Browsing by Author "Kang, Hoonjong"
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Item Open Access Circularly configured multi-SLM holographic display system(IEEE, 2011) Yaraş, Fahri; Kang, Hoonjong; Onural, LeventThe designed circular holographic display system produces ghost-like 3D optical reconstructions of a computer generated 3D model. System uses six phase-only reflective-type spatial light modulators (SLMs) that are configured circularly. Alignment of the SLMs are successful and gap problem is solved by using half-mirrors. The total number of pixels of the resultant display is 11520 1080. Reconstructions show that increase in the viewing angle is significant compared to the single SLM case. With the help of the proposed system, observer can see the reconstructions binocularly. As a result, comfortable 3D perception is achieved. In order to avoid eye-hazard, LED illumination is also used as an alternative light source. Experimental results are satisfactory. Proposed system can be used as a holographic display system.Item Open Access Current research activities on holographic video displays(SPIE, 2010) Onural, Levent; Yaraş, Fahri; Kang, Hoonjong"True 3D" display technologies target replication of physical volume light distributions. Holography is a promising true 3D technique. Widespread utilization of holographic 3D video displays is hindered by current technological limits; research activities are targeted to overcome such difficulties. Rising interest in 3D video in general, and current developments in holographic 3D video and underlying technologies increase the momentum of research activities in this field. Prototypes and recent satisfactory laboratory results indicate that holographic displays are strong candidates for future 3D displays.Item Open Access Multi-SLM holographic display system with planar configuration(IEEE, 2010) Yaraş, Fahri; Kang, Hoonjong; Onural, LeventHolographic display system that uses six phase-only spatial light modulators (SLMs) performs holographic reconstructions from the phase-hologram of a point cloud that is extracted from 3D object. The SLMs are tiled as a three by two matrix on a virtual planar surface. The alignment is successful and the display system generates large holographic reconstructions. The proposed system can be used either to obtain reconstructions of large objects with a narrow field of view or reconstructions of smaller objects with a broader field of view. Therefore, since field of view is broader for smaller objects, observer has the flexibility to move around the reconstruction within a larger angle. This flexibility increases the motion parallax and as a consequence it increases the quality of 3D perception. Results show that even with three SLMs in horizontal direction the 3D perception is significantly increased. Experimental results are satisfactory.Item Open Access Quality comparison and acceleration for digital hologram generation method based on segmentation(IEEE, 2009) Kang, Hoonjong; Yaraş, Fahri; Onural, LeventA holographic fringe pattern generation methods is based on Fraunhofer diffraction and subsequent segmentation and approximation of the fringe pattern. Several modifications of the original algorithm are already proposed to improve the quality of reconstructions. We compare the quality of to the reconstructed images from different versions of this algorithm by taking the reconstructions from the Fresnel hologram as a reference. Since, there is not any generally accepted objective quality assessment method for such reconstructions, we used some experimental methods such as intensity spread over the reconstructed images, total noise power, and peak-signal-to-noise for comparison. Then we chose the best performing algorithm in terms of ireconstruction quality, and developed a GPU-based implementation to accelerate the computation speed. The quality of the resultant reconstructions is comparable to reconstructions from Fresnel holograms; much higher speed is achieved due to multi-GPU implemetation.Item Open Access Real-time color holographic video display system(IEEE, 2009) Yaraş, Fahri; Kang, Hoonjong; Onural, LeventA real-time multi-GPU color holographic video display system computes holograms from 3D video of a rigid object. System has three main stages; client, server and optics. 3D coordinate and texture information are kept in client and sent online to the server through the network. In the server stage, with the help of the parallel processing ability of the GPUs and segmentation algorithms, phase-holograms are computed in real-time. The graphic card of the server computer drives the SLMs and red, green and blue channels are controlled in parallel. Resultant color holographic video is loaded to the SLMs which are illuminated by expanded light from LEDs. In the optics stage, reconstructed color components are combined by using beam splitters. Reconstructions are captured by a CCD array without any supporting optics. Experimental results are satisfactory.Item Open Access Real-time fringe pattern generation with high quality(OSA, 2009) Kang, Hoonjong; Yaraş, Fahri; Onural, Levent; Yoshikawa, H.A hologram computation procedure and its GPU implementation are presented. The procedure is based on partitioning. Each segment has an approximate but simpler frequency domain representation. Quality of the results is comparable to Fresnel holograms.Item Open Access Real-time multiple SLM color holographic display using multiple GPU acceleration(OSA, 2009) Yaraş, Fahri; Kang, Hoonjong; Onural, LeventA real-time color holographic video display system computes holograms from point cloud of a rigid object by using multi-GPU system and uses three different colored LEDs for reconstruction. Experimental results are satisfactory.Item Open Access Thereconstruction quality improvement of holographic stereograms via variable size segmentation(IEEE, 2010) Şahin, Erdem; Onural, Levent; Kang, HoonjongAs computer generated holograms becomes more common, the fast computation of holographic interference patterns in digital environment becomes a necessity. Since the computation time of holograms via Fresnel (or Rayleigh-Sommerfeld) diffraction models makes real time applications impossible, the holographic stereograms are developed to be a solution for this problem. Holographic stereograms divide the hologram plane into segments. In phase added stereograms the coordinates of 3D source points are used while calculating the diffraction field. And that enables to calculate the diffraction field with appropriate sized FFTs. Although the phase added stereograms are advantageous in terms of computation time, the quality of the reconstructed three dimensional images may not be satisfactory. The main reason is that the diffraction field of a given point source is approximated as a pure complex sinusuoid in each segment. To increase the reconstruction quality, we propose a method that uses variable sized segments, as opposed to previously developed holographic stereograms that use fixed sized segments. While approximating the diffraction field of a point source, higher frequency regions are covered with smaller segments and lower frequency regions with larger segments. As a result of this, we keep the total number of oscillations of pure sinusoidal waves constant in each segment. The simulations that we carried out for a point source show that we are able to obtain better quality reconstruction with our method. ©2010 IEEE.