Browsing by Author "Wakunami, Koki"

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Digitally designed holographic optical element for light field displays
(2018-08-01)
Jackin, Boaz Jessie
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Jorissen, Lode
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Oi, Ryutaro
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Wu, Jui Yi
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Wakunami, Koki
Concave micro-mirror arrays fabricated as holographic optical elements are used in projector-based light field displays due to their see-through characteristics. The optical axes of each micro-mirror in the array are usually made parallel to each other, which simplifies the fabrication, integral image rendering, and calibration process. However, this demands that the beam from the projector be collimated and made parallel to the optical axis of each elemental micro-mirror. This requires additional collimation optics, which puts serious limitations on the size of the display. In this Letter, we propose a solution to the above issue by introducing a new method to fabricate holographic concave micro-mirror array sheets and explain how they work in detail. 3D light field reconstructions of the size 20 cm x 10 cm and 6 cm in depth are achieved using a conventional projector without any collimation optics. (C) 2018 Optical Society of America
Projection-type see-through holographic three-dimensional display
(2016-10-03)
Wakunami, Koki
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Hsieh, Po-Yuan
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Oi, Ryutaro
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Senoh, Takanori
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Sasaki, Hisayuki
Owing to the limited spatio-temporal resolution of display devices, dynamic holographic three-dimensional displays suffer from a critical trade-off between the display size and the visual angle. Here we show a projection-type holographic three-dimensional display, in which a digitally designed holographic optical element and a digital holographic projection technique are combined to increase both factors at the same time. In the experiment, the enlarged holographic image, which is twice as large as the original display device, projected on the screen of the digitally designed holographic optical element was concentrated at the target observation area so as to increase the visual angle, which is six times as large as that for a general holographic display. Because the display size and the visual angle can be designed independently, the proposed system will accelerate the adoption of holographic three-dimensional displays in industrial applications, such as digital signage, in-car head-up displays, smart-glasses and head-mounted displays.
Reconstruct Holographic 3D Objects by Double Phase Hologram
(2015-01-01)
Ting, Chih-Hung
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Wakunami, Koki
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Yamamoto, Kenji
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Huang, Yi-Pai
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光電工程學系
To develop a 3D display which can show true 3D images is very important and necessary. Holography has great potential to achieve the objective because holography can actually reconstruct the recorded object in space by reconstruction of wavefront. Further, computer generated hologram (CGH) is used to solve the major issue of conventional holography, which means the recoding process is quite complicated and needs the real objects. The reconstructed image, however, will be blurred and with the unexpected light if using only one phase-only spatial light modulator (PSLM). Although to use two PSLMs by dual-phase modulation method (DPMM) can modulate the phase and the amplitude information simultaneously to enhance the quality of the reconstructed image, it is hard to use in practical application because of the extremely high accurate calibration of the two PSLMs. Therefore, double phase hologram (DPH) was proposed to use only one PSLM to modulate the phase and the amplitude information simultaneously to make the reconstructed image be more focused and eliminate the unexpected light.
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
;
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
;
Chou, Ping-Yen
;
Jackin, Boaz Jessie
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Wakunami, Koki
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Ichihashi, Yasuyuki