Two-Stage Electron Biprism Interferometer for Independent Fringe Control
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Solution Overview
Problem
Conventional wavefront-splitting type electron interferometers using a single electron biprism lack flexibility in controlling interference fringe spacing and width, leading to issues with specimen imaging, especially when dealing with large specimens or high carrier-spatial frequency interferograms, resulting in low-quality images due to degraded spatial coherence.
Innovation Solution
The implementation of a combined lens system formed by two stages of objective lenses allows for independent adjustment of focal lengths, enabling flexible magnification and demagnification of specimen images and filament electrode sizes, thereby controlling the interference fringe spacing and width without altering other imaging lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electron biprism is used in a wavefront-splitting type electron interferometer, then the device structure is simple, but the interference fringe spacing and interference width cannot be independently controlled
Solution Approach 1:
The single electron biprism is divided into two separate electron biprisms: a first electron biprism for controlling interference fringe spacing and a second electron biprism for controlling interference width. This segmentation allows independent adjustment of each parameter without affecting the other, resolving the technical contradiction between device simplicity and functional versatility.
2Area of stationary object
If the interference width is increased to accommodate large specimens, then the coverage area is improved, but the interference fringe spacing becomes narrow requiring analysis of interferograms with high carrier-spatial frequency
Solution Approach 1:
By separating the control functions into two biprisms, the system can independently set a large interference width using the second biprism while maintaining appropriate interference fringe spacing through the first biprism, eliminating the trade-off between coverage area and fringe spacing quality.
3Manufacturing precision
If the interference fringe spacing is increased to improve image quality, then the carrier-spatial frequency is reduced, but the interference width becomes narrower limiting the observable specimen area
Solution Approach 1:
The divided biprism system allows the first biprism to set optimal interference fringe spacing for high-quality imaging while the second biprism simultaneously ensures sufficient interference width to cover the required specimen area, resolving the contradiction between image quality and observable area.
4Adaptability or versatility
If two stages of objective lenses are implemented, then independent control of specimen and filament electrode magnification is achieved, but the device complexity increases
Solution Approach 1:
The two-stage objective lens system serves multiple functions: the first objective lens forms an intermediate image and the second objective lens forms the final image while also enabling independent magnification control of the filament electrode. This multi-functionality justifies the increased structural complexity by providing versatile control capabilities.
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 allows for arbitrary control of specimen and filament electrode magnifications, enhancing imaging flexibility and reducing the need for multiple apertures, improving image quality and observational range without changing the filament electrode size, and enabling independent operation of selected area apertures.
Implementation Method 1
An electron beam is deflected by applying the voltage to the central filament electrode
Implementation Method 2
because electron optical systems usually use a magnetic-field-type lens as an electron lens
Implementation Method 3
Optical interferometers are roughly classified into optical interferometers based on amplitude-splitting and those based on wavefront-splitting
Data Source
AI summary
In an electron beam interference system using an electron biprism, which is capable of independently controlling each of the interference fringe spacing s and the interference width W, both of which are important parameters for an interferometer and for an interferogram acquired by the interferometer, an optical system used in a two-stage electron biprism interferometer is adopted. The optical system uses two stages of electron biprisms in an optical axis direction to give the flexibility to the relative magnification relative to a specimen image and that relative to an image of a filament electrode of the electron biprism. In addition, as a two-stage configuration in which two objective lenses (51, 52) are combined, independently controlling the focal length of each objective lens makes it possible to set the relative magnification relative to a specimen image and that relative to an image of the filament electrode of the electron biprism at arbitrary values.