Browsing by Subject "Holography"
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Item Open Access A aurvey of signal processing problems and tools in holographic three-dimensional television(Institute of Electrical and Electronics Engineers, 2007) Onural, L.; Gotchev, A.; Özaktaş, Haldun M.; Stoykova, E.Diffraction and holography are fertile areas for application of signal theory and processing. Recent work on 3DTV displays has posed particularly challenging signal processing problems. Various procedures to compute Rayleigh-Sommerfeld, Fresnel and Fraunhofer diffraction exist in the literature. Diffraction between parallel planes and tilted planes can be efficiently computed. Discretization and quantization of diffraction fields yield interesting theoretical and practical results, and allow efficient schemes compared to commonly used Nyquist sampling. The literature on computer-generated holography provides a good resource for holographic 3DTV related issues. Fast algorithms to compute Fourier, Walsh-Hadamard, fractional Fourier, linear canonical, Fresnel, and wavelet transforms, as well as optimization-based techniques such as best orthogonal basis, matching pursuit, basis pursuit etc., are especially relevant signal processing techniques for wave propagation, diffraction, holography, and related problems. Atomic decompositions, multiresolution techniques, Gabor functions, and Wigner distributions are among the signal processing techniques which have or may be applied to problems in optics. Research aimed at solving such problems at the intersection of wave optics and signal processing promises not only to facilitate the development of 3DTV systems, but also to contribute to fundamental advances in optics and signal processing theory.Item Open Access Computation of holographic patterns between tilted planes(SPIE - International Society for Optical Engineering, 2006-05) Esmer, Gökhan Bora; Onural, LeventComputation 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°.Item Open Access Design of a 360-degree holographic 3D video display using commonly available display panels and a paraboloid mirror(SPIE, 2017) Onural, LeventEven barely acceptable quality holographic 3D video displays require hundreds of mega pixels with a pixel size in the order of a fraction of a micrometer, when conventional flat panel SLM arrangement is used. Smaller pixel sizes are essential to get larger diffraction angles. Common flat display panels, however, have pixel sizes in the order of tens of micrometers, and this results in diffraction angles in the order of one degree. Here in this design, an array of commonly available (similar to high-end mobile phone display panels) flat display panels, is used. Each flat panel, as an element of the array, directs its outgoing low-diffraction angle light beam to corresponding small portion of a large size paraboloid mirror; the mirror then reflects the slowly-expanding, information carrying beam to direct it at a certain exit angle; this beam constitutes a portion of the final real ghost-like 3D holographic image. The collection of those components from all such flat display panels cover the entire 360-degrees and thus constitute the final real 3D table-top holographic display with a 360-degrees viewing angle. The size of the resultant display is smaller compared to the physical size of the paraboloid mirror, or the overall size of the display panel array; however, an acceptable size table top display can be easily constructed for living-room viewing. A matching camera can also be designed by reversing the optical paths and by replacing the flat display panels by flat wavefront capture devices.Item Open Access Detection of Calcium-induced morphological changes on RBCs by digital holographic microscopy and blinking optical tweezers(IEEE, 2016) Rad, V. F.; Tavakkoli, R.; Moradi, Ali-Reza; Anand, A.; Javidi, B.Ca+2 level in the circulating red blood cells (RBCs) takes part not only in controlling biophysical properties, but also affects the membrane composition, and its morphological and rheological properties. Excessive accumulation of Ca2+ within the cells is associated with a number of important pathological diseases. In this paper, by the use of digital holographic microscopy (DHM), we quantitatively analyzed the volumetric behavior of RBC membrane under influence of excess Calcium ions. DHM in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes 3D information on the morphology variation of the cells at arbitrary time scales is obtained. Individual cells are immobilized by the use of optical tweezers and are monitored live with DHM system, while the concentration of Ca2+ ions in the buffer is changed simultaneously. We utilized blinking optical tweezers, by inserting an optical chopper to modulate intensity of the trapping laser beam. Blinking optical tweezers, while keeping the cell trapped during the experiments, ensures of minimizing the photo-damage of trapping laser beam on the cell. Our experimental results are in agreement with previous biological studies and predictions, and experimental observations of living RBCs under Ca2+ influence.Item Open Access Diffraction and holography from a signal processing perspective(SPIE, 2006) Onural, Levent; Özaktaş, Haldun M.The fact that plane waves are solutions of the Helmholtz equation in free space allows us to write the exact solution to the diffraction problem as a superposition of plane waves. The solution of other related problems can also be expressed in similar forms. These forms are very well suited for directly importing various signal processing tools to diffraction related problems. Another signal processing-diffraction link is the application of novel sampling theorems and procedures in signal processing to diffraction for the purpose of more convenient and efficient discrete representation and the use of associated computational algorithms. Another noteworthy link between optics and signal processing is the fractional Fourier transform. Revisiting diffraction from a modern signal processing perspectiv is likely to yield both interesting viewpoints and improved techniques.Item 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, LeventThe 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 AmericaItem Open Access Microsphere-Assisted Super-Resolved Mirau Digital Holographic Microscopy for Cell Identification(OSA - The Optical Society, 2017) Aakhte, M.; Abbasian, V.; Akhlaghi, E. A.; Moradi, A. R.; Anand, A.; Javidi, B.In this paper, we use a glass microsphere incorporated into a digital holographic microscope to increase the effective resolution of the system, aiming at precise cell identification. A Mirau interferometric objective is employed in the experiments, which can be used for a common-path digital holographic microscopy (DHMicroscopy) arrangement. High-magnification Mirau objectives are expensive and suffer from low working distances, yet the commonly used low-magnification Mirau objectives do not have high lateral resolutions. We show that by placing a glass microsphere within the working distance of a low-magnification Mirau objective, its effective numerical aperture can be increased, leading to super-resolved three-dimensional images. The improvement in the lateral resolution depends on the size and vertical position of microsphere, and by varying these parameters, the lateral resolution and magnification may be adjusted. We used the information from the super-resolution DHMicroscopy to identify thalassemia minor red blood cells (tRBCs). Identification is done by comparing the volumetric measurements with those of healthy RBCs. Our results show that microsphere-assisted super-resolved Mirau DHMicroscopy, being common path and off-axis in nature, has the potential to serve as a benchtop device for cell identification and biomedical measurements.Item Open Access A new approach to holographic video imaging: principles and simulations(SPIE, 1992) Onural, Levent; Bozdağı, Gözde; Atalar, AbdullahAs the importance of 3-dimensional information displays in many fields increases, more attention is given to holographic displays. Different kinds of holographic displays are reported in the literature, but the resolution of the available display media is not sufficient to support the extraordinary spatial detail of holograms. In this paper, we propose a new acousto-optical holographic display device which solves significantly the display resolution and the refreshing problems that are common to available holographic displays. The technique is based on the reproduction of the hologram using traveling surface waves. The SAW device that is used as the medium of display has an array of electrodes attached to it. An electrical signal applied to one of these electrodes generates an acoustical wave propagating on the surface of the crystal where the electrodes are the sources. If signals are applied to all of the electrodes simultaneously, propagating waves from the electrodes superpose to form a time-varying surface field pattern on the crystal. This pattern, at a specific time, forms the hologram. The signals which should be applied to the electrodes, in order to have a specified field pattern on the crystal at a specified time instant are found through a mathematical inversion relation. The inversion relationship is derived from the underlying physics. Computer simulations of the proposed TV display show that the proposed system will work as desired. In addition, our preliminary studies show that the proposed system can be constructed with the available acoustical, optical, electronic technology, and with the application of digital signal processing techniques.Item Open Access New high-resolution display device for holographic three-dimensional video: principles and simulations(SPIE, 1994) Onural, L.; Bozdağı, G.; Atalar, AbdullahA new acousto-optical holographic display device, which is expected to solve the display resolution and refresh problems that are common to available holographic displays, is proposed. The device is based on the reproduction of a hologram as a surface pattern using traveling surface acoustic waves (SAWs). There is an array of electrodes attached to the SAW device. An electrical signal applied to any one of these electrodes generates an acoustical wave propagating on the surface of the crystal. If signals are applied to all of the electrodes simultaneously, propagating waves from the electrodes superpose to form a time-varying SAW pattern on the crystal. This pattern forms the hologram at a specific time. The signals that should be applied to the electrodes are found through a mathematical inversion relation that is derived from the underlying physics. The inversion relation is checked by computer simulations. Simulations also show that the image quality of the proposed 3-D TV display is satisfactory.Item Open Access A novel approach to 3-dimensional holographic television display: principles and simulations(IEEE, 1992-03) Bozdağı, Gözde; Onural, Levent; Atalar, AbdullahThe authors present a new technique for the display end of a holographic three-dimensional television system and describe the computer simulations. The technique is based on the reproduction of the desired pattern, in this case the hologram, using traveling surface waves. The proposed method is simpler and more efficient than the methods available in the literature and it solves the display resolution and refreshing rate problems completely. Simulations show that the proposed system will work as desired when implemented in real time.Item Open Access An optical microcantilever with integrated grating coupler(IEEE, 2009-06) Olcum, Selim; Karademir, Ertuğrul; Taş. Vahdettin; Akça, İmran; Kocabaş, Aşkın; Atalar, Abdullah; Aydınlı, AydınlıIn this paper, we have fabricated an optical cantilever with an integrated grating coupler. We have used an inexpensive and repeatable method for integrating the grating to the silicon cantilever with a microfabrication compatible process. The sensitivity of the method can be further increased by integrating the detection circuitry onto the cantilever substrate. We believe that this is a promising method for sensing applications which provide a simple yet sensitive measurement technique using microcantilevers.Item Open Access Optimal image restoration with the fractional Fourier transform(OSA - The Optical Society, 1998-04) Kutay, M. A.; Özaktaş, Haldun M.The classical Wiener filter, which can be implemented in O(N log N) time, is suited best for space-invariant degradation models and space-invariant signal and noise characteristics. For space-varying degradations and nonstationary processes, however, the optimal linear estimate requires O(N2) time for implementation. Optimal filtering in fractional Fourier domains permits reduction of the error compared with ordinary Fourier domain Wiener filtering for certain types of degradation and noise while requiring only O(N log N) implementation time. The amount of reduction in error depends on the signal and noise statistics as well as on the degradation model. The largest improvements are typically obtained for chirplike degradations and noise, but other types of degradation and noise may also benefit substantially from the method (e.g., nonconstant velocity motion blur and degradation by inhomegeneous atmospheric turbulence). In any event, these reductions are achieved at no additional cost. © 1998 Optical Society of America.Item Open Access An overview of research in 3DTV(IEEE, 2007) Onural, Levent3DTV 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.Item Open Access Signal processing issues in diffraction and holographic 3DTV(Elsevier BV, 2007) Onural, L.; Özaktaş, Haldun M.Image capture and image display will most likely be decoupled in future 3DTV systems. Due to the need to convert abstract representations of 3D images to display driver signals, and to explicitly consider optical diffraction and propagation effects, it is expected that signal processing issues will be of fundamental importance in 3DTV systems. Since diffraction between two parallel planes can be represented as a 2D linear shift-invariant system, various signal processing techniques naturally play an important role. Diffraction between tilted planes can also be modeled as a relatively simple system, leading to efficient discrete computations. Two fundamental problems are digital computation of the optical field arising from a 3D object, and finding the driver signals for a given optical display device which will then generate a desired optical field in space. The discretization of optical signals leads to several interesting issues; for example, it is possible to violate the Nyquist rate while sampling, but still achieve full reconstruction. The fractional Fourier transform is another signal processing tool which finds applications in optical wave propagation.Item Open Access Trends in development of dynamic holographic displays(SPIE, 2006) Sainov, V. C.; Stoykova, E. V.; Onural, Levent; Özaktaş, H. M.Creation of a dynamic 3-D display based on holography, in which a 3-D scene is encoded in terms of optical diffraction, transformed into the fringe patterns of the hologram that is further converted into a signal for a spatial light modulator (SLM) and displayed in real time, is an extremely challenging enterprise. There are various approaches targeted to solve associated problems.