Tilted Autofocus Sensor for Digital Pathology Scanning
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Solution Overview
Problem
The existing autofocus systems in digital pathology, particularly in whole slide scanning, are prone to errors and time-consuming due to the variation in the axial position of the tissue layer across the slide, which limits system throughput and has insufficient performance.
Innovation Solution
An autofocus imaging system comprising a primary image sensor and an autofocus image sensor, where the autofocus image sensor samples a smaller number of pixels per distance in object space compared to the primary image sensor, with the autofocus sensor tilted with respect to the optical axis and using dark field illumination to improve focus accuracy and reduce computational load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus maps are used to determine optimum focus position at multiple positions before scanning, then focus accuracy is improved, but the procedure becomes time-consuming and reduces system throughput
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing focus correction values at multiple positions across the slide before actual scanning begins. The focus map is created in advance, allowing the scanning process to proceed rapidly by simply looking up pre-determined focus positions rather than performing time-consuming focus optimization during scanning.
2Measurement precision
If a high number of pixels are sampled by the autofocus image sensor to maintain signal quality, then measurement precision is improved, but computational load and sampling time increase
Solution Approach 1:
The patent applies local quality by sampling pixels non-uniformly across the autofocus image sensor. Instead of uniformly sampling all pixels, the system selectively samples pixels at specific locations that provide the most useful focus information. This allows adequate signal quality to be achieved with fewer total samples, reducing computational load and sampling time while maintaining measurement 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 approach enhances the accuracy and speed of focus measurement, reducing noise and computational requirements while maintaining image quality, thereby improving the overall performance and throughput of the autofocus system.
Implementation Method 1
the autofocus imaging system is adapted for dark field illumination of the autofocus image sensor
Implementation Method 2
light reflected from various surfaces (air, cover slip, cover slip-tissue layer, tissue layer-slide, slide-air)
Implementation Method 3
The autofocus image sensor is adapted for acquiring autofocus image data of an oblique section of the object of interest
Data Source
AI summary
The present invention relates to the field of digital pathology and in particular to whole slide scanners. Autofocus imaging can be performed by sampling a first number of pixels of a primary image sensor which is a time delay integration (TDI) sensor, and sampling a second number of pixels of an autofocus image sensor, wherein the second number is between one quarter and three quarters of the first number. Thus, continuous autofocus for rapid light scanning may be provided based on an additional image sensor that is tilted with respect to the optical axis.