Microscope Autofocus Spatial Filter for Transparent Samples
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Solution Overview
Problem
Conventional autofocus systems struggle to accurately focus on transparent samples with multiple small objects near the surface, often resulting in ambiguous or incorrect focus due to larger objects like labels and scratches, leading to out-of-focus issues.
Innovation Solution
A microscope autofocus system that uses a spatial filter applied to images to enhance focus scoring, identifying the best focus position by comparing filtered images and estimating a peak focus score based on standard deviation or pixel intensity thresholds, allowing precise focus adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional autofocus techniques are used to focus on prominent objects in an image, then the focus score is simplified and computation is faster, but the focus becomes ambiguous or incorrect when multiple small objects of interest are present on or near the surface while larger objects are substantially above or below the surface
Solution Approach 1:
The patent segments the image processing into multiple stages: initial focus score calculation using conventional techniques, identification of ambiguous cases, and secondary processing using spatial filtering and alternative focus scores. This segmentation allows the system to use simple methods when sufficient and complex methods only when necessary, resolving the contradiction between accuracy and complexity.
Solution Approach 2:
The patent applies preliminary spatial filtering to images before calculating focus scores in ambiguous cases. By pre-processing the image data to enhance small surface features and suppress larger out-of-focus objects, the system prepares the data for more accurate focus measurement, enabling precise focusing without requiring complete system complexity for all cases.
2Measurement precision
If spatial filtering is applied to enhance small surface features, then focus accuracy on small objects improves, but computational complexity and processing time increase
Solution Approach 1:
The patent applies spatial filtering selectively only to images identified as ambiguous cases, rather than to all images. This partial application of the computationally intensive operation reduces overall processing time while still achieving accurate focus measurement when needed, resolving the contradiction between precision and time loss.
Solution Approach 2:
The patent divides the autofocus process into fast initial assessment using conventional focus scores and slower but more accurate spatial filtering applied only to ambiguous cases. This segmentation of processing paths allows the system to minimize average processing time while maintaining high accuracy when required.
3Productivity
If conventional autofocus scores are used that ignore noise, then processing is simpler and faster, but larger objects like labels and scratches create bimodal focus scores resulting in out-of-focus conditions
Solution Approach 1:
The patent introduces spatial filtering as an intermediary processing step between image acquisition and focus score calculation for ambiguous cases. This intermediary operation enhances the signal from small surface features while suppressing noise from larger out-of-focus objects, enabling reliable focus measurement without sacrificing overall processing efficiency.
Solution Approach 2:
The patent changes the parameters of image processing by applying spatial filters with specific kernel sizes and sigma values tailored to enhance small surface features. By adjusting these parameters selectively for ambiguous cases, the system improves focus reliability while maintaining simple processing for clear cases, resolving the contradiction between speed and reliability.
Data Source
AI summary
An autofocus system includes an imaging device, a lens system and a focus control actuator that is configured to change a focus position of the imaging device in relation to a stage. The electronic control unit is configured to control the focus control actuator to a plurality of predetermined focus positions, and activate the imaging device to obtain an image at predetermined positions and then apply a spatial filter to the obtained images. This generates a filtered image for the obtained images. The control unit determines a focus score for the filtered images such that the focus score corresponds to a degree of focus in the obtained images. The control unit identifies a best focus position by comparing the focus score of the filtered images, and controls the focus control actuator to the best focus position corresponding to the highest focus score.