The signal quality 0L a fiber-optic distributed temperature sensor based on optical time domain reflectometry (OTDR) is improved using a pre-filtering technique in the iterative deconvolution method. Investigation of the performance is proposed using iteration conditions in which recovery rate of the signal-component is equal to that of the unfiltering technique. The recovered signal in the pre-filtering technique gives a good signal-to-noise ratio (SNR), 3 times of the unfiltered signal. Consequently, improvements in the OTDR signal with SNR of from 10 to 100 are obtained under the iterations for both distance and temperature resolutions.
In topography measurements of a local ocular fundus of the human eye using a grating-pattern projection technique, a pre-processing method to detect fringes accurately and a generalized Fourier transform method to analyze the fringe deformations are proposed. The method of analysis compensates for fringe deformations caused by instrumental characteristics. By combining the two methods, depth information can be determined with high accuracy. It is shown that the topographic parameters of the optic disc and the fundus slopes in the rim area are obtained with good reproducibility.
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