EP1010156A1 - Ecran tactile realise sur la base d'une cartographie topographique - Google Patents

Ecran tactile realise sur la base d'une cartographie topographique

Info

Publication number
EP1010156A1
EP1010156A1 EP97946486A EP97946486A EP1010156A1 EP 1010156 A1 EP1010156 A1 EP 1010156A1 EP 97946486 A EP97946486 A EP 97946486A EP 97946486 A EP97946486 A EP 97946486A EP 1010156 A1 EP1010156 A1 EP 1010156A1
Authority
EP
European Patent Office
Prior art keywords
conductive area
potential
electrodes
readings
electrically conductive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97946486A
Other languages
German (de)
English (en)
Other versions
EP1010156A4 (fr
Inventor
G Samuel Hurst
Rufus H. Ritchie
Donald W. Bouldin
Robert J. Warmack
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Elo Touch Systems Inc
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP1010156A1 publication Critical patent/EP1010156A1/fr
Publication of EP1010156A4 publication Critical patent/EP1010156A4/fr
Withdrawn legal-status Critical Current

Links

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
    • G06F3/045—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Definitions

  • touch screens Since their introduction in the early 1970s, touch screens have afforded attractive alternatives to keyboards for certain computer applications. In many situations the keyboard and mouse are eliminated, because the touch screen provides the user with a much easier access to the computer. As a consequence, the market has grown to a substantial size, and a continued rapid growth is anticipated. However, current touch screens are difficult to produce, which creates a price barrier limiting growth into many new areas, such as education.
  • a substantial portion of touch screens produced today are based on the measurement of electrical potentials on substrates that are made of a transparent medium such as glass, coated with an electrically conductive material. Uniform electrical fields must be maintained on the substrate, and these are applied sequentially in the x- and y-directions . In other words, equally spaced equipotential lines are generated orthogonally in a timed sequence.
  • a voltage (or equivalently, a current related to the local potential of the touch point) measured when the field is in the x-direction is directly proportional to the distance along the x coordinate and is independent of the y coordinate .
  • a voltage measured when the field is in the y-direction is directly proportional to the distance along the y coordinate and is independent of the value of x.
  • resistive touch screens are often mounted on LCD or CRT displays, but perhaps most commonly on CRTs used as computer monitors to use as data input devices .
  • a typical monitor 10 will comprise a back case 11 into which is set the CRT.
  • a glass panel 12 with a uniform resistive coating 15 shown in Figure
  • FIG. 7 such as ITO (indium tin oxide) is placed over the face 14 CRT 13.
  • a polyester coversheet is tightly suspended over the top of the glass panel, preferably separated from it by small transparent insulating dots 16 as described in Hurst, U.S. Patent No. 3,911,215 which is incorporated herein by reference.
  • the coversheet 17 has a conductive coating on the inside and a hard durable coating 18 on the outer side.
  • a more detailed view of the layers of the touch screen is shown in Figure 7.
  • a bezel 19 is then placed over the coversheet.
  • a simple computer or controller 20 (shown in Figure 1)
  • the controller 20 may be mounted internal to the monitor 10 or in a slot within the associated main computer 21.
  • the substrate must have very uniform conductivity. Conductive materials are applied to a substrate (usually glass) in elaborate vacuum chambers. When a large substrate is being prepared, the chamber must be still larger, and even then, several sources must be used to cover the substrate uniformly. Some of these coated substrates do not meet specifications and have to be rejected.
  • a resistor divider network must be added to maintain straight equipotentials by eliminating edge effects associated with the field switching matrix. This has independent quality demands that further add to production costs and increase rejection rates.
  • Figure 1(a) shows a contour plot of theoretical equipotentials in the x-direction on a touch screen sensor according to the present invention with four electrodes and non- linear equipotential lines;
  • Figure 1(b) shows a contour plot of theoretical equipotentials in the y-direction on a touch screen sensor according to the present invention with four electrodes and non- linear equipotential lines
  • Figure 2 shows a three-dimensional plot of the potential distribution in the sensor with the configuration shown in Figures 1(a) and (b) ;
  • Figure 3 shows a plot of current flow lines in a sensor having four electrodes at the corners.
  • Figure 4 illustrates a contour plot of theoretical equipotentials in a sensor with non-uniform conductivity to simulate conditions that might result from vacuum evaporation and deposits of the conductive substance.
  • Figure 5 illustrates the special condition when the severe bulging of an equipotential causes a given equipotential to intersect a rectangular function box at four points;
  • Figure 5A illustrates the location of cells by the process of border mapping in the usual case.
  • Figure 6 illustrates a typical monitor with touch screen input device
  • Figure 7 illustrates a detailed view of the layers of a resistive touch screen
  • Figure 8A shows a representative touch screen monitor with an internal controller
  • Figure 8B shows a representative touch screen monitor with an external controller
  • Figure 9 illustrates a contour plot of theoretical equipotentials in a rectangular sensor with an electrode in the center of each side.
  • coordinate mapping can be obtained using any set of electrodes that generates monotonic equipotentials.
  • lines drawn at the same potential in the space between the opposing sets of electrodes are called equipotential lines.
  • Full two-dimensional mapping on that surface can be achieved using two sets on monotonic equipotentials in two different directions.
  • the potential lines need not be straight or uniform, but the key idea is that any point on that surface must have a unique value for the pair of potentials at that point.
  • equipotentials When the battery is switched to produce a field generally in the y-direction, equipotentials will run generally in the x-direction ( Figure lb) .
  • the word "generally” is used to stress that nowhere are we assuming uniform fields or equipotentials that run parallel to the x- or y-axes. There is distortion (i.e., the equipotentials are not evenly spaced nor are they parallel to the x-and y-axes) , since the electrodes are not at all designed to produce uniform fields, and because the electrical conductivity need not be uniform.
  • one set of equipotentials need not be orthogonal to a second set when the voltage source is switched from one direction to another.
  • V(X,y) is used to mean an equipotential when the voltage supply is connected in the x-direction ( Figure la) , and the lower-case y is shown to indicate that the equipotential also depends on y, due to the distortion.
  • V(Y,x) is used for the equipotentials when the voltage supply is connected in the y-direction ( Figure lb) .
  • V(Y,x) Near the edges of the sensor there is appreciable distortion, which is permitted here, but would be fatal to the performance of conventional touch screens that require uniform potential distributions.
  • Certain conditions are required for this uniqueness .
  • One condition is that the field (i.e., potential gradient or change in potential) be continuous over the entire area in each of the directions of application.
  • a related condition is that the field has no singularities over an appreciable area of the substrate.
  • These field conditions imply that the equipotentials must increase continuously in the direction of the applied potential.
  • These conditions impose some moderate conditions on the substrate prepared by vacuum coating.
  • the coating need not be uniform, but it must be continuous without isolated areas of no conductivity. Further, the coating must not be so heavy in the other areas so as to substantially "short" them. Both of these conditions are much more easily satisfied than is required for present touch screens.
  • a weak-field region presents a problem for precisely determining the sensed point.
  • the LUT would be a device or process whereby a potential pair, [V(X, y) , V(Y,x) ] , in suitable digital form would be used to locate in a two-dimensional table the corresponding real-space coordinate pair, (x,y) , also in digital form.
  • Resolutions of 128x128 to 1024x1024 would require 32Kbytes to 4Mbytes of LUT memory, respectively. This option is becoming increasingly attractive as computer chips drop in price.
  • Partial mapping In this case, an active area, such as a menu box, can be defined without complete, one-to-one mapping. For instance, straight-sided boxes (or other shapes) could be defined by their boundaries, stored as potential pairs . A simple logic could be employed to locate the potential pair, [V(X, y) , (Y,x) ] , within or outside the boxes. Typically a limited number of boxes are used in menu selection, so that the memory required would be greatly reduced from complete mapping. Perhaps a small LUT could be used that define areas where this boundary analysis is to be made .
  • a common end-use of the touch screen is the so- called menu application. Choices are made by the user simply by touching menu items typically enclosed by rectangular boundaries .
  • Figures 5A and 5B illustrate the definition of a rectangular box 40 by means of the measured coordinates based on equipotential pairs. This illustration makes it clear that any pair of potentials measured within the box so defined can be assigned uniquely to the box defined by Cartesian coordinates. So, the main design choice is the definition of the perimeter of the box in practical terms.
  • each coefficient is an eight-bit byte, only 192 bits, or 24 bytes, of storage space is required.
  • a box is selected by finding just two potentials on its perimeter, provided that the two potentials are complements; i.e., one value belongs to V(X,y) and one to V(Y,x) .
  • this search procedure is routine. For instance, the two potentials measured could first be stored in a register until the boundary analysis described above is completed.
  • interpolative mapping In practice, intermediate points between two tabulated points can be determined by interpolation. This option would store calibration points and fill in all intermediate points by interpolation. In a sense, interpolative mapping can be regarded as a processor-based method of achieving complete mapping that uses less memory than a complete LUT. In this connection, a mathematical solution of the boundary-value problem would be very powerful, especially if the solution is able to adjust to substrate irregularities.
  • LaPlace's equation a partial differential equation known as LaPlace's equation
  • the interpolation between points could be based on this solution. It is anticipated that the solution to the partial differential equation would automatically take into account non-uniformity in the substrate, and thus serve as an accurate interpolation independent of substrate characteristics.
  • the electrical potential distribution of a conducting sheet is determined by the configuration of electrons, the potentials applied to them, and the conductivity, ⁇ , of the sheet.
  • ⁇ ⁇ (x,y) is a function of position.
  • the conductivity is isotropic (but not necessarily uniform) for conventual conductive coatings applied to screens .
  • V(x,y) is the electric potential at (x,y)
  • the resulting current j (x,y) is given by:
  • the electrodes may be of any shape, including circular spots 31 as shown in the illustrations of Figure la and Figure lb. In that case, the sheet is 20 x 28 cm with 1-c ⁇ n radius circular electrodes centered on the four corners of sheet with uniform conductivity .
  • Figures 2 and 3 show alternative ways of displaying the configuration of Figure la: three-dimensional potential and current distributions, respectively. These are useful to further understand the distorted space of non-uniform potentials that occurs with the simplified electrode configuration .
  • mappings may be chosen, depending upon existing production capabilities and specific application. Complete mapping is often preferred due to its conceptual simplicity. For special applications, such as menu selection, partial mapping would be quite satisfactory. Interpolative mapping might be the most practical way to achieve mapping at the highest-possible resolution.
  • the present invention provides some interesting design considerations. Take the typical case where a vacuum evaporation chamber is of limited size with interior dimensions that are not much larger than the substrates themselves. In this case, the corner regions of the substrates tend to receive a thinner coating than the central portions. This certainly would be the case if there were only a single source of the coating material located at some distance away from the center of the substrate.
  • a convenient scheme for complete mapping is to use a decoding integrated circuit to convert sense readings.
  • Chips are already manufactured very economically that provide this function for 256 x 256 and higher screen resolutions.
  • Such a chip can be combined with the existing electronic sensing circuit to convert a pair of readings, one corresponding to V(X,y) and the other to V(Y,x), to their corresponding Cartesian space coordinates .
  • Specific examples for various screen resolutions follow. For a screen with a resolution of 256 x 256, the raw data in potential space will consist of two 8 -bit measurements. To convert these, a LUT memory component is needed which will accept two 8-bit addresses that point to two 8 -bit values that have been previously loaded during calibration.
  • Chips are available as programmable read-only memory (PROM) or erasable-PROM (EPROM) .
  • the Am27C1024 is a 1-megabit (65,536 x 16-bit) CMOS EPROM that meets the requirements for 256 x 256 resolution.
  • This component is readily available from its manufacturer, AMD, or from a distributor such as Hamilton Hallmark. Typical power consumption is only 125 milliwatts in active mode and only 100 microwatts in standby mode. Only 8 seconds are needed to program the component while look-ups can be performed in 55 nanoseconds.
  • the raw data in potential space will consist of two 9-bit measurements one corresponding to V(X,y) and the other to V(Y,x) .
  • a LUT component is needed which will accept two 9-bit addresses that point to two 9-bit values that have been experimentally determined during calibration.
  • the Am27C4096 is a 4-megabit (262,144 x 16-bit) CMOS EPROM that meets the requirements for 512 x 512 resolution.
  • This component is readily available from its manufacturer, AMD, or from a distributor such as Hamilton Hallmark. Typical power consumption is only 125 milliwatts in active mode and only 125 microwatts in standby mode. Only 32 seconds are needed to program the component while look-ups can be performed in 90 nanoseconds.
  • Both of the components cited above can be purchased in either a package with a ceramic window permitting erasure via ultraviolet light (and thus reprogramming) or in a sealed package for one-time programming.
  • the one-time programmable part has the advantage of being slightly cheaper but the reprogrammable part has the advantage of allowing recalibration after some period of customer use.
  • the contents of the custom component may consist of either full LUT memory just like the EPROMs or a reduced number of memory locations and some associated calculation logic. The exact balance of these resources is dictated by the resolution desired and the area required for logic versus that required for memory. Calibration
  • the screen-response calibration can be determined either empirically, theoretically, or by a combination of both.
  • a purely theoretical approach presupposes a model geometry and a particular screen-conductivity distribution such as detailed in the particular example used to describe LaPlace's equation and would ignore variances that occur in manufacture.
  • a purely empirical approach would involve pressing the screen in a pattern of points to generate all the values that transform potentials into useful coordinates. This latter approach would automatically account for variances but may be too slow or labor-intensive to be cost-effective.
  • the combination approach would determine the transformation data for a number of points and interpolate the rest based upon theory.
  • Calibration values could be determined on an individual basis for each screen or each screen-lot manufactured.
  • the component would be personalized to correspond to the coating of a particular screen and many non- uniformities, distortions and manuf cturing defects would be compensated, producing much higher screen yields at significantly reduced cost.
  • An example of screen calibration compatible with economical production involves manually or robotically touching a grid of points on each screen and interpolating using a computer.
  • the computer applies the data generated by touching the grid points to a theoretical analysis.
  • the Cartesian set of transformation values is generated by the computer and "burned" into the LUT stored in the PROM or EPROM.
  • the number of points is determined by the resolution desired and the amount and kind of manufacturing defects.
  • the program may also indicate defects in a screen and possibly highlight the positions of a few additional points that could immediately be touched. A refined calibration set can then be generated. As a result, quality control is automatic while rejects are reduced.
  • the present invention liberates the design of sensors for touch screen applications. Furthermore, this versatility comes with great simplicity and with no sacrifice of quality.
  • Several versions of the concept have been explored in which a space is defined by measurement of a potential pair on a surface with electric fields applied sequentially in two general directions . Acceptance of some distortion of this space, with respect to a perfect Cartesian space, is the key to simplicity and freedom of sensor design. This distortion poses no fundamental limitations, since the potential-pair space can be uniquely mapped onto a Cartesian space . Complete mapping would use an auxiliary computer of adequate storage for the number of desired pixels.
  • auxiliary computer In some "menu" applications, complete mapping with auxiliary equipment is not required. Several sub-options are available when the auxiliary computer is not used. (1) The measured space can be matched directly to the control space by accepting some distortion in the edges of the menu box. (2) If distortion of menu box edges is not acceptable, electronic blank-out can be used to give the appearance of straight edges. (3) Direct matching of the distorted equipotential space to a rectangular box can be made in our technique of boundary analysis. When boundary mapping is made along the perimeter of a function box, an auxiliary computer is not necessary, since little storage space is needed for the definition of boundaries.

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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)

Abstract

L'invention concerne un nouvel écran tactile réalisé sur la base d'une cartographie de coordonnées allant d'un espace équipotentiel (32), défini par un simple ensemble d'électrodes d'écran, à plusieurs coordonnées utiles, par ex. des coordonnées cartésiennes. L'idée principale réside dans le fait qu'une cartographie unique des cordonnées peut être obtenue au moyen de chaque paire détectrice de lectures électroniques.
EP97946486A 1996-10-29 1997-10-29 Ecran tactile realise sur la base d'une cartographie topographique Withdrawn EP1010156A4 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US2950296P 1996-10-29 1996-10-29
US2950P 1996-10-29
US5258197P 1997-07-15 1997-07-15
PCT/US1997/020001 WO1998019283A1 (fr) 1996-10-29 1997-10-29 Ecran tactile realise sur la base d'une cartographie topographique
2000-02-22

Publications (2)

Publication Number Publication Date
EP1010156A1 true EP1010156A1 (fr) 2000-06-21
EP1010156A4 EP1010156A4 (fr) 2002-02-27

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP97946486A Withdrawn EP1010156A4 (fr) 1996-10-29 1997-10-29 Ecran tactile realise sur la base d'une cartographie topographique

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EP (1) EP1010156A4 (fr)
WO (1) WO1998019283A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7180508B2 (en) 2002-09-17 2007-02-20 Tyco Electronics Corporation Dynamic corrections for a non-linear touchscreen

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69932662T2 (de) * 1998-03-12 2007-08-09 Tyco Electronics Corp. Berührungsempfindlicher Widerstandsbildschirm
US8049740B2 (en) * 2007-10-26 2011-11-01 Tyco Electronics Corporation Method and apparatus for laplace constrained touchscreen calibration

Citations (3)

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Publication number Priority date Publication date Assignee Title
US4650926A (en) * 1984-10-26 1987-03-17 Scriptel Corporation Electrographic system and method
US4752655A (en) * 1984-11-16 1988-06-21 Nippon Telegraph & Telephone Corporation Coordinate input device
JPH0519940A (ja) * 1991-07-11 1993-01-29 Matsushita Electric Ind Co Ltd タブレツト装置

Family Cites Families (3)

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Publication number Priority date Publication date Assignee Title
US4794634A (en) * 1985-12-24 1988-12-27 Kabushiki Kaisha Komatsu Seisakusho Position-sensitive photodetector and light transmissive tablet and light-emitting pen
US5157227A (en) * 1991-01-17 1992-10-20 Summagraphics Corporation Digitizer tablet with regional error correction
US5220136A (en) * 1991-11-26 1993-06-15 Elographics, Inc. Contact touchscreen with an improved insulated spacer arrangement

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4650926A (en) * 1984-10-26 1987-03-17 Scriptel Corporation Electrographic system and method
US4752655A (en) * 1984-11-16 1988-06-21 Nippon Telegraph & Telephone Corporation Coordinate input device
JPH0519940A (ja) * 1991-07-11 1993-01-29 Matsushita Electric Ind Co Ltd タブレツト装置

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 017, no. 296 (P-1551), 7 June 1993 (1993-06-07) & JP 05 019940 A (MATSUSHITA ELECTRIC IND CO LTD), 29 January 1993 (1993-01-29) *
See also references of WO9819283A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7180508B2 (en) 2002-09-17 2007-02-20 Tyco Electronics Corporation Dynamic corrections for a non-linear touchscreen

Also Published As

Publication number Publication date
EP1010156A4 (fr) 2002-02-27
WO1998019283A1 (fr) 1998-05-07

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