Flow Cytometer Laser Diode Optical Subsystem Beam Shaping
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Solution Overview
Problem
Flow cytometers face challenges in producing a focused elliptical beam with a near Gaussian shape along its minor axis and a width along the major axis, leading to reduced signal intensity and increased background scattering, due to the limitations of conventional laser diodes and optical subsystems.
Innovation Solution
A laser diode (LD) based optical subsystem that includes a collimating lens, a plano-convex lens, and a high power cylindrical focusing element, oriented such that the LD's slow axis is perpendicular to the direction of flow, to achieve a tightly focused minor axis and a smooth profile at the viewing zone, while maintaining the major axis width, thus optimizing the beam for flow cytometric applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional laser diodes and optical subsystems are used, then the device complexity is reduced, but the beam profile quality (Gaussian shape along minor axis) deteriorates leading to reduced signal intensity
Solution Approach 1:
The optical subsystem is segmented into distinct functional components: collimating lens for beam collimation, plano-convex lens for focusing in one dimension, and cylindrical lens for focusing in the perpendicular dimension. This segmentation allows each component to optimize a specific aspect of beam shaping, achieving a near-Gaussian profile along the minor axis while maintaining system manageability.
Solution Approach 2:
The patent applies different optical properties to different parts of the beam profile. The collimating lens addresses the major axis, while the plano-convex and cylindrical lenses specifically target the minor axis to achieve Gaussian distribution. This local optimization of beam quality in critical regions enhances signal intensity without requiring complete redesign of the entire optical path.
2Object-affected harmful factors
If conventional optical subsystems are used, then the device complexity is reduced, but background scattering increases due to poor beam profile control
Solution Approach 1:
The optical subsystem is segmented into distinct functional components: collimating lens for beam collimation, plano-convex lens for focusing in one dimension, and cylindrical lens for focusing in the perpendicular dimension. This segmentation allows each component to optimize a specific aspect of beam shaping, achieving a near-Gaussian profile along the minor axis while maintaining system manageability.
Solution Approach 2:
The patent converts the inherent astigmatism and fringe effects of laser diodes from harmful factors into controllable parameters. By using the cylindrical lens to specifically address the minor axis focusing, the system transforms what would be beam quality defects into opportunities for optimized particle illumination, thereby reducing background scattering from out-of-focus regions.
3Ease of manufacture
If laser diodes are used without specialized optics, then ease of manufacture is improved, but fringes and astigmatism in the beam profile increase
Solution Approach 1:
The optical subsystem is segmented into distinct functional components: collimating lens for beam collimation, plano-convex lens for focusing in one dimension, and cylindrical lens for focusing in the perpendicular dimension. This segmentation allows each component to optimize a specific aspect of beam shaping, achieving a near-Gaussian profile along the minor axis while maintaining system manageability.
Solution Approach 2:
The patent changes the optical parameters of the beam through a sequence of optical elements. The collimating lens alters the divergence angle, the plano-convex lens modifies the focal properties in one plane, and the cylindrical lens adjusts the focusing in the perpendicular plane. These parameter transformations convert the raw laser diode output into a controlled beam profile suitable for flow cytometry.
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 signal intensity and reduces background scattering, improving the accuracy and reliability of particle analysis by minimizing the impact of fringes and astigmatism in the laser beam profile.
Implementation Method 1
a collimating lens that converts the diverging beam from the LD into a collimated beam of elliptical shape
Implementation Method 2
a cylindrical lens that reduces the laser beam at the viewing zone to an optimal width in the direction perpendicular to the flow
Implementation Method 3
a composite microscope objective for gathering and imaging light scattered from or fluoresced by particles passing through the viewing zone
Implementation Method 4
a composite microscope objective for gathering and imaging light scattered from or fluoresced by particles passing through the viewing zone
Data Source
Figure 1
Figure 2~2A
Figure 3A
AI summary
The disclosed flow cytometer includes a laser diode ("LD") based optical subsystem for impinging a beam of light upon particles passing through a viewing zone, a composite microscope objective for gathering and imaging light scattered from or fluoresced by particles passing through the viewing zone, a fluidic subsystem for supplying a liquid sheath flow to the viewing zone, a peristaltic pump for injecting into the liquid sheath flow a liquid sample flow carrying particles that passes together with the liquid sheath flow through the viewing zone, a multimode optical fiber that receives scattered and fluoresced light from the viewing zone that the composite microscope objective gathers and images, and a wavelength division multiplexer for optically separating into color bands light received via the optical fiber.