Dynamic Focus Z-Stack Imaging via Optical Path Difference Control
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Solution Overview
Problem
Dynamic focus methods lack the necessary reference information for objective lens positions, making it difficult to capture Z-stack images by simply moving the objective lens relative to the sample stage.
Innovation Solution
An image capturing apparatus with a stage control unit, light source, light guiding optical system, first and second imaging units, focus control unit, and optical-path-difference changing unit, which changes the optical path difference between two optical paths to control focus positions and scan the stage, allowing for the capture of Z-stack images with precise focus intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dynamic focus is used to capture high-magnification images while acquiring focus positions, then productivity is improved, but measurement precision of objective lens position deteriorates due to lack of reference information
Solution Approach 1:
The patent creates a virtual focus map that copies the essential focus position information needed for Z-stack imaging. Instead of requiring actual physical measurement references, the system generates virtual reference data that guides the objective lens movement, enabling both rapid imaging and accurate focus positioning through information replication rather than physical measurement.
Solution Approach 2:
The system performs preliminary acquisition of focus positions during the dynamic focus process, storing this information for subsequent Z-stack imaging. By preparing focus position data in advance during normal imaging operations, the system eliminates the need for separate reference measurement steps, thereby maintaining high productivity while ensuring measurement precision when Z-stack images are captured.
2Productivity
If the number of focus acquisition positions is decreased to reduce processing time, then productivity is improved, but manufacturing precision of focus map deteriorates
Solution Approach 1:
The system uses the imaging system itself to automatically acquire and store focus position information during normal operation. The imaging apparatus performs self-measurement of focus positions without requiring external reference standards or additional measurement devices, enabling rapid focus map creation that maintains accuracy through automated self-calibration.
Solution Approach 2:
The patent changes the parameter of focus position sampling by acquiring focus information at multiple positions during dynamic focus operation. Rather than using a fixed small number of positions, the system adaptively samples focus data throughout the imaging process, transforming the static parameter approach into a dynamic one that maintains precision while improving speed.
3Measurement precision
If conventional virtual microscope method is used to capture Z-stack images by moving objective lens, then measurement precision is improved, but device complexity increases due to requirement of focus map
Solution Approach 1:
The patent merges the focus map creation function with the normal dynamic focus imaging process. Instead of requiring separate focus measurement systems and procedures, the system combines focus position acquisition with routine image capture operations, eliminating the need for additional complex measurement devices while maintaining measurement precision through integrated self-measurement.
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 the efficient capture of Z-stack images using dynamic focus, capturing images along curved surfaces similar to the sample's surface shape, improving focus accuracy and reducing processing time.
Implementation Method 1
a light guiding optical system including a light dividing unit that divides an optical image of the sample into a first optical path for capturing an image and a second optical path for focus control
Implementation Method 2
a focus control unit that analyzes the second image so as to control a focus position of image pickup by the first imaging unit based on an analysis result
Implementation Method 3
an optical-path-difference changing unit that changes an optical path difference between the first optical path and the second optical path based on a predetermined target focus interval
Data Source
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Figure 3(a)~3(b)
AI summary
An image capturing apparatus M comprises an optical-path-difference changing unit which changes an optical path difference between a first optical path L1 and a second optical path L2. A focus position of the image pickup by a first imaging device 18 varies (or moves) in a depth direction of a sample S according to the optical path difference changed by the optical-path-difference changing unit. Therefore, every time the optical-path-difference changing unit changes the optical path difference based on a predetermined target focus interval, while a focus control unit controls the focus position of the image pickup by the first imaging device 18, a stage control unit scans a stage 1 and the first imaging device 18 captures a first image, whereby the apparatus can readily capture Z-stack images consisting of a plurality of the first images in the depth direction of the sample S according to the change of the optical path difference.