fl is an arbitrarily selected point of contact for a first pointing object.
• F2 is an arbitrarily selected point of contact for a second pointing object.
• O is labeled as the midpoint between points of contact Fl and F2.
• Oppositely charged capacitors are applied successively between Detect Electrodes and Drive Electrodes. Charge that is leaving the surface cap panel in a specific aperture of time is accumulated in a specific aperture of time. There are 8 different combinations of electrode patterns and accumulation time apertures. There are a total of 8 different measurements that must be taken. The 8 measurements or combinations of electrodes and time apertures are listed as Iterations in TABLE 1.
• the aspect ratio related to the vertical and horizontal spacing of contacts is determined by the average of the ratio of Ax and Ay for each measurement (Ml through M8) .
• MRn (Axn - Ayn) / (Axn + Ayn) .
• Aspect Ratio (MR1/MR5 + MR2/MR6 + MR3/MR7 + MR4/MR8) / 4.
• Figure 9 is provided as an alternative embodiment of the surface cap panel 40.
• a small slot 80 is created in the surface resistive material at each corner to further separate the electrodes 50, 52, 54, 56, 58, 60, 62 and 64.
• the slot 80 extends from the outside corner protruding up to the active area of the surface cap panel 40 where contacts are made .

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Human Computer Interaction (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Position Input By Displaying (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2010
  • 2010-03-08 EP EP10749068A patent/EP2404229A1/de not_active Withdrawn
  • 2010-03-08 WO PCT/US2010/000708 patent/WO2010101662A1/en active Application Filing
  • 2010-03-08 JP JP2011552949A patent/JP5529172B2/ja not_active Expired - Fee Related
  • 2010-03-08 CN CN2010800108834A patent/CN102341775A/zh active Pending

Non-Patent Citations (1)

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