Oblique Flow Cytometer Optical Axis for High NA Collection
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Solution Overview
Problem
Conventional flow cytometers are limited in measuring small particles such as bacteria, archaea, and viruses due to their optical sensitivity, which is hindered by background noise and the inability to collect light scattered at a wide range of angles simultaneously.
Innovation Solution
An optical system with a high numerical aperture collection lens and spatial filtering using a beam stop and polarized light, allowing light to be collected from a wide range of angles (1 to 140 degrees) and separated into independent detectors, while minimizing noise through careful positioning of the beam stop and aperture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high numerical aperture collection lens is used to collect light from a wide range of angles, then the signal collection efficiency is improved, but the working distance is reduced and there is insufficient space for the incident laser beam
Solution Approach 1:
The patent changes the spatial arrangement from a perpendicular configuration to an oblique configuration. The collection lens optical axis is positioned at an oblique angle (10-75 degrees) relative to the flow cell surface, rather than perpendicular to it. This dimensional change in the optical path allows the collection lens to achieve high numerical aperture while maintaining sufficient working distance and space for the laser beam to pass through the flow cell.
2Measurement precision
If spatial filtering is used to reduce background noise, then the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The patent extracts and blocks the harmful scattered laser light from reaching the detectors by positioning a beam stop at a specific location in the optical path. The beam stop is placed to intercept light scattered at angles greater than the collection numerical aperture, preventing this background noise from reaching the detectors. This selective removal of the harmful component improves the signal-to-noise ratio without requiring complex active filtering systems.
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 enhances the signal-to-noise ratio for light scatter and fluorescence measurements, providing high sensitivity and stability, and allows for adjustable scatter angle ranges, effectively measuring small particles with improved precision.
Implementation Method 1
light scattered through a wide range of angles (including SALS, MALS and LALS sub-ranges) can be collected through the same lens
Implementation Method 2
Background light (noise) may be reduced by the use of spatial filtering and other optical filtering
Implementation Method 3
other optical filtering such as colour filters and polarisation filters
Implementation Method 4
Each fluorescent marker emits light of a characteristic wavelength range (colour) when it is excited by the laser light
Data Source
AI summary
An optical system suited to high sensitivity measurement of small particles as they travel through a point of detection in a flow cell. The system consists of components along two optical axes, preferably but not necessarily, at approximately the Brewster angle to one another. The first axis incorporates a flow cell, high numerical aperture light collection lens, spatial filtering and optical detectors. The second axis incorporates a radiation source (typically a laser or arc-lamp) and beam shaping optics. The two axes are positioned at an angle sufficient to enable collection of small angle light scatter near the edge of the collection lens and to allow collection of medium and large angle light scatter through the centre and opposite side of the collection lens. The invention enables spatial filtering in the image plane of the collection lens to exclude radiation from the dominating sources of unwanted scattering in the flow cell, and also allows the use of a high numerical aperture lens to collect radiation scattered and fluoresced by the sample particles.