The Photon Doppler Velocimetry system is widely used in transient high-speed experiments, due to its advantages of non-contact measurement, low cost, high frequency response and good traceability. When the measured target accelerates from 0 to tens of km/s within a few hundred nanoseconds, its signal frequency can reach tens of GHz, so its dynamic range and time resolution capabilities are greatly challenged. The time-stretched Photon Doppler Velocimetry uses the time-stretched characteristics of pulsed lasers to achieve high-frequency signal scaling, improves the time resolution capability of the Photon Doppler Velocimetry, and breaks the Nyquist limit of analog-to-digital conversion technology. The article completes the experimental verification and system error analysis of the time-stretched Photon Doppler Velocimetry for the simulation study of the time-stretched Photon Doppler scale factor.
This paper introduces a design and implementation of high frequency signal acquisition and control system based on DSP + FPGA. The system supports internal/external clock and internal/external trigger sampling. It has a maximum sampling rate of 400MBPS and has a 1.4GHz input bandwidth for the ADC. Data can be collected continuously or periodically in systems and they are stored in DDR2. At the same time, the system also supports real-time acquisition, the collected data after digital frequency conversion and Cascaded Integrator-Comb (CIC) filtering, which then be sent to the CPCI bus through the high-speed DSP, can be assigned to the fiber board for subsequent processing. The system integrates signal acquisition and pre-processing functions, which uses high-speed A/D, high-speed DSP and FPGA mixed technology and has a wide range of uses in data acquisition and recording. In the signal processing, the system can be seamlessly connected to the dedicated processor board. The system has the advantages of multi-selectivity, good scalability and so on, which satisfies the different requirements of different signals in different projects.
The double-pulse Digital Speckle Pattern Interferometry (DSPI) in the laboratory is established. Two good performances have been achieved at the same time, which is uniform distribution of laser beam energy by space filter and recording two successive pictures by a CCD camera successfully. Then two-dimensional discrete orthogonal wavelet transform method is used for the process of filtering method. By using the DSPI, speckle pattern of a vibrated object is obtained with interval of (2~800)μs, and 3D plot of the transient vibration is achieved. Moreover, good agreements of the mode shapes and displacement are obtained by comparing with Laser Doppler Vibrometer (LDV) .
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