Wolter Condenser for X-ray Microscope Field of View

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Solution Overview

Problem

Microfocus x-ray sources in x-ray microscopes have a small focal spot size that limits the field of view, requiring high magnification and large numerical aperture in the condenser to illuminate the sample effectively, which is challenging due to imaging aberrations and the limited numerical aperture of existing focusing systems.

Innovation Solution

A Wolter condenser with a high magnification of at least four and a numerical aperture of 30 mrad or more is used in conjunction with a microfocus x-ray source to achieve adequate field of view and high efficiency, utilizing a compound system of glass capillary tubes with hyperbolic and ellipsoidal segments to maintain image quality and brightness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a microfocus x-ray source with small focal spot size is used, then the brilliance and resolution are improved, but the field of view is limited

Engineering Contradiction:

ImproveresolutionVSAvoidfield of view

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent introduces a condenser optic system that operates in an intermediate dimension between the microfocus source and the sample. This condenser with magnification M > 1 creates a virtual image of the small focal spot at a larger effective size, allowing the field of view to be extended without sacrificing the high resolution capability of the microfocus source. The condenser essentially adds a dimensional transformation layer that decouples the relationship between source size and field of view.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Area of stationary object

If high magnification is used in the condenser to illuminate the sample effectively, then the field of view is improved, but imaging aberrations increase

Engineering Contradiction:

Improvefield of viewVSAvoidimage quality

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent employs a Wolter-type condenser optic consisting of nested hyperbolic and ellipsoidal surfaces. These curved reflective surfaces are specifically designed to focus x-rays from the microfocus source while minimizing aberrations. The hyperbolic outer surface and ellipsoidal inner surface work together to create a telescope-like geometry that provides high magnification without the severe aberrations that would occur with simple spherical mirrors or flat optics.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Quantity of substance

If a rotating anode source is used, then the x-ray flux is improved, but the cost increases

Engineering Contradiction:

Improvex-ray fluxVSAvoidcost

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The patent creates a virtual copy of the microfocus source through the condenser optic system. Instead of using a expensive rotating anode source that physically produces high flux, the system uses a inexpensive stationary microfocus source and optically creates a magnified virtual image that provides the necessary flux distribution across the field of view. This optical copying approach replaces the need for expensive mechanical rotating anode components.

Inventive Principle:

Principle #26Copying

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 significantly reduces exposure times and lowers the cost of x-ray microscopes by utilizing lower-cost microfocus sources while maintaining high resolution and throughput, ensuring effective illumination and minimal aberrations across the field of view.

Implementation Method 1

Methodology Applied

Scientific EffectX-ray reflection and focusing: Reflection

Implementation Method 2

The first two methods are based on improving the thermal dissipation problem that limited the first x-ray generator invented by Roentgen, which produced x-rays by bombarding a solid target anode with energetic electrons.

Methodology Applied

Scientific EffectBremsstrahlung radiation:

Implementation Method 3

The brilliance of an electron bombardment source is proportional to the flux density of energetic electrons impinging on the x-ray target anode. The brightness is limited by the maximum electron density that can be applied to the target before it melts due to high heat flux.

Methodology Applied

Scientific EffectThermal dissipation:

Implementation Method 4

an x-ray objective, such a zone plate lens. The objective forms the image on the detector.

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS7406151B1X-ray microscope with microfocus source and Wolter condenser

Publication Date: 2008.07.29 CARL ZEISS X-RAY MICROSCOPY INC

AI summary

An x-ray microscope uses a microfocus x-ray source with a focus spot of less than 10 micrometers and a Wolter condenser having a magnification of about four or more for concentrating x-rays from the source onto a sample. A detector is provided for detecting the x-rays after interaction with the sample, and an x-ray objective is used to form an image of the sample on the detector. The use of the Wolter optic addresses a problem with microfocus sources that arise when the size of the focal spot that must then be imaged onto the sample with the condenser is smaller than the field of view.