Focus Oscillation Control for Extended Depth Imaging
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Solution Overview
Problem
Current methods for acquiring high-resolution images of samples, especially thick samples, face challenges in efficiently obtaining extended focus images while scanning, leading to increased file sizes and processing times, particularly in virtual slide applications.
Innovation Solution
An image acquisition apparatus utilizing a TDI image pickup device with focus oscillation control, where the focus oscillation frequency is synchronized with the image pickup period to acquire extended focus images efficiently during scanning, using a sample stage, image pickup optical system, and focus oscillation control means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Z-stack method is used to acquire multiple observation images at different depth positions, then extended focus capability is achieved, but file size increases in proportion to the number of stacked images
Solution Approach 1:
The patent extracts only the essential depth information needed for extended focus by using a single observation image with focus oscillation, rather than storing all Z-stack images. The focus oscillation method captures depth information in one image, eliminating the need to store multiple images while maintaining extended focus capability.
Solution Approach 2:
The patent creates a virtual extended focus image through computational processing from a single physical image capture. By simulating the effect of multiple focal planes through focus oscillation and image processing, it reproduces the extended focus capability without physically capturing multiple images, thus avoiding the file size increase.
2Quantity of substance
If Extended Depth of Focus method is used to create a single observation image with extended depth of focus, then file size does not increase, but the image includes concentration of z-axis information and is not suitable for pathological diagnosis
Solution Approach 1:
The patent introduces dynamic focus oscillation during the image capture process, where the focus position oscillates at a specific frequency synchronized with the image pickup device. This dynamic approach allows the system to capture information from multiple depth positions within a single image exposure, creating an extended focus image that maintains diagnostic quality without the file size increase.
Solution Approach 2:
The patent employs periodic focus oscillation at a frequency that is an integer multiple of the image pickup device's frame rate. This periodic action ensures that during the exposure period, the focus sweeps through multiple depth positions, capturing comprehensive depth information that can be processed into a high-quality extended focus image suitable for pathological diagnosis.
3Reliability
If arithmetic operation method is used to create extended focus image from Z-stack images, then extended focus image can be acquired, but it takes considerable time for processing large-capacity images
Solution Approach 1:
The patent performs focus oscillation during the image capture phase itself, embedding the depth information collection process into the exposure period. This preliminary action eliminates the need for time-consuming post-processing of multiple images, as the extended focus information is already captured in a single image. The subsequent processing only requires extracting information from this single image rather than performing complex operations on multiple large-capacity images.
4Productivity
If high-resolution imaging is performed by scanning the sample two-dimensionally, then high-resolution image of the whole sample can be acquired in short time, but acquisition of z-axis information for thick samples is not achieved
Solution Approach 1:
The patent adds the z-axis dimension to the existing two-dimensional scanning process by introducing focus oscillation in the optical axis direction. During the 2D scan, the focus position oscillates through multiple depth positions, allowing the system to capture x-y-z information simultaneously. This transforms the imaging process from capturing only 2D information to capturing 3D information while maintaining the fast scanning speed, thus acquiring both high-resolution 2D images and z-axis information for thick samples.
Data Source
AI summary
An image acquisition apparatus 1A includes a sample stage 10 for placing a sample S thereon, an image pickup device 20 capable of acquiring a two-dimensional image and TDI driving, an image pickup optical system 30 including an objective lens 32, a scanning unit for acquiring an observation image while scanning the sample S by the image pickup device 20 and the image pickup optical system 30, and a focus oscillation control device 40 for controlling oscillation of a focus in the sample S so that an image pickup focus in the sample S oscillates at an oscillation frequency fs in an optical axis direction. The focus oscillation control device 40 sets the oscillation frequency fs so that the oscillation frequency fs substantially coincides with Ns times (Ns is an integer not less than 1) the basic frequency, which is a reciprocal 1/Ti of an image pickup period Ti of TDI driving in the image pickup device 20. Thus, an image acquisition apparatus capable of efficiently acquiring an observation image with focus extended can be realized.