Degree-of-Focus Determination for Multi-Layer Imaging
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Solution Overview
Problem
Conventional focusing algorithms for deep ultra-violet, ultra-violet, visible, and infrared inspection platforms and digital microscopes struggle to accurately determine the degree of focus, especially in multi-layer structures, leading to poor image quality and inability to distinguish between upper and lower layers.
Innovation Solution
A degree-of-focus determination module and position-of-best-focus selection module are integrated into an imaging system, using spatial filters adapted to the dimensions of topological elements, which calculate the degree of focus using linear or non-linear filtering and assemble images with digital focus extension, ensuring that the focus determination operates within the spatial bandwidth of the microscope optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional focusing algorithms are used, then the system can operate across multiple wavelength ranges, but the ability to accurately determine degree of focus in multi-layer structures deteriorates
Solution Approach 1:
The patent applies local quality by using spatial filters with specific transfer functions tailored to the spatial bandwidth of microscope optics. The filtering operation is performed locally on image stacks to determine degree of focus, allowing accurate focus measurement in multi-layer structures while maintaining adaptability across wavelength ranges through wavelength-appropriate filter design.
2Measurement precision
If spatial filtering is applied to determine degree of focus, then layer distinction capability improves, but computational complexity increases
Solution Approach 1:
The patent extracts the essential focus information by applying spatial filters that isolate relevant spatial frequency components within the optical transfer function bandwidth. This extraction approach separates useful layer distinction information from irrelevant high-frequency noise, improving layer differentiation while managing computational complexity through targeted filtering rather than full-image processing.
3Manufacturing precision
If digital focus extension is implemented, then image quality in multi-layer structures improves, but processing time increases
Solution Approach 1:
The patent performs preliminary actions by calculating degree of focus for each image in the stack using spatial filtering before assembling the final extended focus image. This pre-processing step identifies which images contain in-focus information for each spatial location, enabling efficient assembly of the extended focus image while maintaining high quality and reducing overall processing time through systematic organization.
Data Source
AI summary
A system for imaging a structure of an object is provided. The imaging system includes a degree-of-focus determination module that may comprise logic for taking into account at least one of a first and a second dimension of a topological element of the structure to be imaged. An image processing module of the system may comprise: a control module for controlling a motorized focus driver; a memory for storing images; and said degree-of-focus determination module. The imaging system may comprise: a stage; a motorized focus driver for driving the stage; at least one of microscope optics, a lens, an illumination system; a camera; and an image processing module.