Multipath Interference Suppression in Time-of-Flight Sensors by Exploiting the Amplitude Envelope of the Transmission Signal

Abstract

Time-of-flight (ToF) cameras provide depth information and they have been applied in many areas. However, multipath interference (MpI) affects the depth measurements. This paper proposes an algorithm to suppress MpI during ToF camera depth measurements by exploiting the amplitude envelope of the camera's transmission wave. More precisely, it uses the fact that the amplitude envelope of the ToF camera's transmission wave is constant. The envelope of the reflected signal in the case of MpI deviates from that of the MpI-free envelope. By minimizing the deviation using an adaptive filter, the depth measurement error can be corrected. The method is applied at the sensor side of the ToF camera and lays the theoretical foundation for MpI suppression in ToF cameras. The simulation and experimental results demonstrate that the proposed algorithm is able to significantly improve the depth measurement accuracy.

Modelling of Impulse Functions of Ultrasonic Sensors When Tilt Angle of Reflecting Surface is Changed

“…6). The use of an ultrasound signal envelope is useful precisely in determining the time difference of the ultrasound reflection capture or in analysing the ultrasound signal by convolution (Pare at al., 2020). The Hilbert transform in the general form jh(y) according to Euler was used to obtain the envelope function ye of the sensor impulse function y(t):…”