| 摘要 |
PURPOSE:To provide an ultrasonic detector capable of functioning properly even if it is abnormally close to an object, wherein control output is inverted each time an object enters a detection area. CONSTITUTION:When it can not discriminated that an object 8 is present as the result of the detection and judgement of a reflected wave in a detection gate time zone Tb in addition to operation detecting and judging the reflected wave in the detection gate time zone Tb each time an ultrasonic pulse is emitted from an ultrasonic vibrator, the time To required before the preset detection gate time zone Tb is started from the point of time when the reverberation level of the ultrasonic vibrator lowers to a predetermined value Vth after an ultrasonic pulse is emitted is compared with the time Tc most approaching the detection gate time zone Tb wherein the reverberation level of the ultrasonic vibrator lowers to the predetermined value Vth in the time zone from the point of time when the reverberation level of the ultrasonic vibrator lowers to the predetermined value Vth after an ultrasonic pulse is emitted to the start of the detection gate time zone Tb. When the difference between them becomes smaller than a predetermined value alpha, signal processing discriminating the presence of the object 8 is performed. |
