CALCULATION OF DETECTING DEPTH AND MOVING SPEED OF OBJECTS WITH CODED PULSES BASED ON SPEED CHANGES OF ULTRASOUND/SOUND

摘要

During transmission, a speed of ultrasound pulses gradually reduces due to their energy loss from acoustic impedance. A thickness and a density of piezoelectric (PZT) elements and a sound speed in the PZT elements decides energy of the ultrasound pulses and their detecting depth. A speed of moving objects and an angle of the moving objects with the ultrasound pulses may change a speed of reflected ultrasound pulses and affect their time of flight (TOF) and TOF shift. A method of Coding ultrasound pulses combines advantages of a continuous wave ultrasound and a pulsed wave ultrasound. So, it can be used to obtained the TOF and the TOF shift and calculate the depth and the moving speed of the detecting objects, which also avoids a problem of an aliasing for highly moving speed of the objects.

主权项

1. A method for calculating a detecting depth as speed reduction of ultrasound pulses during a transmission, the method comprising:
calculating a speed reducing coefficient of the ultrasound pulses in a transmitting medium, wherein the speed reducing coefficient of the ultrasound pulses is directly proportional to the density of the transmitting medium and the sound speed in the PZT elements, and inversely proportional to a density and a thickness of the PZT elements, which comprising:Speedreducingcoefficient=mediumdensity×soundspeedinPZTPZTdensity×PZTthickness obtaining an average speed (Vavg) of the ultrasound pulses in the transmitting medium, wherein the average speed of the ultrasound pulses is a difference between the maximal speed (Vm) of the ultrasound pulses in the transmitting medium with a multiplication result of the speed reducing coefficient and the maximal speed of the ultrasound pulses in the transmitting medium, which comprising:
Vavg=Vm×(1−speed reducing coefficient); and determining a detecting depth, wherein the detecting depth is a half multiplication value of the average speed and a traveling time of the ultrasound pulses in the transmitting medium.