Modulated touch entry system and method with synchronous detection
First Claim
1. An input detection system for detecting the presence of an element in a field having a perimeter, which comprises:
- a plurality of light emitters located on said perimeter of said field;
a plurality of light detectors located on said perimeter of said field and aligned so that, for each light emitter there is at least one corresponding light detector;
control means, connected to said light emitters and said light detectors, for selectively activating said light emitters and said light detectors, wherein when a light emitter is activated, said at least one corresponding light detector is activated;
means for modulating said light emitters for producing a plurality of light pulses at a preselected frequency during the activation interval of each light emitter;
signal preconditioning means responsive to a signal from said light detectors for preconditioning said signal to produce a signal preconditioning output;
detecting means responsive to said signal preconditioning output for detecting light pulses, wherein said pulse detecting means are substantially synchronous with said preselected frequency of said light pulses and providing pulse detecting output; and
means responsive to said pulse detecting output for selectively filtering said pulse detecting output and providing a selectively filtered output signal,whereby the output of the light detecting means is progressively processed for transmission to a microprocessor.
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Accused Products
Abstract
A modulated touch entry system and corresponding method for detecting the presence and location of a member within an irradiated field. A touch entry system and corresponding method are disclosed which utilize modulated pulses of light from light emitters, such as light emitting diodes, which are detected by corresponding light detectors, such as phototransistors. The light emitters and the corresponding light detectors are arranged around a frame to provide an irradiated field. The system utilizes circuitry to precondition a signal from the light detectors prior to analyzing the presence of a "hit"; i.e., the presence of a member within the irradiated field. The circuitry includes a differential amplifier and a programmable amplifier, which consists of a digital to analog converter, a current to voltage converter, and a gain stage, to precondition the signal from the light detectors. The portion of the circuit which detects the modulation of the signal from the light detectors is synchronized with the frequency of the modulation of the light pulses so that it detects the presence or absence of modulated light pulses. A filter portion of the circuit for providing an appropriate output signal is also disclosed, as is a circuit for sampling the ambient light strength and selectively disabling the modulation detection circuit when ambient light strength exceeds a preselected value.
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Citations
19 Claims
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1. An input detection system for detecting the presence of an element in a field having a perimeter, which comprises:
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a plurality of light emitters located on said perimeter of said field; a plurality of light detectors located on said perimeter of said field and aligned so that, for each light emitter there is at least one corresponding light detector; control means, connected to said light emitters and said light detectors, for selectively activating said light emitters and said light detectors, wherein when a light emitter is activated, said at least one corresponding light detector is activated; means for modulating said light emitters for producing a plurality of light pulses at a preselected frequency during the activation interval of each light emitter; signal preconditioning means responsive to a signal from said light detectors for preconditioning said signal to produce a signal preconditioning output; detecting means responsive to said signal preconditioning output for detecting light pulses, wherein said pulse detecting means are substantially synchronous with said preselected frequency of said light pulses and providing pulse detecting output; and means responsive to said pulse detecting output for selectively filtering said pulse detecting output and providing a selectively filtered output signal, whereby the output of the light detecting means is progressively processed for transmission to a microprocessor. - View Dependent Claims (2, 3, 7, 11, 12, 13)
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4. An input detection system for detecting the presence of an element in an irradiated field having a perimeter, which comprises:
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a plurality of light emitters located around said perimeter of said field; a plurality of light detectors located around said perimeter of said field and aligned so that, for each light emitter, there is at least one corresponding light detector; control means, connected to said light emitters and said light detectors, for selectively activating said light emitters and said light detectors so that, when a light emitter is activated, at least one corresponding light detector is activated; means for modulating each said light emitter when said light emitter is activated so that each said light emitter emits a plurality of light pulses at a preselected frequency when activated; differential amplification means responsive to said light detectors for amplifying a signal from at least one light detector wherein said light detector and a corresponding light emitter are activated; means responsive to said differential amplification means for removing voltage spikes from a signal amplified by said differential amplification means; programmable amplification means responsive to said spike removal means and to a control signal for selectively amplifying and normalizing an analog signal; and detecting means responsive to said programmable amplification means for detecting said light pulses of a preselected frequency, wherein said detecting means are substantially synchronous with said preselected frequency of said light pulses and for providing an output thereof, said detecting means being of the type operable on an analog signal; and said input detection system further including means for converting said output of said detecting means from analog to digital form and for providing a digital output, whereby the output of the light detecting means is progressively processed and converted to digital form for transmission to a microprocessor. - View Dependent Claims (5, 6)
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8. An input detection system for detecting the presence of an element in an irradiated field having a perimeter, which comprises:
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a plurality of light emitters located around said perimeter of said field; a plurality of light detectors located around said perimeter of said field aligned so that, for each light emitter, there is at least one corresponding light detector; microprocessor control means, connected to said light emitters and said light detectors, for selectively activating said light emitters and said light detectors so that, when a light emitter is activated, at least one corresponding light detector is activated, and for modulating each said light emitter when said light emitter is activated so that each said light emitter emits a plurality of light pulses of a preselected frequency while activated; differential amplification means responsive to said light detectors for amplifying a signal from at least one of said light detectors when said light detector and a corresponding light emitter element are activated; means responsive to said differential amplification means for removing voltage spikes from an output signal of said differential amplification means; programmable amplification means, responsive to said spike removal means and to said microprocessor control means, for selectively amplifying and normalizing a signal to bring said signal within a normalized range in analog form; and detecting means responsive to said analog signal produced by said programmable amplification means for detecting said light pulses at a preselected frequency, wherein said detecting means are substantially synchronous with said preselected frequency of said light pulses and providing an output thereof, whereby the output of the light detecting means is progressively processed for transmission to a microprocessor. - View Dependent Claims (9, 10)
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14. A method for detecting the presence of an element in a field having a perimeter around which a plurality of light emitters and a plurality of light detectors are located, wherein said light emitters and said light detectors are aligned so that for each light emitter, there is at least one corresponding light detector, which comprises the steps of:
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selectively activating said light emitters and said light detectors, wherein when a light emitter is selectively activated, at least one corresponding light detector is activated; modulating each said light emitter when each said light emitter is activated so that each said light emitter emits a plurality of light pulses of a preselected frequency when activated; preconditioning a signal from an activated light detector by amplifying the signal from the activated light detector by a unique gain value for each pair of corresponding light emitters and light detectors to provide a preconditioned output; and detecting light pulses of said preselected frequency with a detector which is of the type operable on analog signals and is substantially synchronous with said preselected frequency of said light pulses, wherein the absence of said light pulses of said preselected frequency indicates an element'"'"'s presence in said field, and providing an output thereof, whereby the output of the light detecting means is progressively processed for transmission to a microprocessor. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification