Holographic Setup Research Articles

Measurement of Fly Ash Particle Size Distribution Using Lensless Digital In-Line Holography

Abstract We propose the use of a lensless digital in-line holography setup for the measurement of particle size distribution (PSD) of fly ash obtained from wet electrostatic precipitators of different power plants. The fly ash samples were prepared by spreading the ash nonuniformly over a glass slide. A number of holograms corresponding to distinct regions of the glass slide were recorded and reconstructed. The particle sizes in each reconstructed image were estimated using a circular Hough transform–based edge detection algorithm. PSDs in the range of 10 to 90 μm were obtained. A numerical scheme to extend the measurement range below 10 μm is discussed. The performance of the proposed method is compared with the laser particle-size analyzer and conventional hydrometer. The experimental results indicate that the performance of the proposed method is similar to the hydrometer, with lower experimental and time complexity.

Modeling mental peculiarities of a decision maker by a Fourier-holography technique

A task of modeling individual mental features of a decision-maker using a Fourier holography setup is considered. The problem is considered for a situation when current conditions of decision-making contradict to the previously learned rule of decision-making logic modeled by the non-cooperative game "Prisoner's Dilemma". The approach to the problem is based on a hypothesis of the correlation between mental features and the properties of the neural network as a material carrier of intelligence. The 6f Fourier holography scheme of the resonant architecture is considered as a three-layer neural network implementing a neuro-physiologically motivated concept of the "excitation ring" proposed by A.M. Ivanitsky. We analytically assess the dependence of the validity limits of the classical total probability formula for a disjunction of incompatible events on the characteristics of low-frequency filters in holograms and the correlation radii of the training image of the basic decision rule. Analytical results are confirmed by results of the numerical simulation.

The contralateral organization of the human nervous system as a quantum unfolded, holographic-like, artifactual representation of the underlying dynamics of a fundamentally two-dimensional universe.

A working hypothesis is put forward in this article that the contralateral organization of the human nervous system appears to function like a quantum unfolded holographic apparatus by appearing to invert and reverse quantum unfolded visual and non-visual spatial information. As such, the three-dimensional contralateral organization would be an artifactual representation of the underlying dynamics of a fundamentally two-dimensional universe. According to the holographic principle, nothing that is experienced as three-dimensional could have been processed in a three-dimensional brain. Everything we would experience at a two-dimensional level would appear as a three-dimensional holographic representation, including the architecture of our brains. Various research observations reported elsewhere are reviewed and interpreted here as they may be related in a process that is fundamental to the underlying two-dimensional dynamics of the contralateral organization. The classic holographic method and characteristics of image formation contained by a holograph are described as they relate to the working hypothesis. The double-slit experiment is described and its relevance to the working hypothesis.

Entanglement entropy and Page curve from the M-theory dual of thermal QCD above Tc at intermediate coupling

Obtaining the Page curve in the context of eternal black holes associated with top-down non-conformal holographic thermal duals at intermediate coupling, has been entirely unexplored in the literature. We fill this gap in the context of a doubly holographic setup relevant to the M-theory dual of thermal QCD-like theories at $T>T_c$ at intermediate coupling. Remarkably, excluding the higher derivative terms, the entanglement entropy(EE) of the Hawking radiation from the on-shell Wald EE (for appropriate choices of constants of integration appearing in the embeddings) increases almost linearly with the boundary time due to dominance of EE contribution from the Hartman-Maldacena(HM)-like surface $S_{EE}^{HM, \beta^0}, \beta\sim l_p^6$. Curiously, this imparts a "Swiss-Cheese" structure to the surface $S_{EE}^{HM, \beta^0}$ at a given time (less than the Page time $t_{P}$), in $\mathbb{R}_{\geq0} \times \mathbb{C}$ effecting what could be dubbed as a "Large N Scenario" (LNS). Then, after $t_{P}$, the EE contribution from the Island Surface (IS) $S_{EE}^{IS, \beta^0}$ dominates and saturates the linear time growth of the EE of Hawking radiation and leads to the Page curve. Requiring $S_{EE}^{IS, \beta^0}/S_{BH}\sim2$ up to LO in the non-conformal analog of "$c G_N^{(11)}/r_h^9$", and positivity of $t_{P}$, set respectively a lower and upper bound on the horizon radius $r_h$ (the non-extremality parameter). With the inclusion of the $O(R^4)$ terms in M theory, the turning point associated with the HM-like surface/IS being in the deep IR, results in a relationship between $l_p$ and $r_h$ along with a conjectural $e^{-{\cal O}(1) N^{1/3}}$-suppression (motivated by $S_{EE}^{IS, \beta^0}/S_{BH}\sim2$). We obtain a hierarchy with respect to this N-dependent exponential in $S_{EE}^{HM, \beta^0}, S_{EE}^{IS, \beta^0} (O(\beta^0))$ and $S_{EE}^{HM, \beta}, S_{EE}^{HM, \beta} (O(\beta))$.

Nanoscale surface profile measurement using state space approach in digital holographic microscopy

Surface profile measurement at the nanoscale level has important applications in non-destructive testing and evaluation. The paper proposes a robust method for surface profilometry using digital holographic microscopy setup. The proposed method relies on extracting the phase map encoded in the hologram signal, which directly corresponds to the surface profile, using state space approach. The main advantage of the proposed method is high robustness against noise, which is demonstrated using numerical simulations. For designing the experimental system, a combination of Raspberry-Pi computer and camera module is used for hologram acquisition and processing, which is a step towards low cost imaging. For surface profile measurement, the experimental system has both temporal and spatial sensitivity parameters within 5 nanometers, which indicates robust design. In addition, experimental results show that the proposed method shows superior performance compared to the existing methods for measuring 100 nanometers surface profile features corresponding to different micro-structure regions of a standard calibration test target. Overall, the proposed method allows for single shot, non-contact and full-field measurement of nanoscale surface profile with additional benefits of noise robustness and low cost imaging design.

Depth resolved imaging by digital holography via sample-shifting

Depth resolved imaging is achieved by evenly displacing the sample in the lateral direction using a standard digital holographic setup. A series of holograms are recorded in the reflection geometry while the sample is evenly moved and an algorithm is developed to selectively construct the complex amplitude of the sample at specific focal depths. The amount of information needed for reconstruction is significantly decreased by the recommended method. The suggested approach is suitable for three-dimensional imaging applications, particularly for high transmittance materials, according to experimental findings obtained using a basic holographic setup.

Повышение пространственного разрешения цифровых голограмм с помощью одномерного субпиксельного сканирования

The article considers the issue of increasing the spatial resolution during the registration of digital holograms. In practice, discretization is carried out by measuring signal samples using sensors with a certain finite aperture. The resolution is determined by the size of the aperture area over which the averaging takes place. The resolution enhancement method is based on the sampling equation for signals obtained by the subpixel shift method using generalized functions. A subpixel shift is carried out using a spatial shift by a value less than the element of resolution. Apertures of various shapes are used, for example, elliptical, diamond-shaped, hexagonal, but rectangular apertures are most commonly used. The discretization equation involves the use of a two-dimensional aperture function. Below is a way to increase the resolution when using a one-dimensional function. This can be done based on the structure of the holographic signal. In this case, you can use a subpixel shift in only one direction. Digital holography is distinguished by the fact that photodetector matrices which have a spatial resolution much lower than photographic media used in traditional holography methods are used to register the signal,. Therefore, digital holography uses optical schemes with small angles between interfering beams. However, certain restrictions are imposed on the shape of the objects under study. If the objects have a shape that is significantly different from a flat one, it is necessary to use traditional schemes. The article presents mathematical modeling of the resolution enhancement method based on the recovery of signals from a real hologram obtained in the usual way. The increase in resolution is achieved using a one-dimensional subpixel shift. The use of a one-dimensional subpixel shift makes it possible to significantly simplify the optical scheme of the holographic setup.

Noninvertible Symmetries from Holography and Branes.

We propose a systematic approach to deriving symmetry generators of quantum field theories in holography. Central to this analysis are the Gauss law constraints in the Hamiltonian quantization of symmetry topological field theories (SymTFTs), which are obtained from supergravity. In turn, we realize the symmetry generators from world-volume theories of D-branes in holography. Our main focus is on noninvertible symmetries, which have emerged in the past year as a new type of symmetry in d≥4 QFTs. We exemplify our proposal in the holographic confinement setup, dual to 4D N=1 Super-Yang Mills. In the brane picture, the fusion of noninvertible symmetries naturally arises from the Myers effect on D-branes. In turn, their action on line defects is modeled by the Hanany-Witten effect.

Development of Simultaneous Dual-Resolution Digital Holography System

This research paper is focused on the development of a digital holography system for simultaneous dual-resolution measurements. Digital holography has been widely used for deformation measurements and non-destructive testing (NDT) due to its advantages of high sensitivity, high accuracy, and whole-field, non-touch measurements. A traditional test only has one spatial resolution, which can cause a big deformation to be indistinguishable or minor defects to be ignored. Both large and small fields of view should be observed to reach a multi-spatial resolution measurement. Usually, multiple separate tests are used to observe the different sized fields of view, resulting in higher costs and longer required testing times. Furthermore, these tests may not be repeatable in some cases. This paper presents research on a novel digital holography system that achieves dual spatial resolution measurements simultaneously by testing different-sized fields of view with a single camera. The novel system has two optical channels with two optical layouts of holography to measure deformation. By changing the combined focus length, the two holographic setups have different fields of view, i.e., one has a large and the other has a small field of view. To realize a simultaneous test, the polarization technique is used to avoid cross-interference between the two optical layouts. Finally, spatial carrier fringes with different orientations are introduced into the two holographic setups by appropriately adjusting the reference beam of each setup. The different oriented spatial carrier fringes enable the spectrums of the two interferograms to be separated after a FT (Fourier transform) and the phase distributions of the two interferograms can be extracted and separated by windowing the spectrum to perform an IFT (inverse Fourier transform). The phase distributions can then be used to analyze and calculate the deformations. The experiment using this system is described in this paper and the practicability of this method is verified by the obtained experimental results.

Holographic duals of N=1 quivers in 5d and their nonrelativistic limits

We explore nonrelativistic limits of $\mathcal{N}=1$ quiver gauge theories in 5d. The stringy counterpart of these Super Conformal Field Theories (SCFTs) is characterized by torsional string Newton-Cartan (TSNC) sigma models which are defined over non-Lorentzian manifolds. We further show that under transverse T duality, these TSNC sigma models are mapped into another new class of nonrelativistic sigma models which are defined over a T-dual TSNC background. Considering nonrelativistic limits of various field theory observables in a holographic setup, we further estimate corresponding entities in the TSNC limit of $\mathcal{N}=1$ quivers. We carry out a parallel analysis on holomorphic functions and the associated pole structures in the nonrelativistic limit of ($p$, $q$) five brane webs. In particular, we investigate the generic structure of various loop operators in a nonrelativistic setup and explore their properties under S duality. Finally, we comment on the large $c$ limit of Ramond-Ramond (RR) fields and discuss the associated S-duality transformation rules in the nonrelativistic limit of $\mathcal{N}=1$ quivers.

Holographic Lieb lattice and gapping its Dirac band

We first point out that the Laia-Tong model realizes the Lieb lattice in the holographic setup. It generates a flat band of sharp particle spectrum together with a Dirac band of unparticle spectrum. We provided an understanding why the Laia-Tong model’s boundary condition generate a flat band and compared it with the mechanism of “compact localized orbits” in the lattice models to provide a physical reason why Lieb and Laia-Tong model should be identified based on the similarity in the flat band generation mechanism. We then construct a model which opens a gap to the Dirac band so that one can realize a well-separated flat band. We then study the phase transition between the gapped and gapless phases analytically. We also made methodological progress to find a few other possible quantizations and we express the Green functions in any quantization in terms of that in the standard quantization. Finally we carried out the problem of back reaction to show that the qualitative feature remains the same.

Three-dimensional spline-based computer-generated holography.

Electro-holography is a promising 3D display technology, as it can, in principle, account for all visual cues. Computing the interference patterns to drive them is highly calculation-intensive, requiring the design and development of efficient computer-generated holography (CGH) algorithms to facilitate real-time display. In this work, we propose a new algorithm for computing the CGH for arbitrary 3D curves using splines, as opposed to previous solutions, which could only draw planar curves. The solutions are analytically expressed; we conceived an efficiently computable approximation suitable for GPU implementations. We report over 55-fold speedups over the reference point-wise algorithm, resulting in real-time 4K holographic video generation of complex 3D curved objects. The proposed algorithm is validated numerically and optically on a holographic display setup.

Phase Modulated Frequency Shifted Digital Holographic Vibrometry with Enhanced Robustness

We report experimental results of a frequency shifted digital holography setup for spatially resolved vibrometry. A spatially homogeneous artificial phase modulation is used as a reference to correct for speckle noise. Furthermore, when superimposed upon the object vibration with slightly different frequency, the resulting beat can be evaluated. The beat frequency is invariant under relative motion between the object and interferometer, providing robustness in presence of parasitic low-frequency vibrations. In addition, the ’working point’ is raised out of the noise floor, providing the opportunity to enhance the sensitivity at small vibration displacements. The method is demonstrated by measurements on a vibrating clarinet reed.

Dual geometry of entanglement entropy via deep learning

For a given entanglement entropy of quantum field theory, we investigate how to reconstruct its dual geometry by applying the Ryu-Takayanagi formula and the deep learning method. In the holographic setup, the radial coordinate is identified with the energy scale of the dual quantum field theory. Therefore, the holographic dual geometry can describe how physical properties of a quantum field theory change along the renormalization group flow. Intriguingly, we show that the reconstructed geometry only from the entanglement entropy data can give us more information about other physical properties like thermodynamic quantities in the infrared region.

Optical trapping and fluorescence control with vectorial structured light

Here we functionalized micro-scaled polymer beads with nano-scaled quantum dots and demonstrate optical trapping and tweezing, with in-situ fluorescence measurement, in an all-digital all-optical configuration. We outline the chemistry required to facilitate this, from deactivating the optical trapping environment to size, adhesion and agglomeration control. We introduce a novel holographic optical trapping set-up that leverages on vectorially structured light, allowing for the delivery of tuneable forms of light from purely scalar to purely vector, including propagation invariant flat-top beams for uniform illumination and tailored intensity gradient landscapes. Finally, we show how this has the potential to quench bleaching in a single wavelength trap by linear (spatial mode) rather than non-linear effects, advancing the nascent field of optics for chemistry.

Programmable Aperture Using a Digital Micromirror Device for In-Line Holographic Microscopy

We present the novel use of a digital micromirror device (DMD) as a digitally adjustable and programmable aperture for lens-free digital in-line holographic microscopy (LFDIHMY). The proposed micro-electro-mechanical system (MEMS) based DMD aperture can be used as a compact and inexpensive replacement for existing mechanical based aperture control methods required for many resolution enhancement methods. Simulation of the DMD aperture in an in-line holography setup is presented using a general DMD model from literature. A hardware prototype was successfully implemented and demonstrated. The resolution of both simulated and experimental holograms recorded with a conventional pinhole aperture and the proposed DMD aperture are compared using a 1951 USAF resolution test target. We show that a resolution of 2.46 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm { \mu {\textbf {m}}}$ </tex-math></inline-formula> , close to the sensor pixel limit, can be obtained with each aperture. This demonstrates that a DMD can be used as a programmable replacement for a pinhole aperture.

Single-shot off-axis digital holographic system with extended field-of-view by using multiplexing method

We propose a new configuration of single-shot off-axis digital holographic system to realize double the camera field-of-view (FOV) of the existing off-axis Mech-Zehnder type holographic setup. The double FOV is obtained by double spatial frequency multiplexing of two different areas of an object beam by inserting a Fresnel bi-prism in it, which divides the object beam into two, both carrying different object information. The image sensor is placed at the plane where these two different FOVs overlap so as to record simultaneously two parts of the wavefront of the object in a single-shot. The multiplexed hologram is carrying two interferometric images corresponding to two different FOVs of the object which are modulated with two different spatial carrier frequencies. The feasibility of the proposed digital holographic system is experimentally demonstrated by imaging two different areas of a resolution test target. The limitation of the proposed system and a method to overcome it, are also discussed. The proposed system is useful in a wide range of applications including microscopy and optical metrology.

Black holes entangled by radiation

We construct three models to describe the scenario where two eternal black holes are separated by a flat space, and can eventually be entangled by exchanging radiation. In the doubly holographic setup, we compute the entanglement entropy and mutual information among subsystems and obtain the dynamic phase structure of the entanglement. The formation of entanglement between these two black holes is delayed by the space which the radiation must travel through. If the black holes exchange sufficient Hawking modes, the final state is characterized by a connected entanglement wedge; otherwise, the final entanglement wedge contains two separate islands. In the former case, the entanglement wedge of the black holes forms at the time scale proportional to the size of the flat space between them. While in both cases, the unitarity of the evolution is preserved. When the sizes of the black holes are not equal, we observe a loss of entanglement between the smaller black hole and the radiation at late times. On the field theory side, we consider two Sachdev-Ye-Kitaev (SYK) clusters coupled to a Majorana chain, which resemble two black holes connected by a radiation region. We numerically compute the same entanglement measures and obtain similar phase structures as the bulk results. In general, a time delay of the entanglement between the SYK clusters is found in cases with a long Majorana chain. In particular, when the SYK clusters are different in size, similar entanglement loss between the smaller SYK cluster and the Majorana chain is observed. Finally, we investigate a chain model composed of EPR clusters with particles exchanging between neighboring clusters and reproduce the features of entanglement observed in the previous models.

Three-dimensional density field of a screeching under-expanded jet in helical mode using multi-view digital holographic interferometry

A synchronised multi-axis digital holographic interferometry set-up is presented for the study of 3-D flow fields with large density gradients. This optical configuration provides instantaneous interferograms with fine spatial resolution in six directions of projection. A regularised tomographic approach taking into account the presence of possible shock waves is furthermore considered to reconstruct 3-D density fields. Applied to a screeching under-expanded supersonic jet with helical dynamics, this set-up is used to provide dense optical phase measurements in the initial region of the jet. The jet mean density field is shown to be satisfactorily estimated with sharply resolved density gradients. In addition, an approach based on azimuthal Fourier transform and snapshot proper orthogonal decomposition (POD) applied to the instantaneous flow observations is proposed to study the main coherent dynamics of the jet. Relying on a cluster analysis of the azimuthal POD mode coefficients, a reduced dynamical model in the POD mode phase space is used as an approximation of the two observed limit cycles. A clear 3-D representation of the density field of a helical instability associated with screech mode C is then evidenced, with two equally probable directions of rotation. Switching between the two directions is reported, highlighting intermittency in the feedback loop. This helical structure is particularly seen to extend to the jet core, driving its internal dynamics and inducing out-of-phase density fluctuations between the outer and inner shear layers. These out-of-phase motions are related to the non-uniform radial distribution of fluctuation phase associated with the outer-layer Kelvin–Helmholtz instability wave.

Developing a Reliable Holographic Flow Cyto-Tomography Apparatus by Optimizing the Experimental Layout and Computational Processing.

Digital Holographic Tomography (DHT) has recently been established as a means of retrieving the 3D refractive index mapping of single cells. To make DHT a viable system, it is necessary to develop a reliable and robust holographic apparatus in order that such technology can be utilized outside of specialized optics laboratories and operated in the in-flow modality. In this paper, we propose a quasi-common-path lateral-shearing holographic optical set-up to be used, for the first time, for DHT in a flow-cytometer modality. The proposed solution is able to withstand environmental vibrations that can severely affect the interference process. Furthermore, we have scaled down the system while ensuring that a full 360° rotation of the cells occurs in the field-of-view, in order to retrieve 3D phase-contrast tomograms of single cells flowing along a microfluidic channel. This was achieved by setting the camera sensor at 45° with respect to the microfluidic direction. Additional optimizations were made to the computational elements to ensure the reliable retrieval of 3D refractive index distributions by demonstrating an effective method of tomographic reconstruction, based on high-order total variation. The results were first demonstrated using realistic 3D numerical phantom cells to assess the performance of the proposed high-order total variation method in comparison with the gold-standard algorithm for tomographic reconstructions: namely, filtered back projection. Then, the proposed DHT system and the processing pipeline were experimentally validated for monocytes and mouse embryonic fibroblast NIH-3T3 cells lines. Moreover, the repeatability of these tomographic measurements was also investigated by recording the same cell multiple times and quantifying the ability to provide reliable and comparable tomographic reconstructions, as confirmed by a correlation coefficient greater than 95%. The reported results represent various steps forward in several key aspects of in-flow DHT, thus paving the way for its use in real-world applications.