Infrared touch input device having ambient compensation
First Claim
1. An input detection system for detecting the presence of an opaque element in an irradiated field, comprising:
- a plurality of light emitting devices located on the periphery of the irradiated field;
a plurality of light detecting devices located on the periphery of the irradiated field, the light emitting devices and the light detecting devices being located on opposite extremities of the irradiated field, individual light detecting devices being aligned with corresponding individual light emitting devices;
means for activating corresponding aligned light emitting devices and light detecting devices during the same time interval;
means for pulsing each activated light emitting device N times during its activated time interval, wherein N is greater than 2;
means for counting the number of pulses received by each corresponding light detecting device during its activated time interval; and
means for reporting the presence of an opaque element in alignment with corresponding aligned and activated light emitting devices and light detecting devices when the number of pulses received by each activated light detecting device during its activated time interval is less than N.
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Accused Products
Abstract
An input device which can be employed to input commands to a computer directly through a CRT display is disclosed. The input device employs a plurality of infrared light emitting diodes and phototransistors aligned in individual emitter-detector pairs. Infrared beams from the emitter cross the display field before striking the corresponding detector. Emitters and detectors are sequentially activated and each emitter is pulsed or modulated at a frequency different from the variation of ambient conditions during each emitter activation interval. The detection circuitry thus can distinguish the varying emitter signal from ambient or spurious variations. A number of pulses at the pulsed or modulated emitter frequency would be detected unless an opaque element were blocking the particular beam.
91 Citations
17 Claims
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1. An input detection system for detecting the presence of an opaque element in an irradiated field, comprising:
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a plurality of light emitting devices located on the periphery of the irradiated field; a plurality of light detecting devices located on the periphery of the irradiated field, the light emitting devices and the light detecting devices being located on opposite extremities of the irradiated field, individual light detecting devices being aligned with corresponding individual light emitting devices; means for activating corresponding aligned light emitting devices and light detecting devices during the same time interval; means for pulsing each activated light emitting device N times during its activated time interval, wherein N is greater than 2; means for counting the number of pulses received by each corresponding light detecting device during its activated time interval; and means for reporting the presence of an opaque element in alignment with corresponding aligned and activated light emitting devices and light detecting devices when the number of pulses received by each activated light detecting device during its activated time interval is less than N. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An input detection system for detecting the presence of an opaque element in an irradiated field in the presence of varying ambient light, comprising:
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a plurality of light emitting devices located on the periphery of the irradiated field; a plurality of light detecting devices located on the periphery of the irradiated field, the light emitting devices and the light detecting devices being located on opposite extremities of the irradiated field, individual light detecting devices being aligned with corresponding individual light emitting devices; means for activating corresponding aligned light emitting devices and light detecting devices during the same time interval; means for modulating each activated light emitting device during its activated time interval, at a frequency greater than the frequency at which the ambient light varies so that each activated light emitting device is pulsed a plurality of times during its activated time interval; means for filtering out electronic signals generated by the light detecting device varying at a frequency less than the frequency at which the light emitting device is modulated; and means for reporting the presence of an opaque element in alignment with corresponding aligned and activated light emitting devices and light detecting devices when the number of pulses received by each activated light detecting devices during its activated time interval is less than the number of times that each light emitting device is pulsed; whereby the presence of light from each light detecting device incident on each corresponding aligned light detecting device can be detected in the presence of ambient light, and the presence of an opaque element in the irradiated field is detected when light emitted from a light emitting device is not incident on the corresponding aligned light detecting device. - View Dependent Claims (9)
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10. An input detection system for detecting the presence of an opaque element in an irradiated field in the presence of varying ambient light comprising:
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a plurality of light emitting devices located on the periphery of the irradiated field; a plurality of light detecting devices located on the periphery of the irradiated field, the light emitting devices and the light detecting devices being located on opposite extremeties of the irradiated field, individual light detecting devies being aligned with corresponding individual light emitting devices; means for activating corresponding aligned light emitting devices and light detecting devices during the same time interval; means for compensating for varying ambient light by maintaining a signal, otherwise responsive to current through the light detecting device varying in response to variations in the intensity of ambient light, at a constant level despite variations in the intensity of ambient light;
means for pulsing each activated light emitting device during its activated time interval, at a frequency greater than the frequency at which the ambient light varies so that each activated light emitting device is pulsed a plurality of times during its activated timer interval;means for detecting the light pulses incident upon the light detecting devices at the frequency at which each light emitting device is pulsed; and means for reporting the presence of an opaque element in alignment with corresponding aligned and activated light emitting devices and light detecting devices when the number of pulses received by each activated light detecting device during its activated time interval is less than the number of times that each light emitting device is pulsed. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification