Optical Multi-Pass Cell Using Relay Mirrors for Compact Path Length
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Solution Overview
Problem
Conventional laser absorption spectroscopy systems face limitations in increasing the optical path length for in-situ sampling due to the need for a large physical distance between the optical source and detector, which is not feasible in compact devices, and existing multi-pass cells require significant space and complex setups.
Innovation Solution
An improved optical multi-pass cell design featuring first and second end mirrors with a center rod that supports and aligns them, along with relay mirrors to create additional beam patterns, increasing the effective optical path length within a smaller sample volume, allowing for more efficient absorption measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the physical distance between optical source and detector is increased to enhance signal-to-noise ratio, then the effective path length increases, but the device size and space requirements increase significantly
Solution Approach 1:
The patent transforms the linear path length extension into a multi-dimensional folded path using mirrors. Instead of increasing distance in one dimension, the light beam is reflected multiple times between mirrors to create a three-dimensional folded optical path, achieving long effective path length within a compact physical volume.
Solution Approach 2:
The optical components (mirrors, beam patterns) are nested within a compact housing structure. The light beam is contained and redirected multiple times within the confined space, similar to nested dolls, maximizing the optical path length within the smallest possible physical envelope.
2Measurement precision
If a folded path cell is used to increase optical path length, then the effective path length increases, but the sample volume and operational complexity increase
Solution Approach 1:
The optical path is segmented into multiple discrete reflection segments between mirrors. Each reflection segment contributes to the total effective path length, and the segmented approach allows precise control over the number of passes and total path length independently of the physical cell size.
Solution Approach 2:
The mirror assembly serves multiple functions: it defines the optical path, controls beam direction, determines effective path length, and confines the sample volume. This multi-functionality reduces the need for separate components and simplifies the overall device operation.
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
This design enhances the signal-to-noise ratio by increasing the effective optical path length while reducing the sample volume and operational complexity, enabling faster sampling and more efficient analysis of gas, liquid, or solid samples.
Implementation Method 1
The first and second mirrors are configured to reflect a beam of light directed at one of the first or second end mirrors off-axis from the optical axis one or more times between the first and second end mirrors through the sample cavity
Implementation Method 2
one or more relay mirrors positioned to intercept the beam of light and configured to reflect the beam of light such that at least a second beam pattern is created between the first and second end mirrors
Implementation Method 3
Absorption spectroscopy, and more particularly, laser absorption spectroscopy (LAS) is a well-known laser-based technique used for detecting and monitoring constituents in a medium
Implementation Method 4
measures the absorption of radiation due to its interaction with a sample medium... the absorption of one media depends upon the media constituents and their concentration... Governed by Beer-Lambert law
Data Source
AI summary
An optical multi-pass cell (100) including a sample cavity (109) is provided. The cell (100) also includes first and second end mirrors (103, 104) positioned within the housing (101). The mirrors (103, 104) are configured to reflect a beam of light directed at one of the first or second end mirrors (103, 104) off-axis from the optical axis (113) one or more times between the end mirrors (103, 104) through the sample cavity (109) at a first distance from the optical axis (113) to create a first beam pattern (330). The cell (100) also includes one or more relay minors (220) positioned to intercept reflect the beam of light such that at least a second beam pattern (331) is created between the end mirrors (103, 104) at a distance from the optical axis (113) different from the first distance of the first beam pattern (330).