Systems and Methods for Resolving Multitouch Scenarios for Optical Touchscreens
First Claim
1. A method of determining multiple touch points, the method comprising:
- detecting a first shadow resulting from an interruption of light at a first point in a touch area using a first detector;
changing light traveling in the touch area so that a length of at least one shadow changes;
based on the length of the shadow as changed, calculating a distance from the first point to the first detector; and
using the distance as calculated to validate a potential touch position coordinate for the first point.
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Abstract
An optical touch detection system may rely on triangulating points in a touch area based on the direction of shadows cast by an object interrupting light in the touch area. When two interruptions occur simultaneously, ghost points and true touch points triangulated from the shadows can be distinguished from one another without resort to additional light detectors. In some embodiments, a distance from a touch point to a single light detector can be determined or estimated based on a change in the length of a shadow detected by a light detector when multiple light sources are used. Based on the distance, the true touch points can be identified by comparing the distance as determined from shadow extension to a distance calculated from the triangulated location of the touch points.
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Citations
19 Claims
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1. A method of determining multiple touch points, the method comprising:
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detecting a first shadow resulting from an interruption of light at a first point in a touch area using a first detector; changing light traveling in the touch area so that a length of at least one shadow changes; based on the length of the shadow as changed, calculating a distance from the first point to the first detector; and using the distance as calculated to validate a potential touch position coordinate for the first point. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A touch detection system, comprising:
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a retroreflector positioned along at least one edge of a touch surface in a touch area; a light detection system having an optical center and positioned to image the retroreflector; an illumination system configured to emit light across the touch surface so that at least some of the light from the illumination system is retroreflected to the light detection system in the absence of an object in the touch area; and a computing system interfaced with the light detection system and the illumination system, the computing system configured to determine a distance from the light detection system to a point at which light in the touch area has been interrupted based on;
(i) a first pattern of detected light indicating an interruption in a first pattern of light from the illumination system due to an object at the point and (ii) a second pattern of detected light representing an interruption in a second pattern of light from the illumination system due to the object at the point. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A computer readable medium embodying program code executable by a computer system, the program code comprising:
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program code for accessing detection data from two light detectors and identifying two shadows detected by each detector, the shadows due to interruptions in a first pattern of light traveling in a touch area; program code for directing a light source to illuminate the touch area using a second pattern of light; program code for accessing detection data from one light detector and identifying a change in the size of a shadow, the change in size occurring when the second pattern of light illuminates the touch area; and program code for determining a distance from a point in the touch area to the detector based on the change in size of the shadow. - View Dependent Claims (16, 17, 18, 19)
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Specification