GRAPHICAL INPUT BOARD

• US 3,806,912 A
• Filed: 06/13/1972
• Issued: 04/23/1974
• Est. Priority Date: 06/13/1972
• Status: Expired due to Term

• Current Assignee: Unisys Corporation
• Original Assignee: Edward R. Eckert
• Inventors: Eckert, Edward R.
• Primary Examiner(s): Miller, Charles D.
• Application Number:
  US05/262,194
• Time in Patent Office: 679 Days
• Field of Search: 340/347AD,347P,347R 235/61.6A 33/1M,23J 178/18,19,20
• US Class Current: 341/5
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A graphical input board and related detection circuitry for determining, and generating both digital and analog outputs representing, the instantaneous coordinate position of a noncaptive stylus being moved upon the writing surface of the board. The smooth graphic input surface of the board comprises a printed circuit including a plurality of uniform parallel conductive and resistive paths, a resistive path lying between a pair of conductive paths, the width and spacing of the paths being structured for bridging of three paths by a conductive end of the stylus at any position on the writing surface of the board. The parallel resistive paths are grounded at one end, while like ones of each of the pairs of parallel conductive paths juxtaposed to the resistive paths are resistively interconnected by proportional resistances, at the opposite side from the grounded ends of the parallel resistive paths, also to ground. The other parallel conductive paths are interconnected to detection circuitry for driving a positive and negative pulse train into the board, for detecting and converting to digital coded signals the analog voltages corresponding to the coordinates on the board where the stylus is positioned, and for outputting both analog and digital signals.

Claims

1. A graphical input board for use with detection circuitry and a non-captive stylus having an electrically conductive tip, wherein the improvement comprises:

a rigid smooth printed circuit board including on one surface thereof;

a plurality of uniform parallel, equally spaced apart first resistive paths;

a plurality of first and second conductive paths, lying in like pairs between said resistive paths and evenly spaced therebetween;

said resistive and conductive paths being structured for bridging of any three consecutive paths by the width of the conductive tip of the stylus at any position on the operating surface of the board;

means for terminating like ends of said first resistive paths to provide unidirectional current flow to ground;

means for terminating each of said first conductive paths resistively and with unidirectionally opposite current flow to ground as that of said first resistive paths, wherein the resistive terminations are proportional, each to the other; and

means for connecting said second conductive paths to said detection circuitry.

2. The apparatus of claim 1, wherein said means for terminating like ends of said first resistive paths to provide unidirectional current flow to ground comprises:

an individual third conductive path interconnecting like ends of said resistive paths; and

a first diode with its anode connected to said third conductive path and its cathode connected to ground.

3. The apparatus of claim 1, wherein said means for terminating each of said first conductive paths resistively and with unidirectionally opposite current flow to ground as that of said first resistive paths, wherein the resistive terminations are proportional each to the other, comprises:

an individual uniform second resistive path interconnecting like ends of said first conductive paths, said first conductive paths being equally spaced therealong; and

a second diode with its cathode connected to an end of said second resistive path, and its anode connected to ground.

4. A graphical input board system comprising:

a graphical input board;

a non-captive stylus having an electrically conductive tip; and

detection circuitry including;

means for alternately driving Calibrated positive and negative pulsed currents into said graphical board only when said stylus tip is in operative contact with said board;

means for detecting and outputting the positive and negative analog voltages developed upon said graphical board and representative of the instantaneous coordinate values respectively of said stylus tip upon said board; and

means for converting the positive and negative analog voltages into digital representations and outputting the same.

5. The apparatus of claim 4, wherein said graphical input board comprises:

a rigid, smooth printed circuit board including on one surface thereof;

a plurality of uniform parallel, equally spaced apart first resistive paths;

a plurality of first and second conductive paths, lying in like pairs between said resistive paths and evenly spaced therebetween;

said resistive and conductive paths being structured for bridging of any three consecutive paths by the width of the conductive tip of the stylus at any position on the operating surface of the board;

means for terminating like ends of said first resistive paths to provide unidirectional current flow to ground;

means for terminating each of said first conductive paths resistively and with unidirectionally opposite current flow to ground as that of said first resistive paths, wherein the resistive terminations are proportional, each to the other; and

means for connecting said second conductive paths to said detection circuitry.

6. The apparatus of claim 5, wherein said means for terminating like ends of said first resistive paths to provide unidirectional current flow to ground comprises:

an individual third conductive path interconnecting like ends of said resistive paths; and

a first diode with its anode connected to said third conductive path and its cathode connected to ground.

7. The apparatus of claim 5, wherein said means for terminating each of said first conductive paths resistively and with unidirectionally opposite current flow to ground as that of said first resistive paths, wherein the resistive terminations are proportional each to the other, comprises:

an individual uniform second resistive path interconnecting like ends of said first conductive paths, said first conductive paths being equally spaced therealong; and

a second diode with its cathode connected to an end of said second resistive path, and its anode connected to ground.

8. The apparatus of claim 7 wherein said means for alternatively driving calibrated positive and negative pulsed currents into said graphical board, when said stylus tip is in operative contact with said board, comprises:

a positive and negative pulse train generator;

third and fourth diodes;

first and second fixed resistors;

first and second variable calibrating resistors;

said first fixed and first variable resistors being connected in series between said pulse generator output and the anode of said third diode, the cathode of said third diode being connected to said second conductive paths, for driving positive pulsed currents thereto; and

said second fixed and second variable resistors being connected in series between said pulse generator output and the cathode of said fourth diode, the anode of said fourth diode being connected to said second conductive paths, for driving negative current thereto.

9. The apparatus of claim 8, wherein said means for detecting and outputting analog voltages developed upon said graphical board and representative of the instantaneous coordinate values of said stylus tip upon said board comprises:

a first output terminal interwired to the anode of said third diode, for detecting and outputting the positive analog voltage representing a first instantaneous coordinate value; and

a second output terminal interwired to the cathode of said fourth diode, for detecting and outputting the negative analog voltage representing a second instantaneous coordinate vaLue.

10. Detection circuitry for use with a graphical input board and a non-captive stylus having an electrically conductive tip, wherein the improvement comprises:

means for alternately driving calibrated positive and negative pulsed currents into said graphical board only when said stylus tip is in operative contact with said board;

means for detecting and outputting the positive and negative analog voltages developed upon said graphical board and representative of the instantaneous coordinate values respectively of said stylus tip upon said board; and

means for converting the positive and negative analog voltages into digital representations and outputting the same.

11. The apparatus of claim 10 wherein said means for alternatively driving calibrated positive and negative pulsed currents into said graphical board, when said stylus tip is in operative contact with said board, comprises:

a positive and negative pulse train generator;

first and second diodes;

first and second fixed resistors;

first and second variable resistors, each being used for calibration purposes;

said first fixed and first variable resistors being connected in series between said pulse generator output and the anode of said first diode, the cathode of said first diode being connected to said graphical board, for driving positive pulsed currents thereto;

said second fixed and second variable resistors being connected in series between said pulse generator output and the cathode of said second diode, the anode of said second diode being connected to said graphical board, for driving negative current thereto; and

wherein said first and second diodes serve to isolate and direct positive and negative current flow.

12. The apparatus of claim 11, wherein said means for detecting and outputting analog voltages developed upon said graphical board and representative of the instantaneous coordinate values of said stylus tip upon said board comprises:

a first output terminal interwired to the anode of said first diode, for detecting and outputting the positive analog voltage representing a first instantaneous coordinate value; and

a second output terminal interwired to the cathode of said second diode, for detecting and outputting the negative analog voltage representing a second instantaneous coordinate value.

13. A graphical input board system for determining the instantaneous coordinate position of a non-captive stylus having a conductive tip when in contact with the operating surface of the board comprising:

a plurality of parallel first conductive paths on said board;

means for driving a positive and negative pulse train into said conductive paths only when said stylus tip is in operative contact with said board;

first circuit means having portions parallel to said conductive paths for determining with infinite resolution the position of said stylus as to a first coordinate axis; and

second circuit means having portions parallel to said conductive paths for determining in finite steps the position of said stylus as to a second coordinate axis;

said conductive paths and said parallel portions of said first and second circuit means being structured as a printed circuit with a combination of one each of said paths and said parallel portions of said first and second circuit means being bridged by the conductive tip of said stylus at any position on said printed circuit.

14. The graphic input board system of claim 13 wherein said first circuit means includes means for detecting an analog voltage representing the position of said stylus as to said first coordinate axis, and said second circuit means includes means for detecting an analog voltage representing the position of said stylus as to said second coordinate axis.

15. The graphical input board system of claim 14 also including means for converting said analog values to digital values.

16. The apparatus of claim 14, wherein said means for drIving a positive and negative pulse train into said conductive paths comprises:

a positive and negative pulse train generator;

first and second diodes;

first and second fixed resistors;

first and second variable resistors, each of said variable resistors being used for calibration purposes;

said first fixed and first variable resistors being connected in series between said pulse generator output and the anode of said first diode, the cathode of said first diode being connected to said conductive paths, for driving positive pulsed currents thereto; and

said second fixed and second variable resistors being connected in series between said pulse generator output and the cathode of said second diode, the anode of said second diode being connected to said conductive paths for driving negative current thereto.

17. The apparatus of claim 14 wherein said means for detecting analog voltages developed upon said graphical board and representative of the instantaneous coordinate values of said stylus tip upon said board includes means to output the analog voltages including:

a first output terminal interwired to the anode of a first diode of said means for driving a positive and negative pulse train into said conductive paths, for detecting and outputting the positive analog voltage representing a first instantaneous coordinate value; and

a second output terminal interwired to the cathode of a second diode of said means for driving a positive and negative pulse train into said conductive paths, for detecting and outputting the negative analog voltage representing a second instantaneous coordinate value.

18. The apparatus of claim 13, wherein said portions of said first circuit means parallel to each of said parallel first conductive paths comprise uniform resistive paths and wherein said first circuit means also includes means for terminating said resistive paths to provide positive unidirectional current flow to ground.

19. The apparatus of claim 18, wherein said means for terminating said resistive paths to provide positive unidirectional current flow to ground, comprises:

an individual conductive path interconnecting like ends of said resistive paths; and

a diode with its anode connected to said conductive path and its cathode connected to ground.

20. The apparatus of claim 13, wherein said portions of said second circuit means parallel to said first conductive paths comprise second conductive paths;

and wherein said second circuit means also includes means for terminating each of said second conductive paths resistively and with negative unidirectional current flow to ground, wherein the resistive terminations of said second conductive paths are proportional each to the other.

21. The apparatus of claim 20, wherein said means for terminating each of said second conductive paths resistively and with negative unidirectional current flow to ground, comprises:

an individual uniform resistive path interconnecting like ends of said second conductive paths, said like ends of said second conductive paths being equally spaced therealong; and

a diode with its cathode connected to an end of said resistive path, and its anode connect to ground.