Method and system for calculating reference value of ultrasonic sensor

A system for calculating a reference value of an ultrasonic sensor comprising:

• a contact device having a first surface;
• an ultrasonic sensor configured to transmit an ultrasonic signal toward the first surface and to generate an ultrasonic image based on an ultrasonic echo signal reflected from the ultrasonic signal;
• and
• a measuring device configured to calculate the reference value of the ultrasonic sensor using the ultrasonic echo signal,
• wherein the ultrasonic sensor transmits a first ultrasonic signal while an object is positioned on the first surface,
• wherein the ultrasonic sensor generates a plurality of ultrasonic images based on a first ultrasonic echo signal,
• wherein the measuring device selects an ultrasonic image having a highest similarity to a reference image from among the ultrasonic images, and stores a first parameter and a second parameter corresponding to a selected ultrasonic image,
• wherein the ultrasonic sensor transmits a second ultrasonic signal based on the first parameter while the object is not positioned on the first surface, and
• wherein the measuring device calculates the reference value of the ultrasonic sensor using the second parameter and a second ultrasonic echo signal reflected from the second ultrasonic signal.