Method and apparatus for detecting the location of an object on a surface

• US 5,635,724 A
• Filed: 06/07/1995
• Issued: 06/03/1997
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: INTECOLOR
• Original Assignee: INTECOLOR
• Inventors: Higgins, James C.
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/478,919
• Time in Patent Office: 727 Days
• Field of Search: 250/559.24, 250/559.19, 250/559.21, 250/559.27, 250/559.12, 250/221, 250/222.2, 250/224, 250/559.29, 340/555-557
• US Class Current: 250/559.19
• CPC Class Codes: G01V 8/20 using multiple transmitters or receivers
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A device and method for detecting the location of an object in a surface employs a first plurality of light sources disposed along a first row adjacent the surface. A first plurality of light detectors is disposed along a second row adjacent the surface and spaced apart from the first row. Each detector outputs an analog signal representative of the intensity of light being detected. A control means causes each of the light sources to be illuminated at a different time. A calculating means determines the location of the object based on the analog signals from the detectors. The calculating means determines the location of the object by determining coordinates of a first line and a second line, the first line extending from a first light source to a centerpoint of a first shadow cast upon a first neighboring group of the detectors and the second line extending from a second light source to a centerpoint of a second shadow cast upon a second neighboring group of the detectors. The calculating means determines the location of each shadow end as being a point a distance from an end of a detector equal to the width of the detector times the value of the signal from the detector divided by the value of the signal corresponding to the detector being fully illuminated by a beam. In an alternative embodiment, the calculating means further determines the width of the object.

Claims

1. A device for detecting the location of an object on a surface, comprising:

a. a first plurality of light sources disposed along a first row adjacent the surface, each said light source producing a divergent beam and each being capable of being illuminated at a different time, so that when the object intersects the surface, the object occludes a portion of the beams from at least two different said light sources at different times;

b. a first plurality of light detectors disposed along a second row adjacent the surface and spaced apart from the first row of said light sources, each said light detector having a detecting surface sensitive to light of the waveband produced by said light sources and each said light detector generating an analog signal representative of the intensity of light being detected, wherein the beam from each of said light sources is directed toward at least one light detector;

c. control means for causing each of said light sources to be illuminated at a selectable time; and

d. calculating means, responsive to said control means and to said analog signal from each of said plurality of light detectors, for determining the location of the object based on the intensity of light being detected by each of said plurality of detectors as the object is being illuminated by one of the first plurality of light sources.

2. The device of claim 1, wherein said light sources produce light in the infra-red waveband.

3. The device of claim 1, wherein said calculating means further comprises means for determining the width of the object.

4. The device of claim 3, wherein the object casts a first shadow, having a first upper end and an opposite first lower end, on said plurality of detectors when illuminated by a first light source of said plurality of light sources, and the object casts a second shadow, having a second upper end and an opposite second lower end, on said plurality of detectors when illuminated by a second light source of said plurality of light sources and wherein said calculating means determines the coordinates of:

a. a first upper line from said first light source to said first upper end of said first shadow;

b. a first lower line from said first light source to an said first lower end of said first shadow;

c. a second upper line from said second light source to said second upper end of said second shadow; and

d. a second lower line from said second light source to said second lower end of said second shadow,

and wherein said calculating means determines the width of the object by calculating a distance between a first intersection point and a second intersection point, said first intersection point being a point where said first upper line intersects said second upper line and said second intersection point being the point where said first lower line intersects said second lower line.

5. The device of claim 1 employed in a touch screen.

6. The device of claim 1, further comprising

a. a second plurality of light sources evenly spaced apart and interleaved with said first plurality of light detectors;

and

b. a second plurality of light detectors evenly spaced apart and interleaved with said first plurality of light sources.

7. A device for detecting the location of an object on a surface, comprising:

a. a first plurality of light sources disposed along a first row adjacent the surface, each said light source producing a divergent beam and each being capable of being illuminated at a different time, so that when the object intersects the surface, the object occludes a portion of the beams from at least two different said light sources at different times;

b. a first plurality of light detectors disposed along a second row adjacent the surface and spaced apart from the first row of said light sources, each said light detector having a detecting surface sensitive to light of the waveband produced by said light sources and each said light detector generating an analog signal representative of the intensity of light being detected, wherein the beam from each of said light sources is directed toward at least one light detector;

c. control means for causing each of said light sources to be illuminated at a selectable time; and

d. calculating means, responsive to said control means and to said analog signal from each of said plurality of light detectors, for determining the location of the object based on the intensity of light being detected by each of said plurality of detectors, as the object is being illuminated by one of the first plurality of light sources,

wherein said calculating means determines the location of the object by determining coordinates relative to the device of a first line and a second line, said first line extending from a first light source to a centerpoint of a first shadow cast by the object upon a first neighboring group of said detectors when said first light source is illuminated and said second line extending from a second light source to a centerpoint of a second shadow cast by the object upon a second neighboring group of said detectors when said second light source is illuminated, the location of the object being at the intersection of the first line and the second line.

8. The device of claim 7, wherein said calculating means determines said centerpoint for each shadow by calculating one half of the distance from a first shadow end to a second shadow end.

9. The device of claim 8, wherein said calculating means determines the location of each shadow end as being at a point from an end of a detector located at a distance equal to the width of said detector times the value of said signal from said detector divided by the value of said signal corresponding to said detector being fully illuminated by a beam.

10. The device of claim 7, wherein said light sources produce light in the infra-red waveband.

11. The device of claim 7, wherein said calculating means further comprises means for determining the width of the object.

12. The device of claim 11, wherein the object casts a first shadow, having a first upper end and an opposite first lower end, on said plurality of detectors when illuminated by a first light source of said plurality of light sources, and the object casts a second shadow, having a second upper end and an opposite second lower end, on said plurality of detectors when illuminated by a second light source of said plurality of light sources and wherein said calculating means determines the coordinates of:

a. a first upper line from said first light source to said first upper end of said first shadow;

b. a first lower line from said first light source to an said first lower end of said first shadow;

c. a second upper line from said second light source to said second upper end of said second shadow; and

d. a second lower line from said second light source to said second lower end of said second shadow,

and wherein said calculating means determines the width of the object by calculating a distance between a first intersection point and a second intersection point, said first intersection point being a point where said first upper line intersects said second upper line and said second intersection point being the point where said first lower line intersects said second lower line.

13. The device of claim 7 employed in a touch screen.

14. The device of claim 7, further comprising

a. a second plurality of light sources evenly spaced apart and interleaved with said first plurality of light detectors;

and

b. a second plurality of light detectors evenly spaced apart and interleaved with said first plurality of light sources.

15. A method of detecting the location of an object on a surface, comprising the steps of:

a. generating a plurality of divergent light beams with a plurality of light sources evenly spaced apart along a first line coplanar with the surface;

b. illuminating the object with said plurality of beams so that each beam illuminates the object at a different time;

c. detecting the intensity of light from at least two of said beams illuminating a plurality of detectors evenly spaced apart along a second line parallel to and coplanar with said first line, each detector generating a signal representative of the intensity of light being received by said detector;

d. determining a first endpoint and a second endpoint of each shadow cast upon said plurality of detectors by the object as it is being illuminated by each of said beams based upon said signals representative of said intensity received from said plurality of detectors;

e. determining the coordinates of a centerline from a light source through a point near the center of the object by determining the point one-halfway between said first endpoint and said second endpoint of each shadow cast upon said plurality of detectors by the object; and

f. determining a centerpoint of the object by determining an intersection point of two centerlines from two of said light sources through the centerpoint of the object.

16. The method of claim 15 employed in a touch screen.

17. A device for determining a distance of an object from an axis, comprising:

a. a first plurality of light sources evenly spaced apart along a first row;

b. a first plurality of light detectors evenly spaced apart along said first row;

c. a second plurality of light sources evenly disposed along a second row;

d. a second plurality of light detectors disposed along said second row and interleaved with said second plurality of light sources;

e. means for determining a length of a shadow cast upon said first plurality of detectors by the object as the object is illuminated by at least one of said first plurality of light sources and for determining the length of a shadow cast upon said second plurality of detectors by the object; and

f. means for determining the distance of the object from the first row by multiplying the distance between said first row and said second row by the ratio of the length of a first shadow cast upon said second plurality of detectors by the object as the object is illuminated by a first light source of said first plurality of light sources, divided by the length of a second shadow cast upon said first plurality of detectors by the object as it is illuminated by a second light source of said second plurality of light sources.

18. The device of claim 17 employed on a touch screen.

19. A method of determining the location of an end of a shadow, comprising the steps of:

a. detecting light with a plurality of light detectors, each detector having a width;

b. generating an analog signal proportional to the intensity of light detected by each of said detectors;

c. determining which detector of said detectors is a partially occluded detector, said partially occluded detector being a detector generating an analog signal having an intermediate value between a value corresponding to a detector that is fully exposed to light and a value corresponding to a detector fully occluded by a shadow, said partially occluded detector having an unoccluded end and an occluded end;

d. determining which end of said partially occluded detector is unoccluded; and

e. multiplying the width of said partially occluded detector by said intermediate value, divided by a value corresponding to a signal from a detector that is completely unoccluded, thereby determining a distance of the end of the shadow from the unoccluded end of said partially occluded detector.

20. The method of claim 19 wherein the step of determining which end of said partially occluded detector is in the relatively bright area further comprises the step of determining which of said detectors adjacent said partially occluded detector are completely unoccluded.