Flow Cytometer Laser Beam Shaping to Prevent Particle Double-Counting
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Solution Overview
Problem
Flow cytometers face challenges in accurately counting particles due to double-counting issues caused by the beam profile disturbances in the fast axis direction of laser beams, leading to incorrect detection signals.
Innovation Solution
The laser light source apparatus incorporates a beam conversion unit using prism pairs to match the slow axis direction with the flow cell length direction, reducing the beam diameter in the fast axis direction and increasing it in the slow axis direction, ensuring a focused beam waist diameter of 10 μm or less in the flow direction and 60 μm or larger perpendicular to it, thereby avoiding double-counting and optimizing particle detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional laser beam configuration is used without beam conversion, then the beam profile may be simple, but beam profile disturbances occur in the fast axis direction causing double-counting of particles
Solution Approach 1:
The optical system is segmented into distinct functional units: a beam conversion unit with cylindrical lenses for fast and slow axis control, and a focusing lens. This segmentation allows independent optimization of beam profile correction and focusing, resolving the contradiction by managing complexity through modular functional division.
Solution Approach 2:
A beam conversion unit acting as an intermediary element is introduced between the laser source and the focusing lens. This intermediary converts the problematic fast-axis beam profile into a controlled elliptical beam, eliminating profile disturbances that cause double-counting while maintaining system functionality.
2Measurement precision
If the beam diameter is reduced in the flow direction to avoid double-counting, then particle detection accuracy improves, but the beam diameter perpendicular to the flow direction becomes too small reducing detection coverage
Solution Approach 1:
The beam conversion unit intentionally creates an asymmetric elliptical beam profile where the beam diameter in the fast axis direction (perpendicular to flow) is reduced to 10 μm or less for accurate particle detection, while the beam diameter in the slow axis direction (parallel to flow) is increased to 60 μm or more for adequate coverage. This asymmetric configuration resolves the contradiction by applying different dimensional constraints to different spatial directions.
Solution Approach 2:
Different beam diameter characteristics are applied to different spatial directions: the fast axis direction receives strong focusing for precision measurement, while the slow axis direction receives beam expansion for coverage. This local quality differentiation allows the beam to simultaneously satisfy both precision and coverage requirements in their respective directions.
3Adaptability or versatility
If multiple semiconductor lasers with different wavelengths are used, then multi-parameter particle analysis capability improves, but beam profile control and focusing alignment become more difficult
Solution Approach 1:
The beam conversion unit is designed as a universal optical component that can process laser beams of different wavelengths. By using achromatic cylindrical lenses or wavelength-insensitive optical materials, the same beam conversion and focusing configuration works for multiple semiconductor lasers with different oscillation wavelengths, enabling multi-parameter particle analysis without proportionally increasing alignment complexity.
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 effectively prevents double-counting of particles, enhances signal reliability, and allows for precise focusing of laser beams in flow cytometers, improving the accuracy of particle analysis.
Implementation Method 1
a collimating lens that is configured to collimate the laser beam emitted from the semiconductor laser in a spread light state
Implementation Method 2
a beam conversion unit that is configured to match the flow cell length direction with a slow axis direction of the laser beam collimated by the collimating lens in the flow cell after reducing the beam diameter of the laser beam in a fast axis direction and increasing the beam diameter in the slow axis direction
Implementation Method 3
a focusing lens that is configured to focus the laser beam that has passed through the beam conversion unit in the flow cell
Data Source
AI summary
A light source apparatus can avoid double-counting of particles in a flow cytometer for measuring and analyzing a plurality of particles flowing in a flow cell. A light source apparatus for a flow cytometer includes a semiconductor laser for emitting a laser beam, a collimating lens for collimating the laser beam emitted from the semiconductor laser in a spread light state, a first beam conversion unit composed of prisms and a second beam conversion unit composed of prisms for matching a flow cell length direction with a slow axis direction of the collimated laser beam in a flow cell after reducing the beam diameter in a fast axis direction and increasing the beam diameter in the slow axis direction, and a focusing lens for focusing the laser beam passed through these beam conversion units in the flow cell.