Interferometer Refractive Index Compensation via Spectroscopy
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Solution Overview
Problem
Current interferometer systems face limitations in measurement accuracy due to refractive index fluctuations in air, particularly in the electronics and semiconductor industries, where high precision is required, and existing methods for compensation are either inaccurate or excessively costly and complex.
Innovation Solution
An interferometer arrangement that uses spectroscopic methods to determine the mean refractive index fluctuations by measuring the absorption of air components along the measurement and reference arms, allowing for real-time correction and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If environmental parameters are recorded using discrete sensors, then the measurement setup is simple, but the measurement precision deteriorates due to approximate recording of the light wavelength course
Solution Approach 1:
The patent replaces mechanical/discrete sensor-based environmental parameter measurement with an optical absorption spectroscopy system. The spectrometer unit uses light absorption characteristics of air components to determine the light wavelength course along the measurement axis, eliminating the need for discrete temperature, pressure, and humidity sensors and their complex calibration requirements.
Solution Approach 2:
The patent changes the measurement parameter from discrete environmental parameters (temperature, pressure, humidity) to continuous optical absorption characteristics. By measuring the absorption of light at different wavelengths by air components along the measurement path, the system continuously determines the effective light wavelength with high precision, resolving the contradiction between simple setup and accurate measurement.
2Measurement precision
If sensor response time is increased to capture short-term fluctuations, then the detection capability improves, but the measurement time and cost increase significantly
Solution Approach 1:
The patent replaces slow-responding environmental sensors with an optical absorption spectroscopy system that provides real-time measurement. The spectrometer unit can rapidly measure absorption characteristics and determine the light wavelength course without the response time limitations of traditional sensors, enabling capture of short-term fluctuations without excessive measurement time.
Solution Approach 2:
The patent implements continuous measurement of the light wavelength course along the measurement axis using the spectrometer unit. Instead of periodic sampling with discrete sensors, the system continuously tracks absorption characteristics, ensuring no short-term fluctuations are missed while maintaining efficient measurement throughput.
3Measurement precision
If sound wave methods are used for temperature compensation, then the average air temperature detection improves, but the measurement accuracy deteriorates due to diffraction effects and interference signals
Solution Approach 1:
The patent replaces acoustic-based temperature measurement with optical absorption spectroscopy. The spectrometer unit measures absorption characteristics of light by air components directly along the laser measurement path, eliminating diffraction effects and interference signals associated with sound waves. This provides both accurate average temperature detection and high measurement reliability.
Solution Approach 2:
The patent uses light absorption characteristics as an intermediary to determine the effective light wavelength. Instead of directly measuring temperature and calculating wavelength, the system measures absorption by air components (N2, O2, CO2, H2O) at specific wavelengths, which provides direct information about the refractive index and effective wavelength along the measurement path, improving both accuracy and reliability.
4Measurement precision
If multiple wavelengths are used for vacuum wavelength correction, then the dispersion behavior correction improves, but the device complexity and cost increase due to optical frequency multiplication
Solution Approach 1:
The patent replaces complex multi-wavelength optical frequency multiplication systems with a simpler absorption spectroscopy approach. The spectrometer unit measures absorption characteristics at specific wavelengths to determine the effective light wavelength, avoiding the need for multiple laser frequencies and complex frequency multiplication hardware while achieving comparable or superior correction accuracy.
Solution Approach 2:
The patent extracts only the necessary information for wavelength correction by measuring absorption characteristics of key air components (N2, O2, CO2, H2O) at specific absorption lines. Instead of using multiple wavelengths across the entire spectrum, the system selectively measures absorption at diagnostically useful wavelengths, simplifying the measurement system while maintaining correction accuracy.
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
Significantly enhances measurement accuracy by precisely compensating for refractive index fluctuations, meeting the high precision requirements of the electronics and semiconductor industries with reduced effort and cost compared to existing methods.
Implementation Method 1
the spectrometer light source emits radiation with a wavelength that is in the range of an absorption line of at least one specific air component
Implementation Method 2
an interferometer with an interferometer light source whose emitted radiation can be divided into a measurement arm and a reference arm
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The present invention relates to an interferometer arrangement and a method for the operation thereof. The interferometer arrangement comprises an interferometer having an interferometer light source, the emitted radiation of which may be divided into a measurement arm and a reference arm, wherein a measured object is disposed in the measurement arm and the interferometer provides interferometer signals as a function of the position of the measured object. Detection means are further provided for detecting fluctuations in the refractive index of the air in the measurement and/or reference arm. The detection means comprise a spectrometer unit; the spectrometer unit comprises at least one spectrometer light source and at least one spectrometer detector unit. The ray bundles emitted by the spectrometer light source are overlaid with the ray bundles of the interferometer light source, wherein the spectrometer light source emits radiation with a wavelength in the range of an absorption line of at least one certain air component. The spectrometer detector unit serves to generate spectrometer signals that characterize the absorption of the air component with regard to the spectrometer light source wavelength in the measurement and/or reference arm.