Masahiro Kawakita

NHK, Edo, Tōkyō, Japan

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Publications (22)15.36 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Integral three-dimensional (3D) television based on integral imaging requires huge amounts of information. Previously, we constructed an Integral 3D television using Super Hi-Vision (SHV) technology, with 7680 pixels horizontally and 4320 pixels vertically. We report on improved image quality through the development of video system with an equivalent of 8000 scan lines for use with Integral 3D television. We conducted experiments to evaluate the resolution of 3D images using an experimental setup and were able to show that by using the pixel-offset method we have eliminated aliasing produced by full-resolution SHV video equipment. We confirmed that the application of the pixel-offset method to integral 3D television is effective in increasing the resolution of reconstructed images.
    Optics Express 02/2013; 21(3):3474-3485. · 3.55 Impact Factor
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    ABSTRACT: We have proposed a glasses-free three-dimensional (3D) display for displaying 3D images on a large screen using multi-projectors and an optical screen consisting of a special diffuser film with a large condenser lens. To achieve high presence communication with natural large-screen 3D images, we numerically analyze the factors responsible for degrading image quality to increase the image size. A major factor that determines the 3D image quality is the arrangement of component units, such as the projector array and condenser lens, as well as the diffuser film characteristics. We design and fabricate a prototype 200-inch glasses-free 3D display system on the basis of the numerical results. We select a suitable diffuser film, and we combine it with an optimally designed condenser lens. We use 57 high-definition projector units to obtain viewing angles of 13.5°. The prototype system can display glasses-free 3D images of a life-size car using natural parallax images.
    Proc SPIE 02/2012;
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    ABSTRACT: Integral 3D television based on integral imaging requires huge amounts of information. Earlier, we built an Integral 3D television using Super Hi-Vision (SHV) technology, with 7680 pixels horizontally and 4320 pixels vertically. Here we report on an improvement of image quality by developing a new video system with an equivalent of 8000 scan lines and using this for Integral 3D television. We conducted experiments to evaluate the resolution of 3D images using this prototype equipment and were able to show that by using the pixel-offset method we have eliminated aliasing that was produced by the full-resolution SHV video equipment. As a result, we confirmed that the new prototype is able to generate 3D images with a depth range approximately twice that of Integral 3D television using the full-resolution SHV.
    Proc SPIE 09/2011;
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    ABSTRACT: An integral 3DTV system needs high-density elemental images to increase the reconstructed 3D image's resolution, viewing zone, and depth representability. The dual green pixel-offset method, which uses two green channels of images, is a means of achieving ultra high-resolution imagery. We propose a precise and easy method for detecting the pixel-offset distance when a lens array is mounted in front of the integral imaging display. In this method, pattern luminance distributions based on sinusoidal waves are displayed on each panel of green channels. The difference between phases (amount of phase variation) of these patterns is conserved when the patterns are sampled and transformed to a lower frequency by aliasing with the lens array. This allows the pixel-offset distance of the display panel to be measured in a state of magnification. The relation between the contrast and the amount of phase variation of the pattern is contradicted in relation to the pattern frequency. We derived a way to find the optimal spatial frequency of the pattern by regarding the product of the contrast and amount of phase variation of the patterns as an indicator of accuracy. We also evaluated the pixel-offset detection method in an experiment with the developed display system. The results demonstrate that the resolution characteristics of the projected image were refined. We believe that this method can be used to improve the resolution characteristics of the depth direction of integral imaging.
    Proc SPIE 02/2011;
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    ABSTRACT: We have developed integral three-dimensional (3D) television using an ultra high definition imaging system. The system uses a device having 7680 pixels in the horizontal direction and 4320 pixels in the vertical direction for each of the red, green, and blue channels. A lens array comprising 400 lenses is configured in the horizontal direction and one comprising 250 lenses is configured in the vertical direction. The system is designed to ensure a maximum spatial frequency of 11.3 cycles/degree and a viewing angle of 24 degrees when the display is observed from three times the display height. The setup described here has simultaneously maintained the balance between the maximum spatial frequency and the viewing angle by shortening the focal length of the elemental lens while narrowing the pitch of the elemental lens. We have confirmed the generation of 3D images with an appearance that varies in a natural manner according to the position of the observer.
    Journal of Display Technology 11/2010; · 1.66 Impact Factor
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    ABSTRACT: Integral imaging system uses a lens array to capture an object and display a three-dimensional (3-D) image of that object. In principle, a 3-D image is generated at the depth position of the object, but for an object located away from the lens array in the depth direction, the modulation transfer function (MTF) of the integral imaging system will be degraded. In this paper, we propose a method that uses pupil modulation and depth-control processing to alleviate this degraded MTF. First, to alleviate changes in the MTF due to differences in depth when capturing the object, we use a pupil-modulated elemental lens to obtain an elemental image. Next, we use a filter having characteristics opposite those of the MTF characteristics of the pupil-modulated elemental lens to restore the degraded image. Finally, we apply depth-control processing to the restored elemental image to generate a reconstructed image near the lens array. This method can alleviate degradation in the MTF of the integral imaging system when an object is located at a distance from the lens array. We also show results of computer simulations that demonstrated the effectiveness of the proposed method.
    Proc SPIE 02/2010;
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    ABSTRACT: — Our research is aimed at developing a spatial-imaging-type integral three-dimensional (3-D) display based on an integral photography method using an extremely high-resolution projector. One problem with the projection-type integral 3-D display is that geometrical distortion in projected elemental images causes spatial deformation of the displayed 3-D image. In this study, a general relationship between the geometric distortion of elemental images and the spatial deformation of reconstructed 3-D images were analyzed. A projection-type integral 3-D display with a distortion compensator which corrects the geometrical distortions of projected images in real-time have been developed. The deformation of the displayed 3-D images was significantly reduced by the distortion compensation, and the displayed 3-D images had a resolution of 182 (H) × 140 (V) pixels and a viewing angle of 24.5°.
    Journal of The Society for Information Display - J SOC INF DISP. 01/2010; 18(9).
  • Masahiro Kawakita, Jun Arai, Fumio Okano
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    ABSTRACT: We developed integral 3-D TV using extremely high-resolution video that had a resolution of 7680 x 4320 pixels. The resolution of the displayed 3-D images was four times higher than that of the previous system.
    Frontiers in Optics; 10/2009
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    ABSTRACT: We have been conducting research on three-dimensional (3D) television using the integral imaging method. To enhance integral 3D image quality, Extremely High-Resolution (EHR) imaging technology would be essential. Now, projection display systems are practical for EHR images and have some advantages for 3D imaging. We theoretically and experimentally analyzed the effects of distorted elemental images on a reconstructed image. We study an image processing method for a compensation of distorted elemental images in projection type D imaging systems. The experimental results show the effectiveness in eliminating distortion of reconstructed 3D images and improving the limitation of the viewing zone.
    Proceedings of the 3rd International Universal Communication Symposium, IUCS 2009, Tokyo, Japan, 3-4 December 2009; 01/2009
  • Fumio Okano, Jun Arai, Masahiro Kawakita
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    ABSTRACT: Light rays from reconstructed 3D images were geometrically analyzed, and sampling of the images by using a lens array with the integral method was demonstrated. The light rays pass through the lens array and form an optical image, part of which enters the observer's pupil and forms an image on the retina. It was assumed that the pupil has a certain diameter. The depth range of the 3D image (whose projected image on the retina is sampled by the lens array) was derived. That is, the depth range is restricted to the surrounding area of the lens array and depends on the pitch of the elemental lenses constituting the lens array. When the reconstructed 3D image is located within the depth range, its visual resolution is limited by the Nyquist frequency. On the other hand, when the 3D image is located out of the depth range, the visual resolution can be increased to the upper limit of frequency by diffraction of the elemental lens.
    01/2009;
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    Fumio Okano, Jun Arai, Masahiro Kawakita
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    ABSTRACT: We geometrically analyzed incident light rays into a pupil of an observer in integral 3D imaging. The object's depth area in which the projected image on the retina is not sampled by lens array was derived. Also, the depth area in which observer's eye focuses on the reconstructed 3D images was found. These depth areas depend on the pitch of an elemental lens constituting the lens array, diameter of the observer's pupil, and viewing distance. Further, we clarified that even when the eye could not focus on the reconstructed 3D image, influence of inconsistency between focus accommodation and convergence can be relieved.
    Proc SPIE 01/2009;
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    ABSTRACT: In projection-type integral imaging, positional errors in elemental images and elemental lenses affect three-dimensional (3D) image quality. We analyzed the relationships between the geometric distortion in elemental images caused by a projection lens and the spatial distortion in the reconstructed 3D image. As a result, we clarified that 3D images that were reconstructed far from the lens array were largely affected, and that the reconstructed images were significantly distorted in the depth direction at the corners of the displayed images.
    Optics Letters 05/2008; 33(7):684-6. · 3.39 Impact Factor
  • Jun Arai, Hiroshi Kawai, Masahiro Kawakita, Fumio Okano
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    ABSTRACT: We present a method for controlling the depth of three-dimensional (3D) images reconstructed by integral photography. Incoherent light is reflected from 3D objects, propagates through a lens array, and is captured as the first elemental images by a capturing device. The second elemental images of the 3D images are generated by numerical processing from the first elemental images in accordance with the desired depth. The optical reconstruction of 3D images at the desired depth by the second elemental images is confirmed experimentally.
    Optics Letters 03/2008; 33(3):279-81. · 3.39 Impact Factor
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    ABSTRACT: The integral method is one of the ideal means for forming 3D spatial images like real objects. It requires, however, extremely high-resolution device in order to satisfy sufficient resolution and wide viewing angle. The authors have been examining integral 3D television systems applying the Super Hi-Vision (SHV) system, which uses ultrahigh-definition LCOS, D-ILA devices. This paper describes the experimental integral 3D display and approaches to improve the quality of elemental images, which are projected behind the lens array, by decreasing blurs and improving registration accuracy. The display panels are four chips of D-ILA (4096 × 2160 pixels), each of which is used for R, B, G1 and G2 (pixel-offset method). The optics of the R/B projector and the G1/G2 projector are accurately aligned by a half mirror and the elemental images are formed on a 22 inches screen. The diffuser of the screen is a thin LC film with sufficient resolution and homogeneous visual field. The lens array consists of newly developed short focus lenses to enable wide viewing angle for multiple viewing. A drastic improvement of the 3D image quality has been achieved together with the electronic distortion correction technique.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    02/2008;
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    Jun Arai, Hiroshi Kawai, Masahiro Kawakita, Fumio Okano
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    ABSTRACT: We propose a method for controlling the depth of three-dimensional (3-D) images by processing the captured elemental image data based on an integral imaging system. Incoherent light is reflected from 3-D objects, propagates through a lens array, and is captured as a first elemental image by a capturing device. Firstly, the electric-field distribution in an arbitrary field is generated by use of the first elemental image data and the second lens array. A computer generated electric-field distribution is referred to as the "intermediate image." Next, the third lens array is assumed, and elemental images of the intermediate image formed by the third lens array are calculated. Finally, to reconstruct the 3-D images, we use a conventional display system of integral imaging. The depth of reconstructed images can be controlled according to the distance from the second lens array to the third lens array. Experimental results showed that the depth of the 3-D image was arbitrarily controlled by the proposed method.
    01/2008;
  • The Journal of The Institute of Image Information and Television Engineers 01/2008; 62(12):2013-2022.
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    ABSTRACT: The integral method is one of the ideal means for forming 3D spatial images like real objects. It requires, however, extremely high-resolution device in order to satisfy sufficient resolution and wide viewing angle. The authors have been examining integral 3D television systems applying the Super Hi-Vision (SHV) system, which uses ultrahigh-definition LCOS, D-ILA devices. This paper describes the experimental integral D display and approaches to improve the quality of elemental images, which are projected behind the lens array, by decreasing blurs and improving registration accuracy. The display panels are four chips of D-ILA (4096 × 2160 pixels), each of which is used for R, B, G1 and G2 (pixel-offset method). The optics of the R/B projector and the G1/G2 projector are accurately aligned by a half mirror and the elemental images are formed on a 22 inches screen. The diffuser of the screen is a thin LC film with sufficient resolution and homogeneous visual field. The lens array consists of newly developed short focus lenses to enable wide viewing angle for multiple viewing. A drastic improvement of the 3D image quality has been achieved together with the electronic distortion correction technique.
    Proc SPIE 01/2008;
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    ABSTRACT: An integral three-dimensional (3-D) system based on the principle of integral photography can display natural 3-D images. We studied ways of improving the resolution and viewing angle of 3-D images by using extremely high-resolution (EHR) video in an integral 3-D video system. One of the problems with the EHR projection-type integral 3-D system is that positional errors appear between the elemental image and the elemental lens when there is geometric distortion in the projected image. We analyzed the relationships between the geometric distortion in the elemental images caused by the projection lens and the spatial distortion of the reconstructed 3-D image. As a result, we clarified that 3-D images reconstructed far from the lens array were greatly affected by the distortion of the elemental images, and that the 3-D images were significantly distorted in the depth direction at the corners of the displayed images. Moreover, we developed a video signal processor that electrically compensated the distortion in the elemental images for an EHR projection-type integral 3-D system. Therefore, the distortion in the displayed 3-D image was removed, and the viewing angle of the 3-D image was expanded to nearly double that obtained with the previous prototype system.
    Proc SPIE 01/2008;
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    ABSTRACT: The integral method enables observers to see 3D images like real objects. It requires extremely high resolution for both capture and display stages. We present an experimental 3D television system based on the integral method using an extremely high-resolution video system. The video system has 4,000 scanning lines using the diagonal offset method for two green channels. The number of elemental lenses in the lens array is 140 (vertical) × 182 (horizontal). The viewing zone angle is wider than 20 degrees in practice. This television system can capture 3D objects and provides full color and full parallax 3D images in real time.
    Proc SPIE 10/2007;
  • Fumio Okano, Jun Arai, Masahiro Kawakita
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    ABSTRACT: We analyze by wave optics an integral method that produces three-dimensional (3D) images. The point light source is given at the pickup stage, and the light wave passing through each elemental lens is obtained at the display stage. The amplitude distributions of the waves from each elemental image are the same around a specific point where a 3D image is formed. Since the light waves approaching the image plane from different elemental lenses are incoherent, the synthesized value is the sum of the squared amplitudes of the waves. Therefore the modulation transfer function of this integral method is given by that of a single elemental lens.
    Optics Letters 03/2007; 32(4):364-6. · 3.39 Impact Factor