Projective capacitive touchscreen

• US 6,297,811 B1
• Filed: 06/02/1999
• Issued: 10/02/2001
• Est. Priority Date: 06/02/1999
• Status: Expired due to Fees

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touchsystems Incorporated (Elo Touch Solutions, Inc.)
• Inventors: Kent, Joel, Ravid, Arie
• Primary Examiner(s): CHANG, KENT WU
• Application Number:
  US09/324,346
• Time in Patent Office: 853 Days
• Field of Search: 345/156, 345/173, 345/174, 178/18.01, 178/18.06
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0448 Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality

Abstract

An improved touchscreen utilizing two sets of electrodes that are fabricated in a single plane is provided. The individual electrodes of each set of electrodes are formed from a continuous length of a conductive material. Suitable electrode materials include fine wire and deposited conductive coatings. The overall electrode pattern is such that there is no overlap of electrodes, thus eliminating the need for insulating layers and/or coatings between electrodes. Although a variety of electrode patterns can be used, preferably the pattern is comprised of a plurality of approximately triangularly shaped electrodes, the pattern such that the base of one triangularly shaped electrode is adjacent to the apex of the next triangularly shaped electrode. The preferred triangular shape of an individual electrode can be achieved by forming a continuous loop of the electrode material into the desired shape or by forming a series of teeth of varying height, the envelope of the teeth approximating the desired triangular shape. A touchscreen sensor employing the disclosed sensing electrodes can use any of a variety of readout systems. For example, a frequency-domain readout approach can be used in which the operating frequency is fixed. In this approach a touch capacitance is detected by observing an impedance change at the operating frequency, typically by measuring a corresponding current change. Alternately changes in a RC decay time τ can be measured, for example by observing frequency shifts in a relaxation oscillator. This technique is typically referred to as a time-domain approach. In a third alternate approach, capacitance changes are detected via frequency shifts of LC oscillators. Touch position information is determined from the capacitance changes of the electrodes using any number of different techniques. Preferably prior to calculating position, a subset of electrodes localized around the touch position is determined. Electrode localization reduces the effects of background signals while increasing the efficiency of the position determining algorithm. Once a set of localized electrodes has been determined the touch coordinates are calculated, one coordinate from the distribution of the touch signal within each set of electrodes and the other coordinate from the distribution of the touch signal between the two sets of electrodes.

Claims

1. A projective capacitive touchscreen, comprising:

a substrate;

a first plurality of non-linear, non-pad, position sensing electrodes coupled to said substrate, said first plurality of electrodes contained within a plane;

a second plurality of non-linear, non-pad, position sensing electrodes coupled to said substrate, said second plurality of electrodes contained within said plane, said second plurality of electrodes interlaced with said first plurality of electrodes in a non-overlapping pattern;

a first plurality of interconnects for coupling said first plurality of electrodes to a control circuit; and

a second plurality of interconnects for coupling said second plurality of electrodes to said control circuit.

2. The projective capacitive touchscreen of claim 1, wherein a sensing portion of each electrode of said first and second pluralities of electrodes is substantially triangularly shaped, wherein said substantially triangularly shaped sensing portion is formed by a continuous length of a conductive material.

3. The projective capacitive touchscreen of claim 2, wherein said conductive material is a fine wire.

4. The projective capacitive touchscreen of claim 3, wherein said fine wire has a diameter between 10 and 25 micrometers.

5. The projective capacitive touchscreen of claim 2, wherein said conductive material is a conductive coating.

6. The projective capacitive touchscreen of claim 5, wherein said conductive coating is selected from the group consisting of ITO, ATO, and fluorine-doped tin oxide.

7. The projective capacitive touchscreen of claim 5, wherein said conductive coating is a non-transparent coating.

8. The projective capacitive touchscreen of claim 2, wherein said continuous length of said conductive material outlines said substantially triangularly shaped sensing portion.

9. The projective capacitive touchscreen of claim 8, wherein a first edge of said outlined substantially triangularly shaped sensing portion is non-linear and a second edge of said outlined substantially triangularly shaped sensing portion is non-linear.

10. The projective capacitive touchscreen of claim 2, wherein said continuous length of said conductive material forms a plurality of teeth of varying height, wherein an imaginary envelop encircling said plurality of teeth is of said substantially triangularly shape.

11. The projective capacitive touchscreen of claim 1, wherein an impedance of said first and second pluralities of interconnects is greater than 1 kΩ

.

12. The projective capacitive touchscreen of claim 1, wherein an impedance corresponding to said first and second pluralities of interconnects is greater than a first impedance and less than a second impedance, wherein said second impedance corresponds to capacitive cross-coupling between electrodes of said first plurality of electrodes and adjacent electrodes of said second plurality of electrodes.

13. The projective capacitive touchscreen of claim 12, wherein said first impedance is greater than 1 kΩ

.

14. The projective capacitive touchscreen of claim 1, wherein said first plurality of electrodes are coupled to a first plurality of electronic channels within said control circuit.

15. The projective capacitive touchscreen of claim 14, wherein at least some of said first plurality of electronic channels are coupled to multiple electrodes of said first plurality of electrodes.

16. The projective capacitive touchscreen of claim 14, wherein at least some of said first plurality of electrodes are coupled to multiple electronic channels of said first plurality of electronic channels.

17. The projective capacitive touchscreen of claim 1, wherein said first plurality of electrodes are coupled to a first plurality of electronic channels within said control circuit, and wherein said second plurality of electrodes are coupled to a second plurality of electronic channels within said control circuit.

18. The projective capacitive touchscreen of claim 17, wherein at least some of said first plurality of electronic channels are coupled to multiple electrodes of said first plurality of electrodes, and wherein at least some of said second plurality of electronic channels are coupled to multiple electrodes of said second plurality of electrodes.

19. The projective capacitive touchscreen of claim 17, wherein at least some of said first plurality of electrodes are coupled to multiple electronic channels of said first plurality of electronic channels, and wherein at least some of said second plurality of electrodes are coupled to multiple electronic channels of said second plurality of electronic channels.

20. The projective capacitive touchscreen of claim 1, wherein said control circuit utilizes a frequency-domain readout technique.

21. The projective capacitive touchscreen of claim 1, wherein said control circuit utilizes a time-domain readout technique.

22. The projective capacitive touchscreen of claim 1, wherein said control circuit determines frequency shifts in a plurality of LC oscillators.

23. The projective capacitive touchscreen of claim 1, wherein said control circuit determines a first touch coordinate from a first signal distribution within said first plurality of electrodes and a second signal distribution within said second plurality of electrodes, and wherein said control circuit determines a second touch coordinate from a third signal distribution between said first and second pluralities of electrodes.

24. A projective capacitive touchscreen, comprising:

a substrate;

a first plurality of non-linear, non-pad, position sensing electrodes coupled to said substrate, said first plurality of electrodes contained within a plane;

a second plurality of non-linear, non-pad, position sensing electrodes coupled to said substrate, said second plurality of electrodes contained within said plane, wherein a portion of said second plurality of electrodes is interlaced with a portion of said first plurality of electrodes in a non-overlapping pattern, said interlaced portion forming a multiple position coordinate determining region, and said non-interlaced portion forming a plurality of simple touch buttons;

a first plurality of interconnects for coupling said first plurality of electrodes to a control circuit; and

a second plurality of interconnects for coupling said second plurality of electrodes to said control circuit.