Step height on-line measuring system using optical fiber grating and wavelength-division multiplex technology

Abstract

The utility model discloses an on-line measuring system for the bench height measuring system of the optical fiber grating and WDM technology. The utility model adopts the Bragg reflection wavelength property of fiber gratings and WDM technology to form a composite fiber interferometer, which comprises two fiber Michelson interferometers with nearly coincident reflector light paths; wherein, one interferometer is used for measuring, while the other is used for stabilizing, compensating the environmental interference to the measuring system through the feedback control circuit, thereby allowing the system to be applied to on-line measurement. The light emitted by the super radiation light emitting diode (LED) with the spectral width of 40 nm is reflected by three fiber gratings with different Bragg wavelengths into the light with three wavelengths. The light is sent into the system; wherein, one wavelength is used in stability interferometer to stabilize system, a second wavelength is used in measurement interferometer to produce a synthetic wave interference for measurement. Different sizes of synthetic wavelengths can be achieved through the regulation of two wavelengths of the measurement interferometer to realize bench height measurement to different heights.

Description

technical field [0001] The invention relates to an online step height measurement system using fiber grating and wavelength division multiplexing technology, in particular to a step height measurement system suitable for on-line measurement, which belongs to the technical field of optical measurement. Background technique [0002] [1] D.P. Hand, T.A. Carolan, J.S. Barton, and J.D.C. Jones, Optics Letters, 1993, Vol. 18, No. 16, pp. 1361-1363. The working principle of the prior art document [1] is shown in Figure 1. The light emitted by the semiconductor laser passes through the Faraday isolator and the optical fiber 50:50 coupler, and then reaches the measuring head. The measuring head is a Fizeau interferometer, and a part of the light is The reflection of the end face of the fiber is used as the reference light, and the other part of the light is projected onto the measured surface after being focused by the self-focusing lens, and then reflected by the measured surface an...

AI Technical Summary

Problems solved by technology

[0009] 1. The measurement system is sensitive to interference such as environmental vibration and temperature drift, and is not suitable for online measurement

[0010] 2. The measured step height is limited by the wavelength λ of the incident light wave. The measurable step height is less than λ / 2, which is only a few hundred nanometers. It is impossible to measure the step height of tens to hundreds of microns.

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