Raman Immersion Probe Collimated Beam Design
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Solution Overview
Problem
Existing Raman probes face challenges with analyzing slurries and solids due to issues like reduced throughput, signal degradation, and laser-induced fouling, and they struggle to maintain accurate Raman signal collection across different sample types.
Innovation Solution
The use of a Raman immersion probe with a collimated laser excitation and collection beam passing through a sealed optical component, combined with a retroreflector and a disposable plastic probe optic, allows for direct analysis of samples without cross-contamination and minimizes interference from window materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens-based focused geometry is used to analyze samples, then the Raman signal can be concentrated, but chromatic aberrations occur and different focal lengths are required for different sample types
Solution Approach 1:
The patent removes the lens-based focusing element from the optical path, extracting the chromatic aberration problem by eliminating the refractive element that causes it. The system uses a focused geometry without a physical lens, allowing a single probe design to work across multiple sample types without requiring focal length adjustments.
Solution Approach 2:
The probe design achieves universality by using a focused geometry that works effectively across gases, liquids, slurries, and solids without requiring different focal lengths or lens configurations. The single probe design serves multiple analytical functions across different sample types.
2Measurement precision
If the focal point is moved closer to the distal end to improve throughput, then signal to noise improves, but laser-induced fouling on the window increases
Solution Approach 1:
The patent extracts the window element from the direct laser path by using a focused geometry that focuses within the sample volume rather than at the window surface. This eliminates the window fouling problem while maintaining the benefits of close focusing for improved signal-to-noise ratio.
3Manufacturing precision
If a ball lens is used to focus directly on the face, then distance and depth of field are controlled, but Raman signals from window material interfere with sample signals
Solution Approach 1:
The patent removes the ball lens from the system, eliminating the source of window material Raman signals that interfere with sample analysis. The focused geometry achieves depth of field control through geometric optics rather than refractive focusing, preventing window signal contamination.
4Measurement precision
If higher power lasers are used to improve signal strength, then Raman analysis sensitivity increases, but laser safety issues and window fouling worsen
Solution Approach 1:
The patent extracts the window element from the direct laser path, allowing higher power lasers to be used without the window fouling constraint. The focused geometry concentrates laser energy within the sample volume rather than at the window surface, improving sensitivity while reducing harmful effects on the probe window.
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 configuration enables efficient Raman analysis of gases, liquids, slurries, and solids by eliminating chromatic aberrations, allowing for higher power lasers and reducing laser-induced fouling, while providing better precision and accuracy through representative sampling and real-time turbidity measurements.
Implementation Method 1
A second hollow tube, permanently, removably or moveably sealed to the first tube, includes a distal end incorporating a retroreflector
Implementation Method 2
Raman immersion probe configurations adapted for use with optical apparatus operative to generate a collimated laser excitation beam and receive a counter-propagating collimated collection beam
Data Source
AI summary
Immersion Raman probes use collimated light as opposed to a diverging fiber bundle or lens-based focusing geometry to deliver and collect light to and from a sample, thereby eliminating problems associated with chromatic aberration. The probes convey counter-propagating excitation and collection beams to and from a distally sealed, signal-transmissive optical component such as a window immersed, in contact with, or otherwise exposed to a sample volume. The counter-propagating excitation and collection beams pass directly through the sealed optical component and into the sample volume in collimated form for Raman analysis thereof. The probe may further include a baffled sample chamber coupled to the distal end of the probe optic body, with one or more optical elements to reflect the counter-propagating beams. The sample chamber may be fixed or axially movable to facilitate path length adjustment. The invention finds utility in process Raman, microscopy and other applications.