Robust optical touch—screen systems and methods using a planar transparent sheet
First Claim
1. A method of establishing positions of touch events on a transparent sheet having a perimeter, with light-source elements and light-sensing elements operably disposed adjacent the perimeter, comprising:
- a) using the light-sensing elements, measuring intensity values of light from the light-source elements, the light traveling internally within the transparent sheet over lines-of-sight between the light-source elements and the light-sensing elements, including generating from the light-sensing elements respective detector signals representative of the intensity values;
b) processing the detector signals with an electrical circuit having an amplifier to determine limiting lines-of-sight for each light-sensing element based on the intensity values as compared to an attenuation threshold, wherein the processing includes;
i) making integrated photocurrent measurements for a fixed total time Δ
T;
ii) breaking the fixed total time Δ
T into N intervals to define N sub-measurements that have corresponding time intervals Δ
T/N;
iii) adding together the N sub-measurements to simulate a single integration; and
iv) dynamically choosing N to avoid overloading the amplifier;
c) overlapping triangles defined by the limiting lines-of-sight for each light-sensing element to establish one or more polygons; and
d) determining centers of the one or more polygons to establish the touch event positions.
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Accused Products
Abstract
An optical touch screen that utilizes a planar transparent sheet and that is configured to determine the position of a touch event on the transparent sheet is disclosed. Light-source elements and light-sensing elements are operably disposed at the transparent sheet perimeter. Light is detected over lines-of-sight between the light-source elements and the light-sensing elements. Attenuated lines-of-sight due to a touch event are determined. Polygons are established by overlapping triangles defined by the limiting lines of sight for each light-sensing element. Polygons with attenuations below the attenuation threshold are eliminated. The centers of the remaining polygons are then determined to establish the locations of the touch events. The systems and methods provide robust detection of multiple touch events.
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Citations
20 Claims
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1. A method of establishing positions of touch events on a transparent sheet having a perimeter, with light-source elements and light-sensing elements operably disposed adjacent the perimeter, comprising:
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a) using the light-sensing elements, measuring intensity values of light from the light-source elements, the light traveling internally within the transparent sheet over lines-of-sight between the light-source elements and the light-sensing elements, including generating from the light-sensing elements respective detector signals representative of the intensity values; b) processing the detector signals with an electrical circuit having an amplifier to determine limiting lines-of-sight for each light-sensing element based on the intensity values as compared to an attenuation threshold, wherein the processing includes;
i) making integrated photocurrent measurements for a fixed total time Δ
T;
ii) breaking the fixed total time Δ
T into N intervals to define N sub-measurements that have corresponding time intervals Δ
T/N;
iii) adding together the N sub-measurements to simulate a single integration; and
iv) dynamically choosing N to avoid overloading the amplifier;c) overlapping triangles defined by the limiting lines-of-sight for each light-sensing element to establish one or more polygons; and d) determining centers of the one or more polygons to establish the touch event positions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A touch-screen system for sensing a location of one or more touch events, comprising:
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a transparent sheet having a perimeter and a top surface where the one or more touch events occur; a plurality of light-source elements that emit light and that are operably disposed adjacent the perimeter to couple the light into the transparent sheet to travel therein via total internal reflection; a plurality of light-sensing elements operably disposed adjacent the perimeter to detect the light from the light-sensing elements and in response thereto generate detector signals having a signal strength representative of a detected light intensity, wherein the one or more touch events cause attenuation of the light intensity along at least one of the lines-of-sight corresponding to the select light-sensing element; an electrical circuit having an amplifier electrically connected to the plurality of light-sensing elements and configured to process the detector signals to;
i) make integrated photocurrent measurements for a fixed total time Δ
T ii) break the fixed total time Δ
T into N intervals to define N sub-measurements that have corresponding time intervals Δ
T/N;
iii) add together the N sub-measurements to simulate a single integration; and
iv) dynamically choose N to avoid overloading the amplifier;a controller operably coupled to the light-source elements and the light-sensing elements and configured to control the emission of the light from the light-source elements and process the detector signals to; I. compare the detector signal strength in each light-sensing element to an attenuation threshold to establish a one or more triangles as defined by limiting ones of the attenuated lines-of-sight for the given light-sensing element; II. establish locations of at least one polygon formed by at least one intersection of the one or more triangles; and III. calculate a center of the at least one polygon to define locations of corresponding one or more touch events. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification