Multi-point laser Doppler velocimeter

This paper describes a novel multi-point laser Doppler velocimeter. By employing two acousto-optic modulators (AOMs) for both beam splitting and frequency shifting, we have demonstrated that multiple measuring volumes can be formed by intersecting the multiple diffraction orders generated by the AOMs. Each measuring volume has its frequency shift, which acts as a carrier frequency to that channel. Since the signals from different channels are multiplexed in the frequency domain, only a single photo-detector and a single-channel signal processor are necessary for multi-point measurements. The system has been demonstrated by making multi-point velocity measurements on a rotating disk.