Axial multipoint laser Doppler velocimetry based on grating guidance

Laser Doppler velocimetry (LDV) technology is highly favored in the field of speed measurement for its high accuracy and resolution. However, it has limitations in specific applications due to its single-point speed measurement capability. To address this issue, a method of axial multi-point laser Doppler velocimetry is proposed to expand the application range of this technology. This method is based on the dual-beam laser Doppler velocimetry mode, utilizing the diffraction characteristics of the reflected grating to achieve spatial separation of measurement points axially. To verify the feasibility of the method, a laser Doppler velocimetry system was constructed, enabling velocity measurements at three axial points within a range of 0–14 m/s, with an average measurement error of less than 4%. Measurements of water flow velocity in a water tank pipeline were conducted, and compared with a standard electronic flowmeter, resulting in an average relative error of approximately 0.77%.