The optic-electro-hybrid feedback laser Doppler anemometer (OEHF-LDA) is designed by using a controlled acousto-optic frequency shift and a hybrid feedback closed loop containing both optic and electronic signals. Instead of a wide frequency bandwidth filter, a narrow one has been used in the signal processor of the OEHF-LDA. The signal-to-noise ratio is significantly improved over that of the conventional LDA under the same frequency dynamic range. The frequency of scattering signal from the measuring volume is almost a time-invariant value determined by selecting the intermediate frequency. The application of the OEHF-LDA is demonstrated by using the system in an unsteady flow experiment made to determine the regurgitant characteristics of a mitral heart valve prosthesis.
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