Herriott Cell Gas Analyzer Nested Elliptical Paths
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Solution Overview
Problem
Existing gas analyzers require multiple detectors and complex, costly structures to achieve different path lengths for multiple laser beams, which is inefficient and prone to malfunctions in industrial environments.
Innovation Solution
A gas analyzer with a static Herriott cell where multiple laser beams are coupled to traverse nested ellipses, allowing different path lengths and all beams to be detected with a single detector by aligning radiation sources to enter and exit at common vertices, eliminating the need for moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple separate measuring cells are used for different laser beams, then different path lengths can be achieved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent merges multiple measuring functions into a single Herriott cell by coupling multiple laser beams at different entry points. Each laser beam traverses a distinct elliptical path with a specific path length determined by its entry point and angle, allowing simultaneous measurement of multiple gas components with different path lengths in one cell rather than requiring separate cells for each laser.
Solution Approach 2:
The patent utilizes the spatial dimension within the Herriott cell by introducing multiple laser beams at different entry points and angles. Each beam creates a unique elliptical trajectory in the three-dimensional space between mirrors, with path lengths varying according to the entry parameters. This dimensional approach allows path length differentiation without adding more cells.
2Device complexity
If a single Herriott cell is used for multiple laser beams, then device complexity is reduced, but achieving different path lengths becomes difficult
Solution Approach 1:
The patent applies local quality by assigning different entry points and entry angles to each laser beam at the Herriott cell interface. These local parameter variations create distinct elliptical paths for each beam within the cell, resulting in different path lengths. The exit geometry is kept uniform (all beams exit through the same window), but the local entry conditions are optimized for each laser to achieve the desired path length.
3Device complexity
If beam superposition methods are used, then a single detector can be used, but expensive optical components and reduced optical power are required
Solution Approach 1:
The patent creates multiple independent optical paths (elliptical trajectories) within the Herriott cell, each serving as a 'copy' of the measurement function for a different gas component. Each laser beam maintains its full optical power throughout its designated path, and all paths are detected by a single detector. This eliminates the need for beam superposition and associated optical power losses while still achieving multi-component measurement with one detector.
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 simultaneous measurement of multiple gas components with different path lengths using a single detector and static structure, reducing costs and maintaining reliability in industrial settings.
Implementation Method 1
The beam is then reflected back and forth between the two mirrors, resulting in different elliptical patterns of reflection points (spot patterns) on the mirror surfaces
Implementation Method 2
Absorption spectroscopy is a widely used technique for determining gas concentrations. The lower the gas concentrations that can be detected, the greater the absorption of light in the gas to be measured. According to the Lambert-Beer law, absorption increases with increasing light path through the medium to be measured.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Gas analyzer or gas analysis method in which rays from at least two different radiation sources are coupled into a Herriott cell containing a measuring gas and, after multiple reflections, are coupled out of it and detected, wherein the rays are aligned such that they strike the mirrors (e.g. 5) in point patterns (20, 21, 22) running along ellipses, wherein - the ellipses are nested on a common axis of symmetry with two common vertices (e.g.24) and, moreover, have different vertices, - the rays from at least two of the different radiation sources - are coupled into the Herriott cell at different points (29, 30, 31) of the associated point patterns (20, 21, 22) and/or - are coupled into the Herriott cell in such a way that they traverse the associated point patterns (20, 21, 22) along the ellipses in opposite directions, and wherein - all rays are coupled out at the location of one of the common vertices (24).