Development of display and its related technologies provides immersive visual experience with head-mounted-display
(HMD). However, most available HMDs provide 3D perception only by stereopsis, lack of accommodation depth cues.
Recently, holographic HMD (HHMD) arises as one viable option to resolve this problem because hologram is known to
provide full set of depth cues including accommodation. Moreover, by virtue of increasing computational power,
hologram synthesis from 3D object represented by point cloud can be calculated in real time even with rigorous
Rayleigh-Sommerfeld diffraction formula. However, in HMD, rapid gaze change of the user requires much faster refresh
rate, which means that much faster hologram synthesis is indispensable in HHMD. Because the visual acuity falls off in
the visual periphery, we propose here to accelerate synthesizing hologram by differentiating density of point cloud
projected on the screen. We classify the screen into multiple layers which are concentric circles with different radii,
where the center is aligned with gaze of user. Layer with smaller radius is closer to the region of interest, hence, assigned
with higher density of point cloud. Because the computation time is directly related to the number of points in point
cloud, we can accelerate synthesizing hologram by lowering density of point cloud in the visual periphery. Cognitive
study reveals that user cannot discriminate those degradation in the visual periphery if the parameters are properly
designed. Prototype HHMD system will be provided for verifying the feasibility of our method, and detailed design
scheme will be discussed.
Autostereoscopic (glasses-free) displays provide perspectives of images according to the position of the observer. This book introduces various autostereoscopic technologies, from the fundamental principles of the parallax-barrier method to the latest multi-projection, super multi-view displays. Display basics and fundamentals of 3D displays are presented first, followed by descriptions of multi-view system configurations. Because the technological advancement of conventional 2D display affects the development of 3D displays, the book also covers the basics of 2D displays, including flat panel and projection-type displays. For readers with some knowledge of 3D display technologies, detailed explanations of advanced display technologies such as the slanted lens technique and multi-projection system are also included. The book is suitable for readers ranging from undergraduate students to display manufacturers in the industry.
Adaptive optics (AO) using digital holography (DH) is more effective in terms of complexity and cost than other AO techniques. However, use of coherent illumination is problematic in applying DHAO for retinal imaging because of speckle noise. Self-interference incoherent digital holography (SIDH) is a technique to record holographic information from the object illuminated by incoherent light. By adopting SIDH for the full-field imaging, the speckle noise problem can be avoided with incoherent illumination. However, the guide-star hologram for AO requires the guide-star to be smaller than retinal cell size to achieve sufficient resolution. Hence, the proposed SIDH AO system is configured with a hybrid illumination system which uses incoherent illumination for recording of full-field hologram while laser is used for guide-star hologram. Preliminary experiment using an array of micro-spheres for the object shows that the full-field hologram and guide-star hologram can be recorded by proposed optical configuration.
Adaptive optics (AO) in astronomical imaging is a technique to improve the quality of image by compensating aberrations induced by atmospheric turbulence. Digital holographic AO (DHAO) is one attractive option to implement AO scheme because it is capable of directly measuring the phase profile of aberration without complicated calculation or loss of resolution of CCD. Hence, if applicable, DHAO is expected to have advantages over traditional AO systems. Recent development of self-interference incoherent digital holography (SIDH) makes it possible to apply the concept of DHAO for an astronomical application where the illumination is incoherent and cannot be controlled. We have investigated the image characteristics according to various parameters of SIDH AO to derive optimum condition or design of the system. We observe not only well-known super-resolution property of SIDH but also interesting and significant improvement of noise behavior by aberration compensation. Because of many beneficial features, we expect that SIDH AO will be a useful tool for astronomical imaging.
Two types of transparent three-dimensional display systems applicable for the augmented reality are demonstrated.
One of them is a head-mounted-display-type implementation which utilizes the principle of the system adopting the
concave floating lens to the virtual mode integral imaging. Such configuration has an advantage in that the threedimensional
image can be displayed at sufficiently far distance resolving the accommodation conflict with the real
world scene. Incorporating the convex half mirror, which shows a partial transparency, instead of the concave
floating lens, makes it possible to implement the transparent three-dimensional display system. The other type is the
projection-type implementation, which is more appropriate for the general use than the head-mounted-display-type
implementation. Its imaging principle is based on the well-known reflection-type integral imaging. We realize the
feature of transparent display by imposing the partial transparency to the array of concave mirror which is used for
the screen of reflection-type integral imaging. Two types of configurations, relying on incoherent and coherent light
sources, are both possible. For the incoherent configuration, we introduce the concave half mirror array, whereas the
coherent one adopts the holographic optical element which replicates the functionality of the lenslet array. Though
the projection-type implementation is beneficial than the head-mounted-display in principle, the present status of the
technical advance of the spatial light modulator still does not provide the satisfactory visual quality of the displayed
three-dimensional image. Hence we expect that the head-mounted-display-type and projection-type implementations
will come up in the market in sequence.
KEYWORDS: Polarizers, Scattering, Light scattering, 3D image processing, Polarization, 3D displays, Linear polarizers, Projection systems, Integral imaging, 3D volumetric displays
A bi-directional 2D/3D convertible integral imaging system is proposed. Two optical modules composed of a scattering
polarizer and a linear polarizer are adopted, and 2D or 3D mode operation is easily changed by converting polarization
states of the projected images. In the 2D mode, the incident light is scattered at the scattering polarizer and the scattered
light facing the lens-array is blocked, a 2D image is observable only at the same side as the projector. In the 3D mode,
the incident light with the transmission polarization is directly projected onto a lens-array, and the 3D images are
integrated. Our proposed system is able to display the 3D images as well as the 2D images for the observers who are
placed in front and rear side of the system.
Accommodation response of super-multiview display device, which is implemented to provide horizontal-only parallax,
has been investigated. Because of astigmatic characteristic of such display, the focal points of horizontal and vertical
directions differ in longitudinal direction. Assuming that the accommodation response to the astigmatic image follows
the distance where the average of bandwidths in vertical and horizontal direction becomes the maximum, numerical
calculations presented that the accommodation restrictedly follows three-dimensional point near the display panel. To
verify the consequence obtained by numerical calculations, experiments has been performed using keratometer to
measure the accommodation under the situation similar to horizontal-only super-multiview display. The images focused
by a cylindrical lens have been provided as stimuli to avoid argues related to the resolution of pixel pitch of display
panel. The measured results show that the accommodation response restrictedly follows astigmatic image as expected by
numerical calculations, however the quantitative investigation is still needed.
KEYWORDS: 3D image processing, 3D image reconstruction, 3D displays, Integral imaging, 3D acquisition, Clouds, Optical flow, 3D modeling, OpenGL, Image processing
Computational reacquisition for real 3D object in integral imaging is proposed. The pseudoscopic problem and matching
of lens array in pickup and display are fundamental problems for real-time broadcasting based on integral imaging. We
propose the reconstruction method of real 3D object and computational reacquisition method without matching of pickup
and display lens array. In reconstruction, the real 3D object is reconstructed with volumetric information using depth
extraction and triangular mesh, which can be rotated and translated in orthoscopic geometry. In reacquisition, the virtual
lens array can generate the elemental image without matching of pickup lens array using OpenGL.
KEYWORDS: 3D image reconstruction, 3D image processing, 3D displays, Lenticular lenses, RGB color model, Error analysis, Integral imaging, Image analysis, Lenses, Distortion
In three-dimensional (3D) display based on lenticular lens method, the focal mode in which the gap between lens and
display panel is almost equal to the focal length is widely used nowadays. However, because each pixel of the display
panel has a finite size, reconstructed 3D image is displayed in virtual mode instead of focal mode. Because the elemental
image which is a source of reconstructed image was generated for focal mode, the 3D image could suffer from image
distortion. In this paper, view image error analysis based on autostereoscopic lenticular lens method and integral imaging
method is presented based on numerical analysis and simulation results.
Integral imaging is a promising way of three-dimensional display because it provides observers with full parallax and continuous view points without the use of glasses. However, the limitation on the viewing angle and the expressible depth should be overcome for integral imaging to be applied to real systems. There have been various methods such as using mechanical movements or polarization switching to improve the viewing angle of integral imaging. In this paper, we propose a viewing angle enhanced integral imaging system without any mechanical movement or polarization control. This new viewing angle enhanced system utilizes lenticular lens sheet to angularly multiplex the information emitted from each pixel. Thus each pixel can affect multiple lenses and the effective area of an elemental image is increased, which brings the enhanced viewing angle. The simulation result of the proposed system and the experimental results are provided.
KEYWORDS: 3D displays, Distortion, Image quality, Integral imaging, Image analysis, Image enhancement, Image processing, Diffraction, 3D image processing, Analytical research
Recently, integral imaging attracted a lot of researchers as one powerful candidate for the three-dimensional display. However the limitation on the image depth of integral imaging is considered as the major obstacle for the practical use. Previously, a number of researches reported on the analysis of such limitation based on the diffraction of light. But there exists the severe mismatch between the experimental results and the simulation results that appear in the previous researches. In this paper, we propose a new assumption that exactly predicts the experimental results. Based on that new assumption, we propose the quantitative method to evaluate the image depth of integral imaging. We also propose the elemental image correction scheme that removes the distortion of the integrated image located out of the central depth plane.
KEYWORDS: 3D image processing, Integral imaging, Imaging systems, 3D displays, Charge-coupled devices, Displays, Image processing, Imaging arrays, Data storage, Distortion
Integral imaging is one of the most attractive methods for displaying three-dimensional images. The lens array mismatch between the pickup and display systems or between different display systems is an important problem for the practical implementation of the three-dimensional display system based on integral imaging. In this paper, we provide a solution to that problem by extracting the three-dimensional information from the elemental images. The extracted three-dimensional information is modified to be suitable for the different lens arrays in the integral imaging display systems. Thus our method gives excellent flexibility on the system parameters of the various integral imaging systems and has additional advantage of reducing the required data size for the three-dimensional data storage or transmission.
The stereovision scheme is a method to extract the three-dimensional information of the original object from two or more images of it. In the conventional scheme, more than two cameras are used to acquire numbers of images with different perspectives. As the numbers of cameras are increased, the complexity of the entire system is also increased and there can be many difficulties such as camera calibration and vibration in the conventional method. In this paper, an improved stereovision scheme using single camera and a composite lens array is proposed. In the proposed system, only one camera and a composite lens array is required and the complexity of the entire system is decreased. With the use of a composite lens array, it is possible to improve the performance of the system compared with the method using a conventional lens array. The proposed method is proven to be useful by simulation and experimental results.
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