Hemispherical Reflecting Surfaces for Raman Spectroscopy
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Solution Overview
Problem
Raman spectroscopy faces challenges due to high costs, fluorescence interference, and low sensitivity, particularly in process applications requiring short integration times, where the low intensity of Raman radiation limits its applicability.
Innovation Solution
An apparatus with a wall structure featuring specularly reflective, concave hemispherical surfaces on both sides, optimized to maximize Raman scattering efficiency by reflecting excitation radiation back to the sample, thereby enhancing the collection of Raman radiation and reducing fluorescence interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional Raman spectroscopy is used with standard optics, then the system structure is simple, but the Raman radiation intensity is low requiring long integration times
Solution Approach 1:
The patent employs concave hemispherical reflecting surfaces instead of flat mirrors to maximize the collection solid angle for Raman scattered photons. The curved geometry allows photons scattered in various directions to be reflected toward the detector, significantly increasing the detected photon rate and reducing required integration time.
Solution Approach 2:
The patent transitions from a conventional linear optical path to a three-dimensional configuration using opposing hemispherical surfaces. This spatial arrangement creates multiple reflection paths and increases the effective collection area, allowing photons to be captured from a broader angular range and improving detection efficiency.
2Illumination intensity
If the excitation power is increased to improve Raman signal, then the Raman radiation intensity increases, but fluorescence interference increases
Solution Approach 1:
The patent converts the harmful effect of scattered excitation light into a beneficial effect by using concave reflecting surfaces to redirect scattered photons back through the sample. This increases the effective excitation path length and enhances Raman signal generation while the spectral filtering components selectively reject the corresponding fluorescence background.
Solution Approach 2:
The patent changes the geometric parameters of the optical system by introducing opposing concave surfaces with specific radii of curvature. This geometric modification increases the collection efficiency for Raman photons while maintaining separation between the excitation and collection paths, allowing better discrimination against fluorescence through angular and spectral filtering.
3Productivity
If the collection solid angle is increased to improve photon collection, then the Raman radiation detection efficiency increases, but the device complexity increases
Solution Approach 1:
The patent uses concave hemispherical reflecting surfaces that passively increase the collection solid angle through their curved geometry. The hemispherical shape naturally captures photons scattered over a wide angular range and redirects them toward the detector, achieving high collection efficiency without requiring complex active scanning or multiple moving components.
Solution Approach 2:
The opposing hemispherical surfaces create a self-focusing effect where scattered photons are automatically redirected back through the sample and toward the collection optics. This passive geometric design eliminates the need for complex active control systems, motorized stages, or sophisticated alignment mechanisms, reducing overall system complexity while maintaining high photon collection rates.
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 significantly increases the detection of Raman photons, allowing for faster signal acquisition and higher accuracy in measuring pharmaceutical samples, enabling high-speed screening and testing of multiple products.
Implementation Method 1
a first concave reflecting surface and a second concave reflecting surface which face each other... reflecting excitation radiation back to the sample
Implementation Method 2
the wall structure being between the concave surfaces and configured to optically isolate the concave surfaces from each other
Data Source
Figure 1~2B
Figure 2C~3B
Figure 3C~4
AI summary
An apparatus and method using the apparatus for measuring target samples, particularly pharmaceutical products using Raman radiation. The sample (212) is located in an optically transparent aperture (210) in an optically non-transparent wall structure (208) with a reflective surface (250) on one or both of the sides of the wall structure (208) facing respectively the excitation radiation transmitter (220) or the Raman radiation detector (222). Preferably two reflective surfaces (250) each in hemispherical shape and facing each other in a spherical arrangement are provided, with the wall structure (208) across the diameter of the sphere.