Optical Acceleration Measurement Method with Large Non-ambiguity Range and High Resolution via Synthetic Wavelength and Single Wavelength Superheterodyne Interferometry

Interferometric optomechanical accelerometers provide superior resolution, but the application is limited due to the non-ambiguity range that is always less than half of the wavelength, which corresponds to the order of mg. This paper proposes a novel acceleration measurement method based on synthetic wavelength and single wavelength superheterodyne interferometry to address this issue. Two acousto-optical modulators and several polarizers are introduced to the two-wavelength interferometry to create four beams with different frequencies and polarization states, and two ultra-narrow bandwidth filters are used to realize the single wavelength measurement simultaneously. This technique offers the possibility to expand the non-ambiguity range without compromising the high resolution. Also, the superheterodyne phase measurement and the corresponding processing algorithm are given to enable real-time measurement. A prototype is built and the preliminary experimental results are compared with the simulation results, showing good agreement. The results prove an estimated acceleration measurement resolution of around 10 μg and a non-ambiguity range of larger than 200 mg, which is more than 100 times that of the single wavelength-based optical accelerometer.

Application of Wavelet Analysis in Denoising Seismic Data

The random noise is the kind of noise with wide frequency band in seismic data detected by the optical acceleration sensors. The noises influence and destroy the useful signal of the seismic information. There are a lot of methods to remove noise and one of the standard methods to remove the noise of the signal was the fast Fourier transform (FFT) which was the linear Fourier smoothing. In this paper, the novel denoising method based on wavelet analysis was introduced. The denoising results of seismic data with the noise with FFT method and wavelet analysis method, respectively. SNRs of the signal with noise, FFT denoisng and wavelet analysis denoising are-8.69, -1.13, and 8.27 respectively. The results show that the wavelet analysis method is prior to the traditional denoising method. The resolution of the seismic data improves.

Design and Simulation of Novel MEMS Optical Acceleration Sensor

A novel MEMS optical acceleration sensor based on a Fresnel diffraction micro-lens is designed in this paper, which is suitable to be used in the fly-by-light system of aviation. The principle of sensor is described. The dynamic performance design of sensor is presented. The constant of silicon micro spring and natural frequency is calculated by using the numerical simulator (ANSYS 8.0) of finite element method. Because the design of the sensor integrates a Fresnel diffraction lens, the optical throughput is high, which brings the advantage of higher signal-to-noise ratio with respect to photon noise. The design of the sensor is well suitable for mass production with normal process of MEMS a low cost. The proof-of-Principle fabrication and experiments show that the principle of this new MEMS optical acceleration sensor is correct.