Holographic Method Research Articles

Efficient numerical Fresnel diffraction with Gabor frames

Numerical Fresnel diffraction is broadly used in optics and holography in particular. So far, it has been implemented using convolutional approaches, spatial convolutions, or the fast Fourier transform. We propose a new way, to our knowledge, of computing Fresnel diffraction using Gabor frames and chirplets. Contrary to previous techniques, the algorithm has linear-time complexity, does not exhibit aliasing, does not need zero padding, has no constraints on changing shift/resolution/pixel pitch between source and destination planes, and works at any propagation distance. We provide theoretical and numerical analyses, detail the algorithm, and report simulation results with an accelerated GPU implementation. This algorithm may serve as a basis for more flexible, faster, and memory-efficient computer-generated holography methods.

Primary beam calibration for commensal telescopes utilizing offset optics

IntroductionAccurate primary beam calibration is essential for precise brightness measurements in radio astronomy. The VLA Low-band Ionosphere and Transient Experiment (VLITE) faces challenges in calibration due to the offset Cassegrain optics used in its commensal observing system. This study aims to develop a novel calibration method to improve accuracy with no impact on the Very Large Array (VLA) primary science observations.MethodsWe used the apparent brightness of standard candles identified in VLITE’s commensal data to develop 1D and 2D primary beam response models. These models accounted for operational changes and asymmetries caused by the subreflector and were validated against holographic methods and compact source light curves.ResultsThe models achieved calibration accuracy within 3% across the field of view, significantly improving the precision of brightness measurements. The results were consistent with holography-derived solutions and performed reliably under different operational conditions.DiscussionThis improved calibration technique expands VLITE’s capabilities for studying active galactic nuclei, transients, and pulsars. It offers a cost-effective alternative to traditional holographic methods, facilitating broader use in commensal observing systems.

Inverse-designed polarization-insensitive metasurface holography fabricated by nanoimprint lithography.

Metasurface holography, capable of fully engineering the wavefronts of light in an ultra-compact manner, has emerged as a promising route for vivid imaging, data storage, and information encryption. However, the primary manufacturing method for visible metasurface holography remains limited to the expensive and low-productivity electron-beam lithography (EBL). Here, we experimentally demonstrate the polarization-insensitive visible metasurface holography fabricated by high-throughput and low-cost nanoimprint lithography (NIL). The high-index titanium dioxide (TiO2) film is thinly deposited on the imprinted meta-atoms via atomic layer deposition (ALD) to achieve sufficient phase coverage. The calculated high-fidelity holograms are obtained by an inverse design method based on gradient-descent (GD) optimization. Under the various polarized light incidence, the correlation coefficients between the experimental reconstructed images and the target images all exceed 0.7 and the measured efficiencies are approximately 20%. The results demonstrate the high-precision, high-throughput, and cost-effective production of visible metaholograms, paving the way for the commercialization of meta-optics.

Sparse holographic tomography reconstruction method based on self-supervised neural network with learning to synthesize strategy

This research proposes a novel method for sparse digital holographic tomography reconstruction. Due to the limitations of numerical aperture and sampling time, the development of a high-precision sparse digital holographic tomography reconstruction techniques is necessitated. Our main innovation is the developing a composite coordinate-based implicit neural network with learning to synthesize strategy. It addresses the information limitations of limited angle by directly mapping the sample’s rotation angle and coordinates to the phase images, allowing for the prediction of phase images at unmeasured angles without requiring external training dataset. Furthermore, it avoids the issue of high-frequency suppression caused by the uneven distribution of frequency information in the images and the network’s characteristics using separately processing low-frequency and high-frequency information in different channels, resulting in higher fidelity of the predicted phase images and the tomographic results. We validated the effectiveness of the proposed method on four different fiber structures at various sampling intervals. This method provides a new perspective for tomographic reconstruction at sparse angles.

Holographic Communication: A Study of the Quality of Holographic Copies Perception

Relevance. Holography is becoming one of the most promising areas of visualization of three-dimensional objects, which justifies the emergence of a certain scientific interest in this area of research. There is a general global trend of intensifying the work of specialists on the problem of using holographic technologies in various areas of human activity. Trends in the implementation of holographic services and holographic communication today already require a revision of the principles of planning, designing and building existing communication networks, as well as approaches to the implementation of sixth-generation networks 6G, which are based on the integration of various technologies and communication networks into a single network. A separate issue is the assessment of the quality of service and the quality of perception of holographic services by both objective and subjective assessment methods. There are practically no criteria for assessing the quality of a holographic image, including scales and methods for subjective assessment of the quality of holographic services. Moreover, the properties of the holographic flow are poorly understood, and even less so its influence on communication networks and requirements for network parameters, which makes the tasks of studying traffic characteristics and assessing the quality of service of holographic services very relevant.The aim of the work is to evaluate the quality of perception of holographic conference calls using a subjective evaluation method on a model network. The work uses methods of subjective assessment of the quality of perception. The materials presented in the article reflect the results of the authors' experimental research work on studying the problem of the quality of perception of holographic copies. A description of the developed scheme of a full-scale experiment is given.Results. The data obtained as a result of the work of an expert group on assessing the quality of perception are presented. The subjective assessment of the quality of perception of a holographic image begins to deteriorate with 8 connections and becomes unsatisfactory with 12 connections, which must be taken into account when planning experimental studies of work on assessing the quality of perception. Novelty. For the first time, an assessment of the quality of perception of the provision of a holographic conferencing service was carried out using a subjective assessment method. Theoretical significance. The influence of increasing the number of holographic traffic flows on the quality of perception of the received content is analyzed. Practical significance. Expanding the possibilities for assessing the degree of user satisfaction with holographic services.

Holographic method of under-water noise source localization in shallow water

The results of a high-frequency experiment for the detection and direction estimation of underwater sound noisy source are presented. The experiment was conducted in the shallow waters of the Black Sea coast. The noise emission of the source was received by three vector-scalar receivers located on the bottom. By using holographic processing, the detection and direction estimation of a moving underwater source against the background of intense shipping in the experiment region were carried out. Estimates of the input signal-to-noise ratio are presented.

Ultrafast imaging of laser-induced modifications in planar targets via single-shot in-line holography

Abstract We present a holographic single-shot coherent diffractive imaging method based on in-line holography that allows the ultrafast characterization of 2D transmission maps of semi-transparent planar targets such as foils in amplitude and phase. Holographic information is obtained from the interference of the transmitted primary beam with the fields scattered from the modified or unknown target regions. A specialized iterative phase retrieval is used to incorporate the holographic nature of the approach and to accelerate and improve convergence. The achievable quality and reproducibility of the reconstructed transmission maps as well as optimal setup parameters are investigated using realistic pre-characterized reference targets. We used non-circular laser-induced hole structures in 30 nm thin gold foils that represent the final state of a laser modification and show that the far field error of the reconstructed diffraction images can be used to estimate and optimize the reconstruction quality in the object plane in order to obtain accurate and reproducible transmission maps. Our results mark the important first step towards the full spatio-temporal analysis of all stages of laser material modification or laser ablation in two-color pump probe experiments, including plasma formation, equilibration, and expansion.

Dynamic Acoustic Holography: One-Shot High-Precision and High-Information Methodology.

Acoustic holography technology is widely used in the field of ultrasound due to its capability to achieve complex acoustic fields. The traditional acoustic holography method based on single-phase holograms is limited due to its inability to complete acoustic field control with high dynamics and accuracy. Here, we propose a method for constructing an acoustic holographic model, introducing an ultrasonic array to provide dynamic amplitude control degrees of freedom, and combining the dynamically controllable ultrasonic array and high-precision acoustic hologram to achieve the highest acoustic field accuracy and dynamic range. This simulation method has been proven to be applicable to both simple linear patterns and complex surface patterns. Moreover, it is possible to reconstruct the degree of freedom of the target plane amplitude effectively and achieve a breakthrough in high information content. This high-efficiency acoustic field control capability has potential applications in ultrasound imaging, acoustic tweezers, and neuromodulation.

Acoustography by Beam Engineering and Acoustic Control Node: BEACON.

Acoustic manipulation has emerged as a valuable tool for precision controls and dynamic programming of cells and particles. However, conventional acoustic manipulation approaches lack the finesse necessary to form intricate, configurable, continuous, and 3D patterning of particles. Here, this study reports acoustography by Beam Engineering and Acoustic Control Node (BEACON), which delivers intricate, configurable patterns by guiding particles along custom paths with independent phase modulation. Leveraging analytical methods of orbital angular momentum beam via iterative Wirtinger hologram algorithm, this study accomplish acoustography by facilitating orbital angular momentum traps, enabling continuous 2D and 3D acoustic manipulation of microparticles in any desired geometry, with phase modulation independent of intensity. Utilizing on-chip acoustography, the BEACON platform markedly increases the space-bandwidth product to 31000 while attaining an enhanced resolution with a pixel size of ≈25µm, surpassing the typical resolution of over 200µm in previous holographic particle manipulation methods. The capabilities of BEACON are demonstrated in creating intricate triple helical tracing structures using microdroplets (20µm in diameter) and those carrying DNA to validate the effectiveness of the acoustography and phase control methods. This study offers new particle manipulation opportunities, paving the way for next-generation biomedical systems and the future of contact-free precision manufacturing.

Hierarchical Holographic Modeling of Network Ideology Risks

The rapid evolution of computer network technology and the proliferation of social information have elevated the role of computer networks in various domains. However, this progress has also introduced new risks to network ideology security within the big data environment. Using a hierarchical holographic modeling method, this study identifies three key risks—subject-related, information-related, and environmental risks—and constructs a comprehensive three-level index framework for evaluating network ideology risks. By integrating network social governance with the complexities of the big data era, the study proposes an optimized pathway for network social governance, enriching traditional research approaches. The introduction of the LR-NSRPM method reduces CPU and RAM utilization by 21.65% compared to existing methodologies. Additionally, the study outlines observable risk indicators and high-risk elements within network ideology, providing valuable insights for managing network ideology risks in the big data environment.

An auto-focusing method for the lens-free single-shot digital holography based on the dissimilar state

Lens-free digital holography enables multi-focus quantitative phase microscopy for imaging both reflective surfaces and transparent objects. For high-resolution reconstruction in lens-free holographic microscopy, precisely and quickly determining the defocusing distance is essential. In this work, we propose a new single-shot method that relies on the disparity between the captured image and the reconstructions on ergodic planes corresponding to different defocusing distances. This approach effectively generates a unimodal curve, providing a robust solution for auto-focusing and avoiding the need to select different values for discriminative factors across distinct sample types. Furthermore, the simulations and experiments demonstrate that the entire focal-plane search process is simpler and quicker, potentially at least doubling the speed compared to traditional methods. The experiments, conducted in a traditional lens-free system, utilize amplitude and phase resolution targets to validate this method’s applicability. We believe that this method will be an alternative refocusing method for lens-free on-chip microscopes.

Holographic Method of Localization of Underwater Noise Source in Shallow Water

Holographic signal processing of noise signals by using of the vector-scalar receivers is described. The results of an experiment on the detection and direction estimation of an underwater noise source are presented. The experiment was conducted in Black Sea. The source noise emission was received by vector-scalar receivers. Holographic signal processing made it possible to detect, localize and resolve an underwater source with a low input signal/interference ratio against the background of intensive surface navigation.

Non-Invasive Blood-Brain Barrier Disruption Using Acoustic Holography With a Clinical Focused Ultrasound System.

Holographic methods can be used with phased array transducers to shape an ultrasound field. We tested a simple method to create holograms with a hemispherical 1024-element phased array transducer and explored how it could benefit ultrasound-mediated blood-brain barrier (BBB) disruption. With this method, individual acoustic simulations for each element of the transducer were simultaneously loaded into computer memory. Each element's phase was systematically modulated until the combined field matched a desired pattern. The method was evaluated with a 220 kHz transducer being tested clinically to enhance drug delivery via BBB disruption. The holograms were evaluated in a tissue-mimicking phantom and in vivo in experiments disrupting the BBB in rats and in a macaque. We also explored whether this approach could mitigate secondary reflections from the skull using simulations of transcranial focusing in clinical treatments of transcranial sonication for BBB disruption. This approach can enlarge the focal volume in a patient-specific manner and could reduce the number of sonication targets needed to disrupt large volumes, improve the homogeneity of the disruption, and improve our ability to detect microbubble activity in tissues with low vascular density. Simulations suggest that the method could also mitigate secondary reflections during transcranial sonication.

SCIENTIFIC AND TECHNICAL SUBSTANTIATION OF THE PARAMETERS OF THE RADIOLOCATION DEVICE FOR THE DETECTION OF PROHIBITED ITEMS

The paper presents a scientific and technical substantiation of the parameters of the radar device, which allows to detect and visualize forbidden objects by means of electromagnetic radiation of the microwave range. A model of a multistatic scheme for measuring waves reflected from an object based on the holographic method is developed. A software complex of simulation modeling of radar device operation has been developed, by means of which reconstructions of object images for different configurations of sparse sensor subsystems of the radar device have been obtained. An optimal configuration of the sparse sensor subsystem was selected by the method of peak signal-to-noise ratio analysis, for which a multi static hologram was modeled and a reconstruction of the metal rod image was generated. The reconstruction of the metal rod image obtained as a result of simulation modeling has a recognizable contour, which confirms the prospect of developing an experimental prototype of a radar device for detecting prohibited objects.

Fast autofocusing in off-axis digital holography based on search region segmentation and dichotomy

Autofocusing is a critical step in digital holography for reconstructing high-quality intensity and phase information, especially for the dynamic detection of moving objects. Some commonly used autofocusing methods in digital holography are time-consuming as they search over a large range to find a unique reconstruction distance. In this study, we propose a new fast autofocusing method based on search region segmentation and dichotomy. First, a new search region is obtained by segmenting the original region and solving a system of inequality equations. Second, improving the focusing evaluation function and combining this function with the dichotomy method transforms the discriminating minimum of the evaluation function into the detection of the zero-crossing position, reducing the number of searches required for the autofocusing method. The effectiveness of the proposed autofocusing method is validated through numerical simulations and experiments. The proposed method can significantly improve computational efficiency while guaranteeing the detection accuracy of the focusing plane compared with conventional methods.

Research of light diffraction on electrically controlled multiplexed multilayer inhomogeneous holographic diffraction structures based on the photopolymerizing compositions with nematic liquid crystals

We presented the developed analytical model of optical radiation diffraction on multiplexed multilayer inhomogeneous diffraction structures formed by the holographic method in photopolymerizing compositions with nematic liquid crystals having smooth optical heterogeneity in the thickness of the layers. By numerical calculation, it was shown that when using an applied electric field with different polarities to the diffraction layers, as well as varying the azimuth of the polarization of the reading beam, the angular selectivity of the diffracted beam can be transformed with a significant shift in angular selectivity, which makes it possible to increase the spectral bandwidth by 4 times compared to conventional multilayer diffraction structures.

Spatiotemporal hologram

Spatiotemporal structured light has opened up new avenues for optics and photonics. Current spatiotemporal manipulation of light mostly relies on phase-only devices such as liquid crystal spatial light modulators to generate spatiotemporal optical fields with unique photonic properties. However, simultaneous manipulation of both amplitude and phase of the complex field for the spatiotemporal light is still lacking, limiting the diversity and richness of achievable photonic properties. In this work, a simple and versatile spatiotemporal holographic method that can arbitrarily sculpt the spatiotemporal light is presented. The capabilities of this simple yet powerful method are demonstrated through the generation of fundamental and higher-order spatiotemporal Bessel wavepackets, spatiotemporal crystal-like and quasi-crystal-like structures, and spatiotemporal flat-top wavepackets. Fully customizable spatiotemporal wavepackets will find broader application in investigating the dynamics of spatiotemporal fields and interactions between ultrafast spatiotemporal pulses and matters, unveiling previously hidden light-matter interactions and unlocking breakthroughs in photonics and beyond.

Holographic transport in anisotropic plasmas

We study energy-momentum and charge transport in strongly interacting holographic quantum field theories in an anisotropic thermal state by contrasting three different holographic methods to compute transport coefficients: standard holographic calculation of retarded Green’s functions, a method based on the null-focusing equation near horizon and the novel method based on background variations. Employing these methods we compute anisotropic shear and bulk viscosities and conductivities with anisotropy induced externally, for example by an external magnetic field. We show that all three methods yield consistent results. The novel method allows us to read off the transport coefficients from the horizon data and express them in analytic form from which we derive universal relations among them. Furthermore we extend the method based on the null-focusing equation to Gauss-Bonnet theory to compute higher derivative corrections to the aforementioned transport coefficients. Published by the American Physical Society 2024

Phase unwrapping in digital holography based on SRDU-net

In digital holographic measurement, the hologram phase is extracted using an inverse tangent function, resulting in a wrapped phase that is constrained to be (-π,π]. However, the phase contains the height information of the object, which is crucial for accurate measurement of the object contour. Therefore, a digital holographic phase unwrapping method based on SRDU-Net (Separable-Residual-Dense-Inverted U-Net) is proposed in this paper. The SRDU-Net network is constructed by introducing depth-separable convolution, inverted residuals and dense blocks with U-Net as the network framework to achieve high-precision hologram phase recovery. This network adopts depth-separable convolution instead of traditional convolution, combines the inverse residual connection to construct a lightweight convolution structure, and defines dense blocks with this structure to form a lightweight grouped deep convolution network. Meanwhile, the Leaky ReLU activation function is used to introduce the learning rate mechanism to optimize the network parameters with Huber and MSE (mean square error) as the combined loss function. The simulated phase dataset is used to train the network, the trained network model is tested for speckle noise immunity, and phase unwrapping experiments are performed on the collected holograms of the test samples. The results show that SRDU-Net improves the SSIM by 0.1% and reduces the RMSE by 86% over Res-UNet (Residual-UNet). Therefore, the proposed method can realize high-precision recovery of digital holographic wrapped phases, and has a good robustness to phase unwrapping of holograms containing a high degree of speckle noise.

Realtime bacteria detection and analysis in sterile liquid products using deep learning holographic imaging

We introduce a digital inline holography (DIH) method combined with deep learning (DL) for real-time detection and analysis of bacteria in liquid suspension. Specifically, we designed a prototype that integrates DIH with fluorescence imaging to efficiently capture holograms of bacteria flowing in a microfluidic channel, utilizing the fluorescent signal to manually identify ground truths for validation. We process holograms using a tailored DL framework that includes preprocessing, detection, and classification stages involving three specific DL models trained on an extensive dataset that included holograms of generic particles present in sterile liquid and five bacterial species featuring distinct morphologies, Gram stain attributes, and viability. Our approach, validated through experiments with synthetic data and sterile liquid spiked with different bacteria, accurately distinguishes between bacteria and particles, live and dead bacteria, and Gram-positive and negative bacteria of similar morphology, all while minimizing false positives. The study highlights the potential of combining DIH with DL as a transformative tool for rapid bacterial analysis in clinical and industrial settings, with potential extension to other applications including pharmaceutical screening, environmental monitoring, and disease diagnostics.