Browsing by Subject "Digital holography"

Now showing 1 - 12 of 12

Open Access
Capture, processing, and display of real-world 3D objects using digital holography
(IEEE, 2010) Naughton, T.J.; Falldorf, C.; Onural, Levent; Ferraro P.; Depeursinge, C.; Krueger, S.; Emery, Y.; Hennelly, B.M.; Kujawifiska, M.
"Digital holography for 3D and 4D real-world objects' capture, processing, and display" (acronym "Real 3D") is a research project funded under the Information and Communication Technologies theme of the European Commission's Seventh Framework Programme, and brings together nine participants from academia and industry (see www.digitalholography.eu).This three-year project marks the beginning a long-term effort to facilitate the entry of a new technology (digital holography) into the three-dimensional capture and display markets. Its progress at the end of year 2 is summarised. © 2010 IEEE.
Open Access
Computation of holographic patterns between tilted planes
(SPIE - International Society for Optical Engineering, 2006-05) Esmer, Gökhan Bora; Onural, Levent
Computation of the diffraction pattern that gives the desired reconstruction of an object upon proper illumination is an important process in computer generated holography. A fast computational method, based on the plane wave decomposition of 3D field in free-space, is presented to find the desired diffraction pattern. The computational burden includes two FFT algorithms in addition to a shuffling of the frequency components that needs an interpolation in the frequency domain. The algorithm is based on the exact diffraction formulation; there is no need for Fresnel or Fraunhofer approximations. The developed model is utilized to calculate the scalar optical diffraction between tilted planes for monochromatic light. The performance of the presented algorithm is satisfactory for tilt angles up to 60°.
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
Digital decoding of in-line holograms
(SPIE, 1987) Onural, L.; Scott, P. D.
Digitally sampled in-line holograms may be linearly filtered to reconstruct a representation of the original object distribution, thereby decoding the information contained in the hologram. The decoding process is performed by digital computation rather than optically. Substitution of digital for optical decoding has several advantages, including selective suppression of the twin-image artifact, elimination of the far-field requirement, and automation of the data reduction and analysis process. The proposed filter is a truncated series expansion of the inverse of that operator that maps object opacity function to hologram intensity. The first term of the expansion is shown to be equivalent to conventional (optical) reconstruction, with successive terms increasingly suppressing the twin image. The algorithm is computationally efficient, requiring only a single fast Fourier transform pair.
Open Access
Digital holographic three-dimensional video displays
(IEEE, 2011-02-04) Onural, L.; Yaras, F.; Kang, H.
Holography aims to record and regenerate volume filling light fields to reproduce ghost-like 3-D images that are optically indistinguishable from their physical 3-D originals. Digital holographic video displays are pixelated devices on which digital holograms can be written at video rates. Spatial light modulators (SLMs) are used for such purposes in practice; even though it is desirable to have SLMs that can modulate both the phase and amplitude of the incident light at each pixel, usually amplitude-only or phase-only SLMs are available. Many laboratories have reported working prototypes using different designs. Size and resolution of the SLMs are quite demanding for satisfactory 3-D reconstructions. Space–bandwidth product (SBP) seems like a good metric for quality analysis. Even though moderate SBP is satisfactory for a stationary observer with no lateral or rotational motion, the required SBP quickly increases when such motion is allowed. Multi-SLM designs, especially over curved surfaces, relieve high bandwidth requirements, and therefore, are strong candidates for futuristic holographic video displays. Holograms are quite robust to noise and quantization. It is demonstrated that either laser or light-emitting diode (LED) illumination is feasible. Current research momentum is increasing with many exciting and encouraging results.
Open Access
Feature issue of digital holography and 3D imaging (DH) introduction
(Optical Society of America (OSA), 2014-07) Hayasaki, Y.; Zhou, C.; Popescu, G.; Onural, Levent
The OSA Topical Meeting "Digital Holography and 3D Imaging (DH)," was held in Seattle, Washington, July 13-17, 2014. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. This year Optics Express (OE) and AO jointly decided to have one such feature issue in each journal. The DH meeting will continue in the future, as expected, and the next meeting is scheduled to be held on 24-28 May 2015, in Shanghai Institute of Optics and Fine Mechanics, Shanghai, China. © 2014 Optical Society of America
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
Preface
(Springer, New York, 2016) Healy, J. J.; Kutay, M. A.; Özaktaş, Haldun M.; Sheridan, J. T.; Healy, J. J.; Kutay, M. A.; Özaktaş, Haldun M.; Sheridan, J. T.
Open Access
Processing of optically-captured digital holograms for three-dimensional display
(2009-04) Naughton, T.J.; Kreis, T.; Onural, Levent; Ferraro, P.; Depeursinge, C.; Emery, Y.; Hennelly, B. M.; Kujawiñska, M.
In digital holography, holograms are usually optically captured and then two-dimensional slices of the reconstruction volume are reconstructed by computer and displayed on a two-dimensional display. When the recording is of a three-dimensional scene then such two-dimensional display becomes restrictive. We outline our progress on capturing larger ranges of perspectives of three-dimensional scenes, and our progress on four approaches to better visualise this three-dimensional information encoded in the digital holograms. The research has been performed within a European Commission funded research project dedicated the capture, processing, transmission, and display of real-world 3D and 4D scenes using digital holography. © 2009 SPIE.
Open Access
Quality comparison and acceleration for digital hologram generation method based on segmentation
(IEEE, 2009) Kang, Hoonjong; Yaraş, Fahri; Onural, Levent
A 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.
Open Access
Some mathematical properties of the uniformly sampled quadratic phase function and associated issues in digital Fresnel diffraction simulations
(SPIE - International Society for Optical Engineering, 2004) Onural, L.
The quadratic phase function is fundamental in describing and computing wave-propagation-related phenomena under the Fresnel approximation; it is also frequently used in many signal processing algorithms. This function has interesting properties and Fourier transform relations. For example, the Fourier transform of the sampled chirp is also a sampled chirp for some sampling rates. These properties are essential in interpreting the aliasing and its effects as a consequence of sampling of the quadratic phase function, and lead to interesting and efficient algorithms to simulate Fresnel diffraction. For example, it is possible to construct discrete Fourier transform (DFT)-based algorithms to compute exact continuous Fresnel diffraction patterns of continuous, not necessarily, periodic masks at some specific distances. © 2004 Society of Photo-Optical Instrumentation Engineers.
Open Access
State of the art in holographic displays: a survey
(IEEE, 2010-05-27) Yaraş, F.; Kang, H.; Onural, L.
True-3D imaging and display systems are based on physical duplication of light distribution. Holography is a true-3D technique. There are significant developments in electro-holographic displays in recent years. Liquid crystal, liquid crystal on silicon, optically addressed, mirror-based, holographic polymer-dispersed, and acousto-optic devices are used as holographic displays. There are complete electro-holographic display systems and some of them are already commercialized.