Browsing by Subject "Spatial light modulators"

Now showing 1 - 14 of 14

Open Access
Circular holographic video display system
(Optical Society of American (OSA), 2011) Yaraş, F.; Kang, H.; Onural, L.
A circular holographic video display system reconstructs holographic video. Phase-only spatial light modulators are tiled in a circular configuration in order to increase the field of view. A beam-splitter is used to align the active area of the SLMs side by side without any gap. With the help of this configuration observers can see 3D ghost-like image floating in space and can move and rotate around the object. The 3D reconstructions can be observed binocularly. Experimental results are satisfactory. © 2011 Optical Society of America.
Open Access
Circularly configured multi-SLM holographic display system
(IEEE, 2011) Yaraş, Fahri; Kang, Hoonjong; Onural, Levent
The 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.
Open Access
Color holographic reconstruction using multiple SLMs and LED illumination
(SPIE, 2009-01) Yaraş, Fahri; Onural, Levent
A color holographic reconstruction technique by using three light emitting diodes (LEDs) is described. Reflective type phase-only spatial light modulators (SLMs) are used since they are suitable for in-line phase holograms. Gerchberg-Saxton iterative algorithm is used for computing phase holograms. Three phase holograms are calculated separately for red, green and blue colors, for a color reconstruction, and separately loaded to corresponding SLMs. Three LEDs are used for illuminating those phase holograms and reconstructions are combined and captured. Experimental results are satisfactory. © 2009 SPIE-IS&T.
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.
Open Access
Infrared digital holography applications for virtual museums and diagnostics of cultural heritage
(SPIE, 2011) Paturzo, M.; Pelagotti, A.; Geltrude, A.; Locatelli, M.; Poggi P.; Meucci, R.; Ferraro P.; Stoykova, E.; Yaraş F.; Yöntem, A. Özgür; Kang H.; Onural, Levent
Infrared digital holograms of different statuettes are acquired. For each object, a sequence of holograms is recorded rotating the statuette with an angular step of few degrees. The holograms of the moving objects are used to compose dynamic 3D scenes that, then, are optically reconstructed by means of spatial light modulators (SLMs) using an illumination wavelength of 532 nm. This kind of reconstruction allows to obtain a 3D imaging of the statuettes that could be exploited for virtual museums. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Open Access
Integral imaging using phase-only LCoS spatial light modulators as Fresnel lenslet arrays
(Optical Society of Amercia, 2011-10-27) Ÿontem, A. O.; Onural, L.
We present a digital integral imaging system. A Fresnel lenslet array pattern is written on a phase-only LCoS spatial light modulator device (SLM) to replace the regular analog lenslet array in a conventional integral imaging system. We theoretically analyze the capture part of the proposed system based on Fresnel wave propagation formulation. Because of pixelation and quantization of the lenslet array pattern, higher diffraction orders and multiple focal points emerge. Because of the multiple focal planes introduced by the discrete lenslets, multiple image planes are observed. The use of discrete lenslet arrays also causes some other artifacts on the recorded elemental images. The results reduce to those available in the literature when the effects introduced by the discrete nature of the lenslets are omitted. We performed simulations of the capture part. It is possible to obtain the elemental images with an acceptable visual quality. We also constructed an optical integral imaging system with both capture and display parts using the proposed discrete Fresnel lenslet array written on a SLM. Optical results when self-luminous objects, such as an LED array, are used indicate that the proposed system yields satisfactory results.
Open Access
Method to enlarge the hologram viewing window using a mirror module
(2009) Kang H.; Ohmura, N.; Yamaguchi, T.; Yoshikawa H.; Kim, S.-C.; Kim, E.-S.
A liquid crystal panel for a video projector is often used for holographic television. However, its pixel size and pixel number are not enough for practical holographic 3-D display. Therefore, a multipanel configuration is generally used to increase the viewing window and displayed image size, and many spatial light modulators should be used in them. We propose a novel method to increase the viewing window of a holographic display system. The proposed method, which is implemented by using a mirror module and 4-f lens set, is to reconfigure the beam shape reflected by a spatial light modulator. The equipment is applied to a holographic display system, which has only a single spatial light modulator; a hologram could be displayed in a wider viewing window by the equipment than that of the conventional method. By the proposed method, the resolution of the reconfigured spatial light modulator has double resolution in the horizontal direction. Inversely, the vertical resolution is decreased. Even if the vertical resolution is decreased, a viewer could get 3-D effect because humans get more 3-D information in the horizontal direction. We have experimented using a liquid crystal on silicon (LcOS), whose resolution is 4096×2160pixels. The reconfigured resolution by the mirror module is 8192×1080pixels. From the experiments, the horizontal viewing window is almost two times wider than that without the mirror module. As a result, the hologram can be observed binocularly. © 2009 Society of Photo-Optical Instrumentation Engineers.
Open Access
Multi-SLM holographic display system with planar configuration
(IEEE, 2010) Yaraş, Fahri; Kang, Hoonjong; Onural, Levent
Holographic 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.
Open Access
An overview of research in 3DTV
(IEEE, 2007) Onural, Levent
3DTV is regarded by the experts and the general public as the next major step in video technologies. The ghost-like images of remote persons or objects are already depicted in many futuristic movies; both entertainment applications, as well as 3D video telephony, are among the commonly imagined utilizations of such a technology. As in every product, there are various different technological approaches also in 3DTV. By the way, 3D technologies are not new; the earliest 3DTV application is demonstrated within a few years after the invention of 2D TV. However, earlier 3D video relied on stereoscopy. Current work mostly focuses on advanced variants of stereoscopic principles like goggle-free autostereoscopic multi-view devices. However, holographic 3DTV and its variants are the ultimate goal and will yield the envisioned high-quality ghostlike replicas of original scenes once technological problems are solved. Stereoscopy is based on exploiting the human perception. Simply, two views, taken at two slightly different angles are then guided to left and right eyes. The two eyes, receiving the two different views of the same scene from two different angles, provide the visual signals to the brain; and then, the brain interprets the scene as 3D. However, there are many different 3D depth cues in perception, and usually, there are contradictory signals received by the brain. Viewers experience a motion-sickness-like feeling as a consequence of such mismatches. This is the major reason which kept 3D from becoming a popular mode of visual communications. However, recent advances in end-to-end digital techniques minimized such problems. Stereoscopic TV broadcasts have been conducted. Novel advances in stereoscopy brought viewing without goggles; however, the viewer and the monitor must have a fixed location and orientation with respect to each other for most autostereoscopic images. Multi-view autostereoscopic displays allow some horizontal parallax within a limited viewing angle. There are experiments in head-tracking autostereoscopic displays, as well as, free-view point video by providing the right pair of images based on the location of the viewer. Holography is not based on human perception, but targets perfect recording and reconstruction of light with all its properties. If such a reconstruction is achieved, the viewer, embedded in the same light distributionas the original, will of course see the same scene as the original.
Open Access
Real-time color holographic video display system
(IEEE, 2009) Yaraş, Fahri; Kang, Hoonjong; Onural, Levent
A 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.
Open Access
Signal processing for three-dimensional holographic television displays that use binary spatial light modulators
(IEEE, 2010) Ulusoy, Erdem; Onural, Levent; Özaktaş, Haldun M.
One of the important techniques used for three dimensional television (3DTV) is holography. In holographic 3DTV, spatial light modulators (SLM) are used as the display device. SLMs that provide the most limited modulation are the binary SLMs, since only two different values can be assigned to their pixels. An important signal processing problem arising here is the determination of the binary signal to be written on the SLM among the possible ones such that the desired light field is generated to the best extent. Many of the proposed methods do not produce satisfactory results in terms of error rate, computational performance or light efficiency. We propose an optical setup to be placed in front of the binary SLM and the associated signal processing algorithm. The proposed system uses a 4-f setup and a periodic mask is placed to the Fourier plane. As a result, the binary SLM is convolved with a series of regularly spaced impulse functions and we get a new SLM which is smaller in pixel count compared to binary SLM but which can provide 16-bit full complex modulation. It becomes easier to generate the desired light field with this new SLM. Also, the required computations are carried out in a fast manner to enable real-time operation. ©2010 IEEE.
Open Access
Synthesis of three-dimensional light fields with binary spatial light modulators
(Optical Society America, 2011-05-24) Ulusoy, E.; Onural, L.; Özaktaş, Haldun M.
Computation of a binary spatial light modulator (SLM) pattern that generates a desired light field is a challenging quantization problem for which several algorithms have been proposed, mainly for far-field or Fourier plane reconstructions. We study this problem assuming that the desired light field is synthesized within a volumetric region in the non-far-field range after free space propagation from the SLM plane. We use Fresnel and Rayleigh-Sommerfeld scalar diffraction theories for propagation of light. We show that, when the desired field is confined to a sufficiently narrow region of space, the ideal gray-level complex-valued SLM pattern generating it becomes sufficiently low pass (oversampled) so it can be successfully halftoned into a binary SLM pattern by solving two decoupled real-valued constrained halftoning problems. Our simulation results indicate that, when the synthesis region is considered, the binary SLM is indistinguishable from a lower resolution full complex gray-level SLM. In our approach, free space propagation related computations are done only once at the beginning, and the rest of the computation time is spent on carrying out standard image halftoning.
Open Access
Toward an optimal foundation architecture for optoelectronic computing. Part II: Physical construction and application platforms
(Optical Society of America, 1997-08-10) Özaktaş, Haldun M.
Various issues pertaining to the physical construction of systems that are based on regularly interconnected device planes, such as heat removal and extensibility of the optical interconnections for larger systems, are discussed. Regularly interconnected device planes constitute a foundation architecture that is reasonably close to the best possible as defined by physical limitations. Three application platforms based on the foundation architecture described are offered.
Open Access
Visible reconstruction by a circular holographic display from digital holograms recorded under infrared illumination
(Optical Society of America, 2012-07-20) Stoykova, E.; Yaras, F.; Kang, H.; Onural, L.; Geltrude, A.; Locatelli, M.; Paturzo, M.; Pelagotti, A.; Meucci, R.; Ferraro, P.
A circular holographic display that consists of phase-only spatial light modulators is used to reconstruct images in visible light from digital holograms recorded under infrared (10.6 μm) illumination. The reconstruction yields a holographic digital video display of a three-dimensional ghostlike image of an object floating in space where observers can move and rotate around it.