On-line measuring system using optical fiber grating synthetic wave for interfering step height

Abstract

The utility model discloses an on-line measuring system for interference step height in composite wave from optical fiber raster. A composite optical fiber interferometer is built by making use of the Bragg wavelength reflective property in the optical fiber raster. The composite interferometer comprises two optical fiber Michelson interferometers with almost coincident light paths. A Michelson interferometer is used for measuring, and the other is used for stabilizing the system. The impact on the measuring system brought by the environmental interference is corrected through the feedback control compensation, so that the system is applicable to online measuring. Three lasers emit lights of slightly different wavelength but within 1550nm waveband. Because of the effects of the optical fiber raster reflecting Bragg wavelength and self-chirped optical fiber raster reflecting the specific spectrum, a wavelength acts on the stabilizing interferometer for stabilizing the measuring system, and the other two wavelengths act on the measuring interferometer to produce composite wave interference for actual measurement. Different composite wavelengths can be gained by regulating the two wavelengths acting on the measuring interferometer; and the measurement of different step heights can be carried out.

Description

Technical field [0001] The invention relates to a synthetic wave interference step height measurement system using a fiber grating, in particular to a step height measurement system suitable for online measurement, and 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, pages 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 before reaching the measuring head. The measuring head is a Fizeau interferometer, and part of the light is The fiber end surface is reflected as the reference light, and the other part of the light is focused by the self-focusing lens and projected on the measured surface, reflected by the measured surface and then returned to the system and interfered with the reference light. T...

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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