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Full-color holographic diffuser using time-scheduled iterative exposure
Piao, Mei-Lan,Kwon, Ki-Chul,Kang, Hoon-Jong,Lee, Kwon-Yeon,Kim, Nam The Optical Society 2015 Applied Optics Vol.54 No.16
<P>A compact wavelength multiplexing technique is proposed and experimentally investigated to improve the efficiency of a full-color holographic diffuser using photopolymer. The exposure responses of a monochromatic hologram and a three wavelength multiplexed hologram recorded in photopolymer film are presented. The time-scheduled exposure energies at wavelengths of 633, 532, and 473??nm were chosen to optimize the uniform diffraction efficiency of the wavelength multiplexed hologram. These three wavelength iterative sequences of exposures are applied to achieve a specific color balance for a multicolor holographic diffuser. The experimental results confirm that the fabrication method is well suited to the manufacture of holographic diffusers for full-color display applications.</P>
Piao, Mei-Lan,Kim, Nam The Optical Society 2014 Applied Optics Vol.53 No.10
<P>We developed a head-mounted display (HMD) that achieved high levels of color uniformity and optical efficiency. The full-color holographic volume grating (HVG) attached on the specially designed wedge-shaped waveguide HMD system provided a 17 horizontal field of view (FOV). Theoretical analyses showed that the proposed waveguide resolved the problems of thickness and limited FOV. In this system, the HVG was recorded using a special sequential recording process on single photopolymer unit with 633, 532, and 473 nm wavelengths. The results confirm that the designed and fabricated waveguide can be employed in future commercial HMS.</P>
Phase Contrast Projection Display Using Photopolymer
Mei-Lan Piao,김남,박재형 한국광학회 2008 Current Optics and Photonics Vol.12 No.4
We propose a phase contrast filter using photopolymer, for the phase contrast projection display. The photopolymer has high photosensitivity such that its optically induced refractive index change has a linear dependency on the illuminating light intensity. We implemented a phase contrast projection display using photopolymer as a phase contrast filter. By controlling the refractive index change of the photopolymer, we successfully convert an input phase image into a high contrast intensity image. We also investigated the effect of the photopolymer illumination condition on the quality of the displayed intensity image. As a projector, we achieved 82% phase to intensity conversion efficiency, which implies that the proposed method can potentially have much higher light efficiency than conventional projection display.
Jing-Ai Piao,Gang Li,Mei-Lan Piao,김남 한국광학회 2013 Current Optics and Photonics Vol.17 No.3
Full color holographic optical element fabrication using a photopolymer is proposed for a waveguide-type head mounted display. The fabricated full color holographic optical elements can be attached to the waveguide to replace the conventional couple-in and couple-out optics in the head mounted display. To implement the system, this study analyzed the optical characteristics of the photopolymer using three lasers (red, green and blue). Considering the color uniformity, a new laminated structure for a full color holographic optical element was also designed. The proposed system was confirmed experimentally.
Zhao, Yu,Piao, Mei-lan,Li, Gang,Kim, Nam Optical Society of America 2015 Optics letters Vol.40 No.13
<P>Fast calculation method for a computer-generated cylindrical hologram (CGCH) is proposed. The method consists of two steps: the first step is a calculation of a virtual wave-front recording surface (WRS), which is located between the 3D object and CGCH. In the second step, in order to obtain a CGCH, we execute the diffraction calculation based on the fast Fourier transform (FFT) from the WRS to the CGCH, which are in the same concentric arrangement. The computational complexity is dramatically reduced in comparison with direct integration method. The simulation results confirm that our proposed method is able to improve the computational speed of CGCH.</P>
김남,박미란,Kim, Nam,Piao, Mei-Lan 한국광학회 2014 한국광학회지 Vol.25 No.3
홀로그래피 광학소자는 투명하고 얇은 필름 또는 플라스틱 형태로 다양한 기능을 포함할 수 있는 장점을 갖고 있어 광학제품, 통신 및 디스플레이 분야에서 다양한 연구 개발이 진행되고 있다. 본 논문에서는 홀로그래피 광학소자의 원리 및 특성, 이를 활용한 회절 광학소자, 홀로그래픽 투영 스크린, HMD 등 응용시스템에 대해 소개한다. 앞으로 홀로그래피 광학소자가 좀 더 보편화되고 활용가치를 높이기 위해 풀어야 할 당면과제에 대해 설명한다. Holographic optical elements (HOEs) provide systems of thin-film optics that could include a variety of functions and have many advantages as optical devices in various research fields. Research and developments based on the use of HOEs in the fields of communications and displays are in progress. This paper introduces the properties of HOEs and their applications in diffractive optical elements (DOEs), holographic projection screens, and head-mounted displays (HMDs). For widespread use of HOE technology in these various applications some challenges need to be solved, as discussed in this paper.