Autofocus Reliability Verification for Observation Apparatus
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Solution Overview
Problem
Existing observation apparatuses face challenges in accurately focusing on diverse objects, such as industrial samples and living cells, due to variations in size and shape, which can lead to unreliable in-focus positions, especially when using passive autofocus schemes.
Innovation Solution
An observation apparatus that includes an image capturing unit, an optical system, and a processor that adjusts the relative positional relationship between the object and the imaging surface. The processor decides an in-focus position based on multiple images acquired at different positions, determines the reliability of this position, and if unreliable, moves the focusing unit to acquire candidate images across a range to ensure accurate focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive autofocus schemes are used to maintain simple equipment configuration, then device complexity is reduced, but focusing reliability deteriorates due to variations in object size and shape
Solution Approach 1:
The system performs contrast AF multiple times and uses reliability determination based on focus scores to verify whether the obtained in-focus position is reliable. This feedback mechanism allows the system to detect unreliable focusing results and trigger corrective actions (acquiring candidate images at multiple positions), thereby resolving the contradiction between simple passive AF configuration and focusing reliability for diverse objects
Solution Approach 2:
The system performs preliminary contrast AF to obtain an initial in-focus position, then performs reliability determination before final image acquisition. This preliminary action approach allows the system to use simple passive AF first, then only when reliability is questionable, additional verification steps are taken, thus maintaining simplicity while ensuring reliability
2Reliability
If contrast AF is performed every time image shooting is performed to ensure accurate focusing, then focusing reliability is improved, but productivity deteriorates due to increased time required
Solution Approach 1:
The system performs contrast AF and then evaluates the reliability of the obtained in-focus position using focus scores from multiple measurements. This feedback mechanism allows the system to determine whether full contrast AF should be re-performed, thereby avoiding unnecessary repeated AF operations and improving productivity while maintaining focusing accuracy
Solution Approach 2:
Instead of performing complete contrast AF every time, the system performs partial verification by acquiring a small number of candidate images at the obtained in-focus position and evaluating reliability. Only when reliability is insufficient does the system perform excessive action by acquiring candidate images at multiple positions. This partial/excessive action approach balances productivity and focusing accuracy
3Measurement precision
If multiple candidate images are acquired at different positions to verify focusing accuracy, then measurement precision is improved, but loss of time increases due to additional image acquisition steps
Solution Approach 1:
The system performs preliminary contrast AF to obtain an initial in-focus position before acquiring candidate images for reliability verification. This preliminary action reduces the need for extensive time-consuming multiple acquisitions, as the initial position is already optimized, and only verification images are needed rather than full search sequences
Solution Approach 2:
The system performs partial verification by acquiring a small number of candidate images (e.g., 3-5 images) at the obtained in-focus position, which is sufficient for reliability determination without requiring exhaustive acquisition at multiple positions. This partial action approach achieves adequate measurement precision with minimal time loss
Data Source
AI summary
An observation apparatus includes: an image capturing apparatus that includes an imaging surface and captures an image of an object to be observed; an optical system that projects an optical image of the object onto the image capturing apparatus; a focusing unit that adjusts, with reference to the optical-axis direction of the optical system, the relative positional relationship between the object and a surface optically conjugate to the imaging surface; and a processor that controls at least the image capturing apparatus and the focusing unit. The processor decides an in-focus position for the focusing unit based on a plurality of images of the object that acquired by the image capturing apparatus, the plurality of images each being an image acquired when the focusing unit is located at a different position; determines the reliability of the decided in-focus position; and when determining that the in-focus position is not reliable, moves the focusing unit sequentially to a plurality of positions and causes the image capturing apparatus to acquire, for each of the plurality of positions, a candidate image of the object.