Apparatus and method to improve resolution of infrared touch systems

• US 6,429,857 B1
• Filed: 12/04/2000
• Issued: 08/06/2002
• Est. Priority Date: 12/02/1999
• Status: Expired due to Term

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touchsystems Incorporated (Elo Touch Solutions, Inc.)
• Inventors: Masters, Timothy E., Knetsch, Robert W., Deacon, John, Grice, Henry A. Jr.
• Primary Examiner(s): Saras, Steven
• Assistant Examiner(s): Maier, Christopher J.
• Application Number:
  US09/728,999
• Publication Number:
  US 20020067348A1
• Time in Patent Office: 610 Days
• Field of Search: 345/175, 345/173, 345/174, 345/176, 345/177, 345/178, 250/221, 250/559.19, 346/176, 178/18-1-
• US Class Current: 345/175
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A touch system using a plurality of infrared (“IR”) transmitters and receivers, and a method of determining with increased resolution the location of a touch between the IR transmitters and receivers using on-axis and off-axis detection are disclosed. The inventive touch system and method use, in conjunction with the on-axis and off-axis detection, a coarse and fine sweep of the transmitters and receivers to increase the resolution of identified touch location. The method of determining a touch location involves selection and activation of particular off-axis infrared transmitter and receiver pairs determined from a triangulation interdependence between the x and y coordinates. The increased resolution of the identified touch location is achievable using the inventive system and method without the need for an increased number of IR transmitters and receivers and without the need for higher speed processing capability.

Claims

1. An infrared touch system having increased resolution for determining position of a touch on a touch screen, said infrared touch system comprising:

a first plurality of infrared transmitters positioned along a first edge of the touch screen, each infrared transmitter of said first plurality of infrared transmitters controllably emitting a cone of infrared light;

a first plurality of infrared receivers positioned along a second edge of the touch screen directly opposite from the first plurality of transmitters, whereby each receiver of said first plurality of infrared receivers is aligned on-axis with one infrared transmitter of the first plurality of transmitters and is off-axis to each of the other first plurality of transmitters;

a second plurality of infrared transmitters positioned along a third edge of the touch screen, said third edge being approximately perpendicular to the first and second edge of the touch screen, each infrared transmitter of said second plurality of infrared transmitters controllably emitting a cone of infrared light;

a second plurality of infrared receivers positioned along a fourth edge of the touch screen opposite from the second plurality of transmitters, whereby each receiver of said second plurality of infrared receivers is aligned on-axis with one infrared transmitter of the second plurality of transmitters and is off-axis to each of the other second plurality of transmitters;

a processor to control activation of the first and second plurality of infrared transmitters and control activation of the first and second plurality of infrared receivers and for calculating the touch position on the touch screen using on-axis and off-axis activation of the infrared transmitters and receivers, wherein in calculating the touch position on the touch screen using on-axis and off-axis activation of the infrared transmitters and receivers, the processor

(a) estimates a coarse touch location based upon a sequential on-axis activation of each infrared transmitter and opposing receiver;

(b) selects off-axis transmitter and receiver pairs based upon the coarse touch location estimate; and

(c) refines the touch location based upon a sequential activation of the selected off-axis transmitter and receiver pairs.

2. An infrared touch system having increased resolution for determining position of a touch on a touch screen, said infrared touch system comprising:

a first plurality of infrared transmitters positioned along a first edge of the touch screen, each infrared transmitter of said first plurality of infrared transmitters controllably emitting a cone of infrared light;

a first plurality of infrared receivers positioned along a second edge of the touch screen directly opposite from the first plurality of transmitters, whereby each receiver of said first plurality of infrared receivers is aligned on-axis with one infrared transmitter of the first plurality of transmitters and is off-axis to each of the other first plurality of transmitters;

a second plurality of infrared transmitters positioned along a third edge of the touch screen, said third edge being approximately perpendicular to the first and second edge of the touch screen, each infrared transmitter of said second plurality of infrared transmitters controllably emitting a cone of infrared light;

a second plurality of infrared receivers positioned along a fourth edge of the touch screen opposite from the second plurality of transmitters, whereby each receiver of said second plurality of infrared receivers is aligned on-axis with one infrared transmitter of the second plurality of transmitters and is off-axis to each of the other second plurality of transmitters;

a processor to control activation of the first and second plurality of infrared transmitters and control activation of the first and second plurality of infrared receivers and for calculating the touch position on the touch screen using on-axis and off-axis activation of the infrared transmitters and receivers, wherein in calculating the touch position on the touch screen using on-axis and off-axis activation of the infrared transmitters and receivers, the processor

(a) estimates a coarse x-coordinate and y-coordinate touch location on the touch screen based upon sequential on-axis activation of each infrared transmitter and opposing receiver;

(b) selects off-axis transmitter and receiver x-coordinate pairs based upon the coarse y-coordinate touch location estimate;

(c) refines the x-coordinate touch location based upon systematic activation of the selected off-axis transmitter and receiver x-coordinate pairs;

(d) selects off-axis transmitter and receiver y-coordinate pairs based upon the coarse x-coordinate touch location estimate; and

(e) refines the y-coordinate touch location based upon systematic activation of the selected off-axis transmitter and receiver y-coordinate pairs.

3. An infrared touch system having a touch screen, said infrared touch system comprising:

a first plurality of infrared transmitters positioned along a first edge of a touch screen, each infrared transmitter of said first plurality of infrared transmitters controllably emitting infrared light;

a first plurality of infrared receivers positioned along a second edge of the touch screen opposite from the first plurality of transmitters, whereby each receiver of said first plurality of infrared receivers is aligned on-axis with one infrared transmitter of the first plurality of transmitters and is off-axis to each of the other first plurality of transmitters, further whereby an infrared beam of light emitted from each transmitter of the first plurality of infrared transmitters is receivable by at least two infrared receivers of the first plurality of infrared receivers;

a second plurality of infrared transmitters positioned along a third edge of the touch screen, each infrared transmitter of said second plurality of infrared transmitters controllably emitting infrared light;

a second plurality of infrared receivers positioned along a fourth edge of the touch screen opposite from the second plurality of transmitters, whereby each receiver of said second plurality of infrared receivers is aligned on-axis with one infrared transmitter of the second plurality of transmitters and is off-axis to each of the other second plurality of transmitters, further whereby an infrared beam of light emitted from each transmitter of the second plurality of infrared transmitters is receivable by at least two infrared receivers of the second plurality of infrared receivers;

a first processor to sequentially activate each of the first and second plurality of infrared transmitters and opposing first and second plurality of infrared receivers; and

a second processor for calculating a touch position on the touch screen, wherein the second processor;

(a) identifies a coarse x-coordinate touch area based upon identification of blocked infrared beams between activated transmitters and receivers;

(b) identifies a coarse y-coordinate touch area based upon identification of blocked infrared beams between activated transmitters and receivers;

(c) calculates a coarse x-coordinate and y-coordinate touch area from the identified coarse x-coordinate and y-coordinate touch areas; and

(d) refines the x-coordinate and y-coordinate touch location based upon systematic activation of off-axis transmitter and receiver pairs having infrared beams that cross the calculated coarse touch area.

4. A method of determining a touch location on a touch system screen, said screen having along first and second adjacent edges a plurality of infrared transmitters and said touch screen further having a plurality of infrared receivers along third and fourth adjacent edges opposing the plurality of infrared transmitters, such that each transmitter is aligned on-axis to one receiver, the method comprising the steps of:

estimating a coarse touch location based upon a systematic on-axis activation of each infrared transmitter and opposing receiver; and

refining the touch location based upon a systematic off-axis activation of selected infrared transmitters and receivers.

5. The method of determining a touch location on a touch system screen, according to claim 4, wherein the systematic on-axis activation step is a sequential activation of each transmitter with its on-axis receiver.

6. The method of determining a touch location on a touch system screen, according to claim 4, herein the estimating step is based upon a systematic on-axis and a systematic off-axis activation of each infrared transmitter and receiver.

7. A method of determining a touch location on a touch system screen, said touch screen having along first and second adjacent edges a plurality of infrared transmitters and said touch screen further having a plurality of infrared receivers along third and fourth adjacent edges opposing the plurality of infrared transmitters, such that each transmitter is aligned on-axis to one receiver, the method comprising the steps of:

estimating a coarse touch location based upon a systematic on-axis activation of each infrared transmitter and opposing receiver;

selecting off-axis transmitter and receiver pairs based upon the coarse touch location estimate; and

refining the touch location based upon a systematic activation of the selected off-axis transmitter and receiver pairs.

8. The method of determining a touch location on a touch system screen according to claim 7, wherein the step of systematic on-axis activation is a sequential activation of the infrared transmitters and on-axis receivers.

9. A method of determining a touch location on a touch system screen, said touch screen having along an x-coordinate edge, a first plurality of infrared x-coordinate transmitters and along a y-coordinate edge, a second plurality of y-coordinate infrared transmitters, said touch screen further having a plurality of infrared receivers along two edges opposing the plurality of infrared transmitters, such that each transmitter is aligned on-axis to one receiver, the method comprising the steps of:

(a) estimating a coarse x-coordinate and y-coordinate touch location on the touch screen based upon systematic on-axis activation of each infrared transmitter and opposing receiver;

(b) selecting off-axis transmitter and receiver x-coordinate pairs based upon the coarse y-coordinate touch location estimate;

(c) refining the x-coordinate touch location based upon systematic activation of the selected off-axis transmitter and receiver x-coordinate pairs;

(d) selecting off-axis transmitter and receiver y-coordinate pairs based upon the coarse x-coordinate touch location estimate; and

(e) refining the y-coordinate touch location based upon systematic activation of the selected off-axis transmitter and receiver y-coordinate pairs.

10. The method of determining a touch location on a touch system screen according to claim 9, wherein the systematic on-axis activation in step (a) is sequential activation of adjacent transmitters and opposing receivers.

11. A method of determining a touch location on a touch system screen, said touch screen having along an x-coordinate edge, a first plurality of infrared x-coordinate transmitters and along a y-coordinate edge, a second plurality of y-coordinate infrared transmitters, said touch screen further having a plurality of infrared receivers along two edges opposing the plurality of infrared transmitters, such that each transmitter is aligned on-axis to one receiver, further wherein when activated, each infrared transmitter generates an infrared beam receivable by the on-axis receiver and at least one receiver adjacent to the on-axis receiver, the method comprising the steps of:

(a) sequentially activating each on-axis x-coordinate infrared transmitter and opposing receiver;

(b) identifying a coarse x-coordinate touch area based upon identification of blocked infrared beams between activated x-coordinate transmitters and receivers;

(c) sequentially activating each on-axis y-coordinate infrared transmitter and opposing receiver;

(d) identifying a coarse y-coordinate touch area based upon identification of blocked infrared beams between activated y-coordinate transmitters and receivers;

(e) calculating a coarse x-coordinate and y-coordinate touch area from the identified coarse x-coordinate and y-coordinate touch areas; and

(f) refining the x-coordinate and y-coordinate touch location based upon systematic activation of off-axis transmitter and receiver pairs having infrared beams that cross the calculated coarse touch area.