Multi-Spectral Imaging Autofocus with Channel-Specific Focal Offsets
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Solution Overview
Problem
Existing digital pathology systems face challenges in achieving optimal focus across multiple color channels due to chromatic aberration, leading to image blur and impaired interpretation, diagnosis, and automated analysis, with current methods requiring extensive Z-stack acquisition and processing time.
Innovation Solution
An imaging system captures images at individually optimized focal planes for each color channel, using model fitting techniques to determine and adjust focal planes based on calibration with phantom slides, reducing blur and distortion by employing offset values for each channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a complete Z-stack of images is acquired for each color channel to reduce blur, then image quality is improved, but acquisition time, memory storage, and processing time increase significantly
Solution Approach 1:
The system performs preliminary calibration to determine chromatic aberration characteristics and establish channel-specific offset values before actual imaging. This pre-characterization allows the system to acquire images at optimized focal planes for each channel without needing to process complete Z-stacks, thereby reducing acquisition and processing time while maintaining image quality
Solution Approach 2:
The imaging process is segmented into calibration phase and scanning phase. During calibration, the system characterizes chromatic aberration for each channel. During scanning, it applies the pre-determined offset values to acquire images at optimized focal planes. This segmentation eliminates the need to acquire and process complete Z-stacks for each channel, reducing time and computational resources
2Device complexity
If a common focus plane is selected for all color channels to simplify acquisition, then device complexity is reduced, but image blur occurs in channels other than the dominant color
Solution Approach 1:
The system applies different focal plane offsets to different color channels based on their specific chromatic aberration characteristics. Each channel (red, green, blue) has its own optimized focal plane determined during calibration, allowing each to be sharply focused at its optimal plane rather than forcing a common focus plane that would result in blur for non-dominant colors
3Manufacturing precision
If Z-stack acquisition is performed to achieve best focus for each channel, then image sharpness is improved, but data storage requirements and processing complexity increase
Solution Approach 1:
The calibration process preliminarily determines the optimal focal plane offset for each color channel, storing only these compact offset values rather than complete Z-stack data. During scanning, these offsets are applied to acquire images directly at the optimized focal planes, eliminating the need to store and process large volumes of Z-stack data while maintaining optical sharpness
Data Source
AI summary
Techniques for acquiring focused images of a microscope slide are disclosed. During a calibration phase, a “base” focal plane is determined using non-synthetic and/or synthetic auto-focus techniques. Furthermore, offset planes are determined for color channels (or filter bands) and used to generate an auto-focus model. During subsequent scans, the auto-focus model can be used to quickly estimate the focal plane of interest for each color channel (or filter band) rather than re-employing the non-synthetic and/or synthetic auto-focus techniques.