Chirped Fiber Bragg Grating Interferometer for High-Speed Distance Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing interferometric systems face limitations in measuring mid-range distances with high speed and precision, as they either provide low speed with moderate repeatability at long ranges or high speed with low repeatability at short ranges, making them unsuitable for covering distances from 0.1 meters to a few meters with high speed and sub-millimeter precision.
Innovation Solution
The use of a dispersion unbalanced interferometer with a chirped fiber Bragg grating or highly dispersive optical fiber, combined with a broadband light source and a spectrometer, allows for the numerical compression of a chirped interferogram to enhance detection sensitivity and achieve high-speed, high-precision distance measurements beyond the coherent length of the light source, using a novel numerical algorithm and system configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional interferometric systems use wavelength-stabilized lasers for long-range measurements, then measurement reliability is improved, but measurement speed deteriorates to low speed
Solution Approach 1:
The patent changes the fundamental parameter from narrowband wavelength-stabilized lasers to broadband light sources (superluminescent diodes with 50-100 nm bandwidth). This parameter change enables simultaneous achievement of long measurement range (beyond coherence length) and high measurement speed while maintaining precision through spectral analysis of the interferogram
Solution Approach 2:
The patent transitions from temporal fringe counting to spectral domain analysis. By measuring the interferogram in the spectral dimension and applying Fourier transformation, the system achieves high-speed absolute distance measurement without requiring continuous fringe counting, thus resolving the speed-reliability contradiction
2Speed
If broadband light sources are used for high-speed measurements, then measurement speed is improved, but measurement precision deteriorates to low repeatability
Solution Approach 1:
The patent replaces the mechanical/fringe-counting approach with optical spectral analysis. By using a spectrometer to analyze the spectral interference pattern and applying Fourier transformation, the system achieves sub-millimeter precision (nanometer to micron repeatability) at high speeds, eliminating the precision loss associated with broadband sources
3Difficulty of detecting and measuring
If dispersion unbalanced interferometer with chirped fiber Bragg grating is used, then signal detection sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent introduces a chirped fiber Bragg grating as an intermediary dispersive element in the reference arm. This grating provides wavelength-dependent optical path delay, creating the dispersion unbalance that enhances signal detection sensitivity. The grating acts as a mediator that transforms the broadband light into a chirped reference beam, improving the interferogram quality without requiring complex modulation systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables cost-effective, high-precision, high-speed measurement capabilities for three-dimensional object scanning, with a measurement range from millimeters to meters and repeatability from nanometers to microns, exceeding the limitations of conventional systems by allowing faster scanning with improved signal detection sensitivity.
Implementation Method 1
a dispersive medium arranged to unbalance the dispersion between the measurement arm and the reference arm
Implementation Method 2
The detector is arranged to detect spectral interference from the interferometer
Implementation Method 3
The use of a dispersion unbalanced interferometer with a chirped fiber Bragg grating or highly dispersive optical fiber
Data Source
AI summary
Disclosed herein are interferometric measurement systems and methods. In one exemplary embodiment an interferometric measuring system for measuring the distance to or displacement of an object includes: a light source; an interferometer with a measuring arm and a reference arm; a dispersive medium; and a detector. The interferometer is disposed between the light source and the object. The dispersive medium is arranged to unbalance the dispersion between the measurement arm and the reference arm. The detector is arranged to detect spectrum interference from the interferometer. In one example, the dispersive medium is a chirped fiber Bragg grating. In another example, the dispersive medium is a highly dispersive optical fiber. In one example, the light source is a broadband light source, and the detector includes a spectrometer. In another example, the light source is a wavelength swept laser, and the detector includes a photodetector or a balanced photodetector.