Detection of occluded small objects in glass bottles filled with beverages via ultrasound center frequency tracing.

Detection of small foreign objects that lie on the bottom or attached to the wall of bottles or containers filled with beverages represents a significant challenge. This is because the echo signals from the object are fused with that reflected from the bottle or container inner surface. The latter has much higher signal energy that masks that of the former. This study formulates the problem as an image construction and processing problem and proposes an algorithm to facilitate object detection using the constructed images. The algorithm is based on the longitudinal (vertical) tracing of a center frequency component obtained using short time Fourier transform (STFT) in conjunction with a transversal (horizontal) differentiation of the image pixels. This method is demonstrated to have improved ability to detect small glass fragments contained inside a glass bottle.