Particle Beam Depth of Field Control via Aperture and Lens Adjustment
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Solution Overview
Problem
Current particle beam devices, such as scanning electron microscopes, can only adjust the depth of field to a limited number of predefined values, which restricts users' ability to select the desired depth of field according to their specific needs, leading to a trade-off between image resolution and depth of field.
Innovation Solution
A method and device that allow users to select and adjust the depth of field by controlling condenser lenses, the relative position of the object to the objective lens, and the aperture unit, enabling specific resolution and image properties tailored to user requirements, with the ability to move the object holder and aperture unit along multiple axes and adjust the aperture opening size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the depth of field is increased by reducing the aperture opening or increasing the working distance, then the depth of field is improved, but the image resolution deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of the aperture opening size through a drive mechanism that allows continuous variation rather than fixed positions. The aperture unit can be moved along the optical axis to change the effective opening size, enabling real-time optimization between depth of field and resolution based on imaging requirements
Solution Approach 2:
The system changes multiple parameters simultaneously - aperture opening size, working distance, and condenser lens excitation - to achieve desired depth of field values while maintaining acceptable resolution. By adjusting these parameters in combination, the patent overcomes the traditional trade-off between depth of field and image quality
2Measurement precision
If the aperture opening is reduced to increase depth of field, then the depth of field is improved, but the primary electron beam diameter increases due to diffraction
Solution Approach 1:
The aperture unit is made movable along the optical axis through a drive mechanism, allowing dynamic adjustment of the aperture opening size. This enables optimization of the balance between depth of field and beam diameter by selecting appropriate aperture positions and opening sizes based on specific imaging requirements
Solution Approach 2:
The system adjusts multiple parameters including aperture opening size, aperture position, condenser lens excitation, and working distance in combination to achieve desired depth of field while minimizing the increase in primary electron beam diameter. By coordinating these parameter changes, the patent mitigates the diffraction effect
3Device complexity
If only two fixed depth of field values are provided, then the device complexity is reduced, but the adaptability to different user needs deteriorates
Solution Approach 1:
The aperture opening size and condenser lens excitation are made dynamically adjustable through drive mechanisms and control units, respectively. This allows continuous or multi-step adjustment of depth of field to many different values rather than just two fixed positions, greatly enhancing adaptability while maintaining manageable device complexity through automated control
Solution Approach 2:
The control unit integrates multiple functions - it controls the drive mechanism for aperture adjustment, adjusts condenser lens excitation, and coordinates working distance changes. This multi-functional control system enables flexible depth of field adjustment across a wide range of values while keeping the overall device structure compact and manageable
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 flexible selection of depth of field and resolution, allowing for high-quality imaging with specific image properties, such as focus and magnification, tailored to user needs, improving the versatility and effectiveness of particle beam device operations.
Implementation Method 1
adjusting an excitation of the condenser lens... controlling a depth of field to a selected value of the depth of field
Implementation Method 2
adjusting an excitation of the objective lens... the image of the object remains in focus
Implementation Method 3
adjusting a position of the aperture unit and/or a size of an aperture unit opening... shaping and/or limiting the particle beam
Implementation Method 4
the electrons of the primary electron beam interact with the material of the sample to be analyzed. In particular, interaction particles and/or interaction radiation arise(s) as a consequence of the interaction
Implementation Method 5
The interaction radiation comprises X-rays and/or cathodoluminescence light and may be detected with a radiation detector
Implementation Method 6
The interaction radiation comprises X-rays and/or cathodoluminescence light
Data Source
AI summary
The invention relates to a method for generating an image of an object (114) using a particle beam device (100) generating a beam of charged particles. Moreover, the invention relates to a particle beam device (100) for carrying out this method. In particular, the particle beam device (100) is an electron beam device and/or an ion beam device. The method comprises selecting a desired value of a depth of field from a plurality of values of the depth of field by a user, wherein each value of the plurality of values of the depth of field is associated with a specific resolution of the particle beam device (100), the specific resolution being achieved when using the desired value of the depth of field. Moreover, the method comprises adjusting the depth of field to the desired value of the depth of field by controlling at least one of: (i) a condenser lens (105, 106), (ii) a relative position of the object (114) to an objective lens (107) and (iii) a position of an aperture unit (108, 109) and/or a size of an aperture unit opening (108A, 118), and imaging the object (114) with the desired value of the depth of field and with the specific resolution associated with the value of the depth of field.