CA1194582A - Method and apparatus for determining the coordinates of a point on a surface - Google Patents
Method and apparatus for determining the coordinates of a point on a surfaceInfo
- Publication number
- CA1194582A CA1194582A CA000420328A CA420328A CA1194582A CA 1194582 A CA1194582 A CA 1194582A CA 000420328 A CA000420328 A CA 000420328A CA 420328 A CA420328 A CA 420328A CA 1194582 A CA1194582 A CA 1194582A
- Authority
- CA
- Canada
- Prior art keywords
- strips
- potential
- emitter
- strip
- conducting
- 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.)
- Expired
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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/004—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring coordinates of points
Abstract
A B S T R A C T
METHOD AND APPARATUS FOR DETERMINING THE COORDINATES
OF A POINT ON A SURFACE.
A screen is disclosed on the surface of which a certain number of resistant conducting emitter strips and insulated conducting receiver strips are laid, the emitter strips being parallel-mounted with the terminals of a voltage generator and the receiver strips being interlaid between the receiver strips such that a conducting receiver strip lies between two resistant emitter strips. The electronics of control comprises an exploring stage to control the receiver strip time-related exploration. Thus, when a sufficiently conducting object used to indicate a point, has touched the surface and bridge an emitter and a receiver strips, a higher potential is detected on the corresponding receiver strip and the ordonate Y is given by the strip order number - while the abscissa X is calculated from measuring the potential between each ends of the emitter strip and the object.
METHOD AND APPARATUS FOR DETERMINING THE COORDINATES
OF A POINT ON A SURFACE.
A screen is disclosed on the surface of which a certain number of resistant conducting emitter strips and insulated conducting receiver strips are laid, the emitter strips being parallel-mounted with the terminals of a voltage generator and the receiver strips being interlaid between the receiver strips such that a conducting receiver strip lies between two resistant emitter strips. The electronics of control comprises an exploring stage to control the receiver strip time-related exploration. Thus, when a sufficiently conducting object used to indicate a point, has touched the surface and bridge an emitter and a receiver strips, a higher potential is detected on the corresponding receiver strip and the ordonate Y is given by the strip order number - while the abscissa X is calculated from measuring the potential between each ends of the emitter strip and the object.
Description
M~T~OD AND APPARATUS FOR DETERMINING TEE COORDIN~TES
OF A POINT ON A SURF~CE.
The presen-t invention relates to a method for determining the coordinates of a point on surface by pin-pointing it,through ccntact of an object with that surface.
The invention further relates to a device permitting, in particular, implementation of this method.
The known methods of this type generally rely on dividing the surface beforehand into a certain number of zones materialized as oiherwise and selectively sensitive to contact with the object.
American patent 3 ~06 91~ presents thus a graphical display board equipped with a printed circuit consisting of evenly spaced parallel paths, one resistive path lying between two conductive paths.
To determine the coordinates X, Y of a point, use is made of a stylus comprising one end consisting of a conducting material which must establish a negligible resistance bridge between three consecutive paths :
one resistive path and two conductive paths. In this device, the resistive paths are all interconnected down to ground via a conductive cross path, whereas one path in each conducting pair is interconnected down to ground via one of its ends by means of a series resistance cross path, the other conductive paths being connected directly by one end thereof to a detection apparatus. This device has the drawback of requiring the lay-up of horizontal and vertical conductive and resistive paths on the board with overlaps for making certain connections. Moreover, coordinate determination of a point is carried out by electrica]ly connecting three consecutive paths using a meta] stylus having a small resistance and ...
specially designed for this application.
Certain methods, which tend in fact to form control key boards utilize capacitive keys laid out in a chequered Eashion over the surface. Each key constitutes a capacitor~ whose dielectric varies upon touching the object, which can Eor example be an operator ' 9 finger. The associated electronics are relatively straight forward, by the location accuracy is rather low since the keys are fixedly positioned with a relatively large pitch.
Be-tter accuracy is achieved with those methods employing an electrically active object, ]cnown as "light pen", which cooperates with a surface in the form of a cathode ray tube~ The location of the contact point results from interaction of the object with the electronic scan of the screen. The equipment that these methods imply involves e~tensive and comple~ electronics stages, that are essentially computer-associated.
The main object of this invention is to provide a method and a device for coordinate determination which conciliates good location accuracy and a straightforward electronics infrastructure.
This problem is resolved, in accordance with the invention by performing the following operations :
OF A POINT ON A SURF~CE.
The presen-t invention relates to a method for determining the coordinates of a point on surface by pin-pointing it,through ccntact of an object with that surface.
The invention further relates to a device permitting, in particular, implementation of this method.
The known methods of this type generally rely on dividing the surface beforehand into a certain number of zones materialized as oiherwise and selectively sensitive to contact with the object.
American patent 3 ~06 91~ presents thus a graphical display board equipped with a printed circuit consisting of evenly spaced parallel paths, one resistive path lying between two conductive paths.
To determine the coordinates X, Y of a point, use is made of a stylus comprising one end consisting of a conducting material which must establish a negligible resistance bridge between three consecutive paths :
one resistive path and two conductive paths. In this device, the resistive paths are all interconnected down to ground via a conductive cross path, whereas one path in each conducting pair is interconnected down to ground via one of its ends by means of a series resistance cross path, the other conductive paths being connected directly by one end thereof to a detection apparatus. This device has the drawback of requiring the lay-up of horizontal and vertical conductive and resistive paths on the board with overlaps for making certain connections. Moreover, coordinate determination of a point is carried out by electrica]ly connecting three consecutive paths using a meta] stylus having a small resistance and ...
specially designed for this application.
Certain methods, which tend in fact to form control key boards utilize capacitive keys laid out in a chequered Eashion over the surface. Each key constitutes a capacitor~ whose dielectric varies upon touching the object, which can Eor example be an operator ' 9 finger. The associated electronics are relatively straight forward, by the location accuracy is rather low since the keys are fixedly positioned with a relatively large pitch.
Be-tter accuracy is achieved with those methods employing an electrically active object, ]cnown as "light pen", which cooperates with a surface in the form of a cathode ray tube~ The location of the contact point results from interaction of the object with the electronic scan of the screen. The equipment that these methods imply involves e~tensive and comple~ electronics stages, that are essentially computer-associated.
The main object of this invention is to provide a method and a device for coordinate determination which conciliates good location accuracy and a straightforward electronics infrastructure.
This problem is resolved, in accordance with the invention by performing the following operations :
2~ a) a certain number of resistant conducting emitter strips are laid on the surface parallel-mounted with -the terminals of a voltage generator, as are a certain number of insulated conducting receiver strips interlaid between the foregoing such that a conducting receiver strip lies be-tween two resistant emitter strips , b) the surEace is touched with a suEEiciently condu~ting object having dimensions such that it establishes an electrical bridge between a re~istant 3S conducting emitter strip and a conducting receiver strip ;
c) the insulated strips in which there has ~een a variation in potential is determined whence one of the contact point coordinates is deduced ;
d) this variation in potential is measured in order to deduce the other contact poin-t coordinate.
The object is not electrically active. It merely needs to be sufficient:ly conductive to make a connection between two neighbouring strips, one emitter and one receiver. This object may then be an operator's finger. This technique therefore does away with any electronic infrastructure associated with the object.
Furthermore, this obviates any division of the surface into a criss-cross of keys set-out in a fixed pattern thus making it possible to obtain excellent point position definition by varying the width and the pitch of the strips, on a basis compatible with the object-sur~ace contact area dimensions.
In a preferred embodiment of the method, the potential of the receiver strips can be cyclically explored until a potential in one c,f these strips different from that in the other strips is detected, whereupon the exploration is halted in order to measure this potential.
By way of this configuration, just one measurement apparatus proves necessary.
In a first embodiment variant of the method, a known potertial is fed into one end of each emitter strip, the other end of each strip being connected to ground.
Onc:e the potential has been measured, the emitter strip polarity is reversed in order to take a furt:her measurement, and this cycle is repeated a certain number o~ times.
These operations make it possible to eliminate certain unknown constant factors, such as the object's resistanc.e,or certain possibly variable ~act6rs, such as the supply voltage.
In a second embodiment variant of the method, an alternating potential wi-th a ~requency o~ approximately l kH~ is ~ed into one end of each emitter strip with the other end of each strip connected down to ground and the measured voltage is filtered.
This there~ore eliminates any parasite voltages induced by the surroundings, notably at the mains frequency o~ 50 or 60 Khz.
As be-ore~ the potenti21 is successively mea~ured a cer-tain num~er of times, the alternating potential and ground reversed and then thesame number o~ measurements taken again.
In every event, an average value is calculated over the potentials measured during -the successive readings to minimize any possible ~ortuitous errors.
Lastly, the exploration is resumed once all the emitterstrips have reverted to the same potential.
In a further aspect of the invention, the device for determining the coordinates o~ a point on a surface comprising a certain nurnber of conductive strips (El to E5 ~ Rl to R4) to form separate zones selectively sensitive to the contact of an object is characterized in that it comprises, on the surEace, a certain number of resistant conducting emitter strips each having one end terminal for the ground connection and one end terminal for the voltage generator connection, ar~a certain nurnber of conducting receiver strips interlaid between the emitter strips s~lch that a conducting receiver strip 11PS between two resistant emitter strips where each of these conducting receiver strips has an end terminal fol- a connection in parallel with/a potential measuriny apparatus and offers a virtually constant linear resistance over its whole length.
Other peculiarities and advantages of the invention will be apparent from-.the following more particular description, as illustrated in the accompanying drawings, given as non e~haustive examples in which :
- figure 1 gives a semi~schematic front view o the strip configuration on the surfaee, as in this invention ;
~ figure 2 gives a partial view of figure 1 e~plaining how the potential is electrically measured ;
- figure 3 gives a view in perspective illustrating how the device is used, as in this invention ;
- figure 4 schematizes the overall device ;
- figure 5 gives a temporal function flow-chart of the measurement processing system ; and - figure 6 depicts embodiment variations of the conducting strips.
With reference to figure 1, the device comprises a transparent surface 1, made of sodio~calcic glass for instance, which forms a eathode display screen. Arranged on this surface are a certain number of parallel emitter strips El to E5,eOg.in thin oxide SnO2 doped with fluor.ine deposited by pyrolysis. These strips are conductive and have a t:hiekness such that the resistanee of strip section equal in lenght to its width is in the order o~ 100 to 200SL.
The strip ends 10 are neutralized by an edging 2 of the surface and serve as electrical connections with the collecting strips 3, 4.
These strips can be made up o~ a metal deposit that is conductive and/or can be soldered in silver or nickel deposited for example in the form o~ a conductive paint, resin or enamel by serigraphy.
~eceiver strips Rl to R4 are interlaid between the emitter strips E~ to E5 end are formed in appreciably the same fashlon and each comprise one neutraLized end constituting the connection terminal 11.
To clarily matters, the strip neutralized parts and the collecting strips have been shaded in.
In the example described, each strip is 3.5 mm wide and the distance from one strip to the next is also 3.5 mm. The presence of these strips has practically no effect on the visibility throughthe transparent surface 1.
The collecting strips 3, 4 are wired to a switch 5 which either connects the strip 3 to a voltage generator 6 and the strip 4 to ground M (~igure 1), or, inversely, connects the strip 3 to ground and the strip 4 to the generator 6.
This switch is activated by a control mechanism 7 which will be covered in more detail later.
The receiver strips Rl to R4 are wired to an exploring stage 8 which successively connects those strips to a voltmeter V.
Utilization of the apparatus whose principle has just been described consists of determining the coordinates ~ and Y of a point on the s~lrface that is ma-texialized by the contact o~ a conducting object 9 (figure l) such as an operator's finger 9a tfigure 3). The object's dimensions must be such that it covers two adjacent strips eg E2 and R2 (figure l), setting up an eLectrical bri~ge P between said two strips.
In the example shown in ~igure l, the receiver strip R2, by contact with the object, is set at a certain potential detected by the voltmeter V,and it is supposed that the ordinate Y
is given by the strip order number.
The abscissa X is calculated from the sketch in ~igure 2, on which it has been as~umed that the voltage generator is a generator 6a delivering a steady voltage U, o~ around 15 volts.
If L is the useful lenght of a receiver strip, then as a result of the high internal resistance in the voltmeter V:
X = u L, U
where u is the voltage measured by the voltmeter If the operation is repeated by inverting the generator 6a and the ground M, then a new voltage u' is measured, giving thus :
L - X = u' L
whence :
X = u.L
u+u' It will be observed that this method renders the measurement independent of the supply voltage U accidental variations in which might adversely affect the measurement, and independent of the resistance value of the contact bridge established by the conduc-ting object 9 providing -this resistance is decidely lower than the voltm~ter internal res:istance to avoicl disturbing the measurement. In one embodiment example, a vol~meter with an internal resistance of 2 ~ ~ has been chosen in the knowledge of the fac-t the rasistance of the operator's ~inger measured at an~applied vol-tage o~ -frequency l ~Iz S is around 500 k3~. It can thus be been that conducting object 9 over a very wide resistance range may be used, from very low values upto values in the order of 1 MSL providing a voltmeter with a suitable internal impedance i9 chosen, i.e. with a much higher impedanceO
A description will now be given, with reference to figure 4, of the electronics surrounding the device and the method description completed.
In this drawing, the strips have been shown in greater numbers than in figure l, but this number is essentially variable in terms of the surface dimensions. Those elements already described have been reshown with the same reference numbers. These elements are for the most part the supply inverting switch 5~ the generator 6, the exploring stage 8 and the voltmeter V which is of the digital type.
A control stage 12 of a calculating unit 13 is wired to the e~ploring stage 8 to ~5 control the receiver strip time-related exploration.
In the example described, the timing gives a S ms pause before going onto the next strip.
The voltmeter V is wired to an input stage 14 on the unit 13 for transmitting a message TAD
to said stage where said message comprises the digital value of the measured voltage and the address of the receiver strip where this measurement was taken~
A further connection permi~s transmission of a signal FC representing the end of analog-to-digital conversion.
The control stage 12 is also wired to the voltme-ter ~ ~or sending it a conversion control signal CC~
Lastly, the exploring stage 8 is controlled by the stage 12 which sends it an exploration timing signal EX~ and the switch 5 is, via -the line 7, controlled by the same s-tage 12 which sends it a signal INV.
The calculating unit 13 further comprises an encoding stage 15 wired to a display unit 16 indicating the measured coordinates X and ~.
A description will now be given, notably in re~erence to ~igure 5, o~ how the overall device works and of the measurement method. On the diagram in ~igure 5, the measurement sequence runs ~rom the top to the bottom.
Initially, the exploring stage 8 successively sweeps the receiver strips at a rate o~ 5 ms per strip and in the absence of the object 9, measures a æero potential each time or, to be more exact, a potential below a predetermined threshold S
Once the object has touched the surface l, a potential higher than the threshold S is detected, causing thus the emission o~ a signal D toward the calculating unit 13. The receiver strip where the detection occurred is stored as a number to give the ordinate Y. The control stage 12 then sends the order INV to invert the polarity across the emitter strips, ~ollowed by a voltage measurement and digital conversion order CC. When the conversion has been completed, the stage 8 emits an order FC
which causes storage ST o~ the converted measurement u.
B~ means o~ a new order INV, the polarity ]o on the emitter strips is reversed and a new measurement u' is taken and stored.
This process is repeated ~ive *imes. The ~irst measurement against each polarity is then eliminated, to avoid any -trans:ient phenomena. Lastly, the averages of the u ancl u' rneasurements are calculated to deduce the abscissa X by means of the formula given earlier.
The results are final:Ly indicated on the display device 16.
The calculation process is halLed and the stage 8 resumes sweeping only once the detected receiver strip potential has dropped back below the threshold S, namely when the object 9 is no longer in contact with the surface.
All the ~oregoing applies to the case of the generator 6 delivering a steady voltage.
~s a variant, an alternating voltage generator may be used with a frequency of 1 k~z.
Under these circumtances, an active band-pass filter 17 corresponding to the lk~Iz band is positioned between the exploring stage 8 and the voltmeter V
followed by an active rectifier 18 which delivers a steady voltage to the voltmeter input.
The measuring method is virtually the same, save that ~ive successive measurements are taken with the generator on one side and the ground on the other, and then five more after having inverted the generator and the ground.
The advantage of using alternating current is that, as a result of the filtering, the 50 or 60 Hz components induced by the surroudings are eliminated, as are any possible interference e~fects brought about by thyristors in the vicinity.
In all events, the invention by indicating æ
with the finger makes it possible to define the coordinates of any point on a fixed or moving image projected onto the surface l, and to repeat this op~eration at close intervals in time. The accuracy achieved is excellent and depends on the surface area of the contac-t object used, e.g. the finger. The apparatusis also most reliable since if some dirt were to ~all on the surface, then the short-circuit it would cause would appear as coordinates in the absence of the object and thus reveal it immediatelyO
The invention further provides for -the predetermining of the abscissa coordinates of contact zones by arranging the widened parts on the strips (figure 6), for -the purposes of a conversational use upon display. By way of an example, widened sections 21 can be positioned on the emitter strips E for defining keys corresponding to alphanumeric values.
In another configuration, the emitter strip can be split into E' and E" on either side of the receiver s-trip R' and comprise widened sections 22' and 22".
Of course, the invention is not restric-ted to the examples described but covers numerous variants accessible to specialists in the field, The strips could take forms varied in terms of the application such as, for instance, a greater density there on the screen whose finer resolution is needed, or instead of being rectilinear have a sinusoidal or castellated form, or be circular and concentric for certain and radial for -the others and thereby define a point in polar coordinates.
Likewise, the strips could consist oE
3S deposits other than tin oxide, for e~ample, indium or cadmium oxide or other mix-tures of various metal o~ides, be doped with dopants other than ~luorine, for example antiMony and be deposited by vapour phase or cathode projection.
They could, moreover, be deposited with no difficulty in thicker layers that are more resistant to abrasion than in the afore-described example offering thus a very wide surface resistance range dropping for instance down to lOsa ~or a strip section equal in length to its width.
These strips could have different widths and spacing than those mentioned, possible only providing they can be easily connected electrically via the finger or any other conducting instrument such as, for example, the tip of a conducting rubber rod or a stylus with flexible metal conducting strands having dimensions suitably matched with the width and spacing of the emitter and receiver stripsO
Furthermore, for the purpose of easing the keyboard-to-electronic circuitry connections, all the receiver Rl to R4 and emitter El to E5 strip connections could be routed to one and the same side of the screen.
Additionally, the strips 3 and 4 could be done away with, in which case the necessary connections would be ensured by a strip of rubber, of the Zebra type for example, composed in a known fashion with alternate conducting and resistant bands whose pitch would be chosen to match the connection with the netwoxk of emitter (El to E5) and receiver (Rl to R4) strips on the one hand and on -the other hand with a flexible printed circui-t linking through to the detection system. This rubber element would be secured in a ,~,f,~
suitable manner between the screen plate and the flexible printed circuit.
Moreover, the strip support can be composed, as described in the example, directly ~y the front Eace of a cathode ray tube and also the front face of any other type of display tube such as plasma, LED or liquid crystal display systems ; the support can also constitute a screen that is placed in front of another screen like those mentioned above or in front of a map (street, or town map etc.).
In the latter cases, this support can be made of glass but also any other insulating transparent mineral or organic substance, a hard plastic such as perspex or soft plastic such as shee-t polycarbonate providing the surfaces are treated in such a way that conducting strips having the same t:ansparency, hard-wearing and electrical resistance characteristics can be laid in place.
c) the insulated strips in which there has ~een a variation in potential is determined whence one of the contact point coordinates is deduced ;
d) this variation in potential is measured in order to deduce the other contact poin-t coordinate.
The object is not electrically active. It merely needs to be sufficient:ly conductive to make a connection between two neighbouring strips, one emitter and one receiver. This object may then be an operator's finger. This technique therefore does away with any electronic infrastructure associated with the object.
Furthermore, this obviates any division of the surface into a criss-cross of keys set-out in a fixed pattern thus making it possible to obtain excellent point position definition by varying the width and the pitch of the strips, on a basis compatible with the object-sur~ace contact area dimensions.
In a preferred embodiment of the method, the potential of the receiver strips can be cyclically explored until a potential in one c,f these strips different from that in the other strips is detected, whereupon the exploration is halted in order to measure this potential.
By way of this configuration, just one measurement apparatus proves necessary.
In a first embodiment variant of the method, a known potertial is fed into one end of each emitter strip, the other end of each strip being connected to ground.
Onc:e the potential has been measured, the emitter strip polarity is reversed in order to take a furt:her measurement, and this cycle is repeated a certain number o~ times.
These operations make it possible to eliminate certain unknown constant factors, such as the object's resistanc.e,or certain possibly variable ~act6rs, such as the supply voltage.
In a second embodiment variant of the method, an alternating potential wi-th a ~requency o~ approximately l kH~ is ~ed into one end of each emitter strip with the other end of each strip connected down to ground and the measured voltage is filtered.
This there~ore eliminates any parasite voltages induced by the surroundings, notably at the mains frequency o~ 50 or 60 Khz.
As be-ore~ the potenti21 is successively mea~ured a cer-tain num~er of times, the alternating potential and ground reversed and then thesame number o~ measurements taken again.
In every event, an average value is calculated over the potentials measured during -the successive readings to minimize any possible ~ortuitous errors.
Lastly, the exploration is resumed once all the emitterstrips have reverted to the same potential.
In a further aspect of the invention, the device for determining the coordinates o~ a point on a surface comprising a certain nurnber of conductive strips (El to E5 ~ Rl to R4) to form separate zones selectively sensitive to the contact of an object is characterized in that it comprises, on the surEace, a certain number of resistant conducting emitter strips each having one end terminal for the ground connection and one end terminal for the voltage generator connection, ar~a certain nurnber of conducting receiver strips interlaid between the emitter strips s~lch that a conducting receiver strip 11PS between two resistant emitter strips where each of these conducting receiver strips has an end terminal fol- a connection in parallel with/a potential measuriny apparatus and offers a virtually constant linear resistance over its whole length.
Other peculiarities and advantages of the invention will be apparent from-.the following more particular description, as illustrated in the accompanying drawings, given as non e~haustive examples in which :
- figure 1 gives a semi~schematic front view o the strip configuration on the surfaee, as in this invention ;
~ figure 2 gives a partial view of figure 1 e~plaining how the potential is electrically measured ;
- figure 3 gives a view in perspective illustrating how the device is used, as in this invention ;
- figure 4 schematizes the overall device ;
- figure 5 gives a temporal function flow-chart of the measurement processing system ; and - figure 6 depicts embodiment variations of the conducting strips.
With reference to figure 1, the device comprises a transparent surface 1, made of sodio~calcic glass for instance, which forms a eathode display screen. Arranged on this surface are a certain number of parallel emitter strips El to E5,eOg.in thin oxide SnO2 doped with fluor.ine deposited by pyrolysis. These strips are conductive and have a t:hiekness such that the resistanee of strip section equal in lenght to its width is in the order o~ 100 to 200SL.
The strip ends 10 are neutralized by an edging 2 of the surface and serve as electrical connections with the collecting strips 3, 4.
These strips can be made up o~ a metal deposit that is conductive and/or can be soldered in silver or nickel deposited for example in the form o~ a conductive paint, resin or enamel by serigraphy.
~eceiver strips Rl to R4 are interlaid between the emitter strips E~ to E5 end are formed in appreciably the same fashlon and each comprise one neutraLized end constituting the connection terminal 11.
To clarily matters, the strip neutralized parts and the collecting strips have been shaded in.
In the example described, each strip is 3.5 mm wide and the distance from one strip to the next is also 3.5 mm. The presence of these strips has practically no effect on the visibility throughthe transparent surface 1.
The collecting strips 3, 4 are wired to a switch 5 which either connects the strip 3 to a voltage generator 6 and the strip 4 to ground M (~igure 1), or, inversely, connects the strip 3 to ground and the strip 4 to the generator 6.
This switch is activated by a control mechanism 7 which will be covered in more detail later.
The receiver strips Rl to R4 are wired to an exploring stage 8 which successively connects those strips to a voltmeter V.
Utilization of the apparatus whose principle has just been described consists of determining the coordinates ~ and Y of a point on the s~lrface that is ma-texialized by the contact o~ a conducting object 9 (figure l) such as an operator's finger 9a tfigure 3). The object's dimensions must be such that it covers two adjacent strips eg E2 and R2 (figure l), setting up an eLectrical bri~ge P between said two strips.
In the example shown in ~igure l, the receiver strip R2, by contact with the object, is set at a certain potential detected by the voltmeter V,and it is supposed that the ordinate Y
is given by the strip order number.
The abscissa X is calculated from the sketch in ~igure 2, on which it has been as~umed that the voltage generator is a generator 6a delivering a steady voltage U, o~ around 15 volts.
If L is the useful lenght of a receiver strip, then as a result of the high internal resistance in the voltmeter V:
X = u L, U
where u is the voltage measured by the voltmeter If the operation is repeated by inverting the generator 6a and the ground M, then a new voltage u' is measured, giving thus :
L - X = u' L
whence :
X = u.L
u+u' It will be observed that this method renders the measurement independent of the supply voltage U accidental variations in which might adversely affect the measurement, and independent of the resistance value of the contact bridge established by the conduc-ting object 9 providing -this resistance is decidely lower than the voltm~ter internal res:istance to avoicl disturbing the measurement. In one embodiment example, a vol~meter with an internal resistance of 2 ~ ~ has been chosen in the knowledge of the fac-t the rasistance of the operator's ~inger measured at an~applied vol-tage o~ -frequency l ~Iz S is around 500 k3~. It can thus be been that conducting object 9 over a very wide resistance range may be used, from very low values upto values in the order of 1 MSL providing a voltmeter with a suitable internal impedance i9 chosen, i.e. with a much higher impedanceO
A description will now be given, with reference to figure 4, of the electronics surrounding the device and the method description completed.
In this drawing, the strips have been shown in greater numbers than in figure l, but this number is essentially variable in terms of the surface dimensions. Those elements already described have been reshown with the same reference numbers. These elements are for the most part the supply inverting switch 5~ the generator 6, the exploring stage 8 and the voltmeter V which is of the digital type.
A control stage 12 of a calculating unit 13 is wired to the e~ploring stage 8 to ~5 control the receiver strip time-related exploration.
In the example described, the timing gives a S ms pause before going onto the next strip.
The voltmeter V is wired to an input stage 14 on the unit 13 for transmitting a message TAD
to said stage where said message comprises the digital value of the measured voltage and the address of the receiver strip where this measurement was taken~
A further connection permi~s transmission of a signal FC representing the end of analog-to-digital conversion.
The control stage 12 is also wired to the voltme-ter ~ ~or sending it a conversion control signal CC~
Lastly, the exploring stage 8 is controlled by the stage 12 which sends it an exploration timing signal EX~ and the switch 5 is, via -the line 7, controlled by the same s-tage 12 which sends it a signal INV.
The calculating unit 13 further comprises an encoding stage 15 wired to a display unit 16 indicating the measured coordinates X and ~.
A description will now be given, notably in re~erence to ~igure 5, o~ how the overall device works and of the measurement method. On the diagram in ~igure 5, the measurement sequence runs ~rom the top to the bottom.
Initially, the exploring stage 8 successively sweeps the receiver strips at a rate o~ 5 ms per strip and in the absence of the object 9, measures a æero potential each time or, to be more exact, a potential below a predetermined threshold S
Once the object has touched the surface l, a potential higher than the threshold S is detected, causing thus the emission o~ a signal D toward the calculating unit 13. The receiver strip where the detection occurred is stored as a number to give the ordinate Y. The control stage 12 then sends the order INV to invert the polarity across the emitter strips, ~ollowed by a voltage measurement and digital conversion order CC. When the conversion has been completed, the stage 8 emits an order FC
which causes storage ST o~ the converted measurement u.
B~ means o~ a new order INV, the polarity ]o on the emitter strips is reversed and a new measurement u' is taken and stored.
This process is repeated ~ive *imes. The ~irst measurement against each polarity is then eliminated, to avoid any -trans:ient phenomena. Lastly, the averages of the u ancl u' rneasurements are calculated to deduce the abscissa X by means of the formula given earlier.
The results are final:Ly indicated on the display device 16.
The calculation process is halLed and the stage 8 resumes sweeping only once the detected receiver strip potential has dropped back below the threshold S, namely when the object 9 is no longer in contact with the surface.
All the ~oregoing applies to the case of the generator 6 delivering a steady voltage.
~s a variant, an alternating voltage generator may be used with a frequency of 1 k~z.
Under these circumtances, an active band-pass filter 17 corresponding to the lk~Iz band is positioned between the exploring stage 8 and the voltmeter V
followed by an active rectifier 18 which delivers a steady voltage to the voltmeter input.
The measuring method is virtually the same, save that ~ive successive measurements are taken with the generator on one side and the ground on the other, and then five more after having inverted the generator and the ground.
The advantage of using alternating current is that, as a result of the filtering, the 50 or 60 Hz components induced by the surroudings are eliminated, as are any possible interference e~fects brought about by thyristors in the vicinity.
In all events, the invention by indicating æ
with the finger makes it possible to define the coordinates of any point on a fixed or moving image projected onto the surface l, and to repeat this op~eration at close intervals in time. The accuracy achieved is excellent and depends on the surface area of the contac-t object used, e.g. the finger. The apparatusis also most reliable since if some dirt were to ~all on the surface, then the short-circuit it would cause would appear as coordinates in the absence of the object and thus reveal it immediatelyO
The invention further provides for -the predetermining of the abscissa coordinates of contact zones by arranging the widened parts on the strips (figure 6), for -the purposes of a conversational use upon display. By way of an example, widened sections 21 can be positioned on the emitter strips E for defining keys corresponding to alphanumeric values.
In another configuration, the emitter strip can be split into E' and E" on either side of the receiver s-trip R' and comprise widened sections 22' and 22".
Of course, the invention is not restric-ted to the examples described but covers numerous variants accessible to specialists in the field, The strips could take forms varied in terms of the application such as, for instance, a greater density there on the screen whose finer resolution is needed, or instead of being rectilinear have a sinusoidal or castellated form, or be circular and concentric for certain and radial for -the others and thereby define a point in polar coordinates.
Likewise, the strips could consist oE
3S deposits other than tin oxide, for e~ample, indium or cadmium oxide or other mix-tures of various metal o~ides, be doped with dopants other than ~luorine, for example antiMony and be deposited by vapour phase or cathode projection.
They could, moreover, be deposited with no difficulty in thicker layers that are more resistant to abrasion than in the afore-described example offering thus a very wide surface resistance range dropping for instance down to lOsa ~or a strip section equal in length to its width.
These strips could have different widths and spacing than those mentioned, possible only providing they can be easily connected electrically via the finger or any other conducting instrument such as, for example, the tip of a conducting rubber rod or a stylus with flexible metal conducting strands having dimensions suitably matched with the width and spacing of the emitter and receiver stripsO
Furthermore, for the purpose of easing the keyboard-to-electronic circuitry connections, all the receiver Rl to R4 and emitter El to E5 strip connections could be routed to one and the same side of the screen.
Additionally, the strips 3 and 4 could be done away with, in which case the necessary connections would be ensured by a strip of rubber, of the Zebra type for example, composed in a known fashion with alternate conducting and resistant bands whose pitch would be chosen to match the connection with the netwoxk of emitter (El to E5) and receiver (Rl to R4) strips on the one hand and on -the other hand with a flexible printed circui-t linking through to the detection system. This rubber element would be secured in a ,~,f,~
suitable manner between the screen plate and the flexible printed circuit.
Moreover, the strip support can be composed, as described in the example, directly ~y the front Eace of a cathode ray tube and also the front face of any other type of display tube such as plasma, LED or liquid crystal display systems ; the support can also constitute a screen that is placed in front of another screen like those mentioned above or in front of a map (street, or town map etc.).
In the latter cases, this support can be made of glass but also any other insulating transparent mineral or organic substance, a hard plastic such as perspex or soft plastic such as shee-t polycarbonate providing the surfaces are treated in such a way that conducting strips having the same t:ansparency, hard-wearing and electrical resistance characteristics can be laid in place.
Claims (17)
1. A method for determining the coordinates (X,Y) of a point on a surface comprising a certain number of conducting strips by pin-pointing it through contact of an object with the surface, wherein the following operations are performed :
a) a certain number of resistant conducting emitter strips are laid on the surface parallel-mounted with the terminals of a voltage generator, as are a certain number of insulated conducting receiver strips interlaid between the foregoing such that a conducting receiver strip lies between two resistant emitter strips ;
b) the surface is touched with a sufficiently conducting object having dimensions such that it establishes an electrical bridge between one resistant conducting emitter strip and a conducting receiver strip ;
c) the insulated strips in which there has been a variation in potential is determined whence one of the contact point coordinates (Y) is deduced, and d) this variation in potential is measured in order to deduce the other contact point coordinate (X).
a) a certain number of resistant conducting emitter strips are laid on the surface parallel-mounted with the terminals of a voltage generator, as are a certain number of insulated conducting receiver strips interlaid between the foregoing such that a conducting receiver strip lies between two resistant emitter strips ;
b) the surface is touched with a sufficiently conducting object having dimensions such that it establishes an electrical bridge between one resistant conducting emitter strip and a conducting receiver strip ;
c) the insulated strips in which there has been a variation in potential is determined whence one of the contact point coordinates (Y) is deduced, and d) this variation in potential is measured in order to deduce the other contact point coordinate (X).
2. A method as claimed in claim 1, wherein the potential of the receiver strips is cyclically explored until a potential in one of these strips different from that in the other strips is detected, whereupon the exploration is halted in order to measure this potential.
3. A method as claimed in claim 2, wherein a known potential is applied to one end of each emitter strip, the other end of each strip being connected to ground.
4. A method as claimed in claim 3, wherein after measuring the potential, the polarity of the emitter strips is reversed to take a further measurement, and this cycle is repeated a certain number of times.
5. A method as claimed in claim 2, wherein an alternating potential of around 1 kHz is fed into one end of each emitter strip, the other end of each strip being connected down to ground and the measured voltage is filtered.
6. A method as claimed in claim 5, wherein the potential is successively measured a certain number of times, the alternating potential and ground in-verted and then the same number of measurements taken again.
7. A method as claimed in any one of claim 2, 3 or 4, wherein an average value of the potentials measured during the successive readings is calculated.
8. A method as claimed in any one of claim 2, 3 or 4, wherein the exploration is resumed once all the emitter strips have dropped to a potential below a threshold level.
9. A device for determining the coordinates (X,Y) of a point on a surface comprising a certain number of conducting strips to form separate zones selec-tively sensitive to the contact of an object, wherein it comprises:
a certain number of resistant conducting emitter strips each having one end terminal for the ground connection and one end terminal for the voltage gene-rator connection, and a certain number of conducting receiver strips interlaid between the emit-ter strips such that a conducting receiver strip lies between two resistant emitter strips where each of these conducting receiver strips has one end termi-nal for a connection in parallel with a potential measuring apparatus and offers a virtually constant linear resistance over its whole length.
a certain number of resistant conducting emitter strips each having one end terminal for the ground connection and one end terminal for the voltage gene-rator connection, and a certain number of conducting receiver strips interlaid between the emit-ter strips such that a conducting receiver strip lies between two resistant emitter strips where each of these conducting receiver strips has one end termi-nal for a connection in parallel with a potential measuring apparatus and offers a virtually constant linear resistance over its whole length.
10. A device as claimed in claim 9, wherein the emitter and receiver strips are rectilinear, parallel and evenly spaced.
11. A device as claim in claim 9, wherein it comprises an exploring stage for successively switching the receiver strips with the potential measuring apparatus.
12. A device as claimed in claim 11, wherein it comprises a calculating unit wired to the exploring stage and potential measuring apparatus in order to calculate the coordinates of the object's point of contact with the surface, based on the number of the receiver strip upped in potential to a value greater than a predetermined threshold and the value of this potential.
13. A device as claimed in claim 12, wherein it comprises a steady volt-age generator wired in parallel to one of the terminals on each emitter strip.
14. A device as claimed in claim 12, wherein it comprises an alternating voltage generator wired in parallel to one of the terminals on each emitter strip.
15. A device as claimed in claim 14, wherein it comprises a filtering stage and a rectifying stage inserted between the exploring stage and the potential measuring apparatus.
16. A device as claimed in one of claim 9, 10 or 11, wherein it comprises an inverting stage wired to the calculating unit for inverting the ground con-nection and the voltage generator connection on the emitter strips.
17. A device as claimed in one of claim 1, 2 or 9, wherein the surface is a display screen.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8201234A FR2520498A1 (en) | 1982-01-27 | 1982-01-27 | METHOD FOR DETERMINING THE COORDINATES OF A POINT ON A SURFACE AND DEVICE FOR IMPLEMENTING IT |
| FR8201234 | 1982-01-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194582A true CA1194582A (en) | 1985-10-01 |
Family
ID=9270354
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000420328A Expired CA1194582A (en) | 1982-01-27 | 1983-01-26 | Method and apparatus for determining the coordinates of a point on a surface |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4571577A (en) |
| EP (1) | EP0085012B1 (en) |
| JP (1) | JPS58149534A (en) |
| AT (1) | ATE21545T1 (en) |
| CA (1) | CA1194582A (en) |
| DE (2) | DE85012T1 (en) |
| DK (1) | DK30683A (en) |
| ES (2) | ES8403612A1 (en) |
| FR (1) | FR2520498A1 (en) |
| HK (1) | HK47787A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4620062A (en) * | 1983-10-11 | 1986-10-28 | Rdi Limited Partnership | Device for forming signals which are characteristic of the position of a point determined on a surface |
| EP0145651A3 (en) * | 1983-10-12 | 1985-07-10 | Battelle Memorial Institute | Device for forming signals characteristic of the position of a predetermined point on a surface |
| EP0147300B1 (en) * | 1983-12-26 | 1988-06-08 | Regie Nationale Des Usines Renault | Process and apparatus for the determination of the coordinates of a contact point on a semi-analog sensitive surface |
| DE3443133C1 (en) * | 1984-11-27 | 1986-02-27 | Dr. Johannes Heidenhain Gmbh, 8225 Traunreut | Measuring arrangement |
| FR2593302B1 (en) * | 1986-01-22 | 1989-07-13 | Boussois Sa | TOUCH SCREEN FOR DETERMINING COORDINATES OF A POINT ON A SURFACE |
| JPS62298820A (en) * | 1986-06-18 | 1987-12-25 | Omron Tateisi Electronics Co | Coordinate input device |
| DE69032091T2 (en) * | 1989-12-28 | 1998-08-20 | Gunze Kk | Input system with touch-sensitive resistance film board |
| EP1469378A1 (en) * | 2003-04-16 | 2004-10-20 | IEE INTERNATIONAL ELECTRONICS & ENGINEERING S.A. | Position detection apparatus |
| EP1818767A1 (en) * | 2006-02-13 | 2007-08-15 | IEE INTERNATIONAL ELECTRONICS & ENGINEERING S.A. | Data input device with encoding of activation direction |
Family Cites Families (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2551942A (en) * | 1947-11-29 | 1951-05-08 | Greene Thomas | Apparatus for locating faults in electric circuits |
| US3234459A (en) * | 1959-01-02 | 1966-02-08 | Whitney Blake Co | Method and apparatus for locating faults in electrical cable lines by comparing the impedance of the entire faulted line to the impedance of a section of the line |
| US3248646A (en) * | 1962-07-19 | 1966-04-26 | Whitney Blake Co | Location of cable faults by comparing a section of the faulted cable with a part of the section |
| US3134099A (en) * | 1962-12-21 | 1964-05-19 | Ibm | Ultrasonic data converter |
| US3399401A (en) * | 1964-06-29 | 1968-08-27 | Army Usa | Digital computer and graphic input system |
| US3365661A (en) * | 1965-04-26 | 1968-01-23 | Anaconda Wire & Cable Co | Method and apparatus for locating leaks in a cable by determining the distance to a short circuit in the cable |
| US3361454A (en) * | 1966-08-11 | 1968-01-02 | Smith Blair Inc | Penstock coupling |
| US3522664A (en) * | 1967-11-20 | 1970-08-04 | Westinghouse Electric Corp | Interface device and display system |
| CA861701A (en) * | 1969-06-13 | 1971-01-19 | M. Hlady Alvin | Touch-sensitive position encoder |
| US3671716A (en) * | 1970-08-24 | 1972-06-20 | Arthur Samuel Slutsky | Method and apparatus of digitizing analog records |
| US3673327A (en) * | 1970-11-02 | 1972-06-27 | Atomic Energy Commission | Touch actuable data input panel assembly |
| US3696409A (en) * | 1970-12-28 | 1972-10-03 | Linquist & Vennum | Finger-touch faceplate |
| US3732557A (en) * | 1971-05-03 | 1973-05-08 | Evans & Sutherland Computer Co | Incremental position-indicating system |
| US3760360A (en) * | 1971-11-01 | 1973-09-18 | E Systems Inc | Matrix switch |
| US3806912A (en) * | 1972-06-13 | 1974-04-23 | Burroughs Corp | Graphical input board |
| GB1541566A (en) * | 1976-05-17 | 1979-03-07 | Secr Defence | Data entry device |
| US4124838A (en) * | 1976-12-29 | 1978-11-07 | Science Accessories Corporation | Apparatus for position determination |
| GB1597374A (en) * | 1977-03-09 | 1981-09-09 | Nat Res Dev | Graphical input apparatus for electrical equipment |
| JPS5633777A (en) * | 1979-08-27 | 1981-04-04 | Oki Electric Ind Co Ltd | Pattern input device |
-
1982
- 1982-01-27 FR FR8201234A patent/FR2520498A1/en active Granted
-
1983
- 1983-01-25 US US06/460,902 patent/US4571577A/en not_active Expired - Fee Related
- 1983-01-26 EP EP83400173A patent/EP0085012B1/en not_active Expired
- 1983-01-26 DK DK30683A patent/DK30683A/en not_active Application Discontinuation
- 1983-01-26 DE DE198383400173T patent/DE85012T1/en active Pending
- 1983-01-26 ES ES519269A patent/ES8403612A1/en not_active Expired
- 1983-01-26 JP JP58010021A patent/JPS58149534A/en active Pending
- 1983-01-26 CA CA000420328A patent/CA1194582A/en not_active Expired
- 1983-01-26 AT AT83400173T patent/ATE21545T1/en not_active IP Right Cessation
- 1983-01-26 DE DE8383400173T patent/DE3365371D1/en not_active Expired
- 1983-12-12 ES ES527953A patent/ES527953A0/en active Granted
-
1987
- 1987-06-18 HK HK477/87A patent/HK47787A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| ATE21545T1 (en) | 1986-09-15 |
| ES519269A0 (en) | 1984-03-16 |
| ES8406718A1 (en) | 1984-08-01 |
| DE85012T1 (en) | 1983-11-10 |
| FR2520498A1 (en) | 1983-07-29 |
| EP0085012A3 (en) | 1984-02-08 |
| US4571577A (en) | 1986-02-18 |
| FR2520498B1 (en) | 1984-12-28 |
| JPS58149534A (en) | 1983-09-05 |
| EP0085012A2 (en) | 1983-08-03 |
| ES527953A0 (en) | 1984-08-01 |
| DE3365371D1 (en) | 1986-09-25 |
| DK30683A (en) | 1983-07-28 |
| EP0085012B1 (en) | 1986-08-20 |
| DK30683D0 (en) | 1983-01-26 |
| ES8403612A1 (en) | 1984-03-16 |
| HK47787A (en) | 1987-06-26 |
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