In the researching field of optical superresolution, a phase or amplitude filter is often utilized. They are easy to build, and
simple to insert to a system. A new idea on design a continuous phase filer is proposed. This type of filter is based on the
law that the focal size is mainly decided by the marginal rays in the aperture. A quadric function consisted of tangent
value is built. Assuming that the radially polarized light incident, passing through a phase filer and being focused by a
lens, the intensity distribution on the focal plane is simulated. The vector diffraction theory is used here. To get a smaller
focus, the parameters in the phase function are optimized in Matlab. The results show the superresolution effects.
Compared with others, the filters maintain higher energy utilization rate. A good prospects for application can be
expected.
Noise in the optical fiber sensing system, produced in laser, transmission, demodulation and environment, reduces the
Signal-to-Noise Ratio (SNR) and the measuring accuracy of the whole system . In this paper, a statistical approach based
on Kalman-filter is undertaken to removal noise of the measured object real time, and then to improve the accuracy of
the fiber sensing system. The temperature induced by fiber sensing is modeled as a discrete-time state variable by a
Gauss-Markov random process with the Gaussian white and additive noise in the linear dynamic system. Based on
Bayesian MAP Inference and minimum mean-square error criterion (MMSE), gain of the kalman-filter and the state
error covariance can be regulated by Measurement Update equations to correct posteriori state estimate. Such recursive
algorithm can finally get the optimum estimator of the state through time.
The performances of the model and the algorithm are investigated in the DOFS temperature sensing system. Variance is
used to evaluate its performance in noise removal. At the same time, the experimental results of the method proposed is
compared with original measurement data analysis. The algorithm performs more improvement in accuracy of the fiber
sensing system, and implements the real-time measurement.
A new white-light interferometric technique using in measurement of thickness based on the theory of spectral-domain
interference is specified in the paper. The theory of spectral-domain interference broke the limitation of coherence
length in interferometry, and gain a much longer measuring range than in time-domain. The optical fiber was applied to
Michelson interferometer with the advantage of much convenience of system design. Spectrometer is used to get the
spectral-domain signal. With a simple arithmetic, the optical path difference which is related to some parameter could
be acquired. A thickness measuring system is designed. The measuring range could be calculated, the error could be
forecasted. The simulated result indicats the error of white-light spectral interferometry can be controlled within several
nanometers.
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