Proximity sensor with adaptive threshold
First Claim
1. A system for sensing the presence of a body part or other object in close proximity to a device, comprising:
- an electromagnetic energy source which can be selectively activated and deactivated;
a receptor which generates an output that varies over time in response to exposure to electromagnetic energy; and
a processor in communication with the source and the receptor, and configured to;
activate and deactivate the source, sample output of the receptor, store a first indicator for receptor output samples bearing a first relation to a threshold value of receptor output, store a second indicator for receptor output samples bearing a second relation to the threshold value, compare a first set of indicators stored during an interval when the source is deactivated with a second set of indicators stored during an interval when the source is activated, and recognize an object-near condition if the comparison identifies a triggering level of difference between the first and second sets.
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Accused Products
Abstract
A proximity sensor measures receptor output with an energy source deactivated. The sensor then measures receptor output with the energy source activated. The measurements with the energy source activated are compared to the measurements with the energy source deactivated to compensate for the effect of ambient conditions. A near condition is recognized if the change between the two groups of measurements exceeds a designated value. To compensate for receptor output that may decrease after reaching a peak value during approach of an object, a near condition can be maintained until the change between the two groups of measurements no longer exceeds a different designated value. Multiple sensors can be used to avoid false near conditions caused by, e.g., placing a device equipped with the sensors next to a stationary object. In one embodiment, a sensor comprises an infrared light emitting diode and a phototransistor.
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Citations
50 Claims
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1. A system for sensing the presence of a body part or other object in close proximity to a device, comprising:
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an electromagnetic energy source which can be selectively activated and deactivated;
a receptor which generates an output that varies over time in response to exposure to electromagnetic energy; and
a processor in communication with the source and the receptor, and configured to;
activate and deactivate the source, sample output of the receptor, store a first indicator for receptor output samples bearing a first relation to a threshold value of receptor output, store a second indicator for receptor output samples bearing a second relation to the threshold value, compare a first set of indicators stored during an interval when the source is deactivated with a second set of indicators stored during an interval when the source is activated, and recognize an object-near condition if the comparison identifies a triggering level of difference between the first and second sets. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A data input device, comprising:
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a first proximity detector located at a first position on the device;
a second proximity detector located at a second position on the device; and
a processor in communication with the first and second proximity detectors, and configured to recognize an object-near condition only if both the first detector and the second detector detect an object in close proximity. - View Dependent Claims (26, 27, 28, 29, 30)
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31. A method of proximity detection that compensates for ambient conditions, comprising:
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sampling, while an electromagnetic energy source is deactivated, output of a receptor which generates an output that varies over time in response to exposure to electromagnetic energy;
storing, in a first set, a first indicator for receptor output samples bearing a first relation to a threshold value of receptor output;
storing, in the first set, a second indicator for receptor output samples bearing a second relation to the threshold value;
sampling output of the receptor while the source is activated;
storing, in a second set, a first indicator for receptor output samples bearing the first relation to the threshold value;
storing, in the second set, a second indicator for receptor output samples bearing the second relation to the threshold value;
comparing the first set with the second set; and
recognizing an object-near condition if the comparison identifies a triggering level of difference between the first and second sets. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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Specification