Search Results (4)

Holographic displays are an upcoming technology for AR and VR applications, with the ability to show 3D content with accurate depth cues, including accommodation and motion parallax. Recent research reveals that only a fraction of holographic pixels are needed to display images with high fidelity, improving energy efficiency in future holographic displays. However, the existing iterative method for computing sparse amplitude and phase layouts does not run in real time; instead, it takes hundreds of milliseconds to render an image into a sparse hologram. In this paper, we present a non-iterative amplitude and phase computation for sparse Fourier holograms that uses Perlin noise in the image–plane phase. We conduct simulated and optical experiments. Compared to the Gaussian-weighted Gerchberg–Saxton method, our method achieves a run time improvement of over 600 times while producing a nearly equal PSNR and SSIM quality. The real-time performance of our method enables the presentation of dynamic content crucial to AR and VR applications, such as video streaming and interactive visualization, on holographic displays. Full article

After the command and control information of the command and control cabin is displayed in the form of mixed reality, the large amount of real-time information and static information contained in it will form a dynamic situation that changes all the time. This brings a great burden to the system operator’s cognition, decision-making and operation. In order to solve this problem, this paper studies the three-dimensional spatial layout of holographic command cabin information display in a mixed reality environment. A total of 15 people participated in the experiment, of which 10 were the subjects of the experiment and 5 were the staff of the auxiliary experiment. Ten subjects used the HoloLens 2 generation to conduct visual characteristics and cognitive load experiments and collected and analyzed the subjects’ task completion time, error rate, eye movement and EEG and subjective evaluation data. Through the analysis of experimental data, the laws of visual and cognitive features of three-dimensional space in a mixed reality environment can be obtained. This paper systematically explores the effects of three key attributes: depth distance, information layer number and target relative position depth distance of information distribution in a 3D space, on visual search performance and on cognitive load. The experimental results showed that the optimal depth distance range for information display in the mixed reality environment is: the best depth distance for operation interactions (0.6 m~1.0 m), the best depth distance for accurate identification (2.4 m~2.8 m) and the overall situational awareness best-in-class depth distance (3.4 m~3.6 m). Under a certain angle of view, the number of information layers in the space is as small as possible, and the number of information layers should not exceed five at most. The relative position depth distance between the information layers in space ranges from 0.2 m to 0.35 m. Based on this theory, information layout in a 3D space can achieve a faster and more accurate visual search in a mixed reality environment and effectively reduce the cognitive load. Full article

Commonly, a three-dimensional (3D) geographic information system (GIS) is based on a two-dimensional (2D) visualization platform, hindering the understanding and expression of the real world in 3D space that further limits user cognition and understanding of 3D geographic information. Mixed reality (MR) adopts 3D display technology, which enables users to recognize and understand a computer-generated world from the perspective of 3D glasses and solves the problem that users are restricted to the perspective of a 2D screen, with a broad application foreground. However, there is a gap, especially dynamically, in modelling and visualizing a holographic 3D geographical Scene with GIS data/information under the development mechanism of a mixed reality system (e.g., the Microsoft HoloLens). This paper attempts to propose a design architecture (HoloDym3DGeoSce) to model and visualize holographic 3D geographical scenes with timely data based on mixed reality technology and the Microsoft HoloLens. The HoloDym3DGeoSce includes two modules, 3D geographic scene modelling with timely data and HoloDym3DGeoSce interactive design. 3D geographic scene modelling with timely data dynamically creates 3D geographic scenes based on Web services, providing materials and content for the HoloDym3DGeoSce system. The HoloDym3DGeoSce interaction module includes two methods: Human–computer physical interaction and human–computer virtual–real interaction. The human–computer physical interaction method provides an interface for users to interact with virtual geographic scenes. The human–computer virtual–real interaction method maps virtual geographic scenes to physical space to achieve virtual and real fusion. According to the proposed architecture design scheme, OpenStreetMap data and the BingMap Server are used as experimental data to realize the application of mixed reality technology to the modelling, rendering, and interacting of 3D geographic scenes, providing users with a stronger and more realistic 3D geographic information experience, and more natural human–computer GIS interactions. The experimental results show that the feasibility and practicability of the scheme have good prospects for further development. Full article

A series of pure congruent lithium niobate (LiNbO₃, CLN) crystals were grown and directly polarized under different electric currents in the growth furnace. Their holographic properties were investigated from the ultraviolet to the visible range. The response time shortened, whereas the diffraction efficiency increased incrementally with the electric current. In particular, the response time of CLN polarized under 100 mA can be reduced by a factor of 10 with a still high saturation diffraction efficiency of about 40.8% at 351 nm. Moreover, its response speed improved by 60 times and 10 times for 473 and 532 nm laser, respectively. The light erasing behavior implies that at least two kinds of photorefractive centers exist in the crystals. Increasing the polarization current induces two pronounced UV absorption peaks and a wide visible absorption peak in CLN crystals. The diffusion effect dominates the photorefractive process and electrons are the dominant carriers. The possible mechanism for the fast photorefractive response is discussed. Increasing the polarization electric current is an effective method to improve the photorefractive response of LN crystal. Full article