The National Institute of Information and Communications Technology (NICT), Tohoku University, Toin University of Yokohama, and Japan Science and Technology Agency (JST) have succeeded in developing a scanless high-speed holographic fluorescence microscopy system with submicron resolution for a 3D space. The system is based on digital holography. The developed microscopy system has an algorithm to acquire 3D information of fluorescent objects toward scanless 3D measurement in less than 1 millisecond. Scanless 3D sensing with submicron resolution and color-multiplexed holographic fluorescence imaging have been demonstrated using the algorithm. The microscopy system will be further developed to achieve holographic 3D motion-picture sensing of specimens with incoherent light.
This achievement was published in Optics Letters as an open-access paper on January 29, 2021.


Figure 1
Figure 1 Overview of the developed high-speed holographic fluorescence microscopy system for scanless 3D measurement with submicron resolution.
[Click picture to enlarge]
The scanless high-speed holographic fluorescence microscopy system shown in Figure 1 was constructed. The system is based on digital holography and is applicable to the sensing of incoherent light such as fluorescence light and natural light. The developed algorithm enables the adoption of a phase modulator to generate two phase values, which is expected to increase the measurement speed. Submicron resolution for a 3D space was successfully demonstrated using fluorescent objects with a diameter of 0.2 μm. The experimental results shown in Figure 2 indicate that the developed microscopy system achieves 3D sensing of nanoparticles and has submicron resolution quantitatively for a 3D space. Scanless 3D measurement in less than 1 millisecond is achievable by using the algorithm with either a ferroelectric liquid crystal on silicon (FLCOS) or an electro-optic (EO) device. Color-multiplexed holographic fluorescence imaging with the algorithm and only four exposures has also been demonstrated by combining the proposed algorithm and computational coherent superposition (CCS). The number of exposures is reduced by the algorithm, and the number of photons per hologram is increased even for ultimately weak light.
Figure 2
Figure 2 Upper left: experimental results of 3D sensing for fluorescent particles with a diameter of 0.2 µm.
Upper right: x-z image of the reconstructed particle marked by the violet arrow.
Bottom left: plots of the particle marked by the violet arrow along the x- and y-axes.
Bottom right: plots of the particle marked by the violet arrow along the z-axis.

Future prospects

  • High-speed holographic motion-picture imaging for 3D dynamics and multiple moving objects in a 3D space.
  • Improvements of the system such as recording of a quantitative phase, sensing of ultimately weak light, and construction of a compact optical setup.

Information of the article

Journal: Optics Letters
DOI: 10.1364/OL.414083
Title: Two-step phase-shifting interferometry for self-interference digital holography
Authors: Tatsuki Tahara, Yuichi Kozawa, Ayumi Ishii, Koki Wakunami, Yasuyuki Ichihashi, and Ryutaro Oi
This work was supported by the Cooperative Research Program of "Network Joint Research Center for Materials and Devices" (No. 20201164); Precursory Research for Embryonic Science and Technology (PRESTO) (JPMJPR15P8, JPMJPR16P8, JPMJPR17P2); Japan Society for the Promotion of Science (JSPS) (18H01456). 


Digital holography

Digital holography is a technique used to record 3D information of a specimen as digital holograms with an image sensor and to reconstruct a 3D image of the specimen numerically using a computer. Figure 3 shows the system constructed for recording digital holograms. Incoherent light such as fluorescence light and natural light can be recorded as holograms using the specially designed optical system shown in Figure 3. An image sensor records fluorescence light that passes through the optical system as digital holograms. A computer numerically reconstructs a 3D image from the recorded holograms. Object-wave extraction from the recorded hologram(s) is numerically calculated using an algorithm such as the proposed algorithm and CCS. Numerical wave propagation is calculated and then images focused on arbitrary depths are reconstructed. 
Figure 3
Figure 3 Schematic of digital holography.
Digital holography consists of two systems: a system for recording digital holograms and a system for reconstructing a 3D image from the recorded digital holograms.

Computational coherent superposition (CCS)

CCS is an in-line holographic multiplexing scheme based on phase-shifting interferometry. Figure 4 schematically illustrates the system for recording digital holograms and the basic concept for object-wave extraction from the recorded holograms. In CCS, a wavelength-multiplexed interferometer in the real world that records wavelength-multiplexed phase-shifted holograms is constructed to conduct color-multiplexed holographic imaging. In the numerical calculation process used to extract object waves at multiple wavelengths from the wavelength-multiplexed holograms, an interferometer in a computer is assumed to reconstruct a color holographic image from the recorded holograms. On the basis of phase-shifting interferometry, the numerical interference is calculated in the computer and only object-wave information at the desired wavelength is extracted.
Figure 4
Figure 4 Schematics of the system for recording digital holograms and of the basic concept for object-wave extraction from the recorded holograms in CCS.

Technical Contact

TAHARA Tatsuki
Electromagnetic Applications Laboratory
Applied Electromagnetic Research Institute

E-mail: tahara_atmark_nict.go.jp

Media Contact

HIROTA Sachiko
Press Office, Public Relations Department

E-mail: publicity_atmark_nict.go.jp

Press Office, IMRAM
Tohoku University

E-mail: press.tagen_atmark_grp.tohoku.ac.jp

Research Promotion Department
Toin University of Yokohama

E-mail: research_atmark_toin.ac.jp

Department of Strategic Basic Research, JST

E-mail: presto_atmark_jst.go.jp