Holographic Display Research Articles

Computational Modelling of Doubly‐Photopolymerized Holographic Biosensors

AbstractHolographic sensors are optical devices capable of tuning reflection wavelength, dependent upon nanostructured variations in refractive index. Computational modelling is utilized to simulate the recording and swelling characteristics of developed doubly photopolymerized (DP) holographic sensors. The holographic devices simplify fabrication processes, reduce financial costs, and improve biocompatibility. A holographic grating is achieved through in situ photopolymerization of a highly crosslinked polymer to produce nanostructured refractive index modulation. The unique swelling characteristics DP holographic sensors possess necessitate the development of system‐specific computational modelling. Hydrogel parameters, including film thickness, refractive index change, layer number, and external medium refractive index are examined for their effect on reflection spectra. Optimized computational models are utilized to study the effect of differential swelling rates of individual layer spacings on sensor response, indicating an idealized reduction in a swelling of 50% for the highly crosslinked region. A 2D photonic crystal geometry with additional periodicity is developed, to inform further sensor design opportunities. Optimized parameters for both 1D and 2D photonic structures will assist the further development of DP holographic sensors.

Tunable liquid crystal grating based holographic 3D display system with wide viewing angle and large size

As one of the most ideal display approaches, holographic 3-dimensional (3D) display has always been a research hotspot since the holographic images reproduced in such system are very similar to what humans see the actual environment. However, current holographic 3D displays suffer from critical bottlenecks of narrow viewing angle and small size. Here, we propose a tunable liquid crystal grating-based holographic 3D display system with wide viewing angle and large size. Our tunable liquid crystal grating, providing an adjustable period and the secondary diffraction of the reconstructed image, enables to simultaneously implement two different hologram generation methods in achieving wide viewing angle and enlarged size, respectively. By using the secondary diffraction mechanism of the tunable liquid crystal grating, the proposed system breaks through the limitations of narrow viewing angle and small size of holographic 3D display. The proposed system shows a viewing angle of 57.4°, which is nearly 7 times of the conventional case with a single spatial light modulator, and the size of the reconstructed image is enlarged by about 4.2. The proposed system will have wide applications in medical diagnosis, advertising, education and entertainment and other fields.

On-chip meta-optics for semi-transparent screen display in sync with AR projection

On-chip integrated meta-optics could enable high-performance, lightweight, and compact integrated photonic devices for augmented reality (AR). Despite previous endeavors in controlling guided waves for holographic phase control, such devices lack versatile performance with the full optical controllability in both amplitude and phase needed to generate multi-functional displays. Here, we propose and experimentally demonstrate an on-chip metasurface integrated on a waveguide to enable a multiplexing semi-transparent screen display in sync with an AR holographic display for human eyes. Through judicious engineering of on-chip meta-diatom displacement and interference at the nanoscale, we can locally modulate the on-chip optical scattering intensities to create a semi-transparent screen display. More intriguingly, we can project a simultaneous dual-channel AR holographic display by incorporating independent encoding freedom of its detour phase. Beyond the all-dielectric properties and high transparency, the projected AR images are free of zeroth-order diffraction interference due to the on-chip optical propagation scheme. We envision that the proposed on-chip meta-optic display could be readily applied to next-generation wearable AR displays, multiplexing optical displays, colored signage, information storage/encryption, and cosmetic visual applications.

Characteristics of Pediatric Hospital Fear and Efficiency of New Distraction Technique Holographic Display for Reducing Fear and Pain in Children

Characteristics of Pediatric Hospital Fear and Efficiency of New Distraction Technique Holographic Display for Reducing Fear and Pain in Children

Bidirectional Phase Compensation for Curved Hologram Generation in Holographic Display

We present a bidirectional phase compensation for curved hologram generation in holographic displays. The proposed bidirectional phase compensation can enlarge the central angle of the curved hologram twice as that of the traditional method which is one-directional phase compensation. Due to the positive relationship between the angle of a curved hologram and its view angle, our proposed method is expected to double the view angle compared with the traditional method. Both numerical simulation and optical experiment results verify the validity and feasibility of the proposed method.

37‐5: Invited Paper: Flat‐Panel Holographic Display

A new architecture for a flat panel three‐dimensional holographic display is proposed. We developed a beam steering backlight, which is achieved by the integration of a beam deflector and a coherent backlight unit. In addition, a hologram processor is implemented as a single‐chip FPGA. We built a flat prototype that is slim as 10cm thick. It shows high‐resolution holographic images with an improved viewing angle.

Dynamic Augmented Reality Display by Layer‐Folded Metasurface via Electrical‐Driven Liquid Crystal (Advanced Optical Materials 12/2022)

A dynamic meta-system for augmented reality (AR) holographic display based on a layer-folded metasurface integrated with electrical-driven liquid crystal (LC) platform is originally proposed and realized by Zhongyang Li and co-workers, as shown in article number 2200418. The layer-folded metasurface enjoys single-time lithography processing with nanoscale horizontal alignment accuracy. Through combining with the electrical-driven LC tuning scheme, it can achieve the AR display dynamics in a real-world scene for human eyes in real-time.

APPLICATION OF PHOTOGRAMMETRY FOR DIGITIZING INFORMATION ABOUT CULTURAL HERITAGE IN THE FORM OF DISPLAY HOLOGRAMS

Abstract. The aim of this article is to demonstrate the possibility of using photogrammetry as a method for documenting and digitizing data reconstructed from a display hologram. We discuss the importance of the task of digitizing information from holograms and the search for its solution, which will allow display holography to gain new distribution. Textured point clouds were obtained for the object and for its image reconstructed from the display reflective type hologram using monochromatic radiation. The requirements for the experimental setup for the digitization of the reconstructed from hologram object wavefront, as well as for the number of photographs for the hologram capturing are formulated and explained. The calculated three-dimensional models of the object and the reconstructed object wavefront were compared according to the Pearson correlation criterion. The achieved correlation value is 0.903. The results of comparison of two 3D models in the estimation of the standard deviation are given.

Independent Light Field Manipulation in Diffraction Orders of Metasurface Holography

AbstractMetasurface holograms are novel optical elements with enormous potential because of the charming electromagnetic features, which can manipulate amplitude, phase, polarization state, and other parameters of light field via an elaborately designed subwavelength nanostructure array. Metagratings are extensively researched for controlling the feature of light in diffraction orders. However, a flexible and simple method is yearned for realizing independent wavefront manipulation in different orders. Here, a metasurface holography that can reconstruct various information in each diffraction order is demonstrated. The physical model is based on Jacobi–Anger expansion and iterative optimization, and both helicity‐dependent and birefringent metasurfaces can work compatibly with this proposed method to achieve arbitrary control of 1D and 2D orders. Specifically, information in 18 channels consisting of diffraction orders and polarization states is encoded in a single metasurface hologram. The approach provides promising and versatile optical elements for beam shaping, holographic display, optical storage, information encryption, etc.

Semiconductor characteristics of tellurium and its implementations

Abstract Tellurium (Te) gained worldwide attention because of its excellent properties, distinctive chained structures, and potential usages. Bulk Te is a p-type elemental helical semiconductor at room temperature and it also having a very limited band gap. Te presents fascinating characteristics such as nonlinear optical response, photoconductivity, good thermoelectric and piezoelectric properties. These charming characteristics induce Te a possible nominee for applications in field-effect transistors, IR acousto-optic deflectors, solar cells, self-developing holographic recording devices, photoconductors, gas sensors, radiative cooling devices, and topological insulators. The developments in these areas are incorporated in great detail. This study opens up the possibility of designing novel devices and considering modern applications of Tellurium.

Application of volume hologram optical elements. Part 1

This paper is devoted to an overview of practical applications of volume holographic optical elements in devices developed at the Siberian State Geodetic Academy (SSGA) and at the CKB «Tochpribor» (Novosibirsk). In the first part of the work, examples of the use of volume holographic optical elements in a holographic level, in a holographic sight and in a holographic spectrum indicator are considered. It is shown that the use of volume holographic optical elements opens up the possibility of developing and creating fundamentally new design solutions for optical and spectral devices. The paper notes both the advantages and some disadvantages of using volume holographic optical elements in the developed holographic devices. It is indicated how the emerging shortcomings of these devices can be corrected with their further improvement.

A Novel Framework for Mixed Reality–Based Control of Collaborative Robot: Development Study

Background Applications of robotics in daily life are becoming essential by creating new possibilities in different fields, especially in the collaborative environment. The potentials of collaborative robots are tremendous as they can work in the same workspace as humans. A framework employing a top-notch technology for collaborative robots will surely be worthwhile for further research. Objective This study aims to present the development of a novel framework for the collaborative robot using mixed reality. Methods The framework uses Unity and Unity Hub as a cross-platform gaming engine and project management tool to design the mixed reality interface and digital twin. It also uses the Windows Mixed Reality platform to show digital materials on holographic display and the Azure mixed reality services to capture and expose digital information. Eventually, it uses a holographic device (HoloLens 2) to execute the mixed reality–based collaborative system. Results A thorough experiment was conducted to validate the novel framework for mixed reality–based control of a collaborative robot. This framework was successfully applied to implement a collaborative system using a 5–degree of freedom robot (xArm-5) in a mixed reality environment. The framework was stable and worked smoothly throughout the collaborative session. Due to the distributed nature of cloud applications, there is a negligible latency between giving a command and the execution of the physical collaborative robot. Conclusions Opportunities for collaborative robots in telerehabilitation and teleoperation are vital as in any other field. The proposed framework was successfully applied in a collaborative session, and it can also be applied in other similar potential applications for robust and more promising performance.

Dynamic Augmented Reality Display by Layer‐Folded Metasurface via Electrical‐Driven Liquid Crystal

AbstractHeading toward the next‐generation versatile meta‐devices and meta‐systems with increasing complexity, it inevitably demands the cascading and coupling between multi‐layer metasurfaces to create new design space for meta‐optics. However, the accurate requirement for multilayer alignment at the nanoscale is significantly challenging due to the actual fabrication limitation, thus hindering the state‐of‐the‐art meta‐optics device integration and its practical application. Herein, a dynamic meta‐system for augmented reality (AR) holographic display functionality based on a layer‐folded metasurface integrated with an electrical‐driven liquid crystal (LC) platform is originally proposed and realized. By ingeniously folding the optical path between meta‐device vertical space, a beam‐steering metasurface in parallel with the other two holographic metasurfaces placed on a single surface is successfully cascaded. Such a layer‐folded scheme enjoys single‐time lithography processing for multi‐patterning with nanoscale alignment accuracy and avoids any vertical alignment issue. Furthermore, by combining with an electrical‐driven LC tuning scheme, the integrated meta‐system could actively switch independent‐encoded holographic images in real‐time floating in the actual‐world scene. Overall, it is envisioned that such a compact dynamic meta‐system suggests a feasible route for dynamic tunable wearable AR displays, intelligent dynamic displays, multi‐functional devices, etc.

End-to-end design of metasurface-based complex-amplitude holograms by physics-driven deep neural networks

Abstract Holograms which reconstruct the transverse profile of light with complex-amplitude information have demonstrated more excellent performances with an improved signal-to-noise ratio compared with those containing amplitude-only and phase-only information. Metasurfaces have been widely utilized for complex-amplitude holograms owing to its capability of arbitrary light modulation at a subwavelength scale which conventional holographic devices cannot achieve. However, existing methods for metasurface-based complex-amplitude hologram design employ single back-diffraction propagation and rely on the artificial blocks which are able to independently and completely control both amplitude and phase. Here, we propose an unsupervised physics-driven deep neural network for the design of metasurface-based complex-amplitude holograms using artificial blocks with incomplete light modulation. This method integrates a neural network module with a forward physical propagation module and directly maps geometric parameters of the blocks to holographic images for end-to-end design. The perfect reconstruction of holographic images verified by numerical simulations has demonstrated that compared with the complete blocks, an efficient utilization, association and cooperation of the limited artificial blocks can achieve reconstruction performance as well. Furthermore, more restricted controls of the incident light are adopted for robustness test. The proposed method offers a real-time and robust way towards large-scale ideal holographic displays with subwavelength resolution.

Holographic super multi-view Maxwellian near-eye display with eyebox expansion.

A holographic super multi-view (SMV) Maxwellian display based on flexible wavefront modulation is proposed for the first time, to the best of our knowledge. It solves the issue that the previous holographic Maxwellian displays could not provide depth cues for monocular vision. Different from the previous methods, two or more parallax images are multiplied by quadric phase distributions and converged to the viewpoints existing in the pupil to provide 3-D vision. A time division method is proposed to eliminate the cross talk caused by the coherence of different spherical waves. Experiments demonstrate that the proposed method can accurately reconstruct images at different depth without cross talk. The proposed method inherits the previous holographic Maxwellian display's advantages of flexible viewpoint position adjustment and large depth of field (DOF). Superior to geometric optics based SMV displays, the proposed system is compact without lens aberration since only a single spatial light modulator (SLM) is needed without any additional optical elements.

Multi-illumination 3D holographic display using a binary mask

We introduce a novel, to the best of our knowledge, method to increase the bandwidth in holographic displays. Here, multi-angle illumination using multiple laser diodes (LDs) is adopted to expand the limited diffraction angle of the spatial light modulator (SLM). To solve the problem of signal repetitions caused by sharing the same SLM pattern, we use a random binary mask (BM). We demonstrate via simulations and experiments that our method effectively increases the bandwidth with sufficient image quality. Furthermore, the speckle noise, a critical issue of the holographic display that decreases the contrast and is potentially harmful to eyes, is reduced by the advantage of incoherent summation in the reconstruction plane. We believe that this method is a practical approach that can expand the bandwidth of the holographic display by alleviating the bottleneck of hardware limitations.

Speckle suppression using F-D2NN in holographic display

We propose a speckle suppression method using Fourier-domain diffraction deep neural networks (F-D2NN) in the holographic display. To the best of our knowledge, it is the first time that F-D2NN is applied for the holographic display quality enhancement. Unlike existing speckle suppression algorithms in the hologram generation, our proposed method works after the hologram reconstruction and improves the reconstructed quality independently of the hologram generation algorithm. The proposed method not only can alone suppress speckle noise generated by different holographic generation algorithms but also is effective to improve reconstruction quality further by jointing with other traditional speckle suppression algorithms. The proposed method provides a new approach for the quality enhancement of the holographic display.

Preview the Products on Display at Display Week 2022

Preview the Products on Display at Display Week 2022

COMPUTER MODEL OF HOLOGRAM SYNTHESIS BY THE REAL PHASE

Computer-synthesized holograms are widely used in areas such as optical information processing, image recognition, three-dimensional display of digital data, and modelling of holographic processes. It is difficult to overestimate the usefulness of the use of synthesized holograms for image reconstruction in acoustic and microwave holography. The use of synthesized holograms as elements of holographic storage devices is promising. Computer synthesis is often the only way to obtain holograms with desired properties. The main advantage of the synthesized hologram is that it is an effective means for converting digital information into optical. Due to this, it is possible to create hybrid-computing systems that are unique in performance, including digital electronic and optical processors and combining the flexibility and versatility of an electronic computer with the enormous performance inherent in an optical processor due to the parallelism of optical information processing. The use of digital holograms as elements in holographic storage devices is promising.

Expanding energy envelope in holographic display via mutually coherent multi-directional illumination

Holographic display is considered as the most promising three-dimensional (3D) display due to its unique feature of reconstructing arbitrary wavefronts. However, the limited étendue, which hinders the immersive experience of observers, remains a major unresolved issue in holographic display technique. In this paper, we propose a novel approach to tweak the constraints of étendue by expanding the energy envelope in holographic display via mutually coherent multi-illumination. The proposed concept contains both a light source design for generating a mutually coherent multi-directional wave and a computer-generated hologram optimization framework for providing high-resolution 3D holograms. To verify the proposed approach, a benchtop prototype of a holographic near-eye display providing an intrinsic large exit-pupil is implemented. The experimental results clearly show that the exit-pupil is effectively expanded by four times and an appropriate viewpoint image is reconstructed according to the view position.