Low coherence interference demodulation method based on any extreme value

Abstract

The invention relates to a low coherence interference demodulation method based on any extreme value, which belongs to the field of optical fiber sensing and is also suitable for the technical fields such as three-dimensional morphology detection and optical chromatography and the like. The method comprises the steps of: selecting a Fabry-Perot (F-P) sensor as a sensing element for sensing a change of external air pressure intensity and an optical wedge as an optical path difference space scanning element for forming interference fringes in a local region of zero optical path difference; firstly, performing adaptive Fourier filtering on an interference signal; then, setting proper upper and lower limit threshold values to extract effective peaks and valleys, and guaranteeing that the number of the peaks and the valleys remains the same, numbering these peaks and valleys in a sequence from left to right respectively, only tracking the valley or the peak of any one number in a demodulation process to obtain the displacement of the interference fringes, and when higher accuracy is required, tracking the peaks and the valleys of a plurality of numbers at the same time for signal averaging treatment. According to the method, high-accuracy demodulation of asymmetric interference fringes caused by distortion can be realized.

Description

technical field [0001] The invention relates to a low-coherence interference demodulation method based on any peak or trough of low-coherence interference fringes, which is suitable for the fields of pressure, temperature, strain and displacement sensing and the like. Background technique [0002] Low-coherence interferometry is an effective method for measuring absolute displacement with high precision, and it is used in the fields of surface three-dimensional profile detection, thickness measurement of transparent materials, and optical coherence tomography. The usual practice is to obtain measurement information by locating the zero-path position of low-coherence interference fringes, so the accuracy and repeatability of zero-path position positioning will directly affect the accuracy and stability of the demodulation device. In the initial stage of the development of low-coherence interference, using the contrast or modulation of interference fringes to determine the pos...

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Problems solved by technology

[0003] However, when the low-coherence interference fringe distortion is large and the signal-to-noise ratio is low, the zero-path position positioning error of the above method is relatively large, resulting in limited measurement accuracy, and it is difficult to meet the field where the measurement accuracy requirement is higher than 0.5% F.S.

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