Laser Beam Scanning for Uniform Illumination
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Solution Overview
Problem
Flow cytometry instruments face measurement variation due to the Gaussian intensity profile of laser beams, leading to inefficient use of light and increased costs, as larger beam sizes are required to maintain uniformity, which results in wasted light and reduced sensitivity.
Innovation Solution
A method involving a rotating mirror to scan the laser beam in a sinusoidal pattern across the sample, balancing dwell time and intensity to create a flat top illumination profile, optimizing photon dose and reducing measurement variation without increasing beam size or using high-power lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the beam size is increased to maintain illumination uniformity, then measurement variation is reduced, but light is wasted and sensitivity decreases
Solution Approach 1:
The patent applies dynamic scanning of the laser beam across the flow cell using a resonant scanner, transforming the static Gaussian beam into a dynamic flat-top profile through controlled motion. The beam is scanned sinusoidally across the sample area, with the scanning speed and amplitude optimized to create uniform illumination. This dynamic approach allows using a smaller beam size (reducing light waste) while maintaining measurement uniformity through the scanning motion that distributes the Gaussian intensity profile across the entire illumination area.
2Measurement precision
If a higher-power laser is used to offset light waste, then sensitivity increases, but instrument cost increases
Solution Approach 1:
The resonant scanning mechanism dynamically redistributes the laser energy across the flow cell, allowing a lower-power laser to achieve the same effective illumination as a higher-power static beam. The scanning motion ensures that each point in the sample area receives adequate photon flux over the integration period, maintaining sensitivity without requiring increased laser power.
Solution Approach 2:
The resonant scanner operates at its natural resonant frequency, creating efficient periodic sinusoidal motion of the laser beam. This periodic scanning at optimized amplitude and frequency creates the flat-top profile while maximizing the utilization of available laser power, reducing the need for higher-power lasers and thereby lowering instrument cost.
3Measurement precision
If diffractive optics are used to generate a flat top profile, then intensity variation is reduced, but light loss occurs reducing overall intensity
Solution Approach 1:
The patent replaces the optical diffractive approach with a mechanical scanning approach. Instead of using diffractive optics that inherently lose light through diffraction patterns, the system uses a resonant scanner to mechanically move the Gaussian beam across the sample area. This substitution eliminates diffraction-related light loss while achieving the same flat-top illumination profile through temporal averaging of the scanning motion.
4Measurement precision
If the core stream is made larger to maintain beam-to-core ratio, then illumination uniformity is maintained, but coincident events increase
Solution Approach 1:
The dynamic scanning of the laser beam across a smaller core stream creates effective uniform illumination without requiring the core stream to be enlarged. The scanning motion ensures that the entire cross-section of the smaller core receives adequate illumination over the integration period, maintaining measurement uniformity while keeping the core stream diameter small enough to minimize coincident events.
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 approach generates a stable, uniform laser beam profile that increases sensitivity by utilizing more of the laser's energy efficiently, allowing for lower-power lasers and reducing instrument costs while maintaining intensity uniformity.
Implementation Method 1
A method involving a rotating mirror to scan the laser beam in a sinusoidal pattern across the sample
Data Source
AI summary
A laser beam is periodically deflected before being directed into a sample volume. The beam is deflected at a frequency such that the beam makes one or more passes through the sample volume while data are collected from the sample volume. The amplitude of motion of the beam, the dwell time of the beam at any given point, and the Gaussian intensity profile of the beam cooperate to produce an effective flat topped illumination profile for the light that is incident on specimens in the sample volume. The total photon exposure at any given point in the sample volume is a function of both the beam intensity and the dwell time at that location. Therefore, a longer dwell time and lower intensity at the edge of the profile are in balance with a shorter dwell time and higher intensity at the center of the profile.