Optical Touchscreen with Improved Illumination
First Claim
1. A touch detection system, comprising:
- a light detection system having an optical center;
a retroreflector positioned along at least one edge of a touch surface in a touch area;
a primary illumination system configured to emit light across the touch surface so that at least some of the light from the primary illumination system is retroreflected to the light detection system in the absence of an object in the touch area; and
a secondary illumination system configured to emit light across the touch surface so that, in the absence of an object in the touch area, less light from the secondary illumination system is retroreflected to the detection system than from the primary illumination system;
wherein the light detection system is configured to detect a pattern of light received by the light detection system from the touch area.
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Accused Products
Abstract
In an optical touch display system, light from a primary source can be retroreflected to a detector in the absence of an object in the detection area. When an object is present, its position can be triangulated based on the direction of its shadows at the detectors. Accuracy can be improved with a secondary light source positioned off-axis from the primary light sources so that minimal light from the secondary source is retroreflected to the detectors. Instead, when an object is present, light from the secondary source may be reflected directly from the object. Each detector signal representing light due to the primary light source can be corrected to remove light reflected directly from the object based on identifying and removing a signal component representing light from the secondary light source. In some embodiments, this is facilitated by phasing the primary and secondary light sources.
253 Citations
17 Claims
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1. A touch detection system, comprising:
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a light detection system having an optical center; a retroreflector positioned along at least one edge of a touch surface in a touch area; a primary illumination system configured to emit light across the touch surface so that at least some of the light from the primary illumination system is retroreflected to the light detection system in the absence of an object in the touch area; and a secondary illumination system configured to emit light across the touch surface so that, in the absence of an object in the touch area, less light from the secondary illumination system is retroreflected to the detection system than from the primary illumination system; wherein the light detection system is configured to detect a pattern of light received by the light detection system from the touch area. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of detecting the position of an object in a touch area, the method comprising:
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emitting light in a primary pattern towards one or more edges defining a touch area of a touch surface, the primary pattern emitted so that, in the absence of an object in the touch area, at least some of the light will be retroreflected to a detection system; emitting light in a secondary pattern across the touch surface, the secondary pattern emitted so that, in the absence of an object in the touch area, at least some of the light from the secondary pattern will not be retroreflected to the detection system; detecting light received by the detection system and generating a detected light signal; adjusting the detected light signal to yield a corrected light signal based on the intensity of detected light that ultimately originated from the secondary pattern; and determining, from the corrected light signal, if an object is interfering with the transmission of light in the touch area and a location of the object relative to the touch area. - View Dependent Claims (10, 11, 12, 13)
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14. A computer system configured to be interfaced with a touch detection system, the computer system comprising at least one computing device configured to:
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direct a primary illumination source and a secondary illumination source to emit light across a touch surface having a touch area; receive, from each of at least two detectors, data representing a pattern of light received from the touch area by each detector; perform a correction operation on the data representing each pattern of received light; and based on the data resulting from the correction operation, determine a location of an object relative to the touch area. - View Dependent Claims (15, 16, 17)
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Specification