Conventional studies on digital hologram printer have mainly been conducted on image generation and reconstruction such as multi-view image generation method, computer-generated hologram (CGH) and a method of displaying a wave-front for a 3D object. However, There should be a criterion to evaluate the quality of the reconstructed image because hologram printer use photosensitive recording interference patterns in holographic material. For this reason, The evaluation method of the completed hologram using a digital hologram printer is focused on how well it came out without aberration or how high intensity of light has been reconstructed. However polarization has an effect on hologram regeneration efficiency because holography uses a laser that generates electromagnetic waves. Hologram recording method is usually to match linear polarization in the same direction. but digital hologram printer composed of complex optical components that causes a phase shifting due to a setup error. it will be a problem for resulting in unwanted polarization at the final recording plane. In this paper, we analyzed the possible polarization changes and analyze the optimal polarization matching status using values from hologram results and use them as a study to improve the efficiency of hologram result from holographic printer.
Blink rate, a major physiological response in humans, directly affects ocular diseases such as keratitis and dry eye. The blink rate in normal eyes appears at a constant frequency of 6–30 times per minute and is constant for each individual. In a previous study, the blink rate decreased when viewing content with high intensity and realism. Therefore, we tried to investigate the change in blink rate when viewing the content in VR HMD (virtual reality head-mounted display) and AR (augmented reality) glasses environments. We compared and analyzed the blink rate in four environments: natural state, viewing monitor, viewing VR HMD, and viewing AR glasses. Twenty-one participants (age, 26.87 ± 3.31 years) viewed the content for 1 min in four environments. One-way repeated ANOVA was used to analyze the blink rate changes. The study showed that the blink rate was decreased in the monitor, VR HMD, and AR glasses environments compared to that in the natural environment. Comparing the VR HMD environment with the AR glasses environment showed that the blink rate decreased in the VR HMD environment. The results of this study can be used for content use safety recommendations (guidelines for safe use of contents due to decreased blink rate) in the VR HMD and AR glasses environments, which are currently attracting attention in the metaverse.
When a near-eye display (NED) device reproduces an image at a location close to the eye, the virtual image is implemented at a large angle. The uniformity of the image is unbalanced due to the change in diffraction efficiency by the hologram recording angle and angular selectivity. This study proposes a method for implementing an optimal uniform image by analyzing the diffraction efficiency and the reconstructed image was analyzed using angular selectivity generated while reproducing the source point of the diffused image as an intermediate element by holographic optical element (HOE). This research provides practical results for displaying high diffraction efficiency and immersive holographic images in the NED system with HOE as uniformed intermediate elements.
Floating holograms using holographic optical element screens differ from existing systems because they can float 2D images in the air and provide a sense of depth. Until now, the verification of such displays has been conducted only on the system implementation, and only the diffraction efficiency and angle of view of the hologram have been verified. Although such displays can be directly observed with the human eye, the eye’s control ability has not been quantitatively verified. In this study, we verified that the focus of the observer coincided with the appropriate depth value determined with experiments. This was achieved by measuring the amount of control reaction from the perspective of the observer on the image of the floating hologram using a holographic optical element (HOE). An autorefractor was used, and we confirmed that an image with a sense of depth can be observed from the interaction of the observer’s focus and convergence on the 2D floating image using a HOE. Thus, the realization of content with a sense of depth of 2D projected images using a HOE in terms of human factors was quantitatively verified.
As highly immersive virtual reality (VR) content, 360° video allows users to observe all viewpoints within the desired direction from the position where the video is recorded. In 360° video content, virtual objects are inserted into recorded real scenes to provide a higher sense of immersion. These techniques are called 3D composition. For a realistic 3D composition in a 360° video, it is important to obtain the internal (focal length) and external (position and rotation) parameters from a 360° camera. Traditional methods estimate the trajectory of a camera by extracting the feature point from the recorded video. However, incorrect results may occur owing to stitching errors from a 360° camera attached to several high-resolution cameras for the stitching process, and a large amount of time is spent on feature tracking owing to the high-resolution of the video. We propose a new method for pre-visualization and 3D composition that overcomes the limitations of existing methods. This system achieves real-time position tracking of the attached camera using a ZED camera and a stereo-vision sensor, and real-time stabilization using a Kalman filter. The proposed system shows high time efficiency and accurate 3D composition.
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