Multi-pass Cell with Concave Reflecting Facets
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Solution Overview
Problem
Existing optical multi-pass cells are often bulky, difficult to manufacture, and suffer from high optical losses due to low reflectivity and inefficient beam confinement, limiting their effectiveness in applications like infrared spectrometry.
Innovation Solution
A compact multi-pass cell design featuring first and second opposing reflectors with discrete concave reflecting facets, arranged to alternately reflect a laser beam multiple times, minimizing beam loss through precise curvature and spatial filtering, and optionally incorporating planar reflecting portions and a spatial filtering mask to enhance beam confinement and detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional planar reflectors are used in multi-pass cells, then the cell can be manufactured with simpler processes, but the optical losses increase due to lower reflectivity and poor beam confinement
Solution Approach 1:
The patent applies spherical curvature to the reflecting facets by forming them on the inner surface of a spherical shell. This curvature enables better beam confinement through total internal reflection and improves optical path stability without requiring complex manufacturing processes, as the spherical geometry can be achieved through conventional glass forming techniques.
2Measurement precision
If the path length through the sample is increased to improve detection sensitivity, then the detection precision improves, but the device size and complexity increase
Solution Approach 1:
The patent embeds the optical path within the spherical shell structure itself, where the sample-containing space is nested within the spherical geometry. The laser beam follows a nested multi-pass trajectory through the sample, confined by the spherical reflector surface, achieving extended path length within a compact nested structure rather than requiring a linear extension of the device.
Solution Approach 2:
The patent transitions from linear or planar optical paths to a three-dimensional spherical optical path. The laser beam traverses the sample in multiple directions through the spherical volume, utilizing spatial dimensions more efficiently to achieve longer effective path lengths within a compact spherical footprint.
3Length of moving object
If more reflecting facets are added to increase beam reflections, then the path length increases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent creates a homogeneous spherical shell structure where the reflecting surface is uniformly curved throughout. This homogeneity in geometry simplifies the relationship between facets, as all facets lie on the same spherical surface with consistent curvature, reducing the precision requirements for individual facet alignment compared to complex polyhedral or planar configurations.
Solution Approach 2:
The spherical curvature of the reflector facets enables the laser beam to maintain stable, predictable reflection paths through the sample. The consistent spherical geometry provides natural beam confinement and reduces sensitivity to minor manufacturing variations in facet positions, allowing for extended optical paths without proportionally increasing precision requirements.
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 a more compact, stable, and efficient optical path with reduced beam loss, enabling longer path lengths for infrared spectrometry and improved sensitivity, while maintaining a compact form factor and ease of manufacture.
Implementation Method 1
each reflector comprising a plurality of discrete concave reflecting facets; the reflecting facets of the first and second reflectors being arranged such that the laser beam is reflected at least once from each of a plurality of the reflecting facets
Data Source
AI summary
The disclosure relates to an infrared spectrometer comprising first and second opposing reflectors spaced apart by a spacing length, and a plurality of discrete concave reflecting facets, the reflecting facets being facets of at least one of the opposing reflectors. An infrared laser source is arranged to form a laser beam. The opposing reflectors are arranged such that the laser beam is reflected alternately from each of the opposing reflectors, including being reflected at least once by each of the reflecting facets. A detector is arranged to detect spectral properties of the laser beam after reflection from each of the plurality of reflecting facets, and an analyser then determines properties of a sample disposed between the first and second opposing reflectors from the detected spectral properties.