The research group led by National Institute of Information and Communications Technology (NICT), Tohoku University and Toin Gakuen (Toin University of Yokohama) has successfully developed a high-performance, ultra-fast holographic fluorescence microscope system with resolution down to the submicron. By recording fluorescent substances as a hologram with 3D data, not only does it obviate the need for scanning, it is also expected to be capable of making measurements at ultra-fast speed, in less than one-thousandth of a second. The group has also proved coloration. If the system can be implemented, it would allow moving objects to be measured. It might also enable microscopy able to observe 3D imagery. These findings were published in the US science journal Optics Letters on January 29.
Digital holography is a sensing tool with holograms created from 3D image data. Holograms can be recorded not just with laser but with natural light. As all light microscopes can be given hologram-sensing functionality, it is expected to be applicable to 3D fluorescence microscopy and other forms of optical microscopy.
To achieve this, the research group including NICT had previously developed a 3D microscope to record color holograms at high speed using natural light, an advance in the research and development of single-exposure color hologram sensing of multiple fluorescent substances to several tens of microns. However, due to the low depth resolution in the findings reported on July 22, 2020, this was unable to sense 3D objects of under 1 micron.
This time, based on digital holography, they achieved development of a high-magnification, high-resolution, ultra-fast holographic fluorescence microscope that does not require scanning. Testing on fluorescent substances of 0.2 micron in diameter, they found it was quantitively capable of submicron resolution sensing, even in depth.
By sensing the fluorescence as a hologram, they achieved 3D sensing of multiple fluorescent substances at the same time. 3D sensing was enabled at each phase modulation of the phase modulator by developing a signal processing algorithm for fast measurement.
They found that by applying an ultra-fast phase modulation device, they should be able to take measurements in under one-thousandth of a second.
Moreover, by fusing the system with computationally coherent multiplex method, they managed to prove coloration. Applying their algorithm to the computationally coherent multiplex method, the group was able to conduct 3D color sensing with just a few holograms, thus taking more light per hologram.
With regard to the system developed by the research group, the plan is to now progress 3D video microscopy to the next step, where sensing to the submicron could be done via video hologram to observe substances and other moving objects within cells.
Obtaining quantitative phase data would further enhance depth resolution. Moreover, the fluorescence emitted by tiny objects is weak to the level of quantum optics, therefore a sensing technique to be developed that creates a vivid color hologram from even that light.