Tilted Autofocus Sensor for Digital Pathology Scanning
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Solution Overview
Problem
Existing autofocus imaging systems in digital pathology and rapid microscanning face challenges with error sign determination in focus control, leading to inefficiencies and reduced throughput due to the inability to determine the sign of focus errors, which is crucial for continuous autofocus systems.
Innovation Solution
A scanning microscope system with a tilted image sensor arrangement that acquires primary and autofocus image data, generating a polar error signal by comparing contrast data from different image sensor positions, allowing for accurate focus position correction and continuous autofocus control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tilted autofocus image sensor is used to acquire autofocus image data, then the ability to determine the sign of focus error is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a tilted autofocus image sensor that captures oblique cross-sections of the specimen at different axial positions. By adding the temporal dimension of sequential imaging at multiple z-positions and the spatial dimension of oblique sectioning, the system generates focus-dependent contrast variations that enable polar error signal determination. The tilted sensor plane intersects the optical axis to create depth-encoded image data, transforming a 2D imaging problem into a 3D depth-resolution problem that yields focus error sign information.
2Productivity
If continuous autofocus control is implemented to handle varying tissue layer positions, then the productivity increases, but the requirement for polar error signal becomes more critical
Solution Approach 1:
The patent implements a feedback-based continuous autofocus system where the polar error signal derived from differential contrast measurements of sequential autofocus images is fed back to dynamically adjust the focus position during scanning. The calculation unit processes contrast data from multiple z-positions to generate real-time focus error signals with polarity information, enabling the autofocus actuator to continuously correct focus drift caused by tissue layer variations. This closed-loop feedback ensures maintained focus accuracy throughout the scanning process, enabling high-speed continuous operation without sacrificing focus precision.
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
This solution enables high-accuracy determination of the polar error signal, improving focus control and increasing scanning throughput by providing a continuous and accurate autofocus system capable of handling varying tissue layer positions.
Implementation Method 1
a tilted autofocus image sensor for acquiring first autofocus image data and, at a later time, second autofocus image data of an oblique cross-section of the object of interest
Implementation Method 2
a calculation unit for generating a polar error signal of a focus position of the microscope on the basis of a comparison of first contrast data relating to the first autofocus image data with second contrast data relating to the second autofocus image data
Data Source
Figure 1~2
Figure 3
Figure 4A~4D
AI summary
The present invention relates to the field of digital pathology and in particular to whole slide scanners. A tilted autofocus image sensor images an oblique cross-section of the slide. For focusing multiple sequential overlapping images, which have been taken by the tilted sensor, are compared. The axial position of the tissue layer can be determined from the polar error signal resulting from this differential measurement.