| 摘要 |
PURPOSE:To detect presence/absence of a vehicle and the vehicle speed by projecting ultrasonic waves to the vehicle to detect reflected waves and measuring the detection duration of infrared rays from a heat source of the vehicle passing a vehicle sense region. CONSTITUTION:A vehicle sensor 1 radiates ultrasonic waves to the vehicle, which runs on a roadway in the vehicle sense region, in accordance with a driving signal S1 from a driving circuit 6, and reflected waves are received by the sensor 1. A vehicle detection signal S2 is inputted to a vehicle presence/ absence decision circuit through the first filter 71, the second amplifier 72, a detecting circuit 73, the second gate circuit 74 operated by a signal S4 from a timing signal generating circuit, and the first holding circuit 75 to decide whether the vehicle exists or not. Meanwhile, infrared rays from the heat source on the vehicle are detected by the sensor 1, and the vehicle detection signal S2 is inputted to a vehicle speed calculating circuit through the third gate circuit 81, the second filter 82, the third amplifier 83, and the second holding circuit 84, and the vehicle speed is calculated in accordance with the detection duration of infrared rays. |
