Atom interferometry is an advanced optical manipulation tool of atoms in precision measurement field. Wavefront aberrations of the Raman beam have become one of the major obstacles impeding the improvement of measurement accuracy. Beforehand measurement of laser wavefront is impractical due to the further wavefront deterioration during optical mounting. In this work, we present a general method for evaluating the effective Raman wavefront that atoms experience and the corresponding phase shift of interferometric fringes. The method extracts the effective Zernike polynomial terms and reconstructs the wavefront using optimal estimation theory. The evaluation accuracy and convergence speed are discussed by simulation. The results predict the method adaptability and provide strong support on analytical and numerical reference for wavefront error compensation.
KEYWORDS: Ultrasonics, LabVIEW, Wavelets, Interference (communication), Signal to noise ratio, Optical testing, Signal detection, Wavelet transforms, Signal processing, MATLAB
Optical methods are used in ultrasonic testing to overcome the limitation of conventional contact transducers in bad situations and have become a hot branch in ultrasonic testing methods. However, the sensitivity in optical methods is lower than that of contact transducers and the use of laser devices brings more noises, which make the signal to be tested more complex. In view of the characteristics of the signal in optical testing, wavelet transform and complex analytic wavelet envelope detection are introduced to extract the signal and its features. Then an optical ultrasonic signal testing virtual instrument system based on LabVIEW is designed, integrating signal acquisition, digital filtering, noise suppression, power spectrum analysis, peak extraction and envelope detection as a whole. Compared with those heavy and expensive equipments, the friendly interface, convenient operation and high extendibility prove its flexibility and value. Finally, experiments are carried out to verify the reliability and precision of the system. Results show a relatively error below 1% in multiple measures.
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