(12)
`
`United States Patent
`Resman
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,459,424 B1
`Oct. 1, 2002
`
`US006459424B1
`
`(54) TOUCH-SENSITIVE INPUT SCREEN
`HAVING REGIONAL SENSITIVITY AND
`RESOLUTION PROPERTIES
`
`(75) Inventor: Mark F. Resman, Boise, ID (US)
`
`1/1999 Gerpheide ................ .. 345/174
`5,861,875 A
`5920327 A * 7/1999 Seidenstickef, JI
`5,943,052 A * 8/1999 Allen et 211.
`6,184,864 B1 * 2/2001 Chao
`* Cited by examiner
`
`(73) Assignee: Hewlett-Packard Company, Palo Alto,
`CA (Us)
`
`P '' imary Examiner—chanh Nguyen
`(57)
`ABSTRACT
`
`( * ) NOIiCeI
`
`Subject I0 any disclaimer, the term Of this
`patent iS eXIended or adjusted under 35
`U.S.C. 154(1)) by 0 days.
`
`(21) Appl, No; 09/371,159
`_
`Aug‘ 10’ 1999
`(22) Flled:
`(51) Int. Cl.7 ................................................ .. G09G 5/00
`(52) US. Cl. ..................................................... .. 345/173
`(58) Field of Search
`345/173 174
`’
`f
`755’; 338129093’
`’
`'
`’
`'
`
`'
`
`"""""""""""""""" "
`113525’
`'
`’
`'
`’
`References Cited
`
`(56)
`
`US. PATENT DOCUMENTS
`
`4,013,835 A
`3/1977 Eachus et a1. .............. .. 178/18
`4,698,461 A 10/1987 Meadows et a1.
`178/19
`5,122,787 A
`6/1992 Fujita et aL _______ __
`340/712
`5,194,862 A
`3/1993 Edwards .................... .. 341/20
`5,543,589 A * 8/1996 Buchana et a1.
`5,777,596 A
`7/1998 Herbert .................... .. 345/104
`5,847,690 A 12/1998 Boie et a1. ................ .. 345/104
`
`F
`
`A touch screen panel having varied region-speci?c combi
`nations of resolution and touch sensitivity may also incor
`porate display functionality. For a ?rst embodiment of the
`invention, the majority of the screen area exhibits loW
`resolution, high touch force characteristics. Asmaller area of
`the screen exhibits loW touch force and high resolution
`properties. For a second embodiment of the invention, at
`least a pom‘)? of the peripheral regions (i'ev regioils near the
`c1rcum eren 121 e e o
`e screen are rov1 e W1
`f
`t
`1 dg )
`f th
`P
`d d
`th
`regions of loW touch force high resolution properties. These
`regions may be programmed to act as scroll bars, Which
`Would alloW the user to change locations in a document of
`Which only a portion is displayed on the screen. In the
`central regions of the screen, higher touch force and loWer
`resolution provide palm rejection and coarse marking or
`movement capability With loW bandwidth utilization. Either
`the varied screen properties may be incorporated into the
`.
`.
`.
`Screen dulmg “5 manufapmre’ or the Screen way be deslgn.ed
`so that different resolution and touch sensitivity properties
`can be assigned to different regions of the screen to Suit the
`user’s needs.
`
`23 Claims, 3 Drawing Sheets
`
`/ LL1L ; \
`
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`U.S. Patent
`
`0a. 1, 2002
`
`Sheet 1 of3
`
`US 6,459,424 B1
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`/--13
`
`12 //
`
`FIG. 1
`
`HF.’- 14
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`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 2 0f 3
`
`US 6,459,424 B1
`
`FIG. 3
`(PRIOR ART)
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`
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`U.S. Patent
`
`0a. 1, 2002
`
`Sheet 3 of3
`
`US 6,459,424 B1
`
`52 x K- 54_x
`
`/
`
`53
`
`FIG. 5
`
`62
`
`65B
`
`67A
`
`675
`
`1/ x68,
`
`7O
`69
`
`FIG. 6
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`US 6,459,424 B1
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`1
`TOUCH-SENSITIVE INPUT SCREEN
`HAVING REGIONAL SENSITIVITY AND
`RESOLUTION PROPERTIES
`
`FIELD OF THE INVENTION
`
`This invention relates to input screens and combined
`input/display screens for inputting and/or displaying graphic
`information in connection With a data storage and/or data
`processing system.
`
`BACKGROUND OF THE INVENTION
`
`Touch-pad display screens have found Wide application in
`Personal Digital Assistants (PDAs), ultra-compact personal
`computers, With built-in operating systems, that are opti
`miZed for scheduling and other high-mobility operations.
`During the past several years, the popularity of PDAs has
`soared. Corporations such as Sharp, Casio, Philips,
`3-Comm, and HeWlett-Packard have entered the fray. Most
`have ?ash memory, a small liquid-crystal-display touch-pad
`screen, a user input device Which may be either a barely
`usable, miniature keyboard, and/or a touch pad incorporated
`into the screen, as Well as a communications port for
`transferring ?les betWeen the PDA and a less-portable
`computer. A high-end PDA may incorporate a modem and
`communications softWare, as Well as draWing, Word
`processing and spreadsheet softWare. A Writing stylus, or
`“pen”, may be supplied, With Which the user may Write and
`draW on the touch-pad screen. The PDA may also be
`equipped With a menu system Which requires loW-resolution
`inputs, thereby alloWing the user to simply touch the screen
`at selected touch key locations With his ?nger to select menu
`options. The touch-pad feature has great utility on a PDA, as
`nearly all PDAs are too small to incorporate a keyboard
`large enough for ef?cient touch typing. Thus, handWriting
`and draWings are initially stored as bit-mapped patterns.
`With Writing recognition softWare that is supplied With many
`of the PDAs, a user’s handWriting can be converted to ASCII
`text. Compared With desk-top and lap-top computer systems,
`PDAs generally have very limited memory storage capa
`bilities. HoWever, the average amount of memory being
`supplied With PDAs is groWing rapidly. Already, PDAs With
`16 megabytes of ?ash memory are available. As it becomes
`possible to load an entire novel or textbook into the memory
`of a PDA, it is likely that they Will ?nd Wide use as
`electronic editing and annotation devices.
`Lap-top computers are equipped, almost exclusively, With
`LCD displays. Within the past year, ?at screen displays
`utiliZing LCD technology have become suf?ciently inexpen
`sive that they are beginning to replace cathoderay-tube
`(CRT) displays used With desk-top systems. Because touch
`pad functionality can be readily incorporated in an LCD
`display, it is likely that large numbers of both lap-top and
`desk-top systems Will soon incorporate LCD display screens
`With touch-pad functionality. The incorporation of touch pad
`functionality promises to facilitate rapid user interaction
`With the computer system. For example, the computer
`system may be programmed to initiate a particular task When
`a certain letter is draWn With a ?nger tip or stylus on the
`touch pad. An additional example is the programming of the
`computer system so that the edges of the touch pad mimic
`on-screen scrollbars. A touch pad Will also permit the user to
`enter data in handWriting and to sign documents With a
`bit-mapped copy of his signature. With the availability of
`touch-pad systems, electronic editing and annotating of
`documents Will become much more Widespread. There is
`little doubt that the incorporation of touch-pad functionality
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`Will greatly enhance the ?exibility of personal computer
`systems. The incorporation of the touch pad feature in a
`desktop system is expected to reduce the frequency of
`repetitive motion injuries, as little arm or Wrist motion is
`required.
`Many different types of devices presently exist Which
`utiliZe tactile sensing to provide inputs to a data processing
`system. These devices sense the position of a ?nger or stylus
`at successive intervals on a touch sensitive surface. The
`touch detection mechanism typically relies on localiZed
`changes in either conductivity or capacitance from a refer
`ence value caused by the presence of the ?nger or stylus on
`or near the touch sensitive surface. A touch screen display
`typically has both horiZontal and vertical scanning circuitry.
`The location and direction of a touch input is determined
`during the periodic scanning of both horiZontal and vertical
`screen elements. For example, if a screen has 600 elements
`arrayed vertically along the screen’s horiZontal axis and 400
`elements arrayed horizontally along the screen’s vertical
`axis, a capacitive change from a standard value at the
`intersection of any horiZontal element and a vertical element
`Will indicate a touch input at the intersection location.
`In US. Pat. No. 4,013,835 to Eachus, et al., a touch pad
`is formed from a layer of a variable-resistance material, such
`as a silicone rubber membrane embedded With silver
`particles, Which overlies a ?rst set of parallel conductor
`strips Which, in turn, overlie a second set of parallel con
`ductor strips. Each conductor strip of the ?rst set incorpo
`rates a plurality of serially-connected, open rectangles. Each
`rectangle surrounds a center conductive island Which is in
`permanent contact With a conductor strip of the second set.
`When the membrane is compressed in the area of an open
`rectangle by pressure exerted by a ?nger or stylus, the
`membrane becomes conductive in the compressed region,
`and electrical contact is made betWeen the rectangle and the
`surrounded island. Position can be determined by sequen
`tially scanning the both sets of conductor strips at the
`periphery of the touch pad and determining current ?oW
`from a conductor of the ?rst set to a conductor of the second
`set. Up to a maximum value, current ?oW Will increase With
`pressure.
`In US. Pat. No. 4,698,461 to MeadoWs, et al., a touch
`panel incorporates an upper layer of uniform resistivity.
`Panel scanning signals are applied to excite selected touch
`surface edges so as to establish an alternating current
`gradient across the panel surface. When the surface is
`touched, a current ?oWs from each excited edge through the
`resistive surface and is either capacitively or conductively
`coupled to earth ground potential through the user’s ?nger
`and body. As resistance increases With the distance from the
`edges of the panel, the touch location can be determined by
`measuring the current ?oWs during the scanning process.
`Cirque Corporation, a company noted for its touch-pad
`sensing devices, has received several patents covering the
`technology Which descend from US. application Ser. No.
`7/914,043 ?led by Gerpheide, et al. On Jul. 13, 1992. One
`of the latest of these is US. Pat. No. 5,861,875. A touch
`sensitive pad includes a plurality of capacitive elements
`formed by tWo perpendicularly-overlapping, dielectrically
`insulated arrays of parallel electrode strips. The capacitive
`coupling of an object, such as a ?nger or stylus, to the
`capacitive elements is sensed to determine the object’s
`horiZontal and vertical (x and y) position With respect to the
`touch surface of the pad. This device is of interest because
`capacitive balance measurement circuitry and capacitive
`balance ratio determination circuitry have been included
`Which increase position detection resolution beyond an
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`US 6,459,424 B1
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`3
`object’s coarse position, Which is a function of the separa
`tion of the parallel electrode strips Within the tWo arrays. In
`addition, the circuitry provides for a determination of the
`vertical proximity of an object to the touch pad so that a
`determination can be made as to Whether or not a determi
`nation of the X and y position is meaningful.
`In US. Pat. No. 5,194,862 to Edwards, a sensor array
`system includes a roW and column array of individual
`sensing elements, each of Which has a bistable circuit Which
`adopts one or the other of tWo stable states depending on
`Whether or not a touch input (made by either a stylus or
`?nger) exists at the sensing element location. The roWs of
`sensing elements are periodically reset in sequence by a
`scanning address circuit and the states of their bistable
`circuits are determined at regular intervals related to reset
`ting by a detection circuit using active matrix addressing of
`the sensing elements. The array of sensing elements is
`fabricated using thin ?lm transistor technology. The system
`can be used as an overlay to a display device such as a matrix
`liquid crystal display screen.
`US. Pat. No. 5,122,787 to Fujita, et al., discloses a
`ferroelectric liquid crystal touch panel that includes tWo
`mutually perpendicular sets of parallel electrodes arrayed in
`spaced-apart parallel planes. A ferroelectric liquid crystal
`positioned betWeen the electrodes at the intersection of each
`electrode pair. The location of touch inputs on the panel are
`determined by scanning peripheral circuitry Which detects
`electromotive forces Which are generated When a ferroelec
`tric crystal is compressed by a touch input.
`A different approach is taken by US. Pat. No 5,777,596
`to Herbert. Touch inputs made With a ?nger or stylus on a
`liquid crystal display are detected by scanning circuitry,
`Which continuously compares charge times of the constitu
`ent liquid crystal elements to a reference value. The results
`of the comparison determine Which elements in the display
`are being touched.
`The combination display and sensing device of Us. Pat.
`No. 5,847,690 to Boie, et al., incorporates modi?ed liquid
`crystal display elements a black matrix layer adapted for
`sensing screen touch locations. A scanned electrical signal
`applied to the display elements produces an output signal
`indicative of a touched location on the screen.
`Touch-sensitive display screens almost invariably require
`conductive circuit elements to be embedded Within the
`display panel itself. Either these elements must be so deli
`cate that they do not substantially interfere With the trans
`mission or re?ection of light, or they must be transparent.
`Indium tin oxide is one of the feW knoWn transparent solid
`materials. As such, it has found Widespread use in the
`manufacture of liquid crystal displays having touch
`sensitive input capability.
`Display screens incorporating touch pad functionality are
`manufactured for a Wide variety of applications. Manufac
`turers design the properties of the touch screen to meet
`certain needs of the consumer. TWo properties Which may
`vary from one screen to another are resolution and touch
`sensitivity.
`Resolution may be de?ned as the ability of the screen to
`resolve tWo nearby points on the screen. It can also be
`de?ned as the smallest area on the screen surface recogniZ
`able as a single point or pixel. LoW-resolution screens Would
`be adequate, or even desirable, for certain applications such
`as region selection, check boxes, or highlighting portions of
`displayed documents. High-resolution screens Would be
`desirable for sketching, handWriting input, digital
`signatures, and any other task Where precise, smoothly
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`draWn lines are required. A draWback of a high resolution
`screen is that greater processing poWer is required to manage
`the resulting greater data input.
`Touch sensitivity, on the other hand, refers to the amount
`of pressure applied to the screen surface that is required to
`activate a pixel. A high level of touch sensitivity (i.e., pixels
`are activated With loW applied pressure) is useful When a
`high level of dexterity is required for a given task. Sketching
`or handWriting, for example, are best registered on a screen
`having high touch sensitivity. Screens possessing loW touch
`sensitivity (i.e., pixels are activated With high applied
`pressure) are less likely to register a touch from either
`inadvertent touching or from resting the palms of the hands
`on the screen.
`What is needed is a touch screen having varying combi
`nations of resolution and touch sensitivity for different
`applications. Different combinations of these tWo properties
`Will enhance the functionality of the user interface and Will
`optimiZe inputs for a particular task.
`
`SUMMARY OF THE INVENTION
`
`This invention includes a touch screen panel having
`varied combinations of resolution and touch sensitivity. The
`touch screen panel may also incorporate display function
`ality. For a ?rst embodiment of the invention, the majority
`of the screen area exhibits loW resolution, high touch force
`characteristics. This large area might be used for highlight
`ing and simple annotation, thereby minimiZing processor
`bandWidth and providing rejection of inadvertent touchings.
`A smaller area of the screen exhibits loW touch force and
`high resolution properties. This smaller area may be used for
`digital signature input or for security marking input. The
`smaller area may be placed in a corner of the screen Where
`it is unlikely to be inadvertently touched. For a second
`embodiment of the invention, the peripheral regions (i.e.,
`regions near the circumferential edge) of the screen are
`provided With regions of high-resolution, loW-touch-force
`properties. These regions may be programmed to act as
`scroll bars, Which Would alloW the user to change locations
`in a document When only a portion of the document is
`displayed on the screen. In the central regions of the screen,
`loWer-resolution, higher-touch-force properties provide
`palm rejection and coarse marking or movement capability
`With loW bandWidth utiliZation.
`Either the varied screen properties may be incorporated
`into the screen during its manufacture, or the screen may be
`designed so that the varied properties are programmable by
`the user. In order to provide regions on the display screen of
`different resolution during the manufacturing process, sev
`eral approaches are possible. One approach requires the
`fabrication of a smaller screen Within the larger screen, With
`both the smaller and larger screens having their oWn dedi
`cated sensing and scanning circuitry. Different properties are
`incorporated into the circuitry of each screen. Another
`approach utiliZes the same scanning circuitry for both high
`and loW-resolution regions of the screen. The screen is
`manufactured in such as manner so as to either accommo
`date high-resolution touch sensing over the entire area of the
`screen or only in certain preset regions. If the entire screen
`can accommodate high-resolution touch sensing, then the
`system is programmed to use loW-resolution scanning as the
`default operational condition. When scanning in the high
`resolution mode, every sensing element is scanned.
`HoWever, When operating in the loW-resolution scanning
`mode, only a fraction of the sensing elements are scanned.
`When a touch input is sensed in the designated high
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`US 6,459,424 B1
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`5
`resolution regions, the system immediately switches to
`high-resolution scanning. High-resolution scanning is main
`tained until the system senses a touch input in a loW
`resolution region of the screen, at Which time the system
`reverts to loW-resolution scanning. It should be readily
`apparent that multiple scanning modes can be hard-Wired
`into the screen’s scanning circuitry at the time of manufac
`ture or the screen can be manufactured so that the scanning
`modes are programmable. Still another approach to provid
`ing for loW and high-resolution detection is through the use
`of a balance detection system, such as that employed in the
`referenced patent to Gerpheide, et al. Balance detection
`circuitry can be activated When a touch input is sensed in the
`a designated high-resolution region, and deactivated When a
`touch input is sensed in a designated loW-resolution region.
`Although programmable region-speci?c resolution may
`be readily implemented for most types of touch screen
`panels, only certain types of touch-sensitive panels may
`readily incorporate programmability for touch sensitivity. As
`a general rule, touch sensitivity programmability may be
`implemented for only those displays for Which a touch input
`results in an analog signal Which varies in strength in
`proportion to the touching force or proximity of an object to
`a sensing element.
`Certain improvements may also be made to existing
`screen designs to provide both programmability of sensitiv
`ity and areas of varying sensitivity at the time of manufac
`ture. For example, screens constructed in accordance With
`either the cited Herbert patent or the Gerpheide, et al. patent
`may be modi?ed by incorporating a resilient, compressible
`layer. The compressible nature of the layer Will result in an
`analog screen output signal. Additionally, a resilient, com
`pressible layer having regions of varied thickness may be
`incorporated in either screen at the time of manufacture to
`provide different levels of touch sensitivity.
`
`DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a top plan vieW of a touch-screen display that,
`except for a loWer right portion Which has high-resolution,
`loW-touch-force properties, has loW resolution, high touch
`force characteristics;
`FIG. 2 is a top plan vieW of a touch-screen display that,
`except for narroW strips along the loWer and right edges
`Which have high-resolution, loW-touch-force properties, has
`loW resolution, high touch force characteristics;
`FIG. 3 is a cross-sectional vieW of a ?rst prior-art touch
`screen display (Eachus, et al.);
`FIG. 4 is a cross-sectional vieW of a second prior-art
`touch-screen display (Fujita, et al.);
`FIG. 5 is a cross-sectional vieW of a modi?ed third
`prior-art touch-screen display (Herbert), Which noW incor
`porates a resiliently compressible pad in order to provide
`touch sensitivity; and
`FIG. 6 is a cross-sectional vieW of a modi?ed fourth
`prior-art touch-screen display of Gerpheide, et al., Which
`noW incorporates a resiliently compressible pad in order to
`provide touch sensitivity.
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`DETAILED DESCRIPTION OF THE
`INVENTION
`
`This invention includes a touch screen panel having
`varying combinations of resolution and touch sensitivity.
`The varying screen properties may be either manufactured
`into the screen, or programmed by the user. Screen con?gu
`ration Will be discussed ?rst, folloWed by a description of the
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`6
`changes Which must be effected to produce a touch screen
`display panel having the desired resolution and touch force
`characteristics. The touch screen panel may also incorporate
`display functionality.
`Certain types of screens, such as those of Fujita, et al. and
`Herbert, incorporate both display and touch detection in a
`single array of elements. Other types of screens may require
`tWo superimposed arrays: one for the visual display, and the
`other for touch detection. For example, if the touch pad of
`Gerpheide, et al. is used as an overlay for a conventional
`liquid crystal display screen, any conductors Within the
`touch pad overlay should, preferably, be transparent in order
`to avoid at least a partial blocking of displayed images.
`Induim tin oxide is presently the preferred material for
`transparent solid conductors.
`For a ?rst embodiment of the invention shoWn in FIG. 1,
`a touch and/or display screen 11 is mounted in Within a
`display housing 12. The screen 11 is divided into tWo regions
`having different properties. The ?rst region 13 incorporates
`the majority of the total display area of the screen 11. The
`?rst region 13 exhibits loW resolution, high touch force
`characteristics. This large ?rst region 13 might be used for
`annotating documents or highlighting certain portions of
`documents displayed on the screen 11, thereby minimiZing
`processor bandWidth and providing rejection of inadvertent
`touchings. By minimiZing processor bandWidth, memory
`requirements are reduced and screen updates can be per
`formed more rapidly. A smaller second region 14 of screen
`11 exhibits loW-touch-force and high-resolution properties.
`This second region 14 may be used for digital signature
`input or for security marking input. It Will be noted that the
`second region 14, Which is at least an order of magnitude
`smaller in area than said major region, has been placed in a
`corner of the screen 11 Where it is unlikely to be inadvert
`ently touched.
`For a second embodiment of the invention shoWn in FIG.
`2, a touch and/or display screen 21 is divided into three
`regions. The ?rst region 22 incorporates the majority of the
`total display area of the screen 21. The ?rst region 22
`exhibits loW-resolution, high-touch-force characteristics.
`This large ?rst region 22 might be used for annotating
`documents or highlighting certain portions of documents
`displayed on the screen 21. The second and third regions 23
`and 24, respectively, are narroW bands along the right and
`bottom peripheral edges of the screen 21 Which have high
`resolution, loW-touch-force characteristics. The second
`region 23 may be programmed to act as a vertical scroll bar,
`While the third region 24 may be programmed to act as a
`horiZontal scroll bar. Scroll bars are typically used to scroll
`Within a document, draWing, or other screen display that is
`too large to ?t on a single screen.
`Either the varied screen properties may be incorporated
`into the screen during its manufacture, or the screen may be
`designed so that the varied properties are programmable by
`the user. In order to provide regions on the display screen of
`different resolution during the manufacturing process, tWo
`basic approaches are possible. The ?rst approach requires
`the fabrication of a smaller screen Within the larger screen,
`With both the smaller and larger screens having their oWn
`dedicated sensing and scanning circuitry. Different proper
`ties are incorporated into the circuitry of each screen. For
`screens Which sense location and movement through the
`presence of discrete sWitches, a greater number of sWitches
`are incorporated into the high-resolution regions of the
`screen. For a screen Which senses location and movement
`With an array of capacitive devices, a greater number of such
`devices are incorporated into the high-resolution regions of
`
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`US 6,459,424 B1
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`7
`the screen. For example, if the array utilizes perpendicularly
`overlapping arrays of parallel conductor strips, then the
`number of conductor strips per centimeter is increased in
`one or both arrays for high-resolution regions. The second
`approach utiliZes the same scanning circuitry for both high
`and loW-resolution regions of the screen. The screen is
`manufactured in such as manner so as to either accommo
`date high-resolution touch sensing over the entire area of the
`screen or only in certain preset regions. If the entire screen
`can accommodate high-resolution touch sensing, then the
`system is programmed to use loW-resolution scanning as the
`default operational condition. When scanning in the high
`resolution mode, every sensing element is scanned.
`HoWever, When operating in the loW-resolution scanning
`mode, only a fraction of the sensing elements are scanned.
`For example, if the loW-resolution mode operates at one
`fourth the resolution of the high-resolution mode, every
`other horiZontal sensing element and every other vertical
`sensing element Would be scanned during loW-resolution
`operation. When a touch input is sensed in the designated
`high-resolution regions, the system immediately sWitches to
`high-resolution scanning. High-resolution scanning is main
`tained until the system senses a touch input in a loW
`resolution region of the screen, at Which time the system
`reverts to loW-resolution scanning. It should be readily
`apparent that multiple scanning modes can be hard-Wired
`into the screen’s scanning circuitry at the time of manufac
`ture.
`The touch pad of Gerpheide, et al. (US. Pat. No. 5,861,
`875) employs capacitive balance to more accurately deter
`mine the position of a touching object. This feature, in
`essence, provides resolution greater than the spacing
`betWeen capacitive electrodes. As an ample description of its
`implementation is given in the patent With reference to
`FIGS. 10(a), 10(b), 11 and 12, that description is incorpo
`rated herein by reference. Using the capacitive balance
`method, there is, of course, a maximum obtainable resolu
`tion. HoWever, balance sensitivity may be reduced beloW the
`maximum level to reduce resolution, if so desired. Modi?
`cations to balance sensitivity may be made using softWare,
`or the setting may be hardWired into the touch pad system.
`It should also be readily apparent that the provision of
`multiple scanning modes lends itself to user programmabil
`ity. An embodiment of this invention is the provision of
`scanning circuitry Which is programmable by the user to
`accommodate his oWn unique needs.
`Although touch sensitivity is readily adjustable during the
`design of a touch screen, programmability of touch sensi
`tivity is more complicated. Generally speaking, only certain
`types of touch-sensitive panels may incorporate program
`mability of touch sensitivity. As a rule, touch sensitivity
`programmability may be implemented for only those dis
`plays Where a touch input results in an analog signal Which
`varies in strength in proportion to the touching force. For
`example, the Eachus, et al. device of Us. Pat. No. 4,013,835
`and the Fujita, et al. device of US. Pat. No. 5,122,787 lend
`themselves to programmability, as the threshold for detect
`ing a touching input may be adjusted Within a ?xed range of
`values. Thus, in accordance With the present invention,
`touch sensitivity can be varied from one region of the screen
`to another by adjusting the capacitive coupling threshold
`value to a higher level When touch inputs are made to one
`region than When made to another region.
`The Eachus, et al. device is shoWn in FIG. 3, Which
`corresponds to FIG. 6 of US. Pat. No. 4,013,835. The touch
`pad is constructed from a tough, ?exible, transparent insu
`lating layer 31, Which overlies a resilient coupling layer 32,
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`8
`the resistance of Which varies inversely With the pressure
`applied to it. A contact pad 33 in physical contact With the
`coupling layer 32 is in electrical contact With a Y-axis
`conductor 34 via a plated hole conductor 35. An open
`rectangular conductor 36, embedded Within a dielectric
`material layer 37 is also in physical contact With the cou
`pling layer 32. Electrical paths betWeen the rectangular
`conductor 36, Which is coupled to an X-axis conductor, and
`the contact pad 33 are formed by applying pressure (P) to the
`coupling layer 32 in the region of the rectangular conductor
`and contact pad 33. The Fujita, et al. device is shoWn in FIG.
`4, Which corresponds to FIG. 1 of US. Pat. No. 5,122,787.
`Aferroelectric liquid crystal layer 42 is sandWiched betWeen
`transparent counterposed electrodes 41H and 41V, Which
`constitute a matrix. Position detecting means 43H and 43V,
`Which may be implemented as voltage detecting operational
`ampli?ers, are provided for detecting a pushed position
`through electrodes 41H and 41V by an electromotive force
`generated betWeen those electrodes When an upper surface
`of the matrix is pushed. Display control means 44H and 44V,
`Which may be implemented as driver circuits, are provided
`for controlling the display state of the liquid crystal panel
`through electrodes 41H and 41V. Selection means 45H and
`45V, Which may be implemented as array-like sWitching
`elements, are provided for selecting the connection of the
`position detecting means 43H and 43V and control means
`44H and 44V to electrodes 41H and 43V, respectively, in a
`time-sharing manner. When position detecting means 43H
`and 43V are connected to electrodes 41H and 41V,
`respectively, by selection means 45H and 45V, also
`respectively, the connection of the display control means
`44H and 44V to electrodes 41H and 41V is cut off.
`Conversely, then the display control means are connected to
`electrodes 41H and 41V by selection means 45H and 45V,
`the connection of position detecting means 43H and 43V to
`electrodes 41H and 41V is cut off. A further control means
`46 is provided for sending control signals to selection means
`45H and 45V.
`The MeadoWs, et al. device of Us. Pat. No. 4,698,461
`and the EdWards device of Us. Pat. No. 5,194,862, on the
`other hand, do not lend themselves to touch sensitivity
`programmability, as the detection devices for each of these
`input screens provide a digital signal.
`Referring noW to FIGS. 5 and 6, With the addition of a
`compressible resilient pad on top of a screen employing