Digital Holography

Sevgili okuyucular, 2015 yılı için hazırladığımız "Eğitim Teknolojileri Okumaları" el kitabı sizlerden gelen katkı ve değerlendirmeler doğrultusunda, bizleri Eğitim Teknolojileri Okumaları 2016 çalışmasını gerçekleştirmeye yönlendirdi. Bu çalışmamızı 2015 yılında olduğu gibi yine IETC-TOJET işbirliği ile sizlere ulaştırıyoruz. Ülkemizin farklı üniversitelerinden 61 akademisyenin 35 bölüme katkıda bulunduğu okumalar alanımızdaki hareketliliğe uygun olarak güncel konuları içermektedir. Bu çalışmanın sizlere ulaşmasındaki katkısından dolayı IETC-TOJET ailesine ve tüm çalışmaların kontrolünü gerçekleştiren Dr. Gökhan DAĞHAN'a sonsuz teşekkürlerimizi sunarız.

In this paper, the phenomenon of virtual idol Hatsune Miku will be analyzed in the context of critical theory, emerging technologies, and theory of digital art practices. The first part focuses on the phenomenon of the virtual celebrity seen as Deleuze and Guattari’s concept of ‘body without organs.’ The second part examines how the state-of-the-art technologies have enabled the existence of Hatsune Miku who is simultaneously a corporate software product, a pop icon, a performance artist, and a collaborative multimedia artwork. Based on the reading of Hatsune Miku as a hybrid product emerging from the fusion of arts and IT, the last part revolves around the concept of ‘aura’ (Benjamin) generated by virtual idol’s presence. Finally, the notion of hyperterminality is introduced not only to differentiate between entities/identities appearing on the surface of the screen and those virtual constructs co-existing with us in the spaces of physical reality, but also to explore how these newly emerging “phygital” entities transform the existing conceptions of body and identity.

Progress in image sensors and computation power has fueled studies to improve acquisition, processing, and analysis of 3D streams along with 3D scenes/objects reconstruction. The role of motion compensation/ motion estimation (MCME) in 3D TV from end-to-end user is investigated in this chapter. Motion vectors (MVs) are closely related to the concept of disparities, and they can help improving dynamic scene acquisition, content creation, 2D to 3D conversion, compression coding, decompression/decoding, scene rendering, error concealment, virtual/augmented reality handling, intelligent content retrieval, and displaying. Although there are different 3D shape extraction methods, this chapter focuses mostly on shape-from-motion (SfM) techniques due to their relevance to 3D TV. SfM extraction can restore 3D shape information from a single camera data.

The emerging technological developments across various scientific fields have brought about radical changes in the ways we perceive and define what it means to be human in today"s highly technologically oriented society. Advancements in robotics, AI research, molecular biology, genetic engineering, nanotechnology, medicine, etc., are mostly still in an experimental phase but it is likely that they will become a part of our daily experience. However, human enhancement and emergence of autonomous artificial beings have long been a part of futures imagined in SF and cyberpunk. While focusing on the phenomenon of cyborg as a product of both social reality and fiction, this paper will attempt to offer a new perspective on selected SF and cyberpunk narratives by treating them not only as fictions but as theories of the future as well.

Phase-only holographic projection has prompted
a great deal of research and has often been cited as a desirable
method of 2-D image formation, since such a technique offers
a number of advantages over conventional imaging projection
technology [1], [2]. Although holographic image formation was
demonstrated some forty years ago [3], efforts at realizing a
real-time 2-D video projection system based on this technique
have not been successful, principally due to the computational
complexity of calculating diffraction patterns in real time and
the poor quality of the resultant images. In this paper, a new
approach to hologram generation and display is presented which
overcomes both of these problems, enabling—for the first time—a high-quality real-time holographic projector.

The emerging technological developments across various scientific fields have brought about radical changes in the ways we perceive and define what it means to be human in today’s highly technologically oriented society. Advancements in robotics, AI research, molecular biology, genetic engineering, nanotechnology, medicine, etc., are mostly still in an experimental phase, but it is likely that they will become a part of our daily experience. However, human enhancement and emergence of autonomous artificial beings have long been a part of futures imagined in SF and cyberpunk. While focusing on the phenomenon of cyborg as a product of both social reality and fiction, this chapter will attempt to offer a new perspective on selected SF and cyberpunk narratives by treating them not only as fictions but as theories of the future as well. Furthermore, selected examples of the existing real-life cyborgs will show that SF narratives are not merely limited to the scope of imagination but are a constituent part of lived experience, thus blurring the boundaries between reality and fiction.

We present a technique for performing three-dimensional (3D) pattern recognition by use of in-line digital holography. The complex amplitude distribution generated by a 3D object at an arbitrary plane located in the Fresnel diffraction region is recorded by phase-shifting interferometry. The digital hologram contains information about the 3D object's shape, location, and orientation. This information allows us to perform 3D pattern-recognition techniques with high discrimination and to measure 3D orientation changes. Experimental results are presented. 

It is shown that the lens count in a Fourier holographic projector can be reduced by encoding the equivalent lens
power in sets of Fresnel holograms. By using appropriately calculated Fresnel holograms in a reflective configuration
to effectively share a lens between the beam-expansion and demagnification stages of a holographic projector, a
reduction in lens count from four to one is demonstrated.

This paper assesses the ergonomics of the air tap, a 3D gesture used to interact with the Hololens™, a head-mounted optical see-through display being developed by Microsoft™. After reviewing ergonomics literature we found the air tap appeared to be outside of known anthropometric and biomechanical limits and tolerances. Because the Hololens was unavailable for testing at the time of writing, the air tap was evaluated using methods that support general, observational data. The Rapid Entire Body Assessment (REBA), Rapid Upper Body Assessment (RULA) and Novel Ergonomic Postural Assessment (NERPA) methods were used to assess the gesture as observed in four videos. For all methods, higher scores suggested further investigation was required to avoid risk of developing musculoskeletal disorders. Although the neck trunk and leg portion of the REBA score was low, the arm and wrist portions gained more points. This was further reflected in overall high RULA and NERPA scores which focused more on the upper region of the body. Although these findings cannot be used to accurately assess whether the air tap suffers from poor ergonomics or puts the user at risk of developing musculoskeletal disorders, they do suggest the gesture might benefit from a more thorough investigation. This paper concludes by proposing future research into developing and validating an ergonomic framework designers and developers can use to develop 3D gestures.

Course Description: This course investigates the use of three-dimensional virtual media in museum, gallery, and online exhibition contexts, with an emphasis on Virtual Reality (VR). This course prepares students both practically and conceptually to work with 3D virtual media in professional contexts of the artworld, especially in museums, art galleries, and online exhibition contexts. It provides students with an understanding of 3D virtual media technology today and the directions it may take in the future, and trains them to think critically about its most effective usage, especially in museum environments.

RESUMEN:
El presente artículo se ocupa de la novela de Adolfo Bioy Casares La invención de Morel (1949) novela fundacional de la literatura de anticipación, en la que a través de la ficción científica, policíaca y amatoria, concurren los tópicos del ingenio técnico, la reduplicación de la vida, los periplos de inmortalidad, los archivos de imágenes, los simulacros y finalmente los hologramas, alumbrando el estatuto ontológico de las imágenes en la nueva ecología de medios, cuestiones problematizadas por teóricos de la imagen como Jean Baudrillard, Paul Virilio o Susan Sontag. Dando lugar, finalmente, a una reflexión en torno al complejo paso de lo real a lo virtual en el cual el mundo de las imágenes amenaza por suplantar al mundo real.
En referencia a 'La invención de Morel':
“He discutido con su autor los pormenores de su trama, la he releído;
no me parece una imprecisión o una hipérbole calificarla de perfecta”. Jorge Luis Borges.

Dr. Adolfo Vásquez Rocca

In this study, we propose a method for calculating a large scale high resolution synthetic color
rainbow hologram using the frequency domain splicing technique. This method is motivated by
the observation that if the plane wave is used as the reference light, the spectra of the three
primary colors of the object light in the color rainbow hologram frequency domain are mutually
separated frequency bands. According to this principle, the color views of different angles of a
colored 3D object are separated and interpolated, and 2D Fourier transform is performed to form
an object light spectrum distribution of the color rainbow hologram. Following the operation,
efficient one-dimensional Fourier inverse transform in the row and column directions of the
frequency is conducted. The proposed method is able to achieve a significant boost in terms of
large scale high resolution hologram computational speed. We demonstrate that a synthetic color
rainbow hologram with a size of 30 × 30 mm and a resolution of 94 340 × 94 340 is achieved
through our holographic printing system with an unprecedented time of only 25 min. The
method is also able to achieve a visually appealing computer generated white light color rainbow
hologram, thus having great potential to be used for a practical holographic 3D display.

We applied phase-shifting digital holography to microscopy by deriving the complex amplitude of light scattered from microscopic three-dimensional objects through a microscope objective by video camera recording, phaseshifting analysis, and computer reconstruction. This method requires no mechanical movement and provides a f lexible display and quantitative evaluation of the reconstructed images. A theory of image formation and experimental verification with specimens are described.

An information security method that uses a digital holographic technique is presented. An encrypted image is stored as a digital hologram. The decryption key is also stored as a digital hologram. The encrypted image can be electrically decrypted by use of the digital hologram of the key. This security technique provides secure storage and data transmission. Experimental results are presented to demonstrate the proposed method.

Direct-write digital holographic printing (DWDH) is a technique by which color reflection holograms or white-light transmission holograms of an object or a scene can be produced out of a series of suitable perspective images. The technique is well suited to the production of scaled up or down holographic images of objects or scenes allowing at the same time slight movements, animation, layering and multiple channels to be encoded. The series of perspective images can be digitally captured in video or photographs or be produced by rendering frames of a 3d model with the aid of 3d computer graphics software. The Hellenic Institute of Holography (HiH) has been testing the process since 2009 producing suitable series of perspective images by using most of the available image capturing techniques and subsequently printing rendered data by Geola Digital for the visualization of artworks and historic sites. The produced holograms range from small artworks to large scale scenes incorporating in most cases layering, movement or animation. It is of great significance that the video or photographically captured perspective views of a real object or scene, as processed by Geola, result in holograms which recreate 3d images with details resolution far better than those of a 3D model produced from the 2D-to-3D conversion of the same set of perspective views. In this paper we present DWDH printed holograms of various artworks and historic sites, the various methods used for capturing perspective views and the underlying printing processes for eventual use in cultural heritage preservation.

Spatial light modulators (SLM) are devices used to modulate amplitude, phase or polarization of a light wave in space and time. Current SLMs are based either on MEMS (micro-electro-mechanical system) or LCD (liquid crystal display) technology. Here we report on the parameters, trends in development and applications of phase SLMs based on liquid crystal on silicon (LCoS) technology. LCoS technology was developed for front and rear projection systems competing with AMLCD (active matrix LCD) and DMD (Digital Mirror Device) SLM. The reflective arrangement due to silicon backplane allows to put a high number of pixels in a small panel, keeping the fill-factor ratio high even for micron-sized pixels. For coherent photonics applications the most important type of LCoS SLM is a phase modulator. In the paper at first we describe the typical parameters of this device and the methods for its calibration. Later we present a review of applications of phase LCoS SLMs in imaging, metrology and beam manipulation, developed by the authors as well as known from the literature. These include active and adaptive interferometers, a smart holographic camera and holographic display, microscopy modified in illuminating and imaging paths and active sensors.

An advanced Digital Holographic Image Processing System (ADHIPS) is presented. ADHIPS incorporates novel compression and processing methods that opens up the potentials of Digital Holography to a wider range of diverse applications.  A comprehensive set of examples are included that demonstrate the performance of the new methods on real and simulated digital holographic data. Three interference patterns are recorded and holographic information is extracted from them using phase-shifting interferometry with the advances of further enhanced propagation and recording processing in the Fractional Fourier domain. The new scheme makes use of standard JPEG (Joint Photographic Experts Group) and standard JPEG-2000 image compression techniques on the recorded interference patterns.  High compression rates are achieved for good reconstructed object image quality. The use of the proposed method is experimentally verified on real holographic data. Results for compression rates of approximately 27 for a normalized root mean square error of approximately 0.7 are demonstrated. The similarities and differences between the Fresnel Transform, used in conventional Holography, and the new Fractional Fourier Transform are analytically described. The Fresnel Transform is replaced by the Fractional Fourier Transform in ADHIPS and demonstrated on real and simulated digital holograms. The numerous benefits of using the Fractional Fourier Transform in the ADHIPS in placed of the Fresnel Transform are described.

Holographic imaging offers a reliable and fast method to capture the complete 3-D information of the scene from a single perspective. We review our recently proposed single-channel optical system for generating digital Fresnel holograms of 3-D real-existing objects illuminated by incoherent light. In this motionless holographic technique, light is reflected, or emitted, from a 3-D object, propagates through a spatial light modulator (SLM), and is recorded by a digital camera. The SLM is used as a beam-splitter of the single-channel incoherent interferometer, such that each spherical beam originated from each object point is split into two spherical beams with two different curve radiuses. Incoherent sum of the entire interferences between all the couples of spherical beams creates the Fresnel hologram of the observed 3-D object. When this hologram is reconstructed in the computer, the 3D properties of the object are revealed.

In this study, we demonstrate a practical synthetic hologram with a size of 30 mm × 30 mm at resolution of 94340 × 94340. The high-definition large-scale computer-generated full-parallax synthetic hologram is achieved through frequency mosaic with different perspective images. The sparsity characteristics mosaic frequency of full parallax synthetic hologram is analyzed for reducing the complexity of computation. Following elimination of the sparsity, the hologram is calculated by normalization of 2D inverse Fourier transform of the mosaic frequency. The error and object point size are analyzed and we conclude that the error is sufficiently small for human visual perception given that parallax angle and object depth are within acceptable limits.

The point spread function is widely used to characterize the three-dimensional imaging capabilities of an optical system. Usually, attention is paid only to the intensity point spread function, whereas the phase point spread function is most often neglected because the phase information is not retrieved in noninterferometric imaging systems. However, phase point spread functions are needed to evaluate phasesensitive imaging systems and we believe that phase data can play an essential role in the full aberrations' characterization. In this paper, standard diffraction models have been used for the computation of the complex amplitude point spread function. In particular, the Debye vectorial model has been used to compute the amplitude point spread function of ×63/0.85 and ×100/1.3 microscope objectives, exemplifying the phase point spread function specific for each polarization component of the electromagnetic field. The effect of aberrations on the phase point spread function is then analyzed for a microscope objective used under nondesigned conditions, by developing the Gibson model , modified to compute the three-dimensional amplitude point spread function in amplitude and phase. The results have revealed a novel anomalous phase behaviour in the presence of spherical aberration, providing access to the quantification of the aberrations.

Recording digital holograms without wave interference simplifies the optical systems, increases their power efficiency and avoids complicated aligning procedures. We propose and demonstrate a new technique of digital hologram acquisition without two-wave interference. Incoherent light emitted from an object propagates through a random-like coded phase mask and recorded directly without interference by a digital camera. In the training stage of the system, a point spread hologram (PSH) is first recorded by modulating the light diffracted from a point object by the coded phase masks. At least two different masks should be used to record two different intensity distributions at all possible axial locations. The various recorded patterns at every axial location are superposed in the computer to obtain a complex valued PSH library cataloged to its axial location. Following the training stage, an object is placed within the axial boundaries of the PSH library and the light diffracted from the object is once again modulated by the same phase masks. The intensity patterns are recorded and superposed exactly as the PSH to yield a complex hologram of the object. The object information at any particular plane is reconstructed by a cross-correlation between the complex valued hologram and the appropriate element of the PSH library. The characteristics and the performance of the proposed system were compared with an equivalent regular imaging system.

Dennis Gabor devised a new concept for optical imaging in 1947 that went by a variety of names over the following decade: holoscopy, wavefront reconstruction, interference microscopy, diffraction microscopy and Gaboroscopy. A well-connected and creative research engineer, Gabor worked actively to publicize and exploit his concept, but the scheme failed to capture the interest of many researchers. Gabor’s theory was repeatedly deemed unintuitive and baffling; the technique was appraised by his contemporaries to be of dubious practicality and, at best, constrained to a narrow branch of science. By the late 1950s, Gabor’s subject had been assessed by its handful of practitioners to be a white elephant. Nevertheless, the concept was later rehabilitated by the research of Emmett Leith and Juris Upatnieks at the University of Michigan, and Yury Denisyuk at the Vavilov Institute in Leningrad. What had been judged a failure was recast as a success: evaluations of Gabor’s work were transformed during the 1960s, when it was represented as the foundation on which to construct the new and distinctly different subject of holography, a re-evaluation that gained the Nobel Prize for Physics for Gabor alone in 1971. This paper focuses on the difficulties experienced in constructing a meaningful subject, a practical application and a viable technical community from Gabor’s ideas during the decade 1947-1957.

Dr. Denis Gabor most probably could not think of every usage of the hologram when he invented it, but he might had a strong feeling that he opened a new window for human being. History has shown that it was not only a scientific discovery, but it also led to a new philosophical explanation of the universe. Although it has not been a century, the technology of the holography already passed the horizon of his vision. Countless inventions and applications on holography have had remarkable influence on our daily lives. We have been using holograms in many places such as security, entertainment, measurement, training and so on. Why wouldn"t we use it for our most essential need which was map? As cartographers we have been discussing this question for more than ten years. Finally, we could achieve to find a new way of presentation of cartographic productions. The restrictions of the conventional medium, the paper, have not obstructed the cartographers to manufacture more visual contents and cognitive products, by using the power of the computers which is unquestionable. The rise of Paper-Era is reaching the saturation point and has been limiting the artists, publishers and cartographers. In this article, we will discuss the usage of holography in a cartographic perspective; interrogate the advantages and disadvantages of the hologram as a hard copy medium, evaluate a prototype of holographic map which is produced by General Command of Mapping, Turkey and exposed by Hangyo International Corp., Korea Republic. Finally what we suggest the future of cartographic publishing.

An approach is proposed for removing the wave front curvature introduced by the microscope imaging objective in digital holography, which otherwise hinders the phase contrast imaging at reconstruction planes. The unwanted curvature is compensated by evaluating a correcting wave front at the hologram plane with no need for knowledge of the optical parameters, focal length of the imaging lens, or distances in the setup. Most importantly it is shown that a correction effect can be obtained at all reconstruction planes. Three different methods have been applied to evaluate the correction wave front and the methods are discussed in detail. The proposed approach is demonstrated by applying digital holography as a method of coherent microscopy for imaging amplitude and phase contrast of microstructures.

Digital holography is an imaging technique that enables recovery of topographic 3D information about an object under investigation. In digital holography, an interference pattern is recorded on a digital camera. Therefore, quantization of the recorded hologram is an integral part of the imaging process. We study the influence of quantization error in the recorded holograms on the fidelity of both the intensity and phase of the reconstructed image. We limit our analysis to the case of lensless Fourier off-axis digital holograms. We derive a theoretical model to predict the effect of quantization noise and we validate this model using experimental results. Based on this, we also show how the resultant noise in the reconstructed image, as well as the speckle that is inherent in digital holography, can be conveniently suppressed by standard speckle reduction techniques. We show that high-quality images can be obtained from binary holograms when speckle reduction is performed.

A technique based on superresolution by digital holographic microscopic imaging is presented. We used a two dimensional (2-D) vertical-cavity self-emitting laser (VCSEL) array as spherical-wave illumination sources. The method is defined in terms of an incoherent superposition of tilted wavefronts. The tilted spherical wave originating from the 2-D VCSEL elements illuminates the target in transmission mode to obtain a hologram in a Mach-Zehnder interferometer configuration. Superresolved images of the input object above the common lens diffraction limit are generated by sequential recording of the individual holograms and numerical reconstruction of the image with the extended spatial frequency range. We have experimentally tested the approach for a microscope objective with an exact 2-D reconstruction image of the input object. The proposed approach has implementation advantages for applications in biological imaging or the microelectronic industry in which structured targets are being inspected.

We demonstrate a novel computational method for high resolution image recovery from a single digital hologram frame. The complex object field is obtained from the recorded hologram by solving a constrained optimization problem. This approach which is unlike the physical hologram replay process is shown to provide high quality image recovery even when the dc and the cross terms in the hologram overlap in the Fourier domain. Experimental results are shown for a Fresnel zone hologram of a resolution chart, intentionally recorded with a small off-axis reference beam angle. Excellent image recovery is observed without the presence of dc or twin image terms and with minimal speckle noise.

| This paper presents an overview of the potential of free space optical technology in information security, encryption, and authentication. Optical waveform posses many degrees of freedom such as amplitude, phase, polarization, spectral content, and multiplexing which can be combined in different ways to make the information encoding more secure. This paper reviews optical techniques for encryption and security of two-dimensional and three-dimensional data.

We discuss quantization effects of hologram recording on the quality of reconstructed images in phase-shifting digital holography. We vary bit depths of phase-shifted holograms in both numerical simulation and experiments and then derived the complex amplitude, which is subjected to Fresnel transformation for the image reconstruction. The influence of bit-depth limitation in quantization has been demonstrated in a numerical simulation for spot-array patterns with linearly varying intensities and a continuous intensity object. The objects are provided with uniform and random phase modulation. In experiments, digital holograms are originally recorded at 8 bits and the bit depths are changed to deliver holograms at bit depths of 1 to 8 bits for the image reconstruction. The quality of the reconstructed images has been evaluated for the different quantization levels.

We report about the implementation of the 10Megapixel phase-only liquid crystal on silicon spatial light modulator for the visible and shortwave infrared spectral bands. The pixel pitch of the SLM is less than 4 micron. Experimental data for diffraction efficiency, reflectivity, phase response, flatness and temporal noises is provided.

Using an 850-nanometer-wavelength free-space optical (FSO) communications system of our own design, we acquired field data for the transmitted and received signals in fog at Point Loma, CA for a range of optical depths within the multiple-scattering regime. Statistical estimators for the atmospheric channel transfer function and the related coherency function were computed directly from the experimental data. We interpret the resulting channel transfer function estimates in terms of the physics of the atmospheric propagation channel and fog aerosol particle distributions. We investigate the behavior of the estimators using both real field-test data and simulated propagation data. We compare the fielddata channel transfer function estimates against the outputs from a computationally-intensive radiative-transfer theory model-based approach, which we also developed previously for the FSO multiplescattering atmospheric channel. Our results show that the data-driven channel transfer function estimates are in close agreement with the radiative transfer modeling, and provide comparable receiver signal detection performance improvements while being significantly less time and computationally-intensive.

Optical scanning holography (OSH) is a powerful holographic recording technique that employs a single-pixel photo-detector and 2D scanning mechanism to capture the hologram of a wide-view and 3D object. However, in OSH experiments, we found that 2D X-Y scanning mirrors would cause unavoidable magnification and lateral resolution issues in 3D recording or sectioning imaging. In this letter, we will discuss this problem both theoretically and experimentally. The experiment results show that our results have a good performance on these issues. Index Terms-Digital holography, optical scanning hologra-phy, computational imaging.

Digital holographic microscopy is an imaging modality that can digitally reconstruct the images of 3-D samples from a single hologram by digitally refocusing it through the entire 3-D sample volume. [27]
Deep learning, which uses multi-layered artificial neural networks, is a form of machine learning that has demonstrated significant advances in many fields, including natural language processing, image/video labeling and captioning. [26]

We show that digital holography can be combined easily with optical coherence tomography approach. Varying the reference path length is the means used to acquire a series of holograms at different depths, providing after reconstruction images of slices at different depths in the specimen thanks to the shortcoherence length of light source. A metallic object, covered by a 150᎑m-thick onion cell, is imaged with high resolution. Applications in ophthalmology are shown: structures of the anterior eye, the cornea, and the iris, are studied on enucleated porcine eyes. Tomographic images of the iris border close to the pupil were obtained 165 m underneath the eye surface.

Using the Chinese cosmological understanding of “shadow and soul” or ying hun (影魂), this chapter seeks to frame innovations in holographic technologies that facilitate the  stereoscopic re-projections of departed Hong Kong- and Taiwan-based transnational Chinese celebrities such as Bruce Lee, Wong Kar Kui and Teresa Teng. It argues that the rising popularity of such presentations in concerts and advertisements stems not just from the visual spectacle of these unprecedented animated holograms. Instead, audiences may be held by latent beliefs of the immanence of departed stars whose presences have been maintained by media technologies from the analogue phonogram of the past, to the digital performance capture and holographic representation of contemporary convergent media. Such developments provide new platforms for the ying hun of these personalities to be replayed and resurrected.

A lossy hologram compression method is investigated to compress three-dimensional (3-D) images holographically recorded with optical scanning holography. Without loss of major reconstruction details, results have shown that the lossy compression method is able to achieve high compression ratio of up to 100.

Holographic Displays (HDs) provide 3D images with all natural depth cues via computer generated holograms (CGHs) implemented on spatial light modulators (SLMs). HDs are coherent light processing systems based on interference and diffraction, thus they generally use laser light. However, laser sources are relatively expensive, available only at some particular wavelengths and difficult to miniaturize. In addition, highly coherent nature of laser light makes some undesired visual effects quite evident, such as speckle noise, interference due to stray light or defects of optical components. On the other hand, LED sources are available in variety of wavelengths, has small die size, and no speckle artifact. However, their finite spatial size introduce some degree of spatial incoherence in an HD system and degrade image resolution, which is the subject of the study in this paper. Our theoretical analysis indicates that the amount of resolution loss depends on the distance between hologram and SLM image planes. For some special configurations, the source size has no effect at all. We also performed experiments with different configurations using lasers and LEDs with different emission areas that vary from 50 µm to 200 µm, and determined Contrast Transfer Function (CTF) curves which agree well with our theoretical model. The results show that it is possible to find configurations where LEDs combined with pinholes almost preserve natural resolution limit of human eye while keeping the loss in light efficiency within tolerable limits.

In-line digital holography based on two-intensity measurements [Zhang et al. Opt. Lett. 29, 1787 (2004)], is modified by introducing a pi shifting in the reference phase. Such an improvement avoids the assumption that the object beam must be much weaker than the reference beam in strength and results in a simplified experimental implementation. Computer simulations and optical experiments are carried

We show how the reconstruction of digital holograms can be speeded up on ordinary computers by precomputing the chirp factor in the Fresnel transform for a given detector array size. The speedup in time is shown for various hologram sizes. We also run the same algorithm on a Nvidia GPU. The speedup and the error introduced due to quantizing to different levels is investigated. Additionally a variance based

Digital holograms recorded with a charge-coupled device array are numerically reconstructed in amplitude and phase through calculation of the Fresnel-Kirchhoff integral. The flexibility offered by the reconstruction process in digital holography allows exploitation of new possibilities of application in microscopy. Through the reconstruction process we will show that it is possible to control image parameters as focus distance, image size, and image resolution. Those explored potentialities open further the novel prospective of application of digital holography in single-and multiwavelengths operation either for display or metrological applications. We demonstrate the concept of controlling parameters in image reconstruction of digital holograms in some real situations for inspecting silicon microelectronic-mechanical systems structures.

We propose a full color computer generated holographic near-eye display (NED) based on white light illumination. The method inspired from color rainbow holography is used for calculation of 2D and 3D color holograms. The parameters of the color hologram calculation are designed based on the parameters of the spatial light modulator (SLM) with 4K resolution. A slit type spatial filter is designed in frequency domain to extract red, green and blue frequency components for full color display. A NED system including a white light source, an achromatic collimating lens, a 4K SLM, a 4f optical filtering system, and an achromatic lens as eyepiece is designed and developed. The main contribution of this paper is the first time to apply the rainbow holography concept to the dynamic full color NED with a compact display system. The optical experiments prove the feasibility of the proposed method.

Advances in image sensors and evolution of digital computation is a strong stimulus for development and implementation of sophisticated methods for capturing, processing and analysis of 3-D data from dynamic scenes. Research on perspective time-varying 3-D scene capture technologies is important for the upcoming 3DTV displays. Methods such as shape-from-texture, shape-from-shading, shape-from-focus, and shape-from-motion extraction can restore 3-D shape information from a single camera data. The existing techniques for 3-D extraction from single-camera video sequences are especially useful for conversion of the already available vast mono-view content to the 3DTV systems. Sceneoriented single-camera methods such as human face reconstruction and facial motion analysis, body modeling and body motion tracking, and motion recognition solve efficiently a variety of tasks. 3-D multicamera dynamic acquisition and reconstruction, their hardware specifics including calibration and synchronization and software demands form another area of intensive research. Different classes of multiview stereo algorithms such as those based on cost function computing and optimization, fusing of multiple views, and feature-point reconstruction are possible candidates for dynamic 3-D reconstruction. High-resolution digital holography and pattern projection techniques such as coded light or fringe projection for real-time extraction of 3-D object positions and color information could manifest themselves as an alternative to traditional camera-based methods. Apart from all of these approaches, there also are some active imaging devices capable of 3-D extraction such as the 3-D time-of-flight camera, which provides 3-D image data of its environment by means of a modulated infrared light source.

Introducing a microscope objective in an interferometric setup induces a phase curvature on the resulting wavefront. In digital holography, the compensation of this curvature is often done by introducing an identical curvature in the reference arm and the hologram is then processed using a plane wave in the reconstruction. This physical compensation can be avoided, and several numerical methods exist to retrieve phase contrast images in which the microscope curvature is compensated. Usually, a digital array of complex numbers is introduced in the reconstruction process to perform this curvature correction. Different corrections are discussed in terms of their influence on the reconstructed image size and location in space. The results are presented according to two different expressions of the Fresnel transform, the single Fourier transform and convolution approaches, used to propagate the reconstructed wavefront from the hologram plane to the final image plane.

The concept of numerical parametric lenses (NPL) is introduced to achieve wavefront reconstruction in digital holography. It is shown that operations usually performed by optical components and described in ray geometrical optics, such as image shifting, magnification, and especially complete aberration compensation (phase aberrations and image distortion), can be mimicked by numerical computation of a NPL. Furthermore, we demonstrate that automatic one-dimensional or two-dimensional fitting procedures allow adjustment of the NPL parameters as expressed in terms of standard or Zernike polynomial coefficients. These coefficients can provide a quantitative evaluation of the aberrations generated by the specimen. Demonstration is given of the reconstruction of the topology of a microlens.

We present a digital holographic microscope that permits one to image polarization state. This technique results from the coupling of digital holographic microscopy and polarization digital holography. The interference between two orthogonally polarized reference waves and the wave transmitted by a microscopic sample, magnified by a microscope objective, is recorded on a CCD camera. The off-axis geometry permits one to reconstruct separately from this single hologram two wavefronts that are used to image the object-wave Jones vector. We applied this technique to image the birefringence of a bent fiber. To evaluate the precision of the phase-difference measurement, the birefringence induced by internal stress in an optical fiber is measured and compared to the birefringence profile captured by a standard method, which had been developed to obtain high-resolution birefringence profiles of optical fibers.