Microscope Autofocusing Using Cover Slip Edge Detection
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Solution Overview
Problem
Existing automatic focusing methods for light microscopes are often sample-dependent and prone to errors due to low image contrast of samples like fluorescent cells or bacteria, and are susceptible to interference from dust particles, requiring specialized hardware and being costly.
Innovation Solution
A method using an image processing algorithm to identify boundaries of objects other than the sample, such as cover slip edges, for coarse focusing, followed by fine focusing on the sample, which is robust against soiling and does not require additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sample-based autofocusing is used, then focusing can be performed on the sample, but it is prone to errors due to low image contrast of samples like fluorescent cells or bacteria
Solution Approach 1:
The patent introduces an intermediary object (such as a coverslip edge or marker structure) that serves as a mediator between the focusing system and the sample. This intermediary has high image contrast and well-defined boundaries, making it easy to detect and use for determining the z-position, while still being part of the sample preparation structure.
Solution Approach 2:
The patent uses a simplified copy or representation of the sample environment (the intermediary structure) instead of directly analyzing the complex sample itself. This copy has clearly defined geometric features that are easier to detect and process, while still providing accurate z-position information for the actual sample.
2Reliability
If sample-based autofocusing is used, then focusing can be performed on the sample, but it is susceptible to interference from dust particles and soiling
Solution Approach 1:
The patent extracts the focusing task from the sample itself and transfers it to a separate, dedicated structure (the intermediary). This separation removes the harmful effect of soiling and dust on the sample from the focusing detection process, as the intermediary structure is less susceptible to these contaminants.
Solution Approach 2:
The patent acknowledges that soiling and dust are inevitable in sample preparation, but converts this potential harm into a benefit by designing the intermediary structure to be either resistant to soiling or positioned such that soiling does not affect its detection. The clearly defined geometric features of the intermediary provide robust focusing signals even in the presence of contaminants.
3Adaptability or versatility
If projection-based methods are used for autofocusing, then focusing can be performed with less sample dependence, but specialized hardware is required which entails additional costs
Solution Approach 1:
The patent makes the existing microscope imaging system perform multiple functions: it both images the sample and detects the intermediary structure for focusing purposes. This eliminates the need for separate projection hardware while achieving sample-independent focusing, as the same camera and optics used for sample imaging are used to detect the intermediary.
Solution Approach 2:
The patent enables the microscope system to perform autofocusing using its own existing imaging capabilities without requiring external specialized hardware. The system services its own focusing needs by detecting the intermediary structure through its standard imaging path, making the additional functionality self-contained and cost-effective.
4Measurement precision
If sample-based autofocusing is used, then focusing can be performed on the sample, but the capture region is small depending on the sample
Solution Approach 1:
The patent transitions from relying solely on the sample's inherent features (which may occupy a small area) to using the intermediary structure that extends across a larger region of the field of view. This dimensional expansion provides a broader capture region for focusing while maintaining precision through the well-defined geometric features of the intermediary.
Data Source
AI summary
In a method for automatically focusing a microscope, an overview image that shows a sample and an environment is recorded. An image processing algorithm ascertains in the overview image at least one boundary of an object that is not the sample itself. A focus setting is then ascertained at a location of at least one of the ascertained boundaries.