US Patent 7362258 Transponder detection system using radio and light wave signals

A target object detection system for detecting a target object using a detector and a tag on the target object; the tag includes a radio wave receiver receiving radio wave from the detector; a light receiver receiving a light signal from the detector; a receipt signal generator generating a receipt signal; and a transmitter which transmits the receipt signal to the detector; and the detector includes a radio wave transmitter transmitting radio wave to the surrounding area; a receiver receiving the receipt signal from the tag; a light emitter irradiating the light signal to a search region; a controller controlling the radio wave transmitter, the receiver, and the light emitter; and a target position measuring unit measuring a distance to the target object based on the intensity of the receipt signal, and regarding the irradiation direction of the light signal from the light emitter as the direction of the target-object.