Position responsive apparatus, system and method having electrographic application

• US 4,678,869 A
• Filed: 05/27/1986
• Issued: 07/07/1987
• Est. Priority Date: 10/25/1985
• Status: Expired due to Term

• Current Assignee: Frances B. Cuniberti, Scriptel Corporation, Walter T. Krumm
• Original Assignee: Scriptel Corporation
• Inventors: Kable, Robert G.
• Primary Examiner(s): Schreyer, Stafford D.
• Application Number:
  US06/865,661
• Time in Patent Office: 406 Days
• Field of Search: 178/18, 178/19, 364/571, 364/520, 340/36.5 C
• US Class Current: 178/18.05
• CPC Class Codes: G06F 2203/04113 Peripheral electrode pattern in resistive digitisers, i.e. electrodes at the periphery of the resistive sheet are shaped in patterns enhancing linearity of induced field
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A position responsive apparatus, system and method which employs a position responsive surface formed of two orthogonally disposed arrays of grid elements which in one embodiment, the elements are coupled along one border with a resistor chain or the equivalent which is excited with an a.c. source at terminal locations. Capacitive coupling between the orthogonally disposed arrays at the cross-over locations of grid elements is significantly reduced by reducing the area of the grid elements at the cross-over positions. Further, intermediate grounding terminals serve to minimize disruptive potentials caused by the capacitive coupling. The control for the system employs a procedure wherein a correction look-up table is developed as part of the manufacture of the apparatus wherein readings are taken at the nodal points of communication between the grid array and the resistor chain and which then are treated to provide a regularly incremented sequence of address values developed from a signal domain computation. Physical domain coordinate values are correspondingly derived and are located in the table with each address value. The control for the embodiment accesses this memory for purpose of developing corrected coordinate outputs, thus eliminating the need for precise calibration of each resistor within the resistor chain. The invention further contemplates the employment of transparent grid array elements. Significant improvements to performance are achieved by exciting these elements from resistor chains located and coupled therewith at oppositely disposed ends of the grid elements. An improved switching approach is provided wherein excitation currents are employed at the switching stage which then are applied to voltage follower stages for coupling with the grid array terminal.

Claims

1. Position responsive apparatus comprising:

an insulative support;

a first array of elongate, thin parallel mutually spaced grid elements located from first to last upon said support,

a second array of elongate, thin parallel mutually spaced grid elements located from first to last upon said support, spaced from said first array of grid elements and angularly oriented with respect thereto;

first resistor means coupled with adjacently disposed grid elements of said first array for providing discrete resistances therebetween;

first terminal means coupled with said first resistor means adjacent said first and last grid elements;

second resistor means coupled with adjacently disposed grid elements of said second array for providing discrete resistances therebetween;

second terminal means coupled with said second resistor means adjacent said first and last grid elements;

a time varying excitation source of select frequency;

switching means controllable for selectively applying an excitation signal corresponding to said source to said first terminal means during a first operational mode and for selectively applying an excitation signal corresponding to said source to said second terminal means during a second operational mode;

locator means movable in adjacency about said support for select interaction with said first and second arrays of said grid elements during said first and second modes to effect the derivation of position signals;

detector circuit means responsive to said position signals for deriving digital position signals;

memory means addressable for providing computed correction values corresponding with the values of said discrete resistances of said first and second resistor means; and

control means for controlling said switching means, responsive to said digital position signal for addressing said memory means to acquire corresponding said correction values and for deriving coordinate pair output signals with respect thereto.

2. The position responsive apparatus of claim 1 in which said switching means is controllable to apply an electrical ground to said second terminal means during said first operational mode to establish a ground plane and to apply an electrical ground to said first terminal means during said second operational mode to establish a ground plane.

3. The position responsive apparatus of claim 1 in which said switching means comprises:

converter means responsive to said source of select frequency for deriving an a.c. current signal therefrom;

solid-state switch means controllable from said control means to provide open and closed conditions and responsive to said a.c. current signal to effect conveyance thereof at an output when in said closed condition;

voltage follower means having input terminals coupled with said solid-state switch means output and with ground and having follower means outputs coupled with said first and second terminal means for convertnig said a.c. current signal from said outputs as a said excitation signal in response to a said solid-state switch means closed condition and for deriving a said ground at said follower means outputs in response to a said solid-state switch means open condition.

4. The position responsive apparatus of claim 3 in which said switching means voltage follower means comprises first and second operational amplifier stages coupled with said first terminal means and third and fourth operational amplifier stages coupled with said second terminal means;

said first, second, third, and fourth operational amplifier stages having respective feedback paths incorporating resistor components of select, mutually matched resistance value.

5. The position responsive apparatus of claim 1 in which said memory means computed correction values are provided as physical domain values corresponding with positional outputs of a signal domain established with respect to each said first and second resistor means discrete resistance derived in a physical domain at said adjacently disposed grid elements, adjusted to correspond with a regularly incremented sequence of addressable values within said signal domain.

6. The position responsive apparatus of claim 5 in which said control means is responsive to said digital position signals for deriving said addressable values therefrom, for accessing said memory means at said addressable values to acquire said correction values and for deriving said coordinate pair output signals by interpolative weighting of said acquired correction values.

7. In a system wherein a position responsive surface is selectively accessed to develop electrical signals which are treated to provide outputs corresponding with the accessed position and wherein said surface is configured having an insulative support, a first array of elongate, thin parallel mutually spaced grid elements located from first to last upon said support a second array of elongate, thin parallel mutually spaced grid elements located from first to last upon said support spaced from said first array of grid elements and angularly oriented with respect thereto, first resistor means coupled at node positions with adjacently disposed grid elements of said first array for providing discrete resistances between said node positions, and second resistor means coupled at node positions with adjacently disposed grid elements of said second array for providing discrete resistances therebetween, the method of correcting the value of given said outputs, comprising:

providing a memory for retaining computed physical domain coordinate values derived from values corresponding with select outputs of a signal domain established for each said node position of said first and second resistor means, adjusted in correspondence with a regularly incremented sequence of address values within said signal domain;

deriving a said address value from a said given output;

accessing said memory at said address value to provide a computed physical domain coordinate value by interpolative weighting thereof in correspondence with said given output to derive a corrected said given output; and

outputting said corrected given output to provide coordinate information representing said accessed position at said surface.

8. The method of claim 7 in which said address value is derived from select high order bits of a digital signal generated as said given output.

9. The method of claim 8 in which said adjustment of the value of said accessed computed physical domain coordinate value by interpolative weighting is carried out with weighting factors derived from said given output and applied to said accessed computed physical domain coordinate value.

10. The method for generating a memory retained look-up table for use in interpolatively correcting the position outputs in a signal domain corresponding to accessed locations within the signal domain of a position responsive surface of a type including an insulative support, a first array of elongate, thin parallel mutually spaced grid elements located from first to last upon said support a second array of elongate, thin parallel mutually spaced grid elements located from first to last upon said support spaced from said first array of grid elements and angularly oriented with respect thereto, first resistor means coupled at node positionswith adjacently disposed grid elements of said first array for providing discrete resistances therebetween, and second resistor means coupled at node positions with adjacently disposed grid elements of said second array for providing discrete resistances therebetween, comprising the steps of:

collecting an input data set from said surface as signal domain outputs established by said discrete resisitances at the said physical domain node positions for said first and second resistor means;

determining the bounds of said input data set as maximum and minimum signal domain values for first and second coordinate directions corresponding, respectively, with said first and second resistor means;

deriving first and second sets of regularly incremented address locatable values extending between said maximum and minimum signal domain values corresponding, respectively, with said first and second coordinate directions;

deriving by linear interpolation the physical domain coordinate location value on said surface corresponding with said address locatable values for each said first and second coordinate directions; and

positioning said interpolated physical domain coordinate location values in said memory in combination with corresponding said signal domain address locatable values.

11. Position responsive apparatus, comprising:

an insulative support;

an x-coordinate array of elongate, transparent grid elements extending between first and second borders and located in mutually spaced parallel relationship from first to last upon said support means;

a y-coordinate array of elongate, transparent grid elements extending between third and fourth borders spaced from said x-coordinate array of grid elements and located in mutually spaced parallel relationship from first to last upon said support means;

first x-coordinate resistor means coupled at said first border with adjacently disposed grid elements of said x-coordinate array for providing discrete resistance therebetween;

second x-coordinate resistor means coupled at said second border with adjacently disposed grid elements of said x-coordinte grid array for providing discrete resistances therebetween;

x-coordinate terminal means coupled with said first and second x-coordinate resistor means adjacent said first and last grid elements for conveying excitation signals thereto;

first y-coordinate resistor means coupled at said third border with adjacently disposed grid elements of said y-coordinate array for providing discrete resistances therebetween;

second y-coordinate resistor means coupled at said fourth border with adjacently disposed grid elements of said y-coordinate grid array for providing discrete resistances therebetween;

y-coordinate terminal means coupled with said first and second y-coordinate resistor means adjacent said first and last grid elements for conveying said excitation signals thereto;

a time varying excitation source of select frequency;

switching means controllable for selectively applying an excitation signal corresponding to said source to said x-coordinate terminal means during a first operational mode and for selectively applying said excitation signal to said y-coordinate terminal means during a second operational mode;

locator means movable in adjacency about said support for select interaction with said x-coordinate and y-coordinate arrays of said grid elements during said first and second modes to effect the derivation of position signals;

detector circuit means responsive to said position signals for deriving digital position signals; and

control means for controlling said switching means and treating said digital position signals to derive coordinate pair output signals with respect thereto.

12. The position responsive apparatus of claim 11 in which said switching means is controllable to apply an electrical ground to said y-coordinate terminal means during said first operational mode to establish a ground plane with said y-coordinate array of grid elements and to apply an electrical ground to said x-coordinate terminal means during said second operational mode to establish a ground plane with said x-coordinate array of grid elements.

13. The position responsive apparatus of claim 11 in which said switching means comprises:

converter means responsive to said source of select frequency for deriving an a.c. current signal therefrom;

solid-state switch means controllable from said control means to provide open and closed conditions and responsive to said a.c. current signal to effect conveyance thereof to an output when in said closed condition; and

voltage follower means having input terminals coupled with said solid-state switch means output and with ground and having follower means outputs coupled with said x-coordinate and y-coordinate terminal means for converting said a.c. current signal from said outputs as a said excitation signal in response to a said solid-state switch means cloud condition and for deriving a said ground at said follower means outputs in response to a said solid-state switch means open condition.

14. The position responsive apparatus of claim 13 in which said switching means voltage follower means comprises first and second operational amplifier stages coupled with said x-coordinate terminal means third and fourth operational amplifier stage coupled with said y-coordinate terminal means said first, second, third and fourth operational amplifier stages having respective feedback paths incorporating resistor components of select, mutually matched resistance value.

15. The position responsive apparatus of claim 11 in which said x-coordinate array and y-coordinate array of said grid elements are provided as indium tin oxide strips.

16. The position responsive apparatus of claim 11 further including:

memory means for retaining computed physical domain coordinate values derived as values corresponding with select said digital position signals of a signal domain and established for each position within a predetermined grid array of pre-established positions of said physical domain, adjusted to establsh a regularly incremented sequence of address values within said signal domain; and

said control means is responsive to each given said digital position signal received thereby for deriving a said address value corresponding therewith, for accessing said memory means at said address value to retrieve computed physical domain coordinate values corresponding therewith and for adjusting the values of said computed physical domain coordinate values by select-dimensional interpolative weighting thereof in correspondence with said received digital position signal to derive corrected said coordinate pair output signals.

17. Position responsive apparatus comprising:

a first array of parallel, spaced grid elements arranged in a sequence from first to last and located for nearest operational adjacency with a locator accessible working surface for developing first coordinate position information;

a second array of parallel, spaced grid elements arranged in a sequence from first to last for developing second coordinate position information, spaced a predetermined distance from said first array and angularly disposed with respect thereto to establish cross-over locations of mutually spaced elements respectively within said first and second arrays;

insulative means intermediate said first and second arrays for effecting said spacing therebetween;

said grid elements within said first array having a first width within said cross-over locations and a second width outwardly thereof greater than said first width;

said grid elements within said second array having a third width within said cross-over locations and a fourth width outwardly thereof greater than said third width;

first resistor means coupled with adjacently disposed grid elements of said first array for providing discrete resistances therebetween;

second resistor means coupled with adjacently disposed grid elements of said second array for providing discrete resistances therebetween;

first terminal means coupled with said first resistor means in the vicinity of said first and last grid elements thereof;

second terminal means coupled with said second resistor means in the vicinity of said first and last grid elements thereof;

a time varying excitation source of select frequency;

switching means controllable for selectively applying an excitation signal corresponding to said source to said first terminal means during a first operational mode to establish a potential gradient along said first resistor means, and for selectively applying an excitation signal corresponding to said source to said second terminal means during a second operational mode; and

control means for controlling said switching means to derive said first and second operational modes.

18. The position responsive apparatus of claim 17 in which said fourth width is greater than said second width.

19. The position responsive apparatus of claim 17 in which said second width is about 0.59 inch and said fourth width is about 0.79 inch.

20. The position responsive apparatus of claim 17 including:

locator means movable in adjacency about said working surface for select interaction with said first and second arrays of said grid elements during said first and second modes to effect the derivation of position signals;

detector circuit means responsive to said position signals for deriving digital position signals;

memory means addressable for providing computed correction values corresponding with the values of said discrete resistances of said first and second resistor means; and

said control means is responsive to said digital position signal for addressing said memory means to acquire corresponding said correction values and for deriving coordinate pair output signals with respect thereto.

21. Position responsive apparatus comprising:

a first array of parallel, spaced grid elements arranged in a sequence from first to last and located for nearest operational adjacency with a locator accessible working surface for developing first coordinate position information;

a second array of parallel, spaced grid elements arranged in a sequence from first to last for developing second coordinate position information, spaced a predetermined distance from said first array and angularly disposed with respect thereto to establish cross-over locations of mutually spaced elements respectively within said first and second arrays;

insulative means intermediate said first and second arrays for effecting said spacing therebetween;

said grid elements within said first array having a first width in the vicinity of said cross-over locations and a second width outwardly thereof greater than said first width;

said grid elements within said second array having a third width in the vicinity of said cross-over locations and a fourth width outwardly thereof greater than said third width;

first resistor means coupled with adjacently disposed grid elements of said first array for providing discrete resistances therebetween;

second resistor means coupled with adjacently disposed grid elements of said second array for providing discrete resistances therebetween;

first terminal means coupled with said first resistor means in the vicinity of said first and last grid elements thereof;

second terminal means coupled with said second resistor means in the vicinity of said first and last grid elements thereof;

third terminal means coupled with said first resistor means at at least one position intermediate said first terminal means;

a time varying excitation source of select frequency;

switching means controllable for selectively applying an excitation signal corresponding to said source to said first terminal means during a first operational mode to establish a potential gradient along said first resistor means, and for selectively applying an excitation signal corresponding to said source to said second terminal means simultaneously connecting said first terminal means and said third terminal means with effective ground during a second operational mode; and

control means for controlling said switching means to derive said first and second operational modes.

22. The position responsive apparatus of claim 21 including:

fourth terminal means coupled with said second resistor means at at least one position intermediate said second terminal means; and

said switching means is controllable for connecting said second terminal means and said fourth terminal means with effective ground during said first operational mode.

23. The position responsive apparatus of claim 22 including:

fifth terminal means coupled with said first resistor means at a predetermined position intermediate said first terminal means; and

said switching means is controllable for applying an excitation signal to said fifth terminal means corresponding to said source and attenuated proportionately with respect to a select value of said potential gradient at said predetermined position during said first operational mode.

24. The position responsive apparatus of claim 23 including:

sixth terminal means coupled with said second resistor means at a predetermined position intermediate said second terminal means; and

said switching means is controllable for applying an excitation signal to said sixth terminal means corresponding to said source and attenuated proportionately with respect to a select value of said potential gradient at said predetermined position during said second operational mode.

25. Position responsive apparatus comprising:

a first array of parallel spaced grid elements arranged in a sequence from first to last and located for nearest operational adjacency with a locator accessible working surface for developing first coordinate position information;

a second array of parallel, spaced grid elements arranged in a sequence from first to last for developing second coordinate position information, spaced a predetermined distance from said first array and angularly disposed with respect thereto to establish cross-over locations of mutually spaced elements respectively within said first and second arrays;

insulative means intermediate said first and second arrays for effecting said spacing therebetween;

first resistor means coupled with adjacently disposed grid elements of said first array for providing discrete resistances therebetween;

second resistor means coupled with said adjacently disposed grid elements of said second array for providing discrete resistances therebetween;

first terminal means coupled with said first resistor means adjacent said first and last grid elements thereof;

second terminal means coupled with said second resistor means adjacent said first and last grid elements thereof;

third terminal means coupled with said first resistor means at at least one position intermediate said first terminal means;

fourth terminal means coupled with said second resistor means at at least one position intermediate said second terminal means;

a time varying excitation source of select frequency;

switching means controllable for selectively applying an excitation signal corresponding to said source across said first terminal means and for simultaneously coupling said second and fourth terminal means with ground during a first operational mode, and for applying an excitation signal corresponding to said source across said second terminal means and for simultaneously coupling said first and third terminal means with ground during a second operational mode; and

control means for controlling said switching means to derive said first and second operational modes.

26. The position responsive apparatus of claim 25 including:

locator means movable in adjacency about said working surface for select interaction with said first and second arrays of said grid elements during said first and second modes to effect the derivation of position signals;

detector circuit means responsive to said position signals for deriving digital position signals;

memory means addressable for providing computed correction values corresponding with the values of said discrete resistances of said first and second resistor means; and

said control means is responsive to said digital position signal for addressing said memory means to acquire corresponding said correction values and for deriving coordinate pair output signals with respect thereto.

27. Position responsive apparatus comprising:

a first array of parallel, spaced grid elements arranged in a sequence from first to last and located for nearest operational adjacency with a locator accessible working surface for developing first coordinate position information;

a second array of parallel, spaced grid elements arranged in a sequence from first to last for developing second coordinate position information, spaced a predetermined distance from said first array and angularly disposed with respect thereto to establish cross-over locations of mutually spaced elements respectively within said first and second arrays;

insulative means intermediate said first and second arrays for effecting said spacing therebetween;

first resistor means coupled with adjacently disposed grid elements of said first array for providing discrete resistances therebetween;

second resistor means coupled with adjacently disposed grid elements of said second array for providing discrete resistances therebetween;

first terminal means coupled with said first resistor means adjacent said first and last grid elements thereof;

second terminal means coupled with said second resistor means adjacent said first and last grid elements thereof;

third terminal means coupled with said first resistor means at a predetermined position intermediate said first terminal means;

fourth terminal means coupled with said second resistor means at a predetermined position intermediate said second terminal means;

a time varying excitation source of select frequency;

switching means controllable for selectively applying an excitation signal corresponding to said source to said first terminal means to establish a first potential gradient along said first resistor means and simultaneously applying an excitation signal to said third terminal means corresponding to said source and attenuated substantially proportionately with respect to a select value of said first potential gradient for said predetermined position during a first operational mode, and for appying an excitation signal corresponding to said source to said second terminal means to establish a second potential gradient along said second resistor means and simultaneously applying an excitation signal to said fourth terminal means corresponding to said source and attenuated substantially proportionately with respect to a select value of said second potential gradient for said predetermined position during a second operational mode; and

control means for controlling said switching means to derive said first and second operational modes.

28. The position responsive apparatus of claim 27 including:

locator means movable in adjacency about said working surface for select interaction with said first and second arrays of said grid elements during said first and second modes to effect the derivation of position signals;

detector circuit means responsive to said position signals for deriving digital position signals;

memory means addressable for providing computed correction values corresponding with the values of said discrete resistances of said first and second resistor means; and

said control means is responsive to said digital position signal for addressing said memory means to acquire corresponding said correction values and for deriving coordinate pair output signals with respect thereto.

29. In a system wherein a position responsive surface is selectively accessed to develop electrical signals which are treated to provide outputs corresponding with the accessed position and wherein said surface is configured having an insulative support, a first array of elongate, thin parallel mutually spaced grid elements located from first to last upon said support, a second aray of elongate, thin parallel mutually spaced grid elements located from first to last upon said support spaced from said first array of grid elements and angularly oriented with respect thereto to establish a plurality of grid element cross-over regions, first resistor means coupled at node positions from first to last with adjacently disposed grid elements of said first array for providing discrete resistances between said node positions, and second resistor means coupled at node positions from first to last with adjacently disposed grid elements of said second array for providing discrete resistances therebetween, the method of deriving given said outputs, comprising:

providing a time varying source of select frequency and an effective ground;

exciting said first array during a first operational mode by applying said source to said first resistor means adjacent said first node while simultaneously applying said ground to said first resistor means adjacent said last node and subsequently alternating said application of source and ground;

electrically coupling said second array to ground during said first operational mode by applying ground to said second resistor means adjacent said first and last nodes thereof and at at least one select location therebetween;

exciting said second array during a second operational mode by applying said source to said second resistor means adjacent said first node while simultaneously applying said ground to said second resistor means adjacent said last node and subsequently alternating said application of source and ground;

electrically coupling said first array to ground during said second operational mode by applying ground to said first resistor means adjacent said first and last nodes thereof and at at least one select location therebetween;

accessing said surface with a signal responsive locator during said first and second operational modes to develop said electrical signals; and

treating said electrical signals to provide coordinate information representing said accessed position at said surface.

30. The method of claim 29 wherein said step of treating said electrical signals comprises the steps of:

providing a memory for retaining computed physical domain coordinate values derived from values corresponding with select outputs of a signal domain established for each said node position of said first and second resistor means, adjusted in correspondence with a regularly incremented sequence of address values within said signal domain;

deriving a said address value from a said given output;

accessing said memory at said address value to provide a computed physical domain coordinate value by interpolative weighting thereof in correspondence with said given output to derive a corrected said given output; and

outputting said corrected given output to provide coordinate information representing said accessed position at said surface.

31. The method of claim 30 in which said address value is derived from select high order bits of a digital signal generated as said given output.