Astigmatic Autofocus via 2D Pattern Projection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing imaging systems face challenges in achieving robust autofocus, particularly in the presence of scratches or dust on sample or sample holder surfaces, with passive autofocus being slow and active autofocus systems being insufficiently robust.
Innovation Solution
An imaging system that projects a two-dimensional pattern onto the sample holder via an astigmatic optical element, analyzing the image data to determine the sharpness along orthogonal axes and calculating the magnitude and direction of defocus, allowing for fast and reliable autofocus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive autofocus is used, then cost is reduced by avoiding dedicated hardware, but autofocus speed decreases due to requiring multiple images at different focal planes
Solution Approach 1:
The patent segments the autofocus function into two independent components: a projection subsystem that projects a two-dimensional pattern onto the sample holder, and a camera subsystem that captures image data. This segmentation allows the system to use existing imaging hardware (avoiding dedicated autofocus hardware costs) while achieving fast autofocus by analyzing sharpness differences in the captured pattern along orthogonal axes, eliminating the need to acquire multiple images at different focal planes.
2Speed
If active autofocus with dedicated hardware is used, then autofocus speed is improved by determining focus from a single measurement, but robustness decreases in presence of scratches or dust on surfaces
Solution Approach 1:
The patent extracts the autofocus measurement function from the main imaging path by projecting a separate two-dimensional pattern onto the sample holder and analyzing its sharpness characteristics. This extracted measurement approach uses the existing camera and optics without requiring dedicated autofocus hardware, achieving single-measurement speed while improving robustness by analyzing pattern distortion rather than relying on reflections or specialized sensors that are sensitive to surface defects.
Solution Approach 2:
The patent applies local quality by analyzing the sharpness of the projected two-dimensional pattern at different locations and orientations. By measuring sharpness along orthogonal axes and comparing the differences, the system can determine defocus magnitude and direction while being less sensitive to local surface defects like scratches or dust, as the analysis is based on the overall pattern geometry rather than specific reflection points.
3Device complexity
If a single spot reference pattern is used, then the autofocus detection pattern is simple, but robustness is insufficient against surface defects
Solution Approach 1:
The patent transitions from using a one-dimensional reference (single spot) to a two-dimensional pattern projected onto the sample holder. This dimensional enhancement provides multiple measurement points and geometric features that can be analyzed for sharpness along orthogonal axes, significantly improving robustness against surface defects while maintaining manageable system complexity through software-based pattern analysis.
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 method provides a more robust and efficient autofocus mechanism by measuring sharpness differences along orthogonal axes, enabling precise focus adjustment and overcoming limitations of previous systems.
Implementation Method 1
a projection subsystem comprising a light source and an astigmatic optical element and configured to project a two-dimensional pattern onto the sample holder via the astigmatic optical element
Implementation Method 2
a camera subsystem comprising an image sensor and magnification optics and configured to image the sample via the magnification optics
Data Source
AI summary
A system 100 and method are provided for imaging a sample in a sample holder. For providing autofocus, a 2D pattern is projected onto the sample holder 050 via an astigmatic optical element 120. Image data 172 of the sample is acquired by an image sensor 140 via magnification optics 150. A difference in sharpness of the two-dimensional pattern in the image data is measured along a first axis and a second axis. Based on the difference, a magnitude and direction of defocus of the camera subsystem is determined with respect to the sample holder. This enables the sample holder, and thereby the sample, to be brought into focus in a fast and reliable manner.