Multipass Cell Retroreflector Stability
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Solution Overview
Problem
Existing multipass cells are sensitive to vibrations and mechanical misalignment, and they are expensive and difficult to align, with limited achievable optical path lengths and high component costs.
Innovation Solution
A multipass cell design using a combination of two prism mirrors and a concave mirror, which provides enhanced stability due to partial retroreflectivity, allowing for longer optical path lengths and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional multipass cells (White cell or Herriott cell) are used to increase optical path length, then sensitivity of absorption spectrometry is improved, but mechanical stability deteriorates due to sensitivity to vibrations and misalignment
Solution Approach 1:
The optical cavity is segmented into multiple discrete reflective elements (first and second reflective surfaces) that can be independently positioned and adjusted. This segmentation allows for modular alignment and reduces the propagation of mechanical errors throughout the system, enabling long optical path lengths while maintaining stability against vibrations and misalignment.
Solution Approach 2:
A support structure acts as an intermediary between the reflective surfaces and the external environment, providing mechanical isolation and stabilization. This intermediary structure minimizes the transmission of vibrations and external disturbances to the optical components, thereby maintaining mechanical stability while enabling the long optical path lengths needed for high sensitivity measurements.
2Measurement precision
If traditional multipass cells are used to achieve long optical path lengths, then detection sensitivity is improved, but device complexity and alignment difficulty increase
Solution Approach 1:
The reflective surfaces are designed with specific local geometric properties (curvature radii, orientations) that are optimized for their particular positions in the optical path. The first reflective surface has a curvature radius R1 and the second has curvature radius R2, with specific relationships between these local properties that simplify alignment while enabling long optical path lengths and high detection sensitivity.
Solution Approach 2:
The system allows for adjustment of key parameters including the curvature radii of the reflective surfaces, the distance between them, and their relative orientations. By changing these parameters, the optical path length can be optimized for detection sensitivity while simultaneously adjusting the system to maintain manageable alignment complexity through parameter optimization.
3Measurement precision
If traditional multipass cells are used to increase optical path length, then absorption measurement sensitivity is improved, but manufacturing cost increases due to expensive components and additional industrial steps
Solution Approach 1:
The invention replaces expensive, custom-manufactured optical components with simpler, more readily available reflective surfaces that can be manufactured using standard industrial processes. By using reflective surfaces with standard curvatures and mounting them on conventional support structures, the system achieves long optical path lengths at reduced manufacturing cost, eliminating the need for expensive custom components and additional industrial steps.
Solution Approach 2:
The reflective surfaces and support structure are designed to serve multiple functions simultaneously: they provide optical reflection, mechanical support, alignment reference, and vibration isolation. This multi-functionality reduces the need for separate specialized components, thereby lowering manufacturing costs while maintaining the long optical path lengths required for sensitive absorption measurements.
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 design achieves high mechanical stability, allowing for optical path lengths of up to 100 meters, and simplifies mechanical alignment, while being cost-effective and suitable for industrial implementation.
Implementation Method 1
the first reflector arrangement is configured such that light incident on the first reflector arrangement is retroreflected towards the second reflector arrangement
Implementation Method 2
Mirrors or other reflective surfaces of the cell are used to redirect light at reflection points and an arrangement of such reflective surfaces can be used to confine light within a defined space
Data Source
AI summary
A multipass cell (300) comprising: a first reflector arrangement (305A, 305B); and a second reflector arrangement (307), the first (305A, 305B) and second (307) reflector arrangements defining an optical cavity (315) therebetween and the cell; wherein the first reflector arrangement (305A, 305B) is configured such that light incident on the first reflector arrangement (305A, 305B) is at least partially retroreflected towards the second reflector arrangement (307), wherein the second reflector (307) arrangement comprises a concave surface that is reflective, wherein at least one of the first (305A, 305B) and second (307) reflector arrangements comprises an aperture (306) for allowing light to enter and/or exit the optical cavity (315).