Stepped Mirror Optics for Laser Treatment of Leading-Edge Interiors

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Solution Overview

Problem

The existing methods for treating the internal surfaces of aircraft engine fan blade leading edges are inefficient due to their complex, narrow, and deep geometry, which prevents effective laser treatment, and are also environmentally harmful and costly, as they require aqueous chemical solutions and cannot utilize laser treatment effectively.

Innovation Solution

An optical device comprising a collimator, cylindrical lens, and a reflection component with stepped mirrors on a dihedral surface, allowing a collimated laser beam to be directed quasi-normally onto internal surfaces, minimizing the device's size and enabling treatment of deep and narrow areas, and an air flow generator to prevent vapor deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If aqueous chemical solutions are used for surface treatment, then the internal surfaces can be treated, but the process is long, expensive and polluting

Engineering Contradiction:
Improvesurface treatment capabilityVSAvoidchemical pollution
Core Design Contradiction:
Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the chemical treatment system with a laser-based optical system. The laser beam, guided by the optical device through the narrow opening, directly treats the internal surfaces through ablation or cleaning effects, eliminating the need for chemical solutions and their associated pollution, cost, and time requirements.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The optical device acts as an intermediary that enables laser beam access to internal surfaces through the narrow opening. It transforms the laser beam into a form that can propagate through the constrained geometry and deliver energy to the internal surfaces, replacing the chemical medium with an optical medium.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of operation

If a single tilted mirror is used to reflect laser beam, then the beam can be directed to internal surfaces, but the device becomes very bulky

Engineering Contradiction:
Improvelaser beam directionVSAvoidoptical device size
Core Design Contradiction:
Ease of operationVSVolume of moving object

Solution Approach 1:

The patent segments the optical component into multiple small mirrors arranged on the dihedral surface. Each mirror handles a specific portion of the laser beam, allowing the system to achieve the required beam redirection within a compact volume. This segmentation enables the optical device to fit through narrow openings while maintaining effective laser delivery.

Inventive Principle:
Principle #1Segmentation

3Length of stationary object

If a driven mirror is used to reach the bottom of the room, then the laser beam can cover the depth, but the mirror becomes very thick

Engineering Contradiction:
Improvelaser beam reach depthVSAvoidmirror thickness
Core Design Contradiction:
Length of stationary objectVSVolume of moving object

Solution Approach 1:

The patent transitions from a single-mirror approach (one-dimensional solution) to a multi-mirror arrangement on a dihedral surface (two-dimensional solution). By distributing the beam redirection function across multiple mirrors in a planar configuration rather than using a single thick mirror, the system achieves the required depth coverage without increasing mirror thickness, allowing the device to remain compact and passable through narrow openings.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

4Manufacturing precision

If laser beam is directed from outside in normal direction, then effective laser treatment is achieved, but the deep and narrow geometry prevents beam access

Engineering Contradiction:
Improvelaser treatment effectivenessVSAvoidgeometric accessibility
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent creates a dynamic optical path where the laser beam is continuously redirected by the multiple mirrors to follow the geometry of the internal surfaces. The optical device adapts the beam direction to match the local surface orientation at each point, maintaining near-normal incidence throughout the deep and narrow geometry despite the constrained access from outside.

Inventive Principle:
Principle #15Dynamics

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

Enables precise, rapid, and non-polluting laser treatment of internal surfaces, effectively addressing the geometric challenges and environmental concerns of existing methods.

Implementation Method 1

a collimator (3) intended to be connected to a laser source (9) via an optical fiber (11) to produce a laser beam (13a) having a flat and collimated spatial pulse profile

Methodology Applied
Scientific EffectOptical fiber transmission: Optical Fibre

Implementation Method 2

a cylindrical lens (5) configured to focus said laser beam along a spatial line transverse to the propagation of said beam -laser thus forming a line-laser-beam

Methodology Applied
Scientific EffectOptical focusing: Focusing

Implementation Method 3

a cylindrical lens (5) configured to focus said laser beam

Methodology Applied
Scientific EffectLens refraction: Lens

Implementation Method 4

an optical reflection component configured to be able to be introduced inside said cover piece and to uniformly reflect said line-laser-beam on at least one internal surface of said cover piece and in local directions of incidence quasi-normal to said at least one internal surface

Methodology Applied
Scientific EffectOptical reflection: Reflection

Data Source

PatentEP3571545B1Optical device for laser treatment of the internal surfaces of a covering part
Publication Date: 2022.07.06 SAFRAN SA
  • EP3571545B1 patent drawingFigure 1
  • EP3571545B1 patent drawingFigure 2A~2B
  • EP3571545B1 patent drawingFigure 3A~3B

AI summary

The invention relates to an optical device that is intended for laser treatment of internal surfaces of a covering part of the leading-edge type, including: - a collimator (3) that is intended to be connected to a laser source (9) via an optical fibre (11) to produce a laser beam (13a) having a collimated and flat spatial pulse profile, - a cylindrical lens (5) that is configured to focus said laser beam (13a) along a spatial line that is transverse to the propagation of said laser beam thus forming a line-laser-beam (13b), - a reflecting optical component (7) that is configured to be able to be introduced into the interior of said covering part (15) and to uniformly reflect said line-laser-beam (13b) onto at least one internal surface (17a, 17b) of said covering part (15) and in directions of incidence that are almost normal to said at least one internal surface.