r19J
`
`United States Patent
`Jr.
`Pepper,
`
`[11]
`
`4,353,552
`[45]
`Oct. 12, 1982
`
`TOUCH PANEL SYSTEM AND METHOD
`[54]
`FOREIGN PATENT DOCUMENTS
`[75]
`
`
`
`Inventor: William Pepper, Jr., Bethesda, Md.
`
`
`
`1133757 11/1968 United Kingdom.
`
`
`
`Peptek, Incorporated, Bethesda, Md.
`Assignee:
`[73]
`Appl. No.: 116,502
`[21]
`Filed: Jan. 29, 1980
`[22]
`
`OTHER PUBLICATIONS
`
`"The Trazor TM -,-A New
`Gametronics Proceedings;
`
`Input Device"; Jan. 1977; pp. 115-120.
`
`
`Journal of Electron Spectroscopy and Related Phenomena;
`
`
`"A Photosensitive Detector for Electrons"; 1975; pp.
`Related U.S. Application Data
`
`151-156.
`
`
`Division of Ser. No. 14,450, Feb. 23, 1979, Pat. No.
`[62]
`Y. Hum
`4,293,734.
`Primary Examiner-Vance
`Zegeer
`
`
`Attorney, Agent, or Firm-Jim
`[51]
`
`
`
`Int. Cl.3 ................................................ A63F 9/22
`[57]
`ABSTRACT
`[52]
`
`
`U.S. Cl ................................... 273/85 G; 273/313;
`
`273/DIG. 28
`
`
`A general method is disclosed for accurately determin­
`
`
`Field of Search ............ 273/85 G, DIG. 28, 1 E,
`[58]
`
`
`
`ing the location or position of a source or sink of electric
`
`
`273/1 GC; 33/1 M; 146/334; 250/207, 211 R;
`
`
`
`
`current on the surface of a resistance element or impe­
`
`
`324/71; 340/365 R, 365 S, 365 A; 178/18, 19;
`
`
`
`
`dance layer. Touch panels are described that detect the
`364/410
`
`
`
`presence of a user's finger on such surface, and produce
`
`
`
`
`output signals corresponding to the position of the fin­
`References Cited
`
`[56]
`
`
`ger in one or more axes. A preferred embodiment dis­
`U.S. PATENT DOCUMENTS
`
`
`
`
`closes a touch panel that includes a signal generator and
`
`
`
`determines the position of the user's finger from current
`
`3,676,676 7/1972 Somer .
`
`
`3,691,382 9/1972 Somer .
`
`
`
`flowing through the user's body to ground. Another
`
`
`
`3,699,439 10/1972 Turner .................................. 178/18
`
`
`
`touch panel embodiment determines the position of the
`
`
`
`4,013,835 3/1977 Eachus et al. ........................ 178/18
`
`
`
`
`user's finger from currents caused by ambient electrical
`
`
`
`4,018,989 4/1977 Snyder et al .......................... 178/19
`
`
`
`noise. A pressure-sensitive touch panel, a transparent
`
`
`4,071,691 1/1978 Pepper .................................. 178/19
`
`touch panel for use with a video display, a touch-panel­
`
`
`
`
`4,121,049 10/1978 Roeber .................................. 178/18
`
`
`controlled audio mixer, and a video game incorporating
`
`
`
`
`
`4,129,747 12/1978 _ Pepper .................................. 178/19
`
`touch panels are also disclosed.
`
`
`4,138,592 2/1979 Capehart et al ...................... 178/19
`
`
`
`4,178,481 12/1979 Kley ...................................... 178/18
`
`
`
`4,198,539 4/1980 Pepper .................................. 178/18
`
`
`11 Claims, 14 Drawing Figures
`
`II
`
`13
`
`16
`
`15
`
`77
`
`75
`
`71
`
`
`
`PLAYER A
`
`PLAYER B
`
`Samsung EX1019 Page 1
`
`

`

`U.S. Patent Oct. 12, 1982
`
`Sheet 1 of 8 4,353,552
`
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`Samsung EX1019 Page 2
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`Samsung EX1019 Page 3
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`

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`U.S. Patent Oct. 12, 1982
`
`Sheet 3 of 8 4,353,552
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`Samsung EX1019 Page 4
`
`

`

`U.S. Patent Oct. 12, 1982
`
`Sheet 4 of 8 4,353,552
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`
`Samsung EX1019 Page 5
`
`

`

`U.S. Patent Oct. 12, 1982
`
`Sheet 5 of 8
`
`4,353,552
`
`42
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`Samsung EX1019 Page 6
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`Samsung EX1019 Page 7
`
`

`

`U.S. Patent Oct. 12, 1982
`
`Sheet 7 of 8 4,353,552
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`Samsung EX1019 Page 8
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`
`Samsung EX1019 Page 9
`
`

`

`4,353,552
`
`1
`
`TOUCH PANEL SYSTEM AND METHOD
`
`In one-axis form, a touch-panel embodiment of the
`
`
`
`
`
`
`
`invention includes an extended resistance or impedance
`
`
`
`element, such as a lenth of nichrome wire, having a
`
`
`
`This is a division of application Ser. No. 014,450, filed
`
`
`
`terminal at each end or boundary and so disposed that it
`
`
`
`
`5 can be touched at different selected points along its
`Feb. 23, 1979 now U.S. Pat. No. 4,293,234.
`
`
`
`
`length; an oscillator that varies the potential of both
`BACKGROUND OF THE INVENTION
`
`
`terminals simultaneously with respect to ground; cur­
`
`
`
`
`rent-sensing circuitry to measure the current through
`
`
`
`
`This invention relates to devices for providing infor­
`
`
`
`
`each terminal; and normalizing circuitry to produce an
`mation, in the form of electrical signals, about the posi­
`
`
`
`
`
`tion of a selected touch point serving.as a source or sink 10
`
`
`
`output signal proportional to the ratio of one of the
`
`
`
`currents to the sum of both currents. A level detector
`
`
`
`
`of electric current relative to a current-carrying resis�
`
`
`
`monitors the sum of both currents and provides a Pres­
`
`
`
`
`tance or impedance element. In particular, it relates to
`
`ence signal when the sum exceeds a set or predeter­
`
`
`
`
`devices for converting selected touch points or posi­
`mined level.
`
`
`
`tions on a surface (reflecting hand motions) into electri­
`
`
`cal signals to provide an interface between man and 15
`In operation, when the user touches the resistance
`
`
`
`
`
`
`
`element, his body presents a relatively low impedance
`machine.
`
`
`to ground for the oscillator signal, arid a small electric
`
`
`As used herein, the term "a selected touch point"
`
`
`
`
`current flows through the user's body. The fraction of
`
`
`
`means a point on a surface selectively touched by a
`
`
`
`this current flowing through a boundary is inversely
`
`portion of a human body, particularly a finger or toe, or
`
`a point on a surface touched by an instrument held in 20
`
`
`
`proportional to the distance from the boundary of the
`
`
`
`
`
`point touched, and directly proportional to the distance
`
`the hand or other portion of a human body and con­
`
`
`
`from the other boundary. An output voltage is pro­
`
`
`trolled by the human, or a point on a surface contacted
`
`
`duced proportional to this fraction, and thus, to the
`
`
`
`by a mechanical contrivance which is guided by a hu­
`
`
`
`distance from the other terminal. The Presence output
`
`
`
`man. In the context of this invention "selected" means
`the direction by the human intellect of the point on the 25
`
`
`
`
`
`
`provides a binary signal to the utilization device indicat­
`
`
`
`
`. ing that the resistance element is being touched.
`
`surface that is touched.
`
`
`In two-axis form, a rectangular surface of uniform
`
`
`
`In the context of this invention the term "point" en­
`
`
`resistivity is used that has four terminals and a resistive
`
`
`
`compasses the area of contact between a human finger
`
`
`
`coupling network. The characteristics of this network
`
`
`and a surface, or the area of contact of an implement,
`30
`are such that the ratio of the sum of the currents
`
`
`
`such as the pointed end of a stylus, with a surface. Thus,
`
`
`through two the terminals to the sum of the currents
`
`it is intended that the term "selected touch point" ex­
`
`
`
`
`
`through all four terminals is proportional to the distance
`
`
`clude non-physically contacting transfers of electrical
`
`
`from one edge. In a manner similar to that described for
`
`
`
`energy between the touch panel surface and a sensing
`
`
`
`
`the one-axis embodiment, output voltages are simulta­
`
`
`
`device or transducer. As used herein the term "current
`35
`
`
`
`
`neously derived proportional to the X-axis and Y-axis
`
`
`
`collecting" includes electrical current passing to or
`
`
`
`coordinates of the point touched. A two-axis touch
`
`from the impedance surface.
`
`
`panel can also be constructed using a triangular surface
`
`
`This invention is an improvement over the touch
`with three terminals.
`
`
`
`panels described in my U.S. Pat. Nos. 4,071,691 and
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`
`
`
`4,129,747, and my pending patent application Ser. No. 40
`
`
`867,256, now U.S. Pat. No. 4,198,539, all incorporated
`
`
`The above and other objectives, advantages and fea­
`
`herein by reference. As discussed in my aforementioned
`
`
`
`
`tures of the invention will be fully understood from the
`
`
`
`patent application Ser. No. 867,256, the phase of the
`
`
`
`
`following detailed description and accompanying draw­
`
`
`
`field produced in the resistive surface was not a linear
`ings wherein:
`
`
`
`
`function of position on the surface, introducing an error 45
`FIG. 1 is a schematic diagram illustrating the basic
`
`
`
`
`
`
`
`
`in the output function unless special techniques were
`
`
`position-locating principle incorporated in the inven­
`
`used to compensate for the error.
`tion.
`
`
`
`
`The present invention substantially overcomes the
`FIG. 2 is a block diagram of a one-axis toucl_J. panel
`
`
`
`
`
`limitations of that earlier system. It does not require a
`
`incorporating the invention.
`
`
`
`
`pickup surface and is therefore easier to package and 50
`
`FIG. 3 shows a four-terminal pattern of conductive
`
`
`
`manufacture than the earlier system. It also has im­
`
`
`segments for use in a two-axis touch panel and corre­
`
`
`proved linearity. It will therefore be seen that it is an
`
`
`
`sponds to FIG. 7 as disclosed and claimed in my appli­
`
`
`improvement in the art of human-machine interfacing.
`
`cation Ser. No. 867,256.
`
`
`
`An article "A Position-Sensitive Detector for Elec­
`FIG. 4 is a block diagram of a two-axis touch panel
`
`
`
`
`
`trons," by C. D. Moak, S. Datz, F. Garcia Santibanez, 55
`
`incorporating the invention.
`
`
`and T. A. Carlson, in the Journal of Electron Spectros­
`FIGS. Sa and Sb taken together constitute a sche­
`
`
`No. 6, 1975, pp. 151-156,
`
`
`matic diagram of the circuitry shown in block diagram
`
`copy and Related Phenomena,
`
`
`
`
`discloses the principle of locating, on one axis, the point
`form in FIG. 4.
`
`
`
`on a linear resistive anode at which electrons emerge
`FIG. 6 is a cross-sectional diagram showing the con­
`
`
`
`from a chevron multiplier (which was impinged upon 60
`
`
`
`
`
`
`struction of a touch panel incorporating pressure-sens­
`
`
`by an electron beam) in a high-resolution electron spec­
`
`ing means.
`
`trometer. In such system, a high D. C. voltage is re­
`
`
`FIG. 7 is a block diagram of circuitry for sensing
`
`
`
`quired between the electr�>n multiplier and the resistive
`
`
`
`pressure on the touch panel shown in FIG. 6.
`
`strip collector.
`
`
`
`FIG. 8 is a three-terminal pattern of conductive seg-
`
`65 ments for use in a two-axis touch panel or in a three­
`BRIEF SUMMARY OF THE INVENTION
`
`
`channel touch-controlled audio mixer.
`The object of the present invention is to provide
`
`
`
`
`FIG. 9 is a block diagram of a three-channel audio
`
`
`improvements in touch panel systems and methods.
`
`
`mixer using the structure of FIG. 8.
`
`Samsung EX1019 Page 10
`
`

`

`4,353,552
`
`4
`3
`FIG. 10 is a block diagram of a one-axis touch panel
`
`
`
`11' and any selected touch point 18'. When the user's
`
`
`
`in which the current source is external to the touch
`
`
`
`
`finger F touches the extended resistance element 10' at
`panel.
`
`
`point 18', a small current flows through his body impe-
`
`FIG. 11 shows a combination of two one-dimensional
`
`
`
`dance, which is schematically represented by a lumped
`
`
`touch panels similar to those shown in FIG. 2 and FIG. s
`
`
`
`
`impedance 17', to ground. Operational amplifiers 20 and
`10.
`
`
`21 maintain the ends 11' and 14', respectively, of the
`
`
`
`FIG. 12 is a sketch showing a transparent touch panel
`
`extended resistance element 10' at the same instanta­
`
`combined with a display device.
`
`
`
`neous potential as the a-c output of signal generator 24
`
`FIG. 13 is a sketch of a video game in which a repre­
`by supplying
`
`
`
`
`currents through feedback resistors 22 and
`sentation of the playing area appears on both the video
`
`
`
`10
`
`
`
`
`23, respectively. The current through feedback resistor
`
`display and the two touch panels.
`
`
`23, which is equal in magnitude and opposite in polarity
`
`
`
`
`to the current through r2, produces a voltage which is
`DETAILED DESCRIPTION
`
`
`added to the output of signal generator 24 to give an
`
`
`
`FIG. 1 is a schematic diagram illustrating the basic
`
`
`instantaneous potential at the output of operational
`
`
`
`position-transducing principle employed by my inven-1s
`
`amplifier 21:
`
`
`tion. Extended impedance or resistance element 10 has
`
`
`
`a boundary terminal 11 connected to voltage source 12
`
`
`
`
`
`
`through a.current-measuring device, ammeter 13, and a
`
`
`
`
`
`boundary terminal 14 connected to voltage source 15
`where v24 is the voltage
`output of signal generator 24, ii
`
`
`
`
`
`
`through a current-measuring device, ammeter 16. The 20
`
`
`
`is the current through r2, and R23 is the resistance of the
`
`
`
`other terminals of the voltage sources have a common
`
`
`
`
`feedback resistor 23. Subtractor 27 instantaneously re­
`
`. connection C, and impedance 17 is connected between
`
`
`
`
`
`
`
`moves the output voltage of signal generator 24 from
`
`
`common connection C and an arbitrary point 18 on the
`
`
`
`v21, and rectifier 28 converts the a-c signal into a d-c
`
`
`
`
`extended resistance element. Let the total resistance of
`
`
`
`level proportional to the average magnitude of current
`
`
`resistance element 10 be R and let the portion between
`25
`ii:
`
`point 11 and point 18 be r1, and the portion between
`point 18 and point 14 be r2, as indicated on the diagram.
`
`
`
`
`Using Kirchofrs voltage law, equatjons can be written
`
`for the two meshes of this circuit:
`i1r1+(i1 +ii)Z+v1=0
`
`Summing (adding) circuit 29 adds level v2 to level v1,
`
`
`
`30
`
`
`
`
`which is similarly derived from the current through r1
`(I)
`
`
`
`by means of similarly connected amplifier 20, subtractor
`
`
`
`25 and rectifier 26. Divider 30 divides v2 by the sum of
`(2)
`
`
`(v1 +v2) to give an output directly proportional to the
`Subtracting Equation 2 from Equation 1 and substitut-
`
`
`
`
`
`
`position of point 18' on touch surface resistance 10':
`35
`
`ing R-r1=r2, it will be found that:
`
`(5)
`
`(6)
`
`(3)
`
`(7)
`
`r1 = i2R -Vt+ v2
`Vout =
`v1 +v2
`i1 + ii
`40 FIG. 3 i� a _modification
`of FIG 7 of my pending
`This can be rearranged
`the dimensionles
`to express
`s
`
`apphcat1on Ser. No. 867,256. It shows a pattern
`patent
`ratio r1/R as the sum of two terms:
`
`
`
`
`of conductive segments 101 that is inlaid or overlaid (as
`
`
`by silk screen printing) on a uniform sheet of resistive
`(4)
`r1 ii v2 -v1
`
`
`what is termed a linearized45 material 100 to produce
`7f = it + ii + (i1 + ii)R
`
`
`
`resistive surface in my application Ser. No. 867,256.
`
`
`
`
`When appropriate voltages are applied to comer termi­
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`
`
`The following three·conclusions relevant to my inven­
`
`
`nations A, B, C, and D, a uniform electric field with
`
`
`tion can be drawn from Equation 4. First, the expression
`
`
`
`
`controllable amplitude and direction is created on the
`
`
`
`for ratio r1/R is independent of impedance Z (hence Z
`surface.
`
`
`
`can vary) except that Z must be finite. Second, if the 50
`I have found that the structure of FIG. 3 has the
`
`
`
`
`relationship between the position of point 18 and ratio
`
`
`
`following useful properties in addition to the useful
`
`ri/R is known, then the position of point 18 can be
`
`
`
`
`properties disclosed in patent application Ser. No.
`
`
`
`determined from measurements of currents ii and i2 and
`
`
`867,256: If the four terminations A, B, C, and Dare held
`
`
`
`voltages v1 and v2 (and knowledge of resistance R).
`
`
`at the same instantaneous potential, and a spot on the
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`
`Third, if v1 = v2, and the relationship between the posi-55
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`
`
`surface is held at a different instantaneous potential,
`
`tion of point 18 and ratio ri/R is known, the position of
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`
`currents will flow through the four terminations. If
`
`
`point 18 can be determined solely from measurements
`
`
`these currents are measured with the spot (correspond­
`
`
`of currents i1 and i2. There are other conclusions that
`
`
`
`ing to selected touch point 18') at various locations, it
`
`can be drawn but the foregoing amply demonstrates
`
`can be shown that they are related to the X and Y coor­
`
`
`that the position of any point of current flow to or from 60
`
`dinates of the spot by the equations:
`
`
`
`
`element 10 can be accurately determined without re­
`
`
`gard for the impedance Z or the actual resistance of
`element 10.
`of a one-axis FIG. 2 is a simplified block diagram
`
`
`
`
`touch panel using the principle illustrated by FIG. 1. 65
`
`
`
`Extended resistance element 10' is in the form of a linear
`
`
`touch panel surface, so that resistance ri is directly
`
`
`
`proportional to the distance between end or boundary
`
`(10)
`
`Samsung EX1019 Page 11
`
`

`

`4,353,552
`
`6
`5
`tional amplifier Al through isolating resistor R2. The
`
`
`
`
`
`wherein kt is an offset, k2 is a scale factor, and iA, iBetc.
`
`
`
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`
`
`noninverting input is connected to Es, the output of a
`
`
`
`
`are the currents through the respective terminations. In
`
`
`
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`Wien-bridge oscillator (operational amplifier A9)
`
`
`FIG. 3, the edges 102 of resistive surface 100 are illus­
`
`
`
`
`through a voltage divider, consisting of R35 and R37
`
`
`
`
`
`trated as extended solely for purposes of clarity in the
`
`
`
`(all of which corresponds to oscillator 120 shown. in the
`
`
`
`
`drawing. In actual practice the resistive layer may be 5
`
`
`block diagram of FIG. 4), which provides a 20 kHz sine
`
`
`
`
`trimmed or limited to the outermost conductive seg­
`
`wave with a peak-to-peak amplitude of about 1.3 volts.
`ments 101.
`
`
`
`The output of operational amplifier Al goes through a
`
`
`
`Similar results have been obtained with a rectangular
`
`
`filter 121 comprising capacitors Cl and C2 and resistors
`
`
`
`
`
`linearized resistive surface possessing a non-square as­
`
`
`R3 and R14. The inverting input of operational ampli­
`
`
`
`pect ratio and fabricated with the construction shown in 10
`
`fier AS is used as a summing node (and hence corre­
`
`
`
`FIG. 3 ofmy patent application Ser. No. 867,256. In this
`
`
`sponds to adder 127 of FIG. 4). A phase shifter, opera­
`
`case constants kt and k2 differ for the X and Y equations.
`
`
`
`tional amplifier AlO (e.g. 126), inverts the oscillator
`
`
`FIG. 4 is a block diagram of the preferred embodi­
`
`output Es to provide an out-of-phase signal Es which is
`
`
`
`
`ment of the invention: a two-dimensional touch panel
`
`
`
`coupled through capacitor C9 and is summed through
`
`
`using the structure of FIG. 3. This embodiment is an 15
`
`
`resistor R13 to cancel Es at the input of AS (adder 127).
`
`
`
`extension to two dimensions of the principle embodied
`
`The amplitude and phase of Es are adjustable, so that the
`
`
`
`in in FIG. 2, and its mathematical basis is as described
`
`the discussion of FIG. 3.
`
`
`
`effect of the capacitance between the linearized resis­
`
`tive surface 110 and ground can also be cancelled.
`
`
`
`When the linearized resistive surface 110 is touched
`
`
`
`The circuit of operational amplifier AS is a precision
`
`
`
`by the user, small currents flow through the four termi-20
`
`
`
`
`rectifier providing a d-c output for constant finger posi­
`
`
`
`nations A, B, C, and D. Voltages proportional to these
`
`
`
`
`
`tion, e.g., selected touch point. Identical circuitry is
`
`
`
`
`currents are developed across the feedback resistors
`111, 112, 113, and 114 of the four input amplifiers 116,
`
`
`provided for the other three terminations B, C and D of
`
`
`the linearized resistive surface, using operational ampli­
`
`
`117, 118 and 119, respectively, as the amplifiers follow
`fiers A2, A3, A4, A6, A 7 and AS.
`
`
`
`
`the output of oscillator 120. The amplifier outputs are 25
`Operational amplifier A11, constituting the Y axis
`
`
`
`
`
`
`applied to four high-pass filters 121, 122, 123 and 124
`
`
`summer 136 of FIG. 4, sums the rectified signals corre­
`
`
`
`respectively. These filters are not essential to system
`
`
`
`sponding to terminations A and B; operational amplifier
`
`
`operation, but were added to eliminate the 60-Hz signals
`
`
`A12, constituting the X-axis summer 137 of FIG. 4,
`
`
`which may be picked up by the user's body from power
`
`
`
`sums the signals corresponding to terminations B and C;
`
`
`
`
`
`wiring. Filters 121-124 attenuate 60-Hz signals while 30
`
`
`
`and operational amplifier A13 constituting the all-chan­
`
`
`
`passing the oscillator 120 frequency, which is typically
`
`nel summer of FIG. 4, sums all four signals A, B, C and
`
`
`20 kHz. In a later-disclosed embodiment, the 60 Hz (or
`
`
`D. Resistors R54, RSS and R56 equalize the loads on the
`
`
`
`
`any radiant ambient environmental energy field) may be
`
`four precision rectifiers AS, A6, A 7 and AS.
`
`
`
`
`used as a source of position signal energy for the touch
`
`Two AD533J analog multipliers 150 and 151 are
`panel surface.
`35
`
`
`
`
`connected to divide (e.g., perform the dividing function
`
`
`
`
`Subtraction of the oscillator signal component from
`
`
`of dividers 139 and 140 of FIG. 4) the outputs of opera­
`
`
`
`the filter outputs is accomplished by first shifting the
`
`
`
`tional amplifiers All and A12 by the output of opera­
`
`phase of the oscillator signal approximately 180° in
`
`
`
`
`
`tional amplifier A13 (all-channel summer 138 of FIG.
`
`phase shifter 126 and then adding the phase-shifted
`
`
`
`signal to the filter outputs in adder circuits 127, 128, 129 40
`
`
`4). Operational amplifiers A15 and A16 (corresponding
`
`
`to output amplifiers 141 and 142 of FIG. 4) are output
`
`
`
`and 130, respectively. The resulting signals are rectified
`
`
`
`
`scalers allowing variation of output gains and offsets
`
`
`in rectifiers 131, 132, 133 and 134, respectively, to pro­
`
`over a wide range to match the characteristics of vari­
`
`
`
`vide d-c levels proportional to the amplitudes of the a-c
`
`
`
`
`ous utilization devices. Operational amplifier A14 (level
`
`
`
`signals. The levels corresponding to the top two termi­
`
`
`detector 143 of FIG. 4) is a level detector with hystere­
`
`
`
`
`nations A and B of the linearized resistive surface 110 45
`
`
`sis and an adjustable trip point. When the linearized
`
`
`are summed by the Y-axis summer 136, the levels corre­
`
`
`
`
`resistive surface 110 is touched at any selected touch
`
`
`
`sponding to the right-hand two terminations B and C
`
`
`
`
`point, a light-emitting diode provides a visual indication
`
`are summed by the X-axis summer 137, and all four
`
`
`
`
`thereof and the Presence output switches from O to + 5
`
`levels A, B, C and D are summed by the all-channel
`
`
`volts. Diodes D12 and D13 and resistors R78 and R82
`
`
`summer 138 to provide a denominator input for the two 50
`
`
`constitute a pull-down circuit to cause the X and Y
`
`
`dividers 139 and 140. These dividers 139 and 140 then
`
`
`
`outputs to go off-scale when the linearized resistive
`
`
`
`
`operate on the Y-axis and X-axis sums to perform the
`
`
`
`
`
`surface is not touched; removing a jumper disables this
`
`
`
`
`divisions of equation 10 above; and output amplifiers
`
`
`141 and 142 with adjustable offset 143 and 144 and gain feature.
`It will be seen that many alternative techniques can
`
`
`
`
`
`
`
`
`provide the desired X-axis and Y-axis outputs described 55
`
`
`
`be used to accomplish the same normalizing function as
`
`
`
`by Equation 10. A level detector 145 monitors the all­
`
`
`the dividers in FIGS. 4 and 5. For instance, digital
`
`
`
`
`channel summer 138 output and switches state when the
`
`
`
`
`outputs can be easily obtained by applying the X and Y
`
`
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`
`
`user's finger touches the linearized resistive surface 110.
`
`
`axis sums to voltage-to-frequency converters, and
`
`
`It is not necessary for the user's finger to make ohmic
`
`
`
`
`counting the output pulses for a period of time propor­
`contact
`
`
`
`with the linearized resistive surface; a thin insu-60
`
`
`
`
`tional to the output of the all-channel summer. Analog
`
`
`
`lating layer may be deposited over the resistance mate­
`
`
`
`normalization can be accomplished by controlling the
`
`
`
`
`rial for protection, and capacitive coupling through the
`
`
`gains of the input amplifiers with a feedback loop so as
`
`
`
`
`
`insulating layer will still provide adequate current for
`
`
`
`to maintain the output of the all-channel summer at a
`
`system operation.
`
`
`
`
`
`constant value. Another normalization technique is
`
`
`FIGS. Sa and Sb taken together constitute a sche-65
`
`illustrated in FIG. 9.
`
`
`matic diagram of the embodiment of the invention
`FIG. 6 is a cross-sectional diagram showing a method
`
`
`
`
`
`shown in FIG. 4. Termination A of the linearized resis­
`
`
`
`of combining pressure-sensing transducers with the
`
`
`
`tive surface is connected to the inverting input of opera-
`
`Samsung EX1019 Page 12
`
`

`

`4,353,552
`
`7
`8
`In this implementation of my invention, the ratios
`
`
`
`
`two-axis touch panel of FIG. 4. The touch panel's lin­
`
`
`
`required by Equation 11 are obtained by maintaining
`
`
`
`
`earized resistive surface 40 is deposited on, or bonded
`
`
`the sum of the three d-c levels at a constant amplitude
`
`to, a rigid supporting plate 41, each corner of which
`
`with a feedback loop. As shown in FIG. 9, a differential
`
`rests on one of four piezoelectric elements. Two of
`
`
`
`
`5 amplifier 223 compares the sum of the three levels with ,
`
`
`
`these, labeled 42 and 43, appear in FIG. 6.
`
`
`
`
`a reference voltage. The output of differential amplifier
`
`
`FIG. 7 is• a block diagram of the circuitry for sum­
`
`
`
`223 is used as an automatic gain control voltage to con­
`ming the voltages developed by the four piezoelectric
`
`
`
`
`
`trol the amplitude of the output of oscillator 210.
`
`elements 42, 43, 44 and 45 of FIG. 6 to produce an
`
`
`Each of the three d-c levels also goes to a digital
`output signal. One terminal of each of the four piezo­
`
`
`
`
`electric elements 42', 43', ·44 and 45 is connected in 10
`
`
`track-and-hold circuit 224, 226 and 227. These circuits,
`
`
`
`
`
`the details of which are described in the literature (See
`
`
`
`common, with the same polarity being observed for all
`
`
`the article by Eugene L. Zuch, entitled "Designing
`
`
`
`four elements. The other terminals are connected to
`
`
`With A Sample-Hold Won't Be A Problem If You
`
`
`
`four inputs of voltage-summing circuit 46. The voltage
`Use The Right Circuit",
`Vol. 26 No.
`
`
`
`outputs of the four piezoelectric elements are summed
`Electronic Designs,
`
`
`23 Nov. 8, 1978 page 84) of analog-digital interfaces, use
`
`
`by voltage-summing circuit 46 to provide a vertical axis 15
`
`
`
`
`
`
`a combination of digital and analog circuitry to follow
`
`
`
`
`output proportional to the net downward pressure ex­
`
`
`an analog input in the track mode and provide a corre­
`
`erted on the linearized resisiive surface by the user's
`
`
`
`
`
`sponding output in either analog or digital form. When
`fmger.
`
`
`these circuits switch from track to hold mode, a stored
`
`FIG. 8 shows a triangular linearized resistive surface
`
`
`
`
`digital number maintains the output at its last value. The
`
`
`
`200 using the edge termination system disclosed in my 20
`
`
`
`
`digital outputs of the track-and hole circuits are con-
`
`
`
`application Ser. No. 867,256. The geometry of the con­
`
`
`nected to logarithmic attenuators 228, 229 and 230.
`
`
`
`ductive segments 201 between each two corners is the
`
`
`
`These are nonlinear digital-to-analog converters whose
`
`
`
`same as the geometry of the conductive segments 101
`
`
`
`
`details are described in the literature (See the article by
`
`
`between adjacent corners in FIG. 3. A uniform electric
`
`
`field can also be established in this triangular surface in 25
`
`
`Walter Jung and Will Retmamch entitled "Get Wide
`
`
`
`
`Range Digitally Controlled Audio Attenuation With A
`
`
`a manner analogous to that described for the rectangu-
`Companding
`Vol. 26, No. 23
`
`DIA", Electronic Design
`
`
`
`
`lar surfaces as described in patent application Ser. No.
`
`
`Nov. 8, 1978, page 92). Adder 232. combines the out­
`
`
`
`867,256. In fact, it is possible to provide a uniform field,
`
`
`puts of the attenuators to produce the mixer output.
`
`
`
`as disclosed in my above-identified patent application,
`
`
`Switching of the operating mode of the track-and­
`30
`
`
`in conjunction with the location-or position-detecting
`
`
`hold circuits 224, 226 and 227 is controlled by a level
`
`
`apparatus and method of the present invention.
`
`
`
`detector 231 analogous in function to the level detector
`
`I have found that if all three terminals A', B', C' are
`
`
`of FIG. 4. When the user touches the linearized resistive
`
`held at the same potential and a spot or selected touch
`
`
`surface 200, the presence of his fmger is sensed by the
`
`
`point on the linearized resistive surface 200 is held at a
`
`
`
`level detector and the track-and-hold circuits 224, 226
`
`different potential, the currents flowing through the 35
`
`
`
`
`and 227 are switched to the track mode of operator.
`
`terminations at corners A', B' and C'. follow the rela­
`
`
`When he removes his fmger, the track-and-hold circuits
`tionship:
`
`224, 226 and 227 switch to the hold mode and maintain
`
`
`
`the last attenuator settings until the user touches the
`(11) 40
`
`
`touch panel again .. It will be appreciated that besides use
`
`
`
`as an audio mixer this technique can be applied to vari-
`
`
`ous other arts where it is desired that a plurality of
`wherein dA is the perpendicular distance from the side
`
`
`
`
`
`
`
`signal levels be provided at a single touch or input by
`
`
`
`opposite corner A' to the current source; iA, iBand icare
`the user.
`
`
`
`
`the currents through the corresponding terminations; 45
`FIG. 10 is a block diagram of another embodiment of
`
`
`
`and kt and k2 are offset and scale constants.
`
`
`the invention (shown in one-dimensional form) in which
`It will be seen that, given any two of the three dis­
`
`
`
`
`the terminations of the linearized resistive surface are
`
`
`
`tances dA, dB and de, the two-dimensional location of
`
`
`maintained at ground potential and the body of the user
`
`
`the selected touch point is determined. FIG. 9 is a block
`
`
`
`serves as an antenna and picks up ambient electrical
`
`
`diagram of an audio mixer using the triangular linear-
`
`
`
`noise which causes current to flow through selected
`50
`
`
`· ized resistive surface 200 of FIG. 8. When the linearized
`
`touch point 18" to the terminations 11" and 14".
`
`
`resistive surface 200 is touched by the user at any se­
`
`
`
`This technique has the advantage that it imposes no
`
`
`
`lected touch point 202, currents flow through the termi­
`
`
`voltage on the body of the user. Although the voltages
`
`
`nations at corners A', B' and C'. Voltages proportional
`
`
`and currents imposed on the user by the previously
`
`
`
`to these currents are developed across the feedback
`
`
`
`discussed embodiments are far below levels that can be
`55
`
`resistors 203, 204 and 206 of the three input amplifiers
`
`
`felt, and even farther below levels that can do bodily
`
`
`207, 208 and 209, respectively as the amplifiers follow
`
`
`harm, some corporations prefer that products they use
`
`
`
`
`the output of oscillator 210. The amplifier outputs go to
`
`
`
`
`impose no voltages or currents whatsoever on the user.
`
`
`
`high-pass filters 211, 212 and 213, and the outputs of
`
`
`
`Touch panels made using this technique should also be
`
`
`
`these filters are supplied to adders 214, 216 and 217 60
`
`
`
`
`less expensive, as fewer circuit elements are required. In
`
`
`
`which receive the Es signal from inverter 218 to remove
`
`
`the touch panel of FIG. 10, stray voltages on the user