Hollow Cone Microscope Illumination for Raman Resolution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current microspectrometry techniques, such as Raman and microellipsometry, face limitations in axial and lateral resolution, leading to low signal-to-noise ratios and reduced intensity of the excitation beam due to the use of confocal and dark field illumination methods, which are unfavorable for thin samples and require expensive filters with high rejection rates.
Innovation Solution
An optical device with hollow cone illumination and point focusing, utilizing a combination of conical lenses and an afocal optical system, generates a collimated incident light beam focused to a point, creating a cylindrical light beam with a dark background, allowing for improved axial and lateral resolution while maintaining signal intensity, and incorporating a collection mirror to separate the Raman backscatter signal effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If confocal illumination is used to improve axial resolution, then axial resolution is improved, but signal intensity is reduced due to beam energy removal
Solution Approach 1:
Instead of removing the central part of the beam (dark-field approach), the invention inverts the approach by using a hollow cone beam that concentrates energy in an annular region while maintaining a dark center. This allows the peripheral rays to provide both the axial resolution improvement and sufficient signal intensity without the need to block the central beam.
Solution Approach 2:
The invention changes the angular distribution parameter of the illumination beam from a conventional Gaussian profile to a hollow cone profile with a specific angular range. This parameter change allows the beam to achieve confocal-like axial resolution while maintaining higher overall intensity by distributing energy in an annular pattern rather than removing it.
2Measurement precision
If dark field illumination is used to improve signal-to-noise ratio, then signal-to-noise ratio is improved, but light intensity collected is greatly reduced
Solution Approach 1:
The invention inverts the conventional dark-field approach by using a hollow cone beam that provides a dark center for background suppression while maintaining an annular bright region that collects sufficient scattered light. This inversion allows simultaneous achievement of high signal-to-noise ratio and adequate light collection efficiency.
3Manufacturing precision
If laser beam is focused to a point to achieve micrometric lateral resolution, then lateral resolution is improved, but axial resolution remains poor due to optical radiation outside focal point
Solution Approach 1:
The invention segments the conventional focused beam into a hollow cone structure where the energy is distributed along a conical path rather than concentrated in a single focal point. This segmentation of the beam energy along the axial direction maintains lateral resolution while improving axial resolution by reducing out-of-focus radiation.
Solution Approach 2:
The invention transitions from a point-focused beam (zero-dimensional focus) to a hollow cone beam that extends in the axial dimension. By adding this dimensional aspect, the beam maintains its lateral focusing capability while distributing energy more favorably along the axial direction, thereby improving axial resolution.
4Measurement precision
If high-rejection filters are used to extract Raman signal, then Raman signal extraction is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts the Rayleigh scattered light (which is the main obstacle to Raman signal detection) by using the hollow cone beam geometry that directs most Rayleigh scattering away from the collection path. This extraction of the dominant background signal reduces the filtering burden and allows simpler filters to be used.
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 solution enhances the signal-to-noise ratio and axial resolution in microspectrometry, reduces the need for high-rejection filters, and allows for more efficient Raman signal extraction, particularly for thin samples, by focusing the illumination to a micrometric area and effectively filtering out the excitation laser beam.
Implementation Method 1
the first conical lens being arranged to receive said collimated incident light beam and to form a first hollow cone light beam
Implementation Method 2
the second conical lens being arranged to receive said first hollow cone light beam and to form a cylindrical light beam with a dark background
Implementation Method 3
the optical objective is arranged to receive said darkfield cylindrical light beam and to form a second hollow cone light beam and to focus said hollow cone light beam at a point of micrometric dimensions in the image focal plane
Data Source
Figure 1~3
Figure 4A~5A
Figure 5B~6
AI summary
The present invention relates to a microscopy method and a hollow cone optical illumination device for a microscope. According to the invention, the illumination device comprises a first conical lens (1) adapted to receive a collimated incident light beam (10) and to form a conical light beam (20), a second conical lens (5) arranged to receive said conical light beam (20, 40) and to form a cylindrical light beam with a dark background (50), and an optical objective (6) having an image focal plane (12) arranged to receive said cylindrical light beam with a dark background (50), to form a hollow cone light beam (60), and to focus said hollow cone light beam (60) at a point (18) in the image focal plane (12).