Dr. Heemin Choi Profile

Dr. Heemin Choi

at Wonkwang Univ

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Publications (2)

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Proceedings Article | 19 December 2022 Presentation + Paper

Volume-reduced floating display based on a holographic optical element

Heemin Choi, Younghun Kim, Hoonjong Kang, Nam Kim

Proceedings Volume 12318, 123181F (2022) https://doi.org/10.1117/12.2643885

KEYWORDS: Holographic optical elements, Holographic displays, Wave propagation, Mirrors, Projection systems, Displays, Diffusers, Holograms, Optical design, Image acquisition

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In this paper, we propose a volume-reduced floating display based on a holographic optical element (HOE). The critical problem of a conventional floating display is a huge size, and this drawback limits its practical application. To overcome this drawback, the proposed floating display used the HOE for a reduction of the volume instead of a half mirror. Generally, the HOE can control the diffraction angle of the propagating wavefield. Also, the suitable HOE can be designed depending on the structure or a requirement of the floating display. So, the volume of the proposed floating display can be reduced through the HOE when the HOE is designed to reduce the diffraction angle. In the proposed floating display, the HOE is inclined at a certain angle in front of the retroreflective film. And, the projector and diffuser are set up the bottom of the inclined HOE. Wavefields propagated from the projector are formed as an image on the diffuser and, diffracted by the HOE into the retroreflective film. These diffracted wavefields are reflected by the retroreflective film back toward the direction of the propagating wavefields. As a result, the floated image is formed in the real space. For the optical experiment, we designed a HOE and set up the proposed floating display. Experimental result shows that the image is formed in real space like the conventional floating display. Also, we confirm that the volume of the floating display is reduced by as much as 35.6 % compared with the conventional floating display.

Proceedings Article | 1 March 2013 Paper

Fast generation of video hologram patterns by use of motion vectors of three-dimensional objects

Xiao-Bin Dong, Hee-Min Choi, Min-Woo Kwon, Seung-Cheol Kim, Eun-Soo Kim

Proceedings Volume 8644, 864418 (2013) https://doi.org/10.1117/12.2006563

KEYWORDS: Computer generated holography, Video, 3D image processing, Holograms, Image segmentation, Fringe analysis, 3D video compression, Video compression, Holography, 3D displays

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Thus far, various approaches to generate the computer-generated holograms (CGHs) of 3-D objects have been suggested but, most of them have been applied to the still images, not to the video images due to their computational complexity. Recently, a method to fast compute the CGH patterns of 3-D video images has been proposed by combined use of data compression and novel look-up table (N-LUT) techniques. In this method, temporally redundant data of 3-D video images are removed with the differential pulse code modulation (DPCM) algorithm and then the CGH patterns for these compressed video images are calculated with the N-LUT method. However, as the 3-D objects move rapidly, image differences between the video frames may increase, which results in a massive growth of calculation time of the video holograms. Therefore, we propose a novel approach to significantly reduce the computation time of 3-D video holograms by employing a new concept of motion-vector of the 3-D object. In the proposed method, 3-D objects are firstly segmented from the 1st frame of the 3-D videos, and the CGH patterns for each segmented object are computed with the N-LUT algorithm. Secondly, motion vectors between each segmented object and the corresponding objects in the consecutive 3-D video frames are calculated. Thirdly, the CGH patterns for each segmented object are shifted with the calculated motion vectors. Finally, all these shifted CGH patterns are added up to generate the hologram patterns of the consecutive 3-D video frames. To confirm the feasibility of the proposed method, experiments are performed and the results are comparatively discussed with the conventional methods in terms of the number of object points and computation time.

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