2023 Fiscal Year Research-status Report
Time- and space-super-resolution holographic microscope for label-free tissue dyanmics imaging
| Project/Area Number |
23KF0186
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| Research Institution | University of Tsukuba |
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Principal Investigator |
安野 嘉晃 筑波大学, 医学医療系, 教授 (10344871)
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| Co-Investigator(Kenkyū-buntansha) |
ZHU YUE 筑波大学, 医学医療系, 外国人特別研究員
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| Project Period (FY) |
2023-11-15 – 2026-03-31
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| Keywords | 4D Microscope. / Imaging formation theory / Aberration. / Computational refocusing |
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| Outline of Annual Research Achievements |
To establish a new microscopy that visualizes tissue viability and metabolic activity, we first proposed an imaging formation theory and built the basement of hardware based on this theory.
Optical coherence tomography is expected to have a high-resolution and extended imaging depth. Cellular-level resolution is essential in recent applications of non-invasive tissue imaging. Hence higher lateral resolution and deep imaging depth are required due to thick tissue in organs. However, the trade-off between lateral resolution and depth-of-focus is problematic especially for high-resolution OCT microscope. The defocus can be holographically corrected. but the maximum correctable defocus was only empirically known. Therefore, the theoretical framework for OCT imaging formation is required.
First, we employed two-dimensional pupil-based function to model the lateral imaging process of optical coherence microscope. Then discuss the defocus issue in complex signal. Finally derive the maximum correctable defocus (MCD) to theoretically evaluate the effect of computational refocusing.
For the hardware, we designed the optical system by Zemax and balance the lateral resolution and depth-of-focus. To address this issue, the defocus was investigated. Then, our colleague took responsibility to make a mechanical design and assemble the parts together. Currently, the optimization about signal processing, and high-speed signal acquisition mechanism are still ongoing.
This OCT microscope was found to have virtually infinitly large MCD and is particularly suitable for microscopy
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The plan for first working package is from Month-1 to 8, and the task is to establish a basement SS-FF-OCM theory and hardware. Currently, the theory has been produced to prepare for the manuscript. At the same time, the hardware is also ongoing and now can take images. More imaging processing steps will be further needed.
So, the progress is on the track smoothly.
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| Strategy for Future Research Activity |
After establishing the imaging formation theory, we will build an optimal system of SS-FF-OCM (Swept-source full-field optical coherence microscope) based on this theory. Because the pupil-function of the full-field illumination is designed to be a delta function, and the delta-function is crucial to achieve an ideal holographic signal correction. Therefore, for the next step, a method of digital adaptive optics will be proposed.
The method is to evaluate the importance of pupil-aperture-function-based computational refocusing and aberration correction for microscopy. In the study of digital adaptive optics, we need to first model the point spread function of complex signal and derive how the aberration is intact with complex signal. By Zernike polynomial fitting, cancel the phase error in the spatial frequency domain.
Currently, there is no changes in the research plan. One of the possible challenges may be the holographic correction of high-order aberration, because these aberrations will be intact with defocus. To address this issue, we need to first consider the maximum correctable defocus, and conduct computational refocusing, and evaluate the pupil-aperture-function-based computational refocusing, which is our current study.
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| Causes of Carryover |
At the beginning of program, the task is to establish a basement imaging formation theory. It does not yet require laboratory consumables, so we need to transfer to next fiscal year.
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