Multi-Wavelength Single-Pulse Raman Spectroscopy for Stand-Off Detection
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Solution Overview
Problem
Conventional Raman spectroscopy systems face challenges in long-distance detection of trace materials due to alignment issues, sample degradation, and limited ability to collect Raman scattered light from large sample areas, which affects sensitivity and accuracy.
Innovation Solution
A multi-wavelength single-pulse stand-off Raman spectroscopy system using an unfocused laser with a hybrid diffraction grating and fiber optic bundle to collect and separate scattered light, allowing for simultaneous detection of multiple spectra without the need for focal alignment, reducing sample damage, and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a focused laser beam is used in conventional Raman spectroscopy systems, then the alignment between incident beam and collection optics can be precise, but the system cannot collect Raman scattered light from large sample areas and requires complex focal alignment
Solution Approach 1:
The patent inverts the conventional approach by using an unfocused laser beam instead of a focused beam. This allows the collection optics to gather Raman scattered light from a large sample area without requiring precise focal alignment between the incident beam and collection optics, thereby resolving the contradiction between sample area coverage and alignment complexity.
Solution Approach 2:
The patent employs a stacked fiber bundle with multiple fibers to collect Raman scattered light from different spatial locations simultaneously. Each fiber acts as an independent collection channel, enabling the system to cover large sample areas while maintaining simple alignment requirements for each individual fiber.
2Measurement precision
If high intensity laser is used to improve detection sensitivity, then trace materials can be detected better, but sample degradation occurs
Solution Approach 1:
The stacked fiber bundle distributes the collection function across multiple fibers, allowing the use of lower intensity laser illumination while still achieving sufficient signal collection from the entire sample area. This segmentation of the collection system enables reduced laser intensity, thereby preventing sample degradation while maintaining detection sensitivity.
3Adaptability or versatility
If multiple wavelengths are used to improve spectral coverage, then more complete Raman spectra can be obtained, but the system complexity increases
Solution Approach 1:
The patent implements a multi-wavelength laser source that provides multiple excitation wavelengths simultaneously. The stacked fiber bundle and spectrograph system are designed to handle multiple wavelengths through a single optical path, enabling complete Raman spectra acquisition without requiring separate optical systems for each wavelength, thus maintaining system simplicity while achieving spectral versatility.
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 efficient detection of trace materials over large areas with minimal sample degradation, improving sensitivity and accuracy by collecting multiple spectra simultaneously and reducing alignment requirements.
Implementation Method 1
When a beam of light impinges on substances, light is scattered. In the type utilized in the present invention, Raman scattering, the scattered light is of different wavelengths than the incident light; photons interact with the substance and are re-emitted at higher and lower wavelengths.
Implementation Method 2
a customized spectrograph, which separates the individual spectra from the scattered wavelengths using a hybrid diffraction grating
Data Source
AI summary
The invention provides methods and apparatus comprising a multi-wavelength laser source that uses a single unfocused pulse of a low intensity but high power laser over a large sample area to collect Raman scattered collimated light, which is then Rayleigh filtered and focused using a singlet lens into a stacked fiber bundle connected to a customized spectrograph, which separates the individual spectra from the scattered wavelengths using a hybrid diffraction grating for collection onto spectra-specific sections of an array photodetector to measure spectral intensity and thereby identify one or more compounds in the sample.