Patent ID: 8555724

Claim:
An ultrasonic sensor comprising: a single element of an ultrasonic transducer including at least one combination of an equivalent series capacitor C 1 , an equivalent series inductor L 1 , and an equivalent series resistance R 1 , and an equivalent parallel capacitor C 0 ; a drive circuit configured to drive the ultrasonic transducer; and an inductor L 2 connected in series between the ultrasonic transducer and the drive circuit, wherein the drive circuit is configured to switch a driving frequency of the ultrasonic transducer, a first resonance frequency of the equivalent series capacitor C 1 and the equivalent series inductor L 1 is F 0 , a second resonance frequency determined by at least the equivalent parallel capacitor C 0 and the inductor L 2 is Fp, the drive circuit is configured to drive the ultrasonic transducer while switching the driving frequency to one of the first resonance frequency F 0 and the second resonance frequency Fp to have two kinds of directivity characteristics in different ranges and to have different detection areas, and the first resonance frequency F 0 is different than the second resonance frequency Fp, the first resonance frequency F 0 is calculated using a first capacitance, and an inductance of the equivalent series inductor L 1 and the second resonance frequency Fp is calculated using a second capacitance different than the first capacitance and an inductance component.