Hollow Waveguide Laser Illumination for PIV

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Solution Overview

Problem

Existing particle image velocimetry (PIV) systems face challenges in delivering high-peak-power laser illumination with uniform beam profiles and high damage thresholds, particularly when using large-core-diameter fibers, which can lead to beam quality issues and safety concerns.

Innovation Solution

The implementation of a hollow tapered optical funnel and a hollow optical waveguide system, combined with a beam shaping optical system, provides a flexible and efficient method for delivering high-peak-power laser illumination, utilizing a grazing-incidence effect for maximum reflectance and mode conversion to achieve a uniform, high-quality beam profile.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If large-core-diameter fibers are used for laser delivery, then flexibility and ease of placement are improved, but beam quality and laser sheet thickness deteriorate

Engineering Contradiction:

Improveflexibility and ease of placementVSAvoidbeam quality and laser sheet thickness

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The invention segments the laser delivery system into two distinct components: a large-core-diameter hollow fiber for flexible laser delivery and a separate beam-shaping optical system for precise beam control. This segmentation allows each component to be optimized independently - the fiber provides flexibility while the optical system ensures beam quality

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The beam-shaping optical system acts as an intermediary between the hollow fiber and the measurement region. It receives the laser output from the fiber and transforms it into the desired sheet geometry, mediating between the flexible but imprecise fiber output and the precise beam requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

2Illumination intensity

If high-peak-power laser emission is used, then illumination intensity is improved, but damage effects on delivery fiber material worsen

Engineering Contradiction:

Improvehigh-peak-power laser deliveryVSAvoiddamage effects on delivery fiber

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the material parameter of the delivery fiber from solid-core silica to hollow-core polymer material. This parameter change enables the system to withstand higher peak power densities without damage, as the hollow polymer structure has higher damage threshold compared to traditional solid silica fibers

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The delivery system uses a composite approach combining hollow fiber technology with specific polymer materials that have high damage thresholds. This allows the system to handle high-peak-power laser emission while preventing damage to the delivery medium

Inventive Principle:

Principle #40Composite materials

3Productivity

If bulk-optics-based illumination technique is used, then laser delivery effectiveness is improved, but device complexity and cost worsen

Engineering Contradiction:

Improvelaser delivery effectivenessVSAvoidcomplexity of articulating arm system

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The invention replaces the complex mechanical bulk-optics system (articulating arm with tubing, gears, and reflectance optics) with a flexible hollow fiber-optic delivery system. This substitution eliminates the need for complex mechanical positioning mechanisms while maintaining effective laser delivery through the flexible fiber

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables the formation of a thin, wide, and uniform laser illumination sheet with high-peak-power delivery without damage effects, offering improved flexibility, miniaturization, and immunity to external influences, while maintaining a high damage threshold and safe laser delivery.

Implementation Method 1

utilizing a grazing-incidence effect for maximum reflectance

Methodology Applied

Scientific EffectGrazing-incidence effect: Reflection

Implementation Method 2

mode conversion to achieve a uniform, high-quality beam profile

Methodology Applied

Scientific EffectMode conversion: Waveguide (optics)

Data Source

PatentUS7787106B2Particle image velocimetry system having an improved hollow-waveguide-based laser illumination system

Publication Date: 2010.08.31 HEALTH AND HUMAN SERVICES GOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY OF THE

AI summary

An illumination system for a particle image velocimetry system has an illumination source, a hollow tapered optical funnel arranged to receive illumination light from the illumination source, a hollow optical waveguide optically coupled to an output end of the hollow tapered optical funnel, and a beam shaping optical system optically coupled to an output end of the hollow optical waveguide. The illumination system is constructed to provide a light sheet to illuminate particles within a fluid under observation. A particle image velocimetry system has such an illumination system.