Microscope Autofocus Using Dual Beam Paths
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Solution Overview
Problem
Existing autofocus systems in microscopes face challenges with precision, speed, and robustness due to wavelength-dependent penetration depth and reflective properties of objects, leading to deviations in focusing and potential failures, especially in modular or continuous zoom systems.
Innovation Solution
A microscope with an autofocus system utilizing two decoupled beam paths and area sensors to determine contrast differences, allowing for flexible and precise focusing by setting the focal plane relative to the object plane within specific tolerance ranges, enabling both coarse and fine focusing modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active autofocus systems use auxiliary structures or auxiliary beams projected onto the object surface, then focusing capability is enabled, but the system complexity increases due to additional optics and alignment requirements
Solution Approach 1:
The patent extracts the autofocus function from the main imaging beam path by using a separate auxiliary beam path. The auxiliary beam is generated separately and projected onto the object surface independently from the main imaging optics, thereby enabling focusing capability without adding complexity to the primary imaging system.
Solution Approach 2:
The patent introduces an intermediary auxiliary beam path that mediates between the light source and the object surface for focusing purposes. This intermediary system includes separate projection optics and detection optics that operate independently from the main imaging system, allowing autofocus functionality without interfering with the primary imaging path.
2Reliability
If paraxial projection with triangulation is used for autofocus, then focusing is enabled, but additional detection optics and alignment mechanisms are required
Solution Approach 1:
The patent merges the projection function and detection function into a single integrated auxiliary beam path. The same optical system is used to project the auxiliary beam onto the object surface and to detect the reflected light for focusing evaluation, thereby reducing the total number of optical components compared to separate projection and detection systems.
3Ease of manufacture
If wavelengths beyond the visible spectrum (IR) are used for auxiliary beam, then object image is not impaired, but longitudinal chromatic aberration causes focus position offset
Solution Approach 1:
The patent changes the wavelength parameter of the auxiliary beam to be within the visible spectrum range, specifically matching the wavelength range of the main imaging system. This parameter change eliminates longitudinal chromatic aberration and focus position offset while still allowing the auxiliary beam to serve its autofocus function without significantly impairing the object image.
4Ease of manufacture
If IR wavelengths are used for auxiliary beam, then visible image is preserved, but chromatic correction becomes complex in modular or zoom systems
Solution Approach 1:
The patent makes the auxiliary beam wavelength universal by selecting it within the visible spectrum range that is common to all imaging scenarios. This universal wavelength selection eliminates the need for wavelength-specific chromatic correction optics, allowing the same autofocus system to work effectively across modular configurations and continuous zoom ranges without additional correction mechanisms.
5Reliability
If autofocus systems rely on reflective properties of objects, then focusing is achieved, but focusing reliability varies with different object types
Solution Approach 1:
The patent introduces dynamic adaptability into the autofocus system by enabling adjustment of the auxiliary beam wavelength according to the specific object type being imaged. The system can dynamically select optimal wavelengths from the visible spectrum range to match the reflective properties of different objects, thereby maintaining high focusing reliability across diverse object types including semiconductors, biological samples, and industrial components.
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
The system achieves high precision, speed, and robustness in focusing, reducing the time required for focusing and minimizing motion blur, while being adaptable to various objects and maintaining image quality across different magnification ranges.
Implementation Method 1
an auxiliary structure or an auxiliary beam is projected onto the surface of the object to be examined and the reflection is evaluated
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
The invention relates to a microscope (10) comprising an automatic focusing system (11) for carrying out a focusing step, with a first image sensor (14a) which is arranged in a first coupled out beam path (12a) and which is used to capture a first image (16a) and a second image sensor (14b) which is arranged in a second coupled out beam path (12b) and which is used to capture a second image (16b). The automatic focusing system (11) is designed in such a manner that, based on contrast values of the first image (16a) captured by the first image sensor (14a) and the second image (16b) captured by the second image sensor (14b) a contrast difference is determined, and based on the determined contrast difference, a relative position of the focus plane (20) to the object plant (22) is adjusted, the first and the second images (16a, 1bb) respectively comprising image information provided by the respective first and second image sensor (14a, 14b) designed as surface sensors.