Obstacle detection sensor using synchronous detection
First Claim
1. An apparatus for detecting an obstacle in a pinch zone, the apparatus comprising:
- a modulator providing a first modulation signal having an active phase having a first duration and an inactive phase having a second duration;
a photo-emitter coupled to said modulator for receiving said first modulation signal and operative so as to provide an optical signal during an active phase in response to said modulation signal and to be turned off during an inactive phase;
an optical detector optically coupled to said photo-emitter and configured to receive a portion of said optical signal that is reflected from said pinch zone and responsive thereto, said optical detector providing a detector output signal indicative of one characteristic of said received optical signal;
a switched amplifier having a first input coupled to said detector output signal and a second input connected to a reference voltage, said switched amplifier also being coupled to said first modulation signal and having a first gain corresponding to said active phase and a second gain corresponding to said inactive phase, said switched amplifier providing an output signal that includes said detector output signal multiplied by said first gain during said active phase and said detector output signal multiplied by said second gain during said inactive phase;
an integrator coupled to said switched amplifier and receiving said switched amplifier output signal, said integrator being configured and arranged to integrate said switched amplifier output signal over a predetermined measurement period corresponding to at least one pair of active and inactive phases, and to provide an integrator output signal; and
a detector for receiving said integrator output signal and configured and arranged to provide indicia of the presence or absence of an object within said pinch zone based on said integrator output signal.
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Accused Products
Abstract
An object detection system employs a photo-emitter and photo-detector for synchronously detecting and processing an optical signal reflected from an object in a pinch zone of a window or door opening. A photo-emitter light signal is modulated by a modulation signal having an active phase and an inactive phase. The optical detector provides an optical detector signal that is a function of the intensity of the received light. The detected light signal is synchronously detected using a switching amplifier that multiplies the reflected modulated light signal by a first gain during the active phase and by a second gain during the inactive phase. The duration of the active and inactive phases and the first and second gains are selected such that the system gain will average to zero for ambient light when integrated over a predetermined measurement period. The synchronously detected signal is subtracted from a predetermined offset voltage, and this difference is then integrated over the measurement period. The output of the integrator is then compared to a predetermined threshold value.
38 Citations
26 Claims
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1. An apparatus for detecting an obstacle in a pinch zone, the apparatus comprising:
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a modulator providing a first modulation signal having an active phase having a first duration and an inactive phase having a second duration;
a photo-emitter coupled to said modulator for receiving said first modulation signal and operative so as to provide an optical signal during an active phase in response to said modulation signal and to be turned off during an inactive phase;
an optical detector optically coupled to said photo-emitter and configured to receive a portion of said optical signal that is reflected from said pinch zone and responsive thereto, said optical detector providing a detector output signal indicative of one characteristic of said received optical signal;
a switched amplifier having a first input coupled to said detector output signal and a second input connected to a reference voltage, said switched amplifier also being coupled to said first modulation signal and having a first gain corresponding to said active phase and a second gain corresponding to said inactive phase, said switched amplifier providing an output signal that includes said detector output signal multiplied by said first gain during said active phase and said detector output signal multiplied by said second gain during said inactive phase;
an integrator coupled to said switched amplifier and receiving said switched amplifier output signal, said integrator being configured and arranged to integrate said switched amplifier output signal over a predetermined measurement period corresponding to at least one pair of active and inactive phases, and to provide an integrator output signal; and
a detector for receiving said integrator output signal and configured and arranged to provide indicia of the presence or absence of an object within said pinch zone based on said integrator output signal. - 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, 25, 26)
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Specification