We propose a lens assessment method based on incoherent holography, offering a novel alternative to conventional optical testing methods that rely on coherent illumination and interferometry. The traditional approach involves the complicated optical configurations and it is hard to accurately model the actual user experience. In contrast, our proposed incoherent holographic system, utilizing self-interference with a geometric phase lens, enables the acquisition of the complex hologram of incoherent illumination in a single exposure. By reconstructing the hologram captured from structured light patterns, we can calculate the wavefront aberration and displacement, providing a comprehensive lens assessment solution.
Incoherent digital holography is a promising idea for holographic teleconferencing because it is free from safety issues by light sources. Here, we propose a fully colored incoherent holographic streaming system that can acquire and reconstruct the incoherent hologram. To capture the real world scene through the natural lights, self-interference incoherent digital holography inferred by the geometric phase optical elements is used. The connection between the hologram pickup system and display system is GPU-based parallel processing which enhances the holographic image quality with phase preserving.
A self-interference digital holographic system based on geometric phase modulation is presented. The holographic recording under the natural light or general illumination sources is possible with simple and compact form factor.
Optical sectioning through the numerical reconstruction of digital holographic data with low diffraction noise is the key process for understanding the structure of a recorded three-dimensional object. Recently, this has been enabled by compressive holography, by virtue of sparse signal processing. However, interpretation of the object signal domain has been limited to predefined domains, such as spatial, discrete cosine transform, and wavelet transform domains. We propose a reconstruction technique of compressive Fresnel holographic data using an overcomplete dictionary learned from natural images to enhance the axial resolution of the sectional images. The redundant (overcomplete) dictionary gives sparser and more flexible solutions for representing the two-dimensional images compared to predefined transforms. We provide simulation results to verify the feasibility of our proposed method.
Three-dimensional (3D) display technology has been studied actively because it can offer more realistic images compared to the conventional 2D display. Various psychological factors such as accommodation, binocular parallax, convergence and motion parallax are used to recognize a 3D image. For glass-type 3D displays, they use only the binocular disparity in 3D depth cues. However, this method cause visual fatigue and headaches due to accommodation conflict and distorted depth perception. Thus, the hologram and volumetric display are expected to be an ideal 3D display. Holographic displays can represent realistic images satisfying the entire factors of depth perception. But, it require tremendous amount of data and fast signal processing. The volumetric 3D displays can represent images using voxel which is a physical volume. However, it is required for large data to represent the depth information on voxel. In order to simply encode 3D information, the compact type of depth fused 3D (DFD) display, which can create polarization distributed depth map (PDDM) image having both 2D color image and depth image is introduced. In this paper, a new volumetric 3D display system is shown by using PDDM image controlled by polarization controller. In order to introduce PDDM image, polarization states of the light through spatial light modulator (SLM) was analyzed by Stokes parameter depending on the gray level. Based on the analysis, polarization controller is properly designed to convert PDDM image into sectioned depth images. After synchronizing PDDM images with active screens, we can realize reconstructed 3D image.
Acknowledgment
This work was supported by ‘The Cross-Ministry Giga KOREA Project’ grant from the Ministry of Science, ICT and Future Planning, Korea
Pickup method adopting the modified algorithm to generate the elemental image from virtual objects is proposed to obtain the elemental image for real objects. In the proposed method, the number of capturing processes is reduced compared with the conventional multiple capturing method. The pseudoscopic image problem can be resolved by controlling the position and the direction of the imaging device in the proposed pickup system. The telecentric lens system is used to capture the orthographic scenes, which are divided and compounded into the elemental image. The validity of the proposal is proved by the experimental results of the pickup and the reconstruction.
This paper proposes a parallax barrier with an elliptical pattern that reduces the cross talk caused by light leakage from adjacent subpixels in autostereoscopic three-dimensional (3-D) displays. To find the optimum size of the elliptical barrier pattern, the relationship between the reduction of the light leakage and that of the luminance is analyzed. In addition, we analyze the relationship between the cross talk and the luminance. By using these relationships, we propose an optimum size of the ellipse. An autostereoscopic 3-D display with the elliptical barrier is compared with 3-D displays with the slanted barrier and the rectangular one. The measured cross talk of the slanted-type 3-D display whose pixel size is 98×294 μm was 57%. However, the cross talk of the ellipse-type 3-D display was 32% at the similar luminance condition when the minor and major axes are 92 and 278 μm, respectively. For generalization, we investigate autostereoscopic 3-D displays with different pixel sizes and different viewing distances. We find the optimum area of the ellipse is 70% of the subpixel area to reduce the cross talk.
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.
We proposed the new optical design of the wedge projection display to enhance the quality of image. Since the thickness
of the wedge plate can be thin enough, this technology makes up for the bulky property in projection type display.
However, the image quality is heavily influenced by “dark zone”. The dark zone means the repeated region that the rays
cannot escape from the waveguide. Thus, these regions present nothing and the image quality is very low. To reduce the
problems, we analyzed the principle of the image formation by the geometrical retracing from the wedged surface to the
aperture of waveguide. The bundle of rays converging into an imaging point on the wedged surface have the same image
information, but can have the different initial position and the angle when started from the aperture. Therefore, each ray
is classified by the position of the imaging points on the inclined surface and the number of reflection. Based on the
classified data, we can obtain the equivalent imaging point which is the intersection when the set of the rays with the
same condition does not experience the reflection at the interface. Because this point is equivalent to the imaging point
on the inclined surface, we can display the image by projecting on the equivalent imaging point. In this paper, the
optimized set of equivalent imaging points is analyzed by retracing method and we designed the improved imaging
system of the wedge projection display by modifying the shape of aperture to equip the optical components in the onaxis.
An elemental image of the pre-distortion image in the off-axis integral floating system using a concave mirror is
generated. The concave mirror can be adopted as the floating device to improve the optical efficiency. The image
deformation due to the tilting axis of the concave mirror is analyzed to generate the pre-distortion image process. In this
paper, we calculate the image deformation in the off-axis structure of the concave mirror using the geometrical optics.
Using the simulation, the pre-distortion image is generated to compensate the 3D image. And the elemental image is
generated for the pre-distortion integrated image, which can be projected to the floating 3D image to resolve the image
deformation. The experiments of the off-axis integral floating are presented to prove and verify the proposal.
We propose Depth Cube Display (DCD) method using depth map. The structure of the proposed method consists of two
parts: A projection part composed of projector for generating image and a Twisted Nematic Liquid Crystal display (TNLCD)
as polarization modulating device for adjusting the proper depth and a display part composed of air-spaced stack
of selective scattering polarizers which make the incident light to scatter selectively as the polarization of light rays. The
image from projector whose depth is determined as passing through the TN-LCD displaying depth map progresses into
the stack of selective scattering polarizers and then three-dimensional image is generated. At that time, the polarization
of each polarizer is set 0°, 45° and 90° sequentially, and then the incident light rays are scattered by different polarizer as
the polarization of these rays. If the light ray has the polarization between those of polarizers, this light ray is scattered
by multi polarizers and the image of this ray is generated on gap between polarizers. The proposed method is more
simple structure and implemented easily than previous DCD method.
We propose novel depth-fused three-dimensional (DFD) method using polarization distribution, which is one kind of
multifocal plane display that provides autostereoscopic image with small visual fatigue. The DFD method is based on the
characteristic of human depth perception when the luminance-modulated two-dimensional (2D) images are overlapped.
The perceived depth position is decided by the luminance ratio of each plane. The proposed system includes the
polarization selective scattering films and the polarization modulating device. The polarization selective scattering film
has the characteristics of partial scattering according to the polarization state and transmits the rest light from the
scattering. When the films are stacked with the scattering axis rotated, each layer of film provides different scattering
ratio according to the incident polarization. Consequently, the appropriate modulation of polarization can provide DFD
image through the system. The depth map provides depth information of each pixel as a gray scale image. Thus, when a
depth map is displayed on a polarization modulating device, it is converted into a polarization distributed depth map. The
conventional twisted nematic liquid crystal display can be used as a polarization modulating device without complicated
modification. We demonstrate the proposed system with simple experiment, and compare the characteristic of the system
with simulated result.
Three-dimensional (3D) display has attracted considerable attention in recent years because of development in display
technology. Various methods for realizing 3D display have been proposed; among them, multi-view display could be
practical to implement before aspiring 3D display. The term of multi-view display system based on autostereoscopic
display has the meaning of view splitting; the view images are projected to the pre-defined positions from the same
display device. Therefore the users located at the correct positions can see corresponding images. Although the multi-view
display technique has been studied by many research groups, the fundamental importance of the sound with display
has not, so far, been noticed nor has been examined in detail. The purpose of this paper is to realize a multi-view display
system with directional sound, which allows the individual observer to experience directional sound in multi-view
display environment. The explanation and experimental results of the proposed system are provided.
The amount of information for 3D display is much bigger than that for 2D display. Therefore, many researches about 3D
display have used multiplexing of conventional display devices sequentially or spatially. We propose a new 3D display
system using a concave cylindrical mirror and tracking technology. The concave cylindrical mirror can be used like a
convex lens in the polar axis. It means that the concave cylindrical mirror can float an image from a 2D display panel
and give directional images to a viewer in the optical axis. To give the parallax to the viewer, the tracking technology
will be used to generate the images according to the position of the viewer. We design a structure with a cylindrical
reflective film and a 2D display panel. And, we use the tracking technology to provide parallax which cannot be made in
the cylindrical reflective film. Further explanations of the proposed structure and experimental results will be presented.
KEYWORDS: LCDs, 3D image processing, 3D displays, Integral imaging, 3D image enhancement, Imaging systems, Polarization, 3D vision, Scattering, 3D image reconstruction
We propose 2D/3D convertible display system with enhanced 3D viewing angle based on integral imaging. We use 3
LCD devices and a lens array in the proposed system. The LCD device 1is used for displaying an elemental image which
turn into a 3D image through the lens array. The LCD device 2 is used as a polarization switcher to control the
transparent and the opaque region of elemental image. The LCD device 3 is used as both mask pattern and 2D image
displaying device. On the back glass of LCD device 3, we attach polarization-selective scattering film which makes LCD
device 3 used as a mask pattern and a 2D display device at the same time. Behind of the LCD device 3, the lens array is
located for displaying 3D image by the integral imaging method. The whole system is as compact as conventional
integral imaging system. With the LCD device 2 and 3, the viewing angle of 3D image can be enhanced both vertically
and horizontally according to the arrangement of elemental image. We prove the feasibility of proposed system by basic
experiments.
Integral floating system is recent development of autostereoscopic display. It consists of the integral imaging system and
the floating device as depicted in the name. The integrated image forms a floating 3D image in the vicinity of the
observer through the floating device which can be either a convex lens or a concave mirror. The integral floating system
can provide dynamic 3D images with great feel of depth. This paper reviews the main concepts and the special
characteristics of the integral floating system. Moreover, some improvements and analysis will be presented with some
basic experimental results.
In this paper, a high-definition integral floating display is implemented. Integral floating display is composed of an
integral imaging system and a floating lens. The integral imaging system consists of a two-dimensional (2D) display and
a lens array. In this paper, we substituted multiple spatial light modulators (SLMs) for a 2D display to acquire higher definition. Unlike conventional integral floating display, there is space between displaying regions of SLMs. Therefore, SLMs should be carefully aligned to provide continuous viewing region and seamless image. The implementation of the system is explained and three-dimensional (3D) image displayed by the system is represented.
An enhanced algorithm of image mapping method is proposed for the computer-generated (CG) integral
imaging system. Integral imaging is one of the attractive autostereoscopic three-dimensional (3D) display methods since
it provides both vertical and horizontal parallaxes with full colors and it needs no special viewing aids on the observer.
The CG integral imaging system uses the set of elemental images generated by computer graphics instead of the pickup
process using the lens array. The process to obtain the set of elemental images using computer graphics is called image
mapping. In this paper, we propose an enhanced image-mapping algorithm, named viewpoint vector rendering, to
improve the speed of the elemental-image generation and to be more robust so that it is less affected by the system
factors and the object image quality, as compared to the previous methods. Since the proposed algorithm can support the
real-time generation of elemental images, it is possible to realize the CG integral imaging system applied for an
interactive multimedia system. The feasibility and the efficiency of the proposed technique is verified and analyzed by
mean of some experimental results.
KEYWORDS: 3D image processing, 3D displays, Displays, Integral imaging, Lithium, Imaging systems, Geometrical optics, Mirrors, Stereoscopy, 3D image reconstruction
Integral floating imaging is a 3D display method which is a combination of integral imaging and floating display. It is a
promising technique of 3D display because it possesses full parallax, continuous viewpoints and can produce large feel
of depth. In this paper, we explain the principle of the integral floating 3D display system and analyze its viewing
characteristics, such as viewing angle, viewing window and the expressible depth range. We analyze these characteristics
by using geometrical optics based on the analyses on the integral imaging. Experimental results which verify the
analyses are provided.
Recently, a floating display system based on integral imaging (InIm) was proposed. Though the floating display system based on InIm can provide moving picture with great feel of depth to the observer, it has limited expressible depth range because the expressible depth range of InIm is limited. In this paper, the expressible depth range of the floating display system based on InIm is analyzed based on the analysis on the expressible depth range of the InIm. Also, a depth-enhanced floating display system based on InIm is proposed. In the proposed depth-enhanced floating display system based on InIm, the lens array of the InIm is placed at the focal plane of the floating lens. Additionally, the seams on the lens array become less distinct since they are also placed at the focal plane of the floating lens. However, the size of the object changes when the object is out of the overall central depth plane. Thus, the size of objects in elemental image should be rescaled to display correct three-dimensional image.
KEYWORDS: Imaging systems, Integral imaging, 3D displays, Image enhancement, 3D image processing, Displays, Image processing, 3D applications, Stereoscopic displays, Glasses
Enhanced integral imaging system based on the image floating method is proposed. The integral imaging is one of the most promising methods among the autostereoscopic displays and the integrated image has the volumetric characteristics unlike the other stereoscopic images. The image floating is a common 3D display technique, which uses a big convex lens or a concave mirror to exhibit the image of a real object to the observer. The image floating method can be used to emphasize the viewing characteristics of the volumetric image and the noise image which is located on the fixed plane can be eliminated by the floating lens through the control of the focal length. In this paper, the solution of the seam noise and the image flipping of the integral imaging system is proposed using the image floating method. Moreover, the advanced techniques of the integral imaging system can be directly applied to the proposed system. The proposed system can be successfully applied to many 3D applications such as 3D television.
Integral imaging (integral photography) is a three-dimensional display technique, first proposed by Lippmann in 1908. Recently the integral imaging attracts much attention as an autostereoscopic three-dimensional display technique for its many advantages. However, the limitation of viewing angle is the primary disadvantage of integral imaging. To overcome the limitation some methods have been proposed. Among them the method that uses a curved lens array has been reported recently. This method widens the viewing angle considerably compared with the conventional method. Generally, in integral imaging each elemental lens has its corresponding area, elemental image region, on the display panel. To prevent the image flipping, the elemental image that exceeds the corresponding area is discarded. Therefore the number of the elemental images is limited. However, in the curved lens array system each elemental image does not exceed the corresponding area. It owes the curved structure and this characteristic widens the viewing angle.
In this paper, we will examine the proposed integral imaging system using a curved lens array and analyze of the representative viewing parameters; viewing angle, image depth, image size, etc. for the curved lens array system. The viewing region, in which the three-dimensional image can be displayed with wide-viewing angle, is closely related with image depth and the corresponding viewing angle of the curved lens array system.
KEYWORDS: 3D displays, Displays, Integral imaging, 3D image processing, Imaging systems, 3D applications, Mirrors, Glasses, Image processing, Stereoscopic displays
New three-dimensional (3D) display system which combines two different display techniques is proposed. One of the techniques is integral imaging. The integral imaging system consists of a lens array and 2D display device, and the 3D image of the system is integrated by the lens array from the elemental images. The other technique is image floating, which uses a big convex lens or a concave mirror to exhibit the image of a real object to the observer. The electro-floating display system, which does not use the real object, needs the volumetric 3D display part because the floating display system cannot make the 3D image, but only carries the image closer to the observer. The integral imaging system can be adopted in the electro-floating display system, because the integrated image has the characteristics of the volumetric image within the viewing angle. Moreover, the many methods to enhance the viewing angle of the integral imaging system can be applied to the proposed system directly. The optimum value of the focal length of the floating lens is related to the central depth plane and the viewing angle. The proposed system can be successfully applied to many 3D applications such as 3D TV.
In this paper, we propose a wide-viewing-angle three-dimensional integral imaging using a curved screen and a curved lens array. Elemental images are projected to the curved screen. Incorporation of the curved screen and the curved lens array instead of a conventional flat display panel and a flat lens array expands the viewing angle remarkably. In addition adopting barriers between a curved lens array and a curved screen eliminates the flipped images effectively without affecting the viewing angle. The principle of the proposed system is explained and the experimental results about the viewing angle of real and virtual images are also presented.
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: Integral imaging, 3D image processing, Imaging systems, 3D image reconstruction, 3D displays, 3D image enhancement, Image enhancement, Computing systems, Image quality, Beam splitters
We present experiments on an enhanced three-dimensional (3D) integral imaging system using double display devices, in which two 3D sub-images that cover different depth ranges are separately generated in each device and then they are combined using a beam splitter to reconstruct the whole 3D image with an enhanced depth of view. In a similar manner, the double-device system can also be used to obtain a wider viewing angle by combining two images with different viewing angle ranges. We discuss the possibility of three-dimensional integral imaging systems using multiple display devices, as extensions of the system with double display devices.
Integral imaging (or called integral photography) is an attractive three-dimensional display method because of its many advantages over other three-dimensional display methods. However, the thickness of the displayed three-dimensional image which can be expressed is limited by various optical parameters of the system and is relatively small. In this paper, we propose a method to increase the thickness of the displayed three-dimensional image without severe resolution degradation by adopting a birefringent material and a dynamic polarizer. We explain the principle of the proposed method and verify it experimentally.
The integral photography which is also called integral imaging (II) is an attractive autostereoscopic display method for its many advantages such as continuous viewpoints and no need for any viewing aids. In spite of many advantages of II, the narrow viewing angle has been a bottleneck of it. In this paper, we propose a method to enhance the viewing angle of II by opening and shutting the elemental lenses sequentially. We prove our idea by using a mask that has patterns of on/off. It has vertical or horizontal apertures in an array form, whose interval matches that of the lenses in the II. Both theoretical discussion and experimental result are presented.
Integral photography, which provides continuous viewpoints and does not require any use of special glasses, is one of the most attractive methods for autostereoscopic display. To overcome the difficulties of pickup process and the pseudoscopic problem, a CGIP(Computer-Generated Integral Photography) method is desirable. In the CGIP scheme, the elemental images of imaginary objects are generated using computer instead of using pickup process. This easiness for generating elemental images makes the system compact and cost effective. For a wide viewing angle system, the f-number (the ratio of focal length to lens diameter) of the elemental lens should be small. However, the lens aberration is the penalty of the lens array with small f-number. Unlike the system using a conventional lens array, aberration occurs little in the case of adopting a well-designed Fresnel lens array which has small f-number. Fresnel lens array contributes to widen the viewing angle in the CGIP system. In addition, to increase the image depth range, dynamic integral photography is also proposed. The gap between a lens array and a display panel changes dynamically. Synchronized elemental image array for real and virtual mode is integrated in front of or behind the lens array. Therefore, observers get enhanced feeling of depth. In this way, autostereoscopic 3-D images with wide viewing angle and increased image depth can be obtained. The method can be usefully applicable to three-dimensional imaging.
Stereovision is an effective method in acquiring three-dimensional data from a real scene and forms a very active field of research. The conventional stereovision system usually consists of two or more cameras and therefore the system is bulky and has some problems like a camera calibration. In this paper, we propose a new scheme to acquire three-dimensional data from one camera and a lens array which consists of many elemental lenses. An algorithm that is appropriate for the proposed scheme is discussed and experimental results are presented.
In this paper, we propose a CGIP (Computer-Generated Integral Photography) method and verify its feasibility. In CGIP, the elemental images of imaginary objects are computer-generated instead of using pickup process. Since this system is composed of only one lens array and conventional display devices, it is compact and cost effective. The animated image can also be presented by the time-varying elemental images. As a result, autostereoscopic images with full color and full parallax were observed in real time. Moreover, this method can be applied to a quasi-3D display system. If each camera picks a scene which is a part of total view and elemental images are generated so that each scene has different depth, real objects captured by ordinary cameras can be displayed in quasi-3D. In addition, since it is easy to change the shape or size of elemental images in this scheme, we can observe the effect of several viewing parameters. This helps us to analyze the basic IP system. We perform an experiment with different lens arrays and compare the results. The lateral and depth resolution of the integrated image is limited by some factors such as the image position, object thickness, the lens width, and the pixel size of display panel.
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