Scanning Electron Microscope Multi-Lens Objective System
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Solution Overview
Problem
Conventional scanning electron microscopes are limited in achieving high resolution, large depth of focus, and wide field of view simultaneously due to the restricted configuration freedom of objective lenses, which is not adequately addressed by existing multi-lens arrangements.
Innovation Solution
A scanning electron microscope design incorporating at least one condenser lens and three objective lenses, including a distant conventional lens, a close conventional or electrostatic lens, and an immersion lens, allowing for independent activation and combination of lenses to achieve various imaging modes with optimal aperture angle control across a range of electron currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single objective lens is optimized for high resolution, then resolution is improved, but field of view and depth of focus become limited
Solution Approach 1:
The patent divides the objective lens system into three separate lenses: a first objective lens optimized for high resolution, a second objective lens optimized for large field of view, and a third objective lens optimized for large depth of focus. Each lens can be independently activated based on imaging requirements, allowing the system to segment the imaging task among specialized components rather than requiring a single compromise lens.
2Productivity
If the electron current is increased to improve signal strength, then productivity is improved, but resolution decreases due to suboptimal aperture angle
Solution Approach 1:
The patent creates a multi-functional objective lens system where three different lenses can serve various imaging needs. The system can universally handle both high-current imaging (using the first lens for resolution) and low-current imaging (using the second or third lens for field of view or depth of focus), allowing optimal aperture angle to be maintained across a wide range of electron currents by selecting the appropriate lens for each current level.
3Measurement precision
If the aperture angle is optimized for high resolution with small current, then resolution is improved, but the system loses resolution when current increases
Solution Approach 1:
The patent implements a dynamic lens selection mechanism where the system can switch between three different objective lenses based on the required electron current and imaging parameters. This dynamic adaptation allows the aperture angle to be optimized for each current level by selecting the lens designed for that current range, rather than being locked into a fixed aperture angle that compromises performance across the full current range.
4Adaptability or versatility
If multiple objective lenses are added to achieve different imaging modes, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent combines three specialized objective lenses into a single integrated objective lens assembly that shares common mounting and control infrastructure. By merging the three lenses (for resolution, field of view, and depth of focus) into one unified system with coordinated control, the patent achieves multi-imaging-mode capability while reducing the overall complexity that would result from three completely separate lens systems.
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
Enables high-resolution imaging with large depth of focus and field of view by strategically activating and combining the objective lenses, accommodating different sample types and imaging requirements, including non-magnetic samples and simultaneous focused ion beam analysis.
Implementation Method 1
The magnetic field which forms the electron beam is generated between the so-called polepieces in the place of the interruption of the yoke
Implementation Method 2
The objective lens is usually electromagnetic. Such lens consists of a coil with a current passing through the coil and of a yoke made of magnetic material
Implementation Method 3
The electromagnetic lenses can be also substituted by electrostatic lenses which utilize electrodes instead of coils
Implementation Method 4
When using the immersion lens, the examined sample is immersed into the magnetic field generated by the lens. The advantage of the immersion lenses over the conventional ones lies in decrease in the optical aberrations of imaging and in improvement of the resolution of the electron microscope
Data Source
AI summary
A scanning electron microscope comprises three objective lenses, including a distant objective lens and a close objective lens, which are of conventional type, and an immersion objective lens of the immersion type below the distant objective lens and the close objective lens. These three objective lenses can be controlled independently, therefor different combinations of active objective lenses can be achieved. The scanning electron microscope therefore offers various imaging modes. There is a possibility to switch between these imaging modes and therefore, choose the most suitable way of imaging for given application.