An ultrasonic 3D image sensor employing PN code

We developed a new 3D image sensor consisting of an FPGA board, an ultrasonic transmitter, an array receiver and an AD converter. The image sensor transmits 41.7 kHz ultrasonic wave modulated with a PN (pseudo noise) code and then the array sensor composed of 160 receivers collects the signals reflected back from objects. We perform down conversion and beamforming of the received signals and then calculate the correlations with the original PN code to construct a 3D image. Plastic balls with a diameter of 5.5 cm that placed in different positions were detected.