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Abstract

An energy field disturbance sensor comprises an energy field emission means such as a light emitting diode; the emitted field may contain a time-varying component. An energy sensing device such as a photodiode receives the field energy to produce a sensing signal related to the intensity of the emitted field and any disturbance therein. A second signal complementary to the sensed signal is added in a summing junction to the sensing signal to create a summation signal. If the emitted energy field contains a time-varying component, a detection circuit is used to sample the summation signal to convert the summation signal to a proportional detection signal. An analog to digital converter converts the detection signal to a digital form. Digital processing circuitry modulates the amplitude of the complementary signal or the intensity of the energy field according to the desired mode of operation, and in accordance with the behavior of the digital detection signal and external control signals. The circuitry is capable of creating a null condition in the detection signal when the received amplitude of the energy field is such that when added to the complementary signal a cancellation effect occurs; the null condition may be transient or continuous in nature depending on the mode of operation and the nature of the field disturbance.

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