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Wide viewing angle dynamic holographic stereogram with a curved array of spatial light modulators.
Hahn, Joonku,Kim, Hwi,Lim, Yongjun,Park, Gilbae,Lee, Byoungho Optical Society of America 2008 Optics express Vol.16 No.16
<P>A novel design of dynamic holographic stereogram with a curved array of spatial light modulators (SLMs) is proposed. In general, it is difficult to simultaneously achieve a wide viewing angle and an available width for the digital holographic display. Moreover, the wide viewing angle of a display system needs a large optical numerical aperture where the paraxial approximation fails, and thus an extremely large planar SLM is necessary in using previous methods. To solve this problem, our proposed display system is composed of a curved array of SLMs to obtain a large number of data points and reduce the spatial bandwidth in SLMs. In the curved array of SLMs, each SLM is individually transformed to display local angular spectra of object wave, which is based on a fundamental idea of holographic stereogram. To embody the dynamic holographic stereogram with SLMs, each SLM is effectively reformed for simplifying the optical structure and reducing the light power loss. In detail, spatially modulated wave is optically divided and transformed, as if each SLM were composed of three sub-SLMs. This design improves the scalability in viewing angle of holographic display and the loss of light power is significantly reduced. With this method, we can achieve the digital holographic display with 22.8 degrees viewing angle.</P>
Uncertainty-managed phase-shifting digital holography.
Hahn, Joonku,Kim, Hwi Optical Society of America 2012 Optics letters Vol.37 No.21
<P>Phase-shifting digital holography is a digital measurement technology of a complex optical field profile that uses focal plane array detectors without the loss of bandwidth. It has been known that the accuracy of phase-shifting digital holography is limited mainly by the phase tolerance of reference. In this Letter, it is revealed that the uncertainty in an expected signal is highly dependent on the phase of the signal itself, as well as the phase tolerance of the reference. Based on the uncertainty analysis, we propose a novel scheme of phase-shifting digital holography that exploits an uncertainty property to enhance the measurement accuracy even under significant reference phase tolerance.</P>
Undistorted pickup method of both virtual and real objects for integral imaging.
Hahn, Joonku,Kim, Youngmin,Kim, Eun-Hee,Lee, Byoungho Optical Society of America 2008 Optics express Vol.16 No.18
<P>Optically corrected pickup method of both virtual and real objects for integral imaging is proposed. The proposed pickup system has imbricate view volumes which are equivalent to those in the integral imaging display. Therefore, there is no distortion resulting from the discord in directions of elemental image between pickup and display. In this system, the view volumes are transformed by 4f optics and the directions of view are defined by lens array and telecentric lens. Without computational cost for compensation, the pickup of both real and virtual objects is confirmed experimentally.</P>
Uniform angular resolution integral imaging display with boundary folding mirrors
Hahn, Joonku,Kim, Youngmin,Lee, Byoungho The Optical Society 2009 Applied Optics Vol.48 No.3
<P>Uniform angular resolution integral imaging display is proposed. Conventionally, inefficient bias of the perspectives around boundaries is disregarded and it is impossible to display the field of view over full spatial resolution. However, the proposed display has four boundary folding mirrors and these mirrors fold the view volumes correctly to form uniform angular resolution within them. The distribution of perspectives and field of view in the proposed system are analyzed and the removal of this boundary effect is confirmed experimentally.</P>
Kim, Hwi,Hahn, Joonku,Lee, Byoungho The Optical Society 2008 Applied optics Vol.47 No.19
<P>We develop a mathematical model of triangle-mesh-modeled three-dimensional (3D) surface objects for digital holography. The proposed mathematical model includes the analytic angular spectrum representation of image light fields emitted from 3D surface objects with occlusion and the computation method for the developed light field representation. Reconstruction of computer-generated holograms synthesized by using the developed model is demonstrated experimentally.</P>
Kim, Hwi,Hahn, Joonku,Choi, Hee-Jin The Optical Society 2011 Applied optics Vol.50 No.11
<P>We investigate the viewing angle enhancement of a lenticular three-dimensional (3D) display with a triplet lens array. The theoretical limitations of the viewing angle and view number of the lenticular 3D display with the triplet lens array are analyzed numerically. For this, the genetic-algorithm-based design method of the triplet lens is developed. We show that a lenticular 3D display with viewing angle of 120° and 144 views without interview cross talk can be realized with the use of an optimally designed triplet lens array.</P>
Image volume analysis of omnidirectional parallax regular-polyhedron three-dimensional displays
Kim, Hwi,Hahn, Joonku,Lee, Byoungho The Optical Society 2009 Optics express Vol.17 No.8
<P>Three-dimensional (3D) displays having regular-polyhedron structures are proposed and their imaging characteristics are analyzed. Four types of conceptual regular-polyhedron 3D displays, i.e., hexahedron, octahedron, dodecahedron, and icosahedrons, are considered. In principle, regular-polyhedron 3D display can present omnidirectional full parallax 3D images. Design conditions of structural factors such as viewing angle of facet panel and observation distance for 3D display with omnidirectional full parallax are studied. As a main issue, image volumes containing virtual 3D objects represented by the four types of regular-polyhedron displays are comparatively analyzed.</P>
Plasmonic Light Beaming Manipulation and its Detection Using Holographic Microscopy
Yongjun Lim,Joonku Hahn,Seyoon Kim,Junghyun Park,Hwi Kim,Byoungho Lee IEEE 2010 IEEE journal of quantum electronics Vol.46 No.3
<P>Plasmonic off axis beaming and focusing of light by the use of asymmetric or non-periodic dielectric gratings around a metallic slit are experimentally demonstrated. The far-field probing was done by holographic microscopy. While the conventional near-field microscopes can probe only near-fields, our four-step phase-shift interferometer provides an efficient way of probing and reconstructing light paths coming out from the plasmonic devices. We hope our experimental work contributes to the practical applications of plasmonics such as optical interconnection and optical data storage.</P>
Accelerated synthesis algorithm of polygon computer-generated holograms.
Im, Dajeong,Cho, Jaebum,Hahn, Joonku,Lee, Byoungho,Kim, Hwi Optical Society of America 2015 Optics express Vol.23 No.3
<P>For the real-time computation of computer-generated holograms (CGHs), various accelerated algorithms have been actively investigated. This paper proposes a novel concept of sparse computation of polygon CGH, which is inspired by an observation of the sparsity in the angular spectrum of a unit triangular polygon and present the accelerated algorithm using the intrinsic sparsity in the polygon CGH pattern for the enhancement of computational efficiency effectively. It is shown with numerical results that computation efficiency can be greatly improved without degrading the quality of holographic image.</P>