| 摘要 |
An elevator system including an elevator car mounted in a structure to serve the landings therein, and an opto-electronic position detector for determining when the elevator car is within a predetermined distance from a selected landing. The position detector includes a source of electromagnetic radiation which is pulsed at a predetermined rate, such as a light emitting diode, and a photovoltaic device which provides an output current having a magnitude responsive to the level of the electromagnetic radiation it is subjected to, such as a photo transistor. The source of electromagnetic radiation and photovoltaic device are mounted in a common housing with a beam splitter, such as a half-silvered mirror, and this assembly is preferably mounted on the elevator car. A control device or target is mounted adjacent each landing to be served by the elevator car, with the control device including a retrodirective reflective surface or retroreflector. The housing is oriented such that the angle of incidence of a beam of electromagnetic radiation provided by the source of electromagnetic radiation strikes the retrodirective surface with an angle other than 90 DEG . The photovoltaic device is electrically biased to provide an output current regardless of the level of the electromagnetic radiation applied to the photovoltaic device. When the photovoltaic device receives electrical radiation, such as from the retrodirective surface, its output current changes, and means responsive to changes in the output current energizes a translating device when the output current changes at a rate indicating the photovoltaic device is receiving the pulsed electromagnetic radiation from the source thereof.
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