The Design Of Laser Doppler Velocimetry

The Laser Doppler velocimetry(LDV) is a non-contact measurement of object velocity precision instruments. It is based on the laser Doppler principle, using photoelectric detector of the measurement volume in the scattering of particles on the incident light frequency shift, and according to the frequency shift to calculate the speed of moving objects. Because of its fast dynamic response, high spatial resolution and wide measurement range, and good real-time, is widely used in industrial fields.This paper describes a laser Doppler velocimetry of the historical background, current situation and development trend of domestic and international applications, and then introduces the basic principles of laser Doppler velocimetry, measurement methods, optical model and the Doppler signal processing method.At last,we design a LDV for measuring the velocity of solid surface. The system consists of optical system parts and the signal processing system components, including optical systems using semiconductor laser as light source, and designed a dual beam backscatter optical structures based on experimental optical path, used the avalanche photodiode (APD) to receive light signals.Digital signal processing system including hardware design and software implementation aspects. Hardware design of the pre-filter, amplifier, analog-digital conversion circuit, display circuit and the USB interface; Software using CCS (Code ComPoser Studio) as a development platform for programming. In signal processing, the first high-pass filtered Doppler signal, and then by fast Fourier transform (FFT) algorithm for extracting the frequency information signal, and frequency information calculated based on the velocity of objects in real time.Finally, the system for measuring speed experimental results to achieve the desired results, verify the feasibility of the design.