Achromatic Optical System for Laser Light Source Aberration Correction

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Solution Overview

Problem

Laser-operated light sources suffer from chromatic, spherical, and coma aberrations, which negatively impact the optical quality and homogeneity of the generated light, particularly when imaging plasma onto an optical fiber.

Innovation Solution

An achromatic or apochromatic optical system is used to correct for chromatic aberration, and the optical system is designed to match the magnification and numerical aperture with the optical fiber, ensuring optimal coupling and minimizing aberrations, thereby enhancing the light source's optical quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a conventional optical system is used to image plasma onto the optical fiber, then the light collection is achieved, but chromatic, spherical, and coma aberrations occur which degrade optical quality

Engineering Contradiction:
Improvelight collection efficiencyVSAvoidoptical quality
Core Design Contradiction:
Illumination intensityVSManufacturing precision

Solution Approach 1:

The optical system is divided into multiple lens elements with different optical properties. Specifically, a first lens element has positive optical power and a second lens element has negative optical power, allowing each element to contribute differently to the overall optical correction and light collection function

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The optical system uses a composite lens design combining elements with different optical characteristics (positive and negative power elements). This composite structure enables simultaneous correction of multiple aberration types while maintaining efficient light collection capability

Inventive Principle:
Principle #40Composite materials

2Manufacturing precision

If the optical system is corrected for chromatic aberration using achromatic or apochromatic correction, then optical quality is improved, but the device complexity increases

Engineering Contradiction:
Improveoptical qualityVSAvoidoptical system complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies achromatic or apochromatic correction by selecting lens materials and designing element geometries that specifically address chromatic aberration. This involves changing optical parameters such as refractive indices, dispersion properties, and focal lengths to achieve wavelength-independent focusing

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The correction for chromatic aberration is merged into the basic light collection function by integrating the corrective elements directly into the imaging optical system. The positive and negative power lens elements work together to simultaneously collect light and correct aberrations in a unified optical train

Inventive Principle:
Principle #5Merging (Combining)

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

The solution significantly improves the optical quality of the light source by reducing aberrations, ensuring homogeneous light distribution and high light yield, even with adjusting tolerances, and maintaining performance across different wavelengths.

Implementation Method 1

a laser for inputting laser energy into the plasma such that, under the impact of the laser radiation, the plasma generates useful light

Methodology Applied
Scientific EffectLaser radiation: Laser

Implementation Method 2

an optical system for imaging the plasma onto the end of the optical fiber, which faces the optical system, wherein the optical system is corrected for reducing the chromatic aberration

Methodology Applied
Scientific EffectChromatic aberration correction: Lens

Implementation Method 3

means for coupling the useful light into a transferring optical fiber

Methodology Applied
Scientific EffectOptical fiber transmission: Optical Fibre

Data Source

PatentEP2851723B1Laser-operated light source
Publication Date: 2022.01.05 ASML NETHERLANDS BV
  • EP2851723B1 patent drawingFigure 1
  • EP2851723B1 patent drawingFigure 2~3
  • EP2851723B1 patent drawingFigure 4

AI summary

A laser-operated light source encompasses a chamber for accommodating an ionizable gas and an ignition source for ionizing the gas in the chamber for generating a plasma. The light source encompasses a laser for inputting laser energy into the plasma such that, under the impact of the laser radiation, the plasma emits useful light, which forms the output signal of the light source, wherein provision is made for means for coupling the useful light into a transferring optical fiber. An optical system for imaging the plasma onto the end of the optical fiber, which faces the optical system, is arranged between the chamber and the transferring optical fiber, wherein the optical system is corrected for reducing the chromatic aberration.