Non-Parallel IR Sample Holder Eliminates Interference Fringes
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Solution Overview
Problem
Infrared spectroscopy faces challenges in quantitative analysis due to interference fringes caused by high-refractive-index materials like silicon, which are difficult to manufacture into thin, mechanically strong windows for consistent path lengths, and existing solutions either sacrifice quantitative analysis or require high maintenance and costly materials.
Innovation Solution
A device with multiple IR windows arranged to create non-parallel cavities, ensuring waves arrive at the detector in random phases, eliminating interference fringes while maintaining consistent path lengths, using materials like silicon with proper thickness and surface modifications for mechanical strength and low cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high-refractive-index materials like silicon are used for IR windows, then cost is reduced and mechanical strength is improved, but interference fringes appear making quantitative analysis difficult
Solution Approach 1:
The patent applies asymmetry by using non-parallel window surfaces with different orientations. The first window has a first orientation and the second window has a second orientation that is not parallel to the first, creating asymmetric light paths that prevent constructive interference and eliminate fringes while maintaining the use of high-refractive-index silicon materials
Solution Approach 2:
The patent changes the geometric parameters of the window configuration by introducing non-parallel orientations and specific angular relationships between windows. This parameter change modifies the light propagation paths to ensure that reflected and transmitted rays do not recombine in phase, thereby eliminating interference fringes while preserving quantitative analysis capability
2Object-affected harmful factors
If thin windows are used to reduce interference fringes, then fringe effect is reduced, but mechanical strength and consistency of path length deteriorate
Solution Approach 1:
Instead of using thin parallel windows that are mechanically weak, the patent employs thicker windows with non-parallel orientations. The asymmetric configuration ensures that even with greater thickness, the windows maintain mechanical strength while the non-parallel geometry prevents interference fringes by creating divergent light paths
Solution Approach 2:
The patent introduces angular orientation differences between windows, creating a form of geometric curvature in the light path. This angular deviation prevents parallel reflection and transmission paths from recombining, thereby eliminating fringes while allowing the use of mechanically stronger, thicker window materials
3Ease of manufacture
If parallel window surfaces are used, then manufacturing is simplified, but interference fringes are generated due to internal reflection
Solution Approach 1:
The patent deliberately introduces asymmetry by making the window surfaces non-parallel with different orientations. This asymmetric design prevents the formation of equal optical path lengths that would cause constructive interference, thereby eliminating fringes while still using straightforward window geometries that are easy to manufacture
Solution Approach 2:
Instead of using parallel surfaces as is conventional, the patent inverts the approach by using non-parallel surfaces. This inversion of the standard parallel-plate configuration fundamentally changes the light propagation characteristics to prevent interference while maintaining manufacturing simplicity
4Measurement precision
If expensive IR-transparent materials are used, then transmissivity and quantitative analysis capability are improved, but cost and maintenance requirements increase
Solution Approach 1:
The patent enables the use of inexpensive silicon windows by configuring them in a non-parallel arrangement that eliminates fringes. This allows the use of low-cost, disposable silicon windows rather than expensive, maintainable crystal windows, reducing both initial cost and ongoing maintenance requirements while preserving quantitative analysis capability
Solution Approach 2:
The patent changes the geometric parameters (orientations) of the windows to eliminate the need for expensive materials. By introducing non-parallel orientations, the system achieves fringe-free operation with inexpensive silicon, thereby reducing cost and maintenance burden while maintaining measurement precision
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
Enables fringe-free quantitative analysis, reduces maintenance and costs, and allows for the analysis of aqueous and high-pressure samples, making infrared spectroscopy more practical and versatile for routine applications.
Implementation Method 1
The interference fringes appear as a sinusoidal pattern seen on the baseline of the spectrum. These fringes are caused by interference between radiation transmitted directly through the cell or sample and the light that has been reflected internally.
Implementation Method 2
Infrared (IR) spectrum of a sample is obtained by passing a beam of infrared light through the sample or reflecting a beam of infrared light on the sample surface.
Implementation Method 3
The peak corresponding to the frequency of absorption is characteristic of the vibrational frequency of a specific chemical bond or collection of chemical bonds.
Data Source
AI summary
A device for holding samples to be analyzed using the infrared transmission spectroscopy comprised of three or more infrared transparent windows that creates unparalleled gaps while maintaining a consistent path length, which eliminates interference fringes and ensures that quantitative analysis can be achieved. The present invention allows the use of high refractive index material, silicon, as window material. The device using silicon windows can serve both purposes of sample storage and infrared measuring cell. All-purpose disposable sample holders are now possible. In one embodiment, a pre-assembled sample holder is most suitable for loading and analyzing flowable liquid samples. In another embodiment, a sample holder can be easily assembled after high-viscosity fluids and deformable solid samples are loaded. In an alternative embodiment, the device comprised of two or more infrared transparent windows and a reflective mirror can be used for quantitative analysis using transflection infrared spectroscopy.