Dispersion Compensation Element for Supercontinuum Interference Measurement
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Solution Overview
Problem
The use of supercontinuum light in interference measurement devices leads to distorted interference waveforms due to wavelength dispersion, resulting in decreased temperature measurement accuracy or rendering temperature measurement impossible.
Innovation Solution
Incorporating a dispersion compensation element with the same dispersion characteristics as the measurement object but differing in thickness by at least the coherence length of the supercontinuum light, which compensates for wavelength dispersion, allowing for accurate measurement of interference peaks and thus improving temperature and thickness measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If supercontinuum light is used in interference measurement, then measurement resolution can be improved, but interference waveform distorts due to wavelength dispersion
Solution Approach 1:
A dispersion compensation element is introduced as an intermediary component between the supercontinuum light source and the measurement object. This element compensates for the wavelength dispersion caused by the measurement object, thereby correcting the interference waveform distortion while preserving the high resolution benefits of supercontinuum light
Solution Approach 2:
The invention changes the optical path length of either the measurement light or reference light to compensate for dispersion effects. By adjusting this parameter, the system maintains accurate interference measurements despite the broad spectrum of supercontinuum light causing wavelength-dependent phase shifts
2Measurement precision
If dispersion compensation element is added, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The dispersion compensation element serves multiple functions simultaneously: it compensates for wavelength dispersion, maintains interference waveform integrity, and enables accurate temperature and thickness measurements. This multi-functionality justifies the added device complexity by delivering comprehensive measurement capabilities
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
The dispersion compensation element narrows the interference peak width, enabling precise measurement of interference peak positions, thereby enhancing the accuracy of temperature, thickness, and refractive index change measurements of the measurement object.
Implementation Method 1
since supercontinuum light (SC light) has a flat spectrum of a wide band and has a short coherence length, conceivably, measurement accuracy can be improved by increasing resolution
Implementation Method 2
The measurement light reflected by the measurement object and the reference light reflected by the mirror are caused to interfere, and the produced interference waveform is measured
Implementation Method 3
a dispersion compensation element which is formed of a material having the same dispersion characteristic as that of the measurement object and which differs in thickness from the measurement object by an amount equal to or greater than the coherence length of the supercontinuum light
Implementation Method 4
the temperature of the measurement object is measured from a change in the position of an interference peak caused by a change in refraction index with temperature or thermal expansion
Data Source
AI summary
[Problem to be Solved] To improve the measurement accuracy of an interference measurement device which utilizes interference of light.[Means for Solution] An interference measurement device includes a light source 10 for emitting supercontinuum light (SC light), an optical fiber coupler 11 for splitting the SC light into measurement light and reference light, a dispersion compensation element 12, a drive unit 13 for moving the dispersion compensation element 12, and light-receiving means 14 for measuring an interference waveform produced as a result of interference between the measurement light and the reference light. A measurement object 15 to be measured is an Si substrate having a thickness of 800 μm. The dispersion compensation element 12 is an Si substrate having a thickness of 780 μm. Namely, the dispersion compensation element 12 is formed of the same material as that of the measurement object 15 and is 20 μm thinner than the measurement object 15. The interference caused by reflection on the back surface of the measurement object 15 and reflection on the back surface of the dispersion compensation element 12 has a narrow peak width because wavelength dispersion is cancelled almost completely. Thus, the accuracy in measuring the peak position improves. As a result, the accuracy in measuring temperature, etc., improves.