Hybrid Autofocus System for Digital Microscope Focal Position Accuracy
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Solution Overview
Problem
Current digital microscope apparatuses face challenges in quickly and efficiently determining the appropriate in-focus position, particularly when dealing with samples that have irregular surfaces or varying staining types, leading to errors and increased photographing time due to the limitations of contrast AF and phase difference AF systems.
Innovation Solution
A hybrid autofocus system that combines phase difference and contrast autofocus methods, using a phase difference AF system for rapid initial focus determination and a simplified contrast AF system for verification, along with feature amount calculations and curve fitting to refine the focus position, thereby reducing errors and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contrast AF system is used to search for in-focus position by repeating photographing and contrast comparison, then measurement precision of focal position is improved, but photographing time increases significantly
Solution Approach 1:
The patent applies preliminary action by performing focus search at representative points before actual photographing at all positions. The focal positions are pre-searched at selected representative points, and then these results are used to estimate focal positions at each photographing position, avoiding repeated contrast comparison photography at every position.
Solution Approach 2:
The patent uses an intermediary approach by introducing representative points as mediators between the focus search process and actual photographing. Instead of directly performing contrast comparison at all photographing positions, the system first searches at representative points and uses these as intermediate reference data to determine focal positions for actual photographing.
2Loss of time
If focal positions are previously searched at selected representative points and used to estimate focal position at each photographing position, then photographing time is reduced, but errors are generated due to estimation and thermal expansion
Solution Approach 1:
The patent applies parameter changes by using temperature information as an additional parameter to compensate for thermal expansion effects. The system acquires temperature information and uses it to correct the estimated focal positions, adjusting for changes in optical path length that occur due to temperature variations between the representative point search and actual photographing.
3Loss of time
If curve fitting is used to estimate in-focus position from minimum photographing points, then photographing time is reduced, but accuracy decreases for samples with irregular surfaces or varying staining
Solution Approach 1:
The patent applies local quality by determining focal positions independently for each photographing position based on local characteristics. Instead of using a single curve fitting approach for the entire sample, the system performs focus search at representative points and uses local interpolation methods that adapt to the specific characteristics of each region, accounting for irregular surfaces and varying staining patterns.
Data Source
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AI summary
This information processing apparatus includes: a search image acquisition unit that acquires enlarged images at focal positions different from each other; a first feature amount calculation unit that obtains, for each of the multiple captured enlarged images, a first feature amount based on a direct current component and a dynamic range of an alternating current component of pixel values for each of blocks forming each of the enlarged images; and an in-focus position determination unit that determines an in-focus position of each enlarged image based on the first feature amount.