Browsing by Author "Chou, Ping-Yen"

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3D Display System Based on Spherical Wave Field Synthesis
(2019-09-01)
Falldorf, Claas
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Chou, Ping-Yen
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Prigge, Daniel
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Bergmann, Ralf B.
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光電工程學系
We present a novel concept and first experimental results of a new type of 3D display, which is based on the synthesis of spherical waves. The setup comprises a lens array (LA) with apertures in the millimeter range and a liquid crystal display (LCD) panel. Each pixel of the LCD creates a spherical wave cutout that propagates towards the observer. During the displaying process, the curvature of the spherical waves is dynamically changed by either changing the distance between LA and LCD or by adapting the focal lengths of the lenses. Since the system, similar to holography, seeks to approximate the wavefront of a natural scene, it provides true depth information to the observer and therefore avoids any vergence-accommodation conflict (VAC).
A Horizontal Parallax Table-top Floating Image System with Freeform Optical Film Structure
(2016-01-01)
Chou, Ping-Yen
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Huang, Yi-Pai
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Liao, Chien-Chung
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Chang, Chuan-Chung
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Chuang, Fu-Ming Fleming
In this paper, a new structure of horizontal parallax light field 3D floating image display system was proposed. The structure consists of pico-projectors, Fresnel lens, micro-lens array and sub-lens array with freeform shape. By the functions of optical components, each light field of projectors could be controlled as a fan ray, which has high directivity in horizontal and wide scattered angle in vertical. Furthermore, according to the reverse light tracing and integral image display technique, horizontal parallax floating 3D could be demonstrated in the system. Simulated results show that the proposed 3D display structure has a good image quality and the crosstalk is also limited below 22.9%. Compared with other 3D technologies, this structure could have more benefits, including displaying real high resolution floating image, unnecessary of physical hardware on the image plane, scalability of large size system, without the noise from spinning component, and so on.
A toroidal-lens designed structure for static type table-top floating image system with horizontal parallax function
(2017-07-01)
Chou, Ping-Yen
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Wu, Jui-Yi
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Hsieh, Po-Yuan
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Chen, Chun-Ho
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Yu, Zih-Sin
A new structure of horizontal parallax table-top floating image system with toroidal-lens optical film was developed. In this design, the circular arranged pico-projectors limit the angular resolution of this system and display the floating image for surrounding viewing zones. In addition, the pinhole array and toroidal-lens layer compose the optical film in the system and correspond with each other; both of them could be considered as a repeatable unit to control the spatial resolution of image. After passing through the optical film, the direction, position, shape, and divergence angle of light field could be controlled as fan ray, which has a widely scattered angle in latitude and high directivity in longitude direction. Moreover, to confirm the optical properties, the proposed structure was built in the commercially optical software, LightTools v8.3, which is widely used in the simulation of light distribution. Based on the imaging principle and the inverse light tracking method, displaying floating image with circular viewing zones would be achieved.
Hybrid light field head-mounted display using time-multiplexed liquid crystal lens array for resolution enhancement
(2019-01-21)
Chou, Ping-Yen
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Wu, Dui-Yi
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Huang, Shang-Hao
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Wang, Chun-Ping
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Qin, Zong
In recent years, head-mounted display technologies have greatly advanced. In order to overcome the accommodation-convergence conflict, light field displays reconstruct three-dimensional (3D) images with a focusing cue but sacrifice resolution. In this paper, a hybrid head-mounted display system that is based on a liquid crystal microlens array is proposed. By using a time-multiplexed method, the display signals can be divided into light field and two-dimensional (2D) modes to show comfortable 3D images with high resolution compensated by the 2D image. According to the experimental results, the prototype supports a 12.28 ppd resolution in the diagonal direction, which reaches 82% of the traditional virtual reality (VR) head-mounted display (HMD). (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Image formation modeling and analysis of near-eye light field displays
(2019-04-01)
Qin, Zong
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Chou, Ping-Yen
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Wu, Jui-Yi
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Chen, Yu-Ting
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Huang, Cheng-Ting
Near-eye light field displays based on integral imaging through a microlens array provide attractive features like ultra-compact volume and freedom of the vergence-accommodation conflict to head-mounted displays with virtual or augmented reality functions. To enable optimal design and analysis of such systems, it is desirable to have a physical model that incorporates all factors that affect the image formation, including diffraction, aberration, defocusing, and pixel size. Therefore, in this study, using the fundamental Huygens-Fresnel principle and the Arizona eye model with adjustable accommodation, we develop an image formation model that can numerically calculate the retinal light field image with near-perfect accuracy, and experimentally verify it with a prototype system. Next, based on this model, the visual resolution is analyzed for different field of views (FOVs). As a result, a rapid resolution decay with respect to FOV caused by off-axis aberration is demonstrated. Finally, resolution variations as a function of image depth are analyzed based on systems with different central depth planes. Significantly, the resolution decay is revealed to plateau when the image depth is large enough, which is different from real-image type light field displays.
Long working range light field microscope with fast scanning multifocal liquid crystal microlens array
(2018-04-16)
Hsieh, Po-Yuan
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Chou, Ping-Yen
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Lin, Hsiu-An
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Chu, Chao-Yu
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Huang, Cheng-Ting
The light field microscope has the potential of recording the all information of biological specimens in real time with a conventional light source. To further extend the depth of field to broaden its applications, in this paper, we proposed a multifocal high-resistance liquid crystal microlens array instead of the fixed microlens array. The developed multifocal liquid crystal microlens array can provide high quality point spread function in multiple focal lengths. By adjusting the focal length of the liquid crystal microlens array sequentially, the total working range of the light field microscope can be much extended. Furthermore, in our proposed system, the intermediate image was placed in the virtual image space of the microlens array, where the condition of the lenslets numerical aperture was considerably smaller. Consequently, a thin-cell-gap liquid crystal microlens array, with fast response time can be implemented for time-multiplexed scanning. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Resolution enhanced light field near eye display using e-shifting method with birefringent plate
(2018-05-01)
Wu, Jui-Yi
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Chou, Ping-Yen
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Peng, Kuei-En
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Huang, Yi-Pai
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Lo, Hsin-Hsiang
Light field near eye displays (LFNED) can produce lightweight devices and address the accommodation-convergence conflict. However, low spatial resolution creates a poor immersive experience in LFNED. In addition, although many e-shifting devices have been proposed to enhance resolution in projection system, yet those devices are too bulky to be applied in an LFNED to keep it lightweight. In this paper, a compact e-shifting component is proposed to enhance image resolution in an LFNED by using a birefringent plate and twisted nematic switch cell. The proposed e-shifting device is a flat and thin component with only 2.6mm of thickness, which could be placed in the gap of an LFNED without increasing the thickness. The results show that the proposed components could be easily integrated in an LFNED with the result of resolution enhancement.
Resolution-enhanced light field displays by recombining subpixels across elemental images
(2019-05-15)
Qin, Zong
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Chou, Ping-Yen
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Wu, Jui-Yi
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Huang, Cheng-Ting
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Huang, Yi-Pai
Light field displays based on integral imaging feature ultra-compact volume and freedom of the vergence-accommodation conflict for advanced virtual reality and augmented reality devices; however, they currently suffer from low visual resolution. Considering that subpixels have an intrinsically tripled resolution compared with triad pixels, this Letter develops a subpixel-level algorithm by recombining subpixels with relatively small raytracing errors from different elemental images. As a result, based on a highly accurate image formation model, the resolution of a typical system (pixel size, 7.8 mu m; system thickness, 4.07 mm) is remarkably enhanced from 8.3 to 20.0 pixels per degree, for a gain of 2.41. In addition, the color breakup introduced by the chromatic subpixels is largely suppressed. (C) 2019 Optical Society of America
Revelation and addressing of accommodation shifts in microlens array-based 3D near-eye light field displays
(2020-01-01)
Qin, Zong
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Wu, Jui-Yi
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Chou, Ping-Yen
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Chen, Yu-Ting
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Huang, Cheng-Ting
In a 3D near-eye light field display using microlens arraybased integral imaging, the accommodation response is presumed to exactly coincide with the reconstructed depth plane (RDP) which, however, has been little examined. By employing a highly accurate image formation model to analyze retinal images, the accommodation response is revealed to significantly shift towards the central depth plane (CDP) because of defocusing. The shift is quantitatively characterized for various CDPs and RDPs with a preliminary verifying experiment to provide content producers an approach to address the accommodation shift to fully mitigate the vergence-accommodation conflict. (C) 2019 Optical Society of America
Three-dimensional reflection screens fabricated by holographic wavefront printer
(2018-06-01)
Oi, Ryutaro
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Chou, Ping-Yen
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Jackin, Boaz Jessie
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Wakunami, Koki
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Ichihashi, Yasuyuki
Several wavefront printers have been recently proposed. Since the printers can record an arbitrary computer-generated wavefront, they are expected to be useful for fabricating complex mirror arrays used in front projection 3-D screens without using real existing optics. We prototyped two transparent reflective screens using our hologram printer in experiments. These screens could compensate fora spherically distorted reference wave caused by a short projection distance to obtain an ideal reference wave. Owing to the use of the wavefront-printed screen, the 3-D display was simply composed of a normal 2-D projector and a screen without using extra optics. In our binocular system, reflected light rays converged to the left and right eyes of the observer and the crosstalk was less than 8%. In the light field system, the reflected light rays formed a spatially sampled light field and focused a virtual object in a depth range of +/- 30 mm with a +/- 13.5-deg viewing angle. By developing wavefront printing technology, a complex optics array may easily be printed by nonprofessionals for optics manufacturing. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
Three-dimensional reflection screens fabricated by holographic wavefront printer (vol 57, 061605, 2018)
(2018-06-01)
Oi, Ryutaro
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Chou, Ping-Yen
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Jackin, Boaz Jessie
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Wakunami, Koki
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Ichihashi, Yasuyuki