1. Technical Field
The present invention relates to an ultrasonic sensor, and more specifically to an ultrasonic sensor for sending and receiving ultrasonic waves in the human body.
2. Related Art
As is well known, ultrasonic sensors determine the position and condition of a test object using ultrasonic transducers that send and receive ultrasonic waves (e.g., see Japanese Laid-open Patent Publication No. 2009-25179).
A liquid detecting unit (ultrasonic sensor) disclosed in Japanese Laid-open Patent Publication No. 2009-25179 includes an ultrasonic output unit having an ultrasonic transducer, and an acoustic impedance matching layer disposed on the ultrasonic output unit. In the liquid detecting unit, an ultrasonic transceiving face is formed on one side of the ultrasonic output unit. Also, the acoustic impedance matching layer is formed on one side of the ultrasonic output unit. An output face for outputting ultrasonic waves is formed in the side opposite the side in contact with the ultrasonic output unit. A fluid binder holding recess is formed in the output face. When the output face of the liquid detecting unit is brought into contact with a container, the fluid binder holding recess is filled with a fluid binder as the output face is brought into contact with the container.
A tube-shaped recess-forming member is disposed on one side of the ultrasonic output unit, and the interior of the recess-forming member is filled with an acoustic impedance layer to form a fluid binder holding recess. When the output face is brought into contact with a container, the fluid binder holding recess is filled with fluid binder.