Holographic Research Articles

Single-exposure multi-wavelength optical diffraction tomography based on space-angle dual multiplexing holography.

We present a space-angle dual multiplexing holographic recording system for realizing single-exposure multi-wavelength optical diffraction tomographic (ODT) imaging. This system is achieved by combining the principle of single-exposure multi-wavelength holographic imaging technique based on angle-division multiplexing with the principle of single-exposure ODT imaging technique based on microlens array multi-angle illuminations and space-division multiplexing. Compared with the existing multi-wavelength ODT imaging methods, it enables the holographic recording of all the diffraction tomography information of a measured specimen at multiple illumination wavelengths in a single camera exposure without any scan mechanism. Using our proposed data processing method, the multi-wavelength three-dimensional (3D) refractive index tomograms of a specimen can be eventually reconstructed from single recorded multiplexing hologram. Experimental results of a static polystyrene bead and a living C. elegans worm demonstrate the feasibility of this system.

Label-Free Three-Dimensional Morphological Characterization of Cell Death Using Holographic Tomography.

This study presents a novel label-free approach for characterizing cell death states, eliminating the need for complex molecular labeling that may yield artificial or ambiguous results due to technical limitations in microscope resolution. The proposed holographic tomography technique offers a label-free avenue for capturing precise three-dimensional (3D) refractive index morphologies of cells and directly analyzing cellular parameters like area, height, volume, and nucleus/cytoplasm ratio within the 3D cellular model. We showcase holographic tomography results illustrating various cell death types and elucidate distinctive refractive index correlations with specific cell morphologies complemented by biochemical assays to verify cell death states. These findings hold promise for advancing in situ single cell state identification and diagnosis applications.

The Designed Phase Mask for Suppressing the Inter-Pixel Crosstalk Noise in Intensity-Modulated Multilevel Holographic Data Storage Systems

Intensity-modulated signals have the advantage of being directly detectable by the image sensor but have the drawback that the signal quality is easily deteriorated by crosstalk noise, in contrast to phase-modulated signals. In order to suppress the crosstalk noise, we propose a new signal arrangement for multilevel intensity-modulated signals. The concept of our method is to reduce the number of adjacent pixels that are a source of inter-pixel crosstalk noise and to minimize intensity modulation owing to interference with crosstalk noise. We have numerically and experimentally demonstrated that our method can reduce the error rate and improve the recording density compared to the conventional signal arrangement. Our proposed method offers a promising solution for achieving higher recording densities in intensity-modulated holographic data storage systems.

Super-resolution imaging and autofocusing via compressive-sensing-based twin-image-free holography

This paper presents an iterative reconstruction framework for super-resolution imaging and autofocusing via compressive-sensing-based twin-image-free holography (SRI-AF-CS-TIFH) for 3D (multi-plane) object in compressed holographic imaging. In our proposed framework, in the first step, the Hough transform edge detection method is incorporated into the eigenvalue-based autofocusing algorithm (dubbed as EIG-AF-Hough) to accurately estimate the focus distances for each plane of multi-plane objects from the snapshot measurements; In the second step, nonlinear optimization is used to achieve the super-resolution reconstruction from the same snapshot measurements. Experimental results demonstrate the effectiveness of our proposed framework for achieving autofocusing and super-resolution in compressed holographic imaging simultaneously in both simulated and real holographic scenarios.

Spray characteristics of different regions downstream of a swirl cup

The spray characteristics of different regions downstream of swirl cups play a critical role in cold start and re-ignition of gas turbines. The spray measurements were performed at the fuel pressures of 0.5, 0.8, 1.0, 1.5, and 2.0 MPa and the fuel temperatures of −23, −13, −3, 7, 17 and 27 ℃, respectively. The droplet size, droplet velocity, droplet number, and instantaneous spatial spray image of sprays from an aviation kerosene Jet-A were measured using a two-component phase Doppler particle analyzer and a digital off-axis holography system. As the fuel pressure and temperature increase, the Sauter Mean Diameter (SMD) and spray non-uniformity of the Spray Shear Layer (SSL) gradually decrease. As the fuel pressure increases, the SMD and spray non-uniformity of the Central Toroidal Recirculation Zone (CTRZ) gradually decrease, and the slopes of these curves both decrease. As the fuel pressure increases, the SMD and spray non-uniformity of the CTRZ rapidly decrease at the fuel temperature of −23 ℃, while slightly decrease at the fuel temperature of 27 ℃. The droplets in the CTRZ come from 3 different sources: simplex nozzle, venturi, and outside the CTRZ. As the fuel pressure increases, the proportion of droplets recirculated from outside the CTRZ decreases. This study proposed the concept of the “pressure critical point” for the swirl cups. As the fuel temperature decreases, the proportion of droplets recirculated from outside the CTRZ increases below the critical pressure, while decreases above the critical pressure. In addition, through the models of liquid film formation and breakup on the curved cylindrical wall, a semi-theoretical model was established to predict the SMD of SSL for swirl cups. The prediction uncertainty of this model is less than 6% for all 14 conditions in this paper.

Cylindrical Vector Beam Holography without Preservation of OAM Modes.

Orbital angular momentum (OAM) multiplexed holograms have attracted a great deal of attention recently due to their physically unbounded set of orthogonal helical modes. However, preserving the OAM property in each pixel hinders fine sampling of the target image in principle and requires a fundamental filtering aperture array in the detector plane. Here, we demonstrate the concept of metasurface-based vectorial holography with cylindrical vector beams (CVBs), whose unlimited polarization orders and unique polarization distributions can be used to boost information storage capacity. Although CVBs are composed of OAM modes, the holographic images do not preserve the OAM modes in our design, enabling fine sampling of the target image in a quasi-continuous way like traditional computer-generated holograms. Moreover, the images can be directly observed by passing them through a polarizer without the need for a fundamental mode filter array. We anticipate that our method may pave the way for high-capacity holographic devices.

Visiting experience of digital museum interior design based on virtual reality and sensor networks

China's computer technology and image sensor technology are both rapidly developing, and the related advantages of digital holography technology are gradually expanding. These technologies have been applied in many fields. For example, three-dimensional measurement, deformation measurement, and anti-counterfeiting fields. This article combines holographic technology and virtual reality technology, and applies them to the interior design of digital museums and the optimization of auxiliary visits. A corresponding mathematical calculation model is established for digital holographic images, and in-depth research is conducted on this mathematical calculation model. Relevant personnel have also conducted relevant research on commonly used digital holography technology, and provided a detailed introduction to the principles of virtual reality technology. They have also conducted in-depth research on the specific working principles of VR technology and the application technology of virtual reality systems. Finally, an analysis and research were conducted on the development of Chinese museums, and a new perspective was proposed on the indoor space of museums under the new digital concept, which has certain reference significance. Currently, Chinese museums are thriving, so deepening the interior space of museums is very important. This article hopes to provide some guidance and practical value for the development of Chinese museums.

Holographic images of an AdS black hole within the framework of f(R) gravity theory

Holographic images of an AdS black hole within the framework of f(R) gravity theory

Direct Imaging of Radiation-Sensitive Organic Polymer-Based Nanocrystals at Sub-Ångström Resolution.

Seeing the atomic configuration of single organic nanoparticles at a sub-Å spatial resolution by transmission electron microscopy has been so far prevented by the high sensitivity of soft matter to radiation damage. This difficulty is related to the need to irradiate the particle with a total dose of a few electrons/Å2, not compatible with the electron beam density necessary to search the low-contrast nanoparticle, to control its drift, finely adjust the electron-optical conditions and particle orientation, and finally acquire an effective atomic-resolution image. On the other hand, the capability to study individual pristine nanoparticles, such as proteins, active pharmaceutical ingredients, and polymers, with peculiar sensitivity to the variation in the local structure, defects, and strain, would provide advancements in many fields, including materials science, medicine, biology, and pharmacology. Here, we report the direct sub-ångström-resolution imaging at room temperature of pristine unstained crystalline polymer-based nanoparticles. This result is obtained by combining low-dose in-line electron holography and phase-contrast imaging on state-of-the-art equipment, providing an effective tool for the quantitative sub-ångström imaging of soft matter.

Nanoimprinted TiO2 Metasurfaces with Reduced Meta-Atom Aspect Ratio and Enhanced Performance for Holographic Imaging.

Metasurface holograms, with the capability to manipulate spatial light amplitudes and phases, are considered next-generation solutions for holographic imaging. However, conventional fabrication approaches for meta-atoms are heavily dependent on electron-beam lithography (EBL), a technique known for its expensive and time-consuming nature. In this paper, a polarization-insensitive metasurface hologram is proposed using a cost-effective and rapid nanoimprinting method with titanium dioxide (TiO2) nanoparticle loaded polymer (NLP). Based on a simulation, it has been found that, despite a reduction in the aspect ratio of meta-atoms of nearly 20%, which is beneficial to silicon master etching, NLP filling, and the mold release processes, imaging efficiency can go up to 54% at wavelength of 532 nm. In addition, it demonstrates acceptable imaging quality at wavelengths of 473 and 671 nm. Moreover, the influence of fabrication errors and nanoimprinting material degradation in terms of residual layer thickness, meta-atom loss or fracture, thermal-induced dimensional variation, non-uniform distribution of TiO2 particles, etc., on the performance is investigated. The simulation results indicate that the proposed device exhibits a high tolerance to these defects, proving its applicability and robustness in practice.

Label-free, high-throughput holographic imaging to evaluate mammalian gametes and embryos†.

Assisted reproduction is one of the significant tools to treat human infertility. Morphological assessment is the primary method to determine sperm and embryo viability during in vitro fertilization cycles. It has the advantage of being a quick, convenient, and inexpensive means of assessment. However, visual observation is of limited predictive value for early embryo morphology. It has led many to search for other imaging tools to assess the reproductive potential of a given embryo. The limitations of visual assessment apply to both humans and animals. One recent innovation in assisted reproduction technology imaging is interferometric phase microscopy, also known as holographic microscopy. Interferometric phase microscopy/quantitative phase imaging is the next likely progression of analytical microscopes for the assisted reproduction laboratory. The interferometric phase microscopy system analyzes waves produced by the light as it passes through the specimen observed. The microscope collects the light waves produced and uses the algorithm to create a hologram of the specimen. Recently, interferometric phase microscopy has been combined with quantitative phase imaging, which joins phase contrast microscopy with holographic microscopy. These microscopes collect light waves produced and use the algorithm to create a hologram of the specimen. Unlike other systems, interferometric phase microscopy can provide a quantitative digital image, and it can make 2D and 3D images of the samples. This review summarizes some newer and more promising quantitative phase imaging microscopy systems for evaluating gametes and embryos. Studies clearly show that quantitative phase imaging is superior to bright field microscopy-based evaluation methods when evaluating sperm and oocytes prior to IVF and embryos prior to transfer. However, further assessment of these systems for efficacy, reproducibility, cost-effectiveness, and embryo/gamete safety must take place before they are widely adopted.

Assessment of pulmonary vascular anatomy: comparing augmented reality by holograms versus standard CT images/reconstructions using surgical findings as reference standard

BackgroundWe compared computed tomography (CT) images and holograms (HG) to assess the number of arteries of the lung lobes undergoing lobectomy and assessed easiness in interpretation by radiologists and thoracic surgeons with both techniques.MethodsPatients scheduled for lobectomy for lung cancer were prospectively included and underwent CT for staging. A patient-specific three-dimensional model was generated and visualized in an augmented reality setting. One radiologist and one thoracic surgeon evaluated CT images and holograms to count lobar arteries, having as reference standard the number of arteries recorded at surgery. The easiness of vessel identification was graded according to a Likert scale. Wilcoxon signed-rank test and κ statistics were used.ResultsFifty-two patients were prospectively included. The two doctors detected the same number of arteries in 44/52 images (85%) and in 51/52 holograms (98%). The mean difference between the number of artery branches detected by surgery and CT images was 0.31 ± 0.98, whereas it was 0.09 ± 0.37 between surgery and HGs (p = 0.433). In particular, the mean difference in the number of arteries detected in the upper lobes was 0.67 ± 1.08 between surgery and CT images and 0.17 ± 0.46 between surgery and holograms (p = 0.029). Both radiologist and surgeon showed a higher agreement for holograms (κ = 0.99) than for CT (κ = 0.81) and found holograms easier to evaluate than CTs (p < 0.001).ConclusionsAugmented reality by holograms is an effective tool for preoperative vascular anatomy assessment of lungs, especially when evaluating the upper lobes, more prone to anatomical variations.Trial registrationClinicalTrials.gov, NCT04227444Relevance statementPreoperative evaluation of the lung lobe arteries through augmented reality may help the thoracic surgeons to carefully plan a lobectomy, thus contributing to optimize patients’ outcomes.Key points• Preoperative assessment of the lung arteries may help surgical planning.• Lung artery detection by augmented reality was more accurate than that by CT images, particularly for the upper lobes.• The assessment of the lung arterial vessels was easier by using holograms than CT images.Graphical

Smart Restaurant Using 3D Holographic Projection Menu and Waiter Robot

This project aims to construct an inventive 3D holographic restaurant system by integrating cutting-edge technology such as Raspberry Pi, LCD monitor, L298N motor driver, keyboard, speaker, DC motor, ESP8266, and IR sensor. The system incorporates a robotic waiter equipped with a holographic display, capable of interacting with customers, taking orders, and serving food. The robot navigates between three tables, displaying holographic menus and confirming orders through a keypad. The system aims to revolutionize the dining experience by combining robotics, holography, and smart technology for an engaging and futuristic restaurant environment. This paper explores the innovative integration of advanced technologies, specifically 3D holographic projection menus and waiter robots, to create a smart restaurant aimed at revolutionizing the traditional dining experience. The incorporation of these cutting-edge technologies offers a unique and immersive approach to menu visualization and customer service. Keyword: 3D Holographic Projection, Robotics, Smart technology, Customer engagement.

Large-scale high-quality full-color computer-generated volume hologram fabricated by the stacking and tiling technique.

A technique is presented to produce very high-quality full-color holographic 3D images in large-scale computer holography, which uses over a billion pixels. In this technique, three large-scale computer-generated holograms, printed using laser lithography, are transferred to three computer-generated volume holograms (CGVH) using a method called tiling contact-copy. Then, the full-color holographic image is created by stacking the three CGVHs. We demonstrate a 10-cm square stacked CGVH that reconstructs full-parallax full-color 3D images at high quality with a viewing angle of more than 35°.

Full-colour 3D holographic augmented-reality displays with metasurface waveguides

Emerging spatial computing systems seamlessly superimpose digital information on the physical environment observed by a user, enabling transformative experiences across various domains, such as entertainment, education, communication and training1–3. However, the widespread adoption of augmented-reality (AR) displays has been limited due to the bulky projection optics of their light engines and their inability to accurately portray three-dimensional (3D) depth cues for virtual content, among other factors4,5. Here we introduce a holographic AR system that overcomes these challenges using a unique combination of inverse-designed full-colour metasurface gratings, a compact dispersion-compensating waveguide geometry and artificial-intelligence-driven holography algorithms. These elements are co-designed to eliminate the need for bulky collimation optics between the spatial light modulator and the waveguide and to present vibrant, full-colour, 3D AR content in a compact device form factor. To deliver unprecedented visual quality with our prototype, we develop an innovative image formation model that combines a physically accurate waveguide model with learned components that are automatically calibrated using camera feedback. Our unique co-design of a nanophotonic metasurface waveguide and artificial-intelligence-driven holographic algorithms represents a significant advancement in creating visually compelling 3D AR experiences in a compact wearable device.

Fractional Fourier-transform off-axis digital holographic imaging

A fractional Fourier-transform digital holographic imaging method with resolution enhancement features is presented. In an optical configuration, an extended fractional Fourier-transform optical setup is set in the object arm of an off-axis digital holographic recording system to record a fractional Fourier-transform hologram via the optical interference of the fractional Fourier-transform wavefront of an object wave with a reference wave. For reconstruction imaging, the reconstruction approach for fractional Fourier-transform holograms is given. In the experiment, the fractional Fourier-transform digital holograms are recorded under the different recording parameters, and their amplitude images are effectively reconstructed. The imaging results demonstrate that the reconstruction-imaging resolution of fractional-order Fourier-transform holograms is obviously enhanced compared to that of conventional image-plane holograms. The presented fractional Fourier-transform digital holographic imaging with resolution enhancement and optical configuration flexibility provides, to our knowledge, a novel way for off-axis digital holographic imaging.

Multi‐Wavelength Metasurface Empowered Cryptography for Heightened Security and Improved Fidelity

AbstractInformation security holds paramount importance in the contemporary information society. Here, a novel cryptography method is proposed based on the multi‐wavelength complex‐amplitude metasurface, which can achieve a high security level by generating a frequency‐selective key as an additional layer of protection. Moreover, the quality of the decrypted holographic images can be significantly improved by employing the complex‐amplitude encoding method and the modified visual secret sharing scheme, which adopts a new superposition operator to prevent fidelity loss. As a proof‐of‐concept demonstration, a prototype metasurface sample is designed, fabricated, and characterized, where the measured results agree very well with the numerical ones and the design goals. The proposed method can reinforce security level and improve fidelity of the decrypted message, rendering it appealing for applications in communication and anti‐counterfeiting.

Holographic voice-interactive system with Taylor Rayleigh-Sommerfeld based point cloud gridding

In recent years, intelligent voice interaction technology and holographic display technology have garnered significant attention. We propose a holographic voice-interactive system. The holographic voice interaction system can provide users with a virtual assistant proficient in accurately handling user voice queries, facilitating smoother interactions. Additionally, users can interact with virtual objects via holographic projection, enhancing realism and engagement. In this research, we introduce the U-blocks and U-net based reverse attention residual algorithm to generate more effective and accurate point cloud datasets during the acquisition phase. Furthermore, we integrate the ChatGLM pre-trained language model as the core module for voice interaction in the holographic display system, covering aspects such as text interaction and output control. Additionally, we propose a Taylor Rayleigh-Sommerfeld point cloud gridding method aimed at improving the computational speed of hologram generation. We validate the feasibility of our proposed methods through numerical simulations and optical experiments.

Application of deep learning and inline holography to estimate the droplet size distribution

We examine five machine learning-based architectures to estimate the droplet size distributions obtained using digital inline holography. The architectures, namely, U-Net, R2 U-Net, Attention U-Net, V-Net, and Residual U-Net, are trained using synthetic holographic images. Our assessment focuses on evaluating the training, validation, and prediction performance of these architectures. Our results indicate that U-Net and R2 U-Net are the most proficient architectures, consistently demonstrating superior performance trends and achieving the highest Intersection Over Union (IOU) scores among the five architectures studied. We employ additional training using experimental holographic images for the two top-performing architectures to validate their efficacy further. Subsequently, they are employed to segment an experimental dataset illustrating the bag breakup phenomenon, facilitating the extraction of size distribution. The extracted size distribution from U-Net and R2 U-Net segmentation is then compared with the analytical model proposed by Jackiw and Ashgriz (2022) by employing the gamma and log-normal distributions. Our findings indicate that the gamma distribution provides a more accurate prediction of the multi-modal size distribution than the log-normal distribution owing to its long exponential tail. The present study offers valuable insights into the effectiveness of machine learning architectures in estimating particle/droplet sizes, highlighting their practical application in real-world experimental scenarios.

Optical Information Encryption Based on Secret Sharing Liquid Crystal Elements with Spatial Dislocation

AbstractOptical encryption is an increasingly significant technique in the realm of information security. In the recent decade, there has been considerable interest in using planar optics elements for information encryption. However, information leakage possibly occurs due to limited encrytion channels available for single‐layer devices. To circumvent this problem, a novel encryption method is put forward using secret sharing cascaded liquid crystal (LC) elements with spatial dislocation, which can produce near‐field patterns and far‐field holographic images under different illumination conditions. Specifically, Malus's Law and its inherent one‐to‐four mapping of rotational degeneracy, along with the Pancharatnam‐Berry (PB) phase introduced by LC molecules, to achieve multi‐channel encryption are utilized. Therefore, each cascaded LC unit can manipulate the amplitude and phase imparted to output light independently, thus only by obtaining both LC devices can decryption be realized. To further enhance the encryption security, the author purposely divide each LC device into multiple regions and find that the encrypted patterns can only be recovered when the two LC elements align precisely with a specific dislocation. These experimental measurements agree well with the design, thus demonstrating the strong encryption capability and broad application prospects of the design approach in the field of optical encryption with high cost‐effectiveness.