Reflective Optics System Polarization Preservation

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Solution Overview

Problem

Existing beam focusing systems using reflective optics often alter the polarization state of electromagnetic radiation, which can be undesirable in applications like ellipsometry, and require specific mirror configurations that limit flexibility and efficiency.

Innovation Solution

A reflective optics system comprising four mirrors, including both convex and concave mirrors, where the first and second mirrors have flat surfaces and the third and fourth mirrors provide convex and concave surfaces respectively, arranged such that the planes of incidence are orthogonal, minimizing polarization state changes and allowing for flexible angle settings to maintain beam focus.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional reflective optics are used to focus beams, then focusing capability is achieved, but polarization state of the beam is altered

Engineering Contradiction:
Improvefocusing capabilityVSAvoidpolarization state alteration
Core Design Contradiction:
Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The beam path is divided into two orthogonal planes of incidence, with each plane containing specific mirrors. The first plane contains mirrors M1 and M2, while the second plane contains mirrors M3 and M4. This segmentation allows independent optimization of each plane to achieve both focusing and polarization preservation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system uses asymmetric mirror configurations where M3 is a convex mirror and M4 is a concave mirror, rather than using identical mirrors. This asymmetry in mirror geometry allows the system to achieve focusing capability while maintaining polarization state through careful design of the optical path.

Inventive Principle:
Principle #4Asymmetry

2Object-affected harmful factors

If four similar mirrors are used in orthogonal planes, then polarization state is preserved, but focusing capability is lost

Engineering Contradiction:
Improvepolarization state preservationVSAvoidfocusing capability
Core Design Contradiction:
Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

Different mirrors in the system have different local qualities - M1 and M2 are flat mirrors for beam direction, while M3 is convex and M4 is concave to provide focusing. This local differentiation of mirror properties allows the system to simultaneously achieve polarization preservation and beam focusing.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The system incorporates curved mirror surfaces (convex M3 and concave M4) to provide focusing capability. The curvature of these mirrors enables beam convergence while the orthogonal plane configuration maintains polarization state, resolving the contradiction between focusing and polarization preservation.

Inventive Principle:
Principle #14Spheroidality (Curvature)

3Object-affected harmful factors

If complex mirror configurations are used to preserve polarization, then device complexity increases, but flexibility in angle adjustment decreases

Engineering Contradiction:
Improvepolarization state preservationVSAvoidangle adjustment flexibility
Core Design Contradiction:
Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The orthogonal plane configuration serves multiple functions simultaneously: it preserves polarization state by canceling reflection effects, provides beam focusing through curved mirrors, and allows flexible angle adjustment. This multi-functionality enables the system to achieve polarization preservation without sacrificing operational flexibility.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 effectively minimizes the effects on the polarization state of the input beam, providing a focused beam onto a sample with minimal polarization alteration, enhancing the system's focusing capability and flexibility compared to previous designs.

Implementation Method 1

an input beam (IB) of electromagnetic radiation having a specific polarization state is directed toward said first (M1) mirror and reflects from said reflective surface thereof

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 2

provide both convex and concave mirrors in a system that also utilizes the effect of substantially orthogonal planes, but does not require that four primary mirrors involved to be of similar construction

Methodology Applied
Scientific EffectFocusing: Focusing

Data Source

PatentEP3152536B1Beam focusing and beam collecting optics
Publication Date: 2020.05.13 J A WOOLLAM CO
  • EP3152536B1 patent drawingFigure 1a
  • EP3152536B1 patent drawingFigure 1b
  • EP3152536B1 patent drawingFigure 2a~3c

AI summary

A reflective optics system (RFO) that preferably requires the presence of both convex (M3) and concave (M4) mirrors that have beam reflecting surfaces, the application of which achieves focusing of a beam of electromagnetic radiation onto a sample (OB), (which can be along a locus differing from that of an input beam (IB)), with minimized effects on a polarization state of an input beam state of polarization based on adjusted angles of incidence and reflections from the various mirrors involved (M1) (M2) (M3) (M4).