Showing papers by "Osamu Matoba published in 2020"

Roadmap on holography

Abstract: This work was supported by Ministerio de Economia, Industria y Competitividad (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER), and by Generalitat Valenciana (Spain) under project PROMETEO II/2015/015.

Common-path multimodal three-dimensional fluorescence and phase imaging system.

Abstract: A stable multimodal system is developed by combining two common-path digital holographic microscopes (DHMs): coherent and incoherent, for simultaneous recording and retrieval of three-dimensional (3-D) phase and 3-D fluorescence imaging (FI), respectively, of a biological specimen. The 3-D FI is realized by a single-shot common-path off-axis fluorescent DHM developed recently by our group. In addition, we accomplish, the phase imaging by another single-shot, highly stable common-path off-axis DHM based on a beam splitter. In this DHM configuration, a beam splitter is used to divide the incoming object beam into two beams. One beam serves as the object beam carrying the useful information of the object under study, whereas another beam is spatially filtered at its Fourier plane by using a pinhole and it serves as a reference beam. This DHM setup, owing to a common-path geometry, is less vibration-sensitive and compact, having a similar field of view but with high temporal phase stability in comparison to a two-beam Mach–Zehnder-type DHM. The performance of the proposed common-path DHM and the multimodal system is verified by conducting various experiments on fluorescent microspheres and fluorescent protein-labeled living cells of the moss Physcomitrella patens . Moreover, the potential capability of the proposed multimodal system for 3-D live fluorescence and phase imaging of the fluorescent beads is also demonstrated. The obtained experimental results corroborate the feasibility of the proposed multimodal system and indicate its potential applications for the analysis of functional and structural behaviors of a biological specimen and enhancement of the understanding of physiological mechanisms and various biological diseases.

Digital Holographic Multimodal Cross-Sectional Fluorescence and Quantitative Phase Imaging System.

Abstract: We present a multimodal imaging system based on simple off-axis digital holography, for simultaneous recording and retrieval of cross-sectional fluorescence and quantitative phase imaging of the biological specimen. Synergism in the imaging capabilities can be achieved by incorporating two off-axis digital holographic microscopes integrated to record different information at the same time. The cross-sectional fluorescence imaging is realized by a common-path configuration of the single-shot off-axis incoherent digital holographic system. The quantitative phase imaging, on the other hand, is achieved by another off-axis coherent digital holographic microscopy operating in transmission mode. The fundamental characteristics of the proposed multimodal system are confirmed by performing various experiments on fluorescent beads and fluorescent protein-labeled living cells of the moss Physcomitrella patens lying at different axial depth positions. Furthermore, the cross-sectional live fluorescence and phase imaging of the fluorescent beads are demonstrated by the proposed multimodal system. The experimental results presented here corroborate the feasibility of the proposed system and indicate its potential in the applications to analyze the functional and structural behavior of biological cells and tissues.

Single-shot common-path off-axis dual-wavelength digital holographic microscopy

Abstract: A single-shot common-path off-axis self-interference dual-wavelength digital holographic microscopic (DHM) system based on a cube beam splitter is demonstrated to expand the phase range in a stepped microstructure and for simultaneous measurement of the refractive index and physical thickness of a specimen. In the system, two laser beams with wavelengths of 532 nm and 632.8 nm are used. These laser beams are combined to transilluminate the object under study, then the object beam is divided into two beams by using a beam splitter oriented in such a way that both the beams propagate in almost the same direction, with an appropriate lateral separation between them. One of the object beams is spatially filtered at its Fourier plane, using a pinhole to generate a reference spherical beam free from the object information. The reference beam interferes with the object beam to form a digital hologram at the faceplate of the image sensor. The phase information is extracted from a single recorded digital hologram using the phase aberration compensation method that is based on principal component analysis (PCA). Owing to the common-path configuration, the system shows high temporal phase stability and it is less vibration-sensitive compared to counterparts such as a Mach-Zehnder type DHM. The performance of the dual-wavelength DHM system is verified in two different application fields by conducting the experiments using microsphere beads and living plant cells.

Interferenceless coded aperture correlation holography with synthetic point spread holograms

Abstract: Lensless, interferenceless coded aperture correlation holography (LI-COACH) is an incoherent computational optical technique for three-dimensional (3D) imaging. In direct imaging, the image of the object is generated by a lens, whereas the LI-COACH is an indirect imaging technique that consists of two steps: one-time point spread hologram (PSH) training and then many times imaging of multiple-point objects. In the one-time training step, a point object moves in the object space along the optical axis. Light emitted from the point is modulated by a quasi-random phase mask, and the PSH library is recorded. In the imaging step, an object is mounted within the axial boundaries of the PSH library, and the object holograms are recorded using the same quasi-random phase masks. The 3D image of the object is reconstructed by the cross correlation of the object holograms with the PSH library. In this study, the entire PSH library is digitally synthesized from a single PSH, recorded at one plane only. The recorded PSH is scaled by magnification factors corresponding to the various axial planes. The reconstruction results from the synthetic PSH library are comparable with those from the recorded PSH library. The proposed approach can reduce the time of the training step in LI-COACH.

Astigmatism correction and quality optimization of computer-generated holograms for holographic waveguide displays.

Abstract: In this manuscript, the astigmatism of the waveguide combiner with a pair of symmetry HOEs was analyzed. The light field can be predicted by the modified convolution formulation of Fresnel diffraction when the information of light passes through the astigmatism causing element. Then the astigmatism can be corrected. The theory was experimentally proved by the system with a phase-only SLM and a diffraction planar waveguide. Furthermore, the image quality of astigmatism corrected phase-type CGHs can be improved via the iteration process. Since the coherence of light source was employed, the temporal averaging method was utilized to avoid speckle noise.

Riesz transform for fringes pattern analysis: advantages and limitations

Abstract: Fringe pattern analysis is an essential step in optical techniques including the digital speckle pattern interferometry (DSPI), digital speckle shearing interferometry (DSPSI), digital holographic interferometry (DHI), moire interferometry, and others. This step enables to evaluate the coded phase distribution related to a physical magnitude of the material under study such as deformation, displacement, refractive index, strain, temperature. Several methods have been proposed for the extraction of phase distribution such as phase-shifting techniques and other transform-based methods like Fourier, Hilbert, and wavelet transforms. In phase-shifting techniques, the intensity is sampled spatially or temporally, and the object should be stable during the acquisition of at least three frames. So, this technique is not suitable for the analysis of dynamic events. Recently, Riesz transform, two-dimensional extension of the Hilbert transform, has been exploited in several works including the phase evaluation. In this work, we present a variety of methods based on the Riesz transform for fringe pattern analysis. The analysis concerns the extraction of the encoded phase distribution from the recorded/processes fringe patterns obtained from the interferometric techniques and their horizontal and vertical phase derivatives. Using numerical simulation, we study the performance of these Riesz transform-based methods with a quantitative appraisal, and finally, the experimental application will be presented. The advantages and limitations of the Riesz transform-based methods will be discussed.

Wavelets Teager-Kaiser Hilbert approach for AM-FM signal demodulation: application in the field of speckle metrology

Abstract: In this work, we propose a combination of the Teager–Kaiser energy operator (TKEO) and the spiral phase transform (SPT) for robust instant energy estimation of amplitude-modulated and frequency-modulated (AM–FM) signals, where the energy extraction is followed by a high-frequency component, generally considered as noise. We demonstrate that this noise component can be subtracted mathematically using the SPT transformation applied to the AM–FM signal. The improvement in demodulation is tested using a simulated AM–FM image and evaluated by the image quality index. An experimental speckle fringe pattern obtained by digital speckle pattern interferometry on a hard disk is denoised using a multiband approach and demodulated using the proposed method.

3D trajectory of minute object by parallel phase-shifting digital holographic microscope

Abstract: The authors review three-dimensional (3D) trajectory of minute object by parallel phase-shifting digital holography. Parallel phase-shifting digital holography is a technique capable of single-shot recording of a complex amplitude distribution of object wave from a dynamic object. The authors constructed an inverted microscope based on parallel phase-shifting digital holography. The microscope consisted of a continuous-wave laser, a Mach–Zehnder interferometer, a polarization imaging camera, and a magnification optical system. A high-speed polarization imaging camera was employed to record motion picture of holograms of the dynamic specimen. Motion picture of the holograms of a minute alum crystal sinking down in the solution of alum was recorded by the microscope at the rate of 60 frames per seconds (FPS). Refocused images of the crystal were successfully obtained for all of the sinking time. The 3D trajectory of the crystal was derived from the refocused images. Also, the authors constructed an inverted and vertical microscope based on parallel phase-shifting digital holography. A Volvox swimming in a water as a living microbe was recorded by the microscope at the rate of 1000 FPS. The 3D trajectory of the microbe curvedly moving in the area of 500 μm × 500 μm × 500 μm was successfully demonstrated from the reconstructed images of the microbe.

Modularized microscope based on parallel phase-shifting digital holography for imaging of living biospecimens.

Abstract: Significance: Parallel phase-shifting digital holographic microscope (PPSDHM) is powerful for three-dimensional (3D) measurements of dynamic specimens. However, the PPSDHM reported previously was directly fixed on the optical bench and imposed difficulties case, thus it is required to modify the specification of the microscope or transport the microscope to another location. Aim: We present a modularized PPSDHM. We construct the proposed PPSDHM and demonstrate the 3D measurement capability of the PPSDHM. Approach: The PPSDHM was designed as an inverted microscope to record transparent objects and modularized by integrating the optical elements of the PPSDHM on an optical breadboard. To demonstrate the effectiveness of the PPSDHM, we recorded a 3D motion-picture of moving Volvoxes at 1000 frames / s and carried out 3D tracking of the Volvoxes. Results: The PPSDHM was practically realized and 3D images of objects were successfully reconstructed from holograms recorded with a single-shot exposure. The 3D trajectories of Volvoxes were obtained from the reconstructed images. Conclusions: We established a modularized PPSDHM that is capable of 3D image acquisition by integrating the optical elements of the PPSDHM on an optical breadboard. The recording capability of 3D motion-pictures of dynamic specimens was experimentally demonstrated by the PPSDHM.

Speckle denoising by the family of non-local means methods

Abstract: We demonstrate the performance of nonlocal means (NLM) and its related adaptive kernel-based methods for speckle denoising for the intensity and phase images acquired from the digital speckle pattern interferometric (DSPI) and digital holographic interferometric (DHI) techniques, respectively. The speckle denoise capabilities of NLM and its variant denoising methods such as NLM-average (NLM-av), NLM-local polynomial regression (NLM-PLR), and NLM-shape adaptive patches (NLM-SAP), and various NLM-reprojection schemes are implemented on simulated. Their performances are quantified on the basis of two metric criteria – peak signal-to-noise ratio (PSNR) and the image quality index (Q). The effectiveness of these denoising methods is compared with other existing speckle denoising methods. The obtained results suggest that these denoising methods have the ability to denoise speckles from the DSPI/DHI fringes and provide better visual and quantitative results.

Three-dimensional tracking of moving Volvox by parallel phase-shifting digital holographic microscope

Abstract: We report the three-dimensional (3D) trajectory of a Volvox moving in water was recorded by parallel phase-shifting digital holographic microscope providing 10X magnification. The recording frame rate, the shutter speed, and the total recording time were 1000 fps, 0.25 ms, and 2.1 s, respectively. In the reconstructed phase image of the Volvox, the shape of the Volvox is regarded as a circle. The lateral coordinates of the Volvox were determined as the center of the circle. The depth coordinates of the Volvox were determined as the propagation distance where the edge of the Volvox in the reconstructed amplitude image was clearest while the propagation distance was varied. We successfully demonstrated the 3D tracking of curvedly moving Volvox.

Phase imaging of radiated sound field by parallel phase-shifting digital holography

Abstract: We report imaging of a sound field radiated from a sound source by parallel phase-shifting digital holography. We used a Nd:YVO4 laser emitting light with a wavelength of 532 nm as a light source and a polarization imaging camera to record holograms. The holograms were recorded 40000 Hz sound with 100000 frame per second. To adjust one wavelength of sound to the recordable area of the image sensor, we introduced a demagnification optical system in the path of the object beam. The phase difference images were calculated from the recorded holograms. Thus, we observed propagation of periodical phase distributions of sound and succeeded in sound field imaging.

Special Section Guest Editorial: Holography

Abstract: Abstract. This guest editorial introduces the Special Section on Holography.

Riesz transform-based digital four-step phase-shifting interferometer

Abstract: Phase-shifting interferometry is a highly accurate technique for obtaining phase distribution from the recorded fringe patterns. Generally, phase-shifting interferometry requires recording several fringe patterns with varying phase shifts experimentally and during the acquisition, the object must be stable. Also, the atmospheric turbulence and mechanical conditions should also remain constant during this time. These requirements limit the use of these phase-shifting interferometric techniques in dynamic event studies. In the present work, we introduce Riesz transformed based digital four-step phase-shifting interferometer to obtain phase distribution from a single recorded fringe pattern. All the experimental phase-shifting setups necessary to realize the phase-shifting are removed. The idea is based on the recording of a single fringe pattern, and computes its Riesz transform at first, second and third-orders. The obtained Riesz transform components are combined to generate three π/2 phase-shifted fringe patterns, and then, the phase distribution is obtained from these phase-shifted fringe patterns. The performance of this method is demonstrated first by using numerical simulation and the quantitative appraisal is given by using image quality index. Further, we apply this technique on a real fringe pattern recorded in digital speckle pattern interferometry (DSPI). The obtained results reveal that our method provides a simple and accurate solution for phase evaluation, therefore, makes it suitable for real-time measurements.

Multi-wavelength digital holographic microscopy for bio-imaging and applications

Abstract: A single-shot common-path off-axis multi-wavelength digital holographic microscopic (MW-DHM) system for phase imaging of biological specimens is proposed. The DHM system is based on a cube beam splitter which divides the object beam into two beams: one beam is spatially filtered at its Fourier plane to make a reference spherical beam and another beam acts as the object beam. Three wavelengths: 473, 532, and 632.8 nm are used to illuminate the object under observation. The obtained experimental results on various objects corroborate the imaging capability of the proposed single-shot common-path off-axis multi-wavelength MW-DHM system. The proposed system may open new possibilities in bio-imaging and real-time simultaneous measurement of various parameters including the thickness, refractive index, etc.

Plant Cell Observation by TIE-based Fluorescence Imaging

Abstract: We present fluorescence imaging of plant cells based on transport of intensity equation and Fresnel propagation. At first, the phase distribution is obtained from the recorded three- defocus fluorescence intensity images and then from phase and corresponding intensity defocus image, the focus images of plant cell sample can be retrieved at various planes after free space propagation.

Non-interferometric 3D fluorescence imaging for bio-applications

Abstract: Non-interferometric three-dimensional (3D) fluorescence imaging techniques for bio-applications are presented. For bioapplications, the efficient illumination is very important to avoid the damage of living cells. We have proposed a method to obtain the complex amplitude of the fluorescence light wave with partially coherence by using the transport of intensity equation (TIE). We will show some experimental results of the reconstructed fluorescence distributions of fluorescence beads and living plant cells by TIE.

Holographic three-dimensional multi-spot light stimulation device and method

Abstract: Provided is a holographic three-dimensional multi-spot light stimulation device capable of rapidly sensing the three-dimensional positions of a plurality of target objects, and imparting light stimulation simultaneously to the plurality of target objects, which are positioned three-dimensionally, on the basis of three-dimensional fluorescence distribution information that has been obtained. The light stimulation device is provided with: a three-dimensional imaging holographic optical system A which employs fluorescent exciting light to acquire three-dimensional fluorescence distribution information resulting from fluorescent signal light from a plurality of stimulation target objects; and a three-dimensional light stimulation holographic optical system B which employs a light stimulation hologram generated on the basis of the acquired three-dimensional fluorescence distribution information to form a plurality of light spots in space, to impart stimulation simultaneously to the plurality of stimulation target objects. Furthermore, the three-dimensional light stimulation holographic optical system B is provided with a spatial light phase modulating element 22 and a control unit 25, wherein the control unit 25 generates the light stimulation hologram by controlling the spatial light phase modulating element 22 on the basis of the three-dimensional fluorescence distribution information.

Multimodal two-photon microscopy with electrical tunable lens

Abstract: In this research, we have proposed a multimodal fast fluorescent imaging by an electrical tunable lens, and quantitative phase imaging by digital holography. In conventional confocal microscopy, sectioning in z direction is realized either by moving objective lens or sample stage. In order to speed up the imaging, and utilize in the specific applications such as light stimulation system in optogenetics, the sectioning is realized by changing the focal power of an electrical tunable lens. The preliminary experiment using fluorescence beads and its relation between focal power and depth change is shown.