Laser Beam Polarizer Plate Assembly With Spacer-Based Angular Alignment

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Solution Overview

Problem

Existing optical assemblies for polarizing laser beams face challenges in achieving precise angular alignment and minimizing space requirements due to interference effects between plate-shaped optical elements, which can be mitigated by using spacers for precise positioning but require complex holders and clamping systems.

Innovation Solution

The use of spacers with point-shaped contact and adjustable spherical surfaces allows for precise angular alignment of plate-shaped optical elements, enabling closer spacing and reducing the need for extensive holders, while also allowing for tilted alignments and varying gap widths to minimize interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If plate-shaped optical elements are arranged at a relatively small distance from each other, then space requirements are reduced, but constructive and destructive interference effects arise between partial beams reflected at the beam entry and exit surfaces

Engineering Contradiction:
Improveinstallation spaceVSAvoidinterference effects
Core Design Contradiction:
Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent introduces spacers as intermediary elements positioned between adjacent plate-shaped optical elements. These spacers maintain a controlled gap distance that prevents reflected partial beams from overlapping and causing interference effects, while still allowing the optical elements to be arranged at relatively small distances to minimize installation space requirements.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If the distance between two plates in succession along the beam path is chosen to be large enough to avoid interference effects, then interference is minimized, but the polarizer arrangement requires a potentially considerable amount of installation space

Engineering Contradiction:
Improveinterference effectsVSAvoidinstallation space
Core Design Contradiction:
Object-generated harmful factorsVSVolume of moving object

Solution Approach 1:

The patent applies parameter changes by precisely controlling the gap distance between optical plates through spacers. Instead of using arbitrarily large distances to avoid interference, the spacers maintain an optimized gap size that is sufficient to prevent beam overlap and interference effects while minimizing the overall space required for the polarizer arrangement.

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If spacers are used to achieve precise angular alignment of plate-shaped optical elements, then alignment precision is improved, but the complexity of holders and clamping systems increases

Engineering Contradiction:
Improveangular alignment precisionVSAvoidholder and clamping system complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent employs spacers with spherical contact surfaces that interface with the plate-shaped optical elements. The spherical geometry provides point contact that naturally defines precise angular relationships between adjacent plates, eliminating the need for complex holders and clamping systems while achieving high angular alignment precision.

Inventive Principle:
Principle #14Spheroidality (Curvature)

4Manufacturing precision

If a holder with clamping systems is used to fix plate-shaped optical elements in precise positions, then positioning precision is improved, but device complexity increases

Engineering Contradiction:
Improvepositioning precisionVSAvoidholder structure complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts the alignment function from complex holders and clamping systems by using spacers with spherical contact surfaces. These spacers independently provide precise positioning and angular alignment through their geometry alone, eliminating the need for elaborate holding structures while maintaining high positioning precision.

Inventive Principle:
Principle #2Taking out (Extraction)

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 achieves high precision in angular alignment with minimal space requirements, reducing the complexity of holders and enabling efficient polarization of laser beams with reduced interference effects.

Implementation Method 1

The use of spacers with point-shaped contact and adjustable spherical surfaces allows for precise angular alignment of plate-shaped optical elements

Methodology Applied
Scientific EffectGeometric constraint:

Implementation Method 2

A plate-shaped transmitting optical element can be used to polarize light, for example, in the form of an (e.g., unpolarized) laser beam, if the laser beam strikes a beam entrance surface of the optical element at the so-called Brewster angle

Methodology Applied
Scientific EffectBrewster's angle reflection: Brewster's Angle

Implementation Method 3

a component of the radiation reflected from the beam entrance surface is almost exclusively polarized perpendicular to the plane of incidence of the laser beam (s-polarization), meaning that the reflectivity for a second, perpendicular (p-polarized) component of the radiation is nearly zero

Methodology Applied
Scientific EffectPolarization: Polarisation

Implementation Method 4

the problem of constructive and destructive interference arises between partial beams reflected at the beam entry and exit surfaces of the plane-parallel plates

Methodology Applied
Scientific EffectInterference: Interference

Implementation Method 5

it is proposed to avoid the interference effects described above by aligning the beam entry and exit surfaces of the plate-shaped optical elements at a minimum wedge angle to each other

Methodology Applied
Scientific EffectWedge angle: Wedge

Data Source

PatentEP3850412B1Optical assembly, in particular for polarization of a laser beam, and EUV radiation generating device therewith
Publication Date: 2023.12.06 TRUMPF LASERSYSTEMS FOR SEMICONDUCTORMANUFACTURING SE
  • EP3850412B1 patent drawingFigure 1~2b
  • EP3850412B1 patent drawingFigure 3~5
  • EP3850412B1 patent drawingFigure 6~8

AI summary

The invention relates to an optical assembly (23), in particular for polarization of a laser beam (30), comprising a plurality of plate-shaped optical elements (5, 6,…) having a beam entry surface (5a, 6a,...) and a beam exit surface (5b, 6b,...), and a holder (1) for jointly fixing the plate-shaped optical elements (5, 6,...). Between each two adjacent plate-shaped optical elements (5, 6,...), at least three spacers (11a, 11b,…) are arranged, each designed for punctiform attachment on a beam exit surface (5a, 6a,...) of a first plate-shaped optical element (5), and for punctiform attachment on a beam entry surface (6b, 7b,...) of a second, adjacent plate-shaped optical element (6). The invention further relates to an EUV radiation generating device comprising at least one such optical assembly (23).