Dual Line Scan Detector Focus Estimation for Image Scanning
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Solution Overview
Problem
Existing image scanning technologies face challenges in maintaining focus over large sample areas with varying topography, leading to out-of-focus regions in the output image, especially when scanning speed and accuracy are critical.
Innovation Solution
A method using a first line scan detector and a second line scan detector to obtain image and focus scan lines at different focus levels, with the second detector's focus level modulated to estimate the nominal in-focus level quickly and adjust the first detector accordingly, allowing for fast and accurate in-focus imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single line scan detector is used to scan the sample, then the scanning speed can be increased, but the focus accuracy deteriorates due to inability to compensate for surface topography variations
Solution Approach 1:
The imaging function is segmented into two specialized detectors: a first line scan detector optimized for capturing image scan lines at a fixed focus level, and a second line scan detector optimized for capturing focus scan lines at variable focus levels. This segmentation allows each detector to specialize in its specific function, enabling high-speed imaging while separately measuring focus variations to compensate for surface topography.
Solution Approach 2:
The second line scan detector acts as an intermediary device that measures focus variations across the sample surface without interfering with the primary imaging function of the first detector. By introducing this intermediate measurement system, the patent enables real-time focus compensation while maintaining high scanning speeds.
2Measurement precision
If focus adjustment is performed during scanning to compensate for surface topography, then focus accuracy improves, but the scanning speed decreases due to time required for focus search
Solution Approach 1:
The second line scan detector continuously measures focus variations across the sample surface in advance, building a focus map that predicts the optimal focus level at each position. This preliminary focus measurement allows the system to pre-calculate compensation values, eliminating the need for time-consuming focus searches during the actual scanning process.
Solution Approach 2:
The second line scan detector operates continuously throughout the scanning process, constantly monitoring focus variations and providing real-time feedback. This continuous measurement ensures that focus compensation can be applied without interrupting the scanning flow, maintaining high scanning speeds while improving focus accuracy.
3Measurement precision
If a 2D imaging detector is used to perform focus calculation during scanning, then focus accuracy improves, but the data rate requirement increases significantly
Solution Approach 1:
The patent extracts only the essential focus information from the optical path by using a second line scan detector that captures one-dimensional focus scan lines at variable focus levels. This extracted focus data is sufficient for calculating focus compensation without requiring the full two-dimensional image data, thereby significantly reducing the data rate requirement while maintaining focus accuracy.
Solution Approach 2:
Instead of using the full 2D image data for focus calculation, the system creates a simplified copy of the focus information through the second line scan detector. This copy contains only the necessary focus variations needed for compensation, reducing data processing requirements while preserving the essential focus measurement functionality.
4Measurement precision
If focus is adjusted by moving the imaging lens during scan, then focus accuracy improves, but the complexity of image interpolation increases
Solution Approach 1:
The patent replaces the mechanical approach of moving the imaging lens for focus adjustment with an optical/electronic approach. The second line scan detector measures focus variations, and the system calculates compensation values that are applied to the image data through electronic processing rather than mechanical lens movement. This substitution simplifies the interpolation process by working with measured focus offsets rather than physically repositioning optical elements.
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
Enables quick and accurate estimation of the in-focus level without sacrificing image lines, allowing for fast and high-quality scanning of samples with varying topography, improving scanning speed and image clarity.
Implementation Method 1
wherein image information is reflected to the second line scan detector using a mirror; wherein the mirror is rotated so as to provide focus scan lines of the target at different focus levels
Data Source
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AI summary
A method of estimating an in-focus level of a target in an image scanning apparatus is provided, wherein the image scanning apparatus comprises a first line scan detector configured to obtain one or more image scan lines of the target and a second line scan detector configured to obtain one or more focus scan lines of the target. The method comprises obtaining at least one focus scan line of the target using the second line scan detector, each at least one focus scan line being obtained at a respective focus level and wherein the focus level of the at least one image scan line is different from the focus level of the at least one focus scan line. The method further comprises calculating at least one focus parameter using at least the at least one focus scan line, and estimating a nominal in-focus level of the target using the calculated focus parameter(s). The image and focus scan lines are obtained from different positions in the target and image information is obtained by the said first and second line scan detectors along different optic axes from the target so as to produce the said respective image and focus scan lines. Image information is reflected to the second line scan detector using a mirror; and the mirror is rotated so as to provide focus scan lines of the target at different focus levels