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Holographic optical element (HOE) recording technique using holographic printing is presented. Holographic printer has the potential to realize complex optical functions with high diffraction efficiency and provides wide field of view for augmented-reality near-eye display.

In this paper, potential distortions corresponding to the hologram printed by a holographic wave-front printer are analyzed. Potential distortions are classified as the magnification(demagnification) distortion, barrel distortion, pincushion distortion, SLM mounting distortion, and translation distortion, respectively. These distortions are grouped as the optics distortion, SLM mounting distortion and the translation distortion depending on the process of recording the hologram in the holographic wave-front printer. In order to evaluate each distortion, a distortion analysis method based on a local spatial frequency is proposed. Through the proposed method, a diffracted wavefield reconstructed from a quantitatively distorted hologram is theoretically analyzed, and the validity of this analysis is verified by applying the numerical reconstruction method. In the numerical reconstruction, a propagation of a distorted wavefield reconstructed from the quantitatively distorted hologram is confirmed and contributed to generate the distorted reconstruction plane, such as a focal cloud plane and a convergence plane, depending on the types of distortion.

Pointwise intensity-based statistical processing of dynamic laser speckle patterns formed on the surface of a diffusely reflecting object is perspective for monitoring of ingoing processes of physical or biological activity within the object. The output of the measurement is a two-dimensional map, which shows qualitatively regions of higher or lower activity on the object surface. In the paper, we have proposed transforming the captured 8-bit encoded speckle patterns into binary patterns by applying a pointwise threshold. Motivation behind this study is the need for an algorithm, which is robust to non-uniform illumination and offers lowered computational complexity as time and memory consumption. We showed by simulation and experiment that quality of the map obtained by processing of correlated binary patterns approached that achieved with 8-bit encoded patterns. We analyzed statistical behavior of the estimates built from binary patterns and proved applicability of a non-stochastic threshold as e.g. a constant intensity level at uniform illumination. The proposed algorithm was applied for processing polymer drop drying experimental data.

Some optical and mechanical distortions may occur in holographic wave front printer. The effect of these distortions on the optical reconstruction plane is analyzed

Comparison of rectangular and hexagonal hogel printing for holographic stereogram printer based on integral imaging is presented. The hexagonal hogel printing is efficient than rectangular hogel printing and enhances the reconstruction image quality. Numerical simulation and optical reconstructions are implemented.

In this paper, a depth-related uniform multiple wavefront recording plane (UM-WRP) method is proposed for enhancing the image quality of point cloud-based holograms. Conventional multiple WRP methods, based on full-color computer-generated holograms, experience a color uniformity problem caused by intensity distributions. To solve this problem, the proposed method generates depth-related WRPs to enhance color uniformity, thereby accelerating hologram generation using a uniform active area. The aim is to calculate depth-related WRPs with designed active area sizes that then propagate to the hologram. Compared with conventional multiple WRP methods, reconstructed images have significantly improved quality, as confirmed by numerical simulations and optical experiments.

Pointwise intensity-based algorithms are the most popular algorithms in dynamic laser speckle measurement of physical or biological activity. The output of this measurement is a two-dimensional map which qualitatively separates regions of higher or lower activity. In the paper, we have proposed filtering of activity maps to enhance visualization and to enable quantitative determination of activity time scales. As a first step, we have proved that the severe spatial fluctuations within the map resemble a signal-dependent noise. As a second step, we have illustrated implementation of the proposed idea by applying filters to non-normalized and normalized activity estimates derived from synthetic and experimental data. Statistical behavior of the estimates has been analyzed to choose the filter parameters, and substantial narrowing of the probability density functions of the estimates has been achieved after the filtering. The filtered maps exhibit an improved contrast and allowed for quantitative description of activity. publishedVersion

This paper presents design and implementation of a color wavefront holographic printer. The printer output is a white light viewable volume hologram composed as a two-dimensional (2-D) array of elemental holograms. The three-dimensional (3-D) input data for the printer are encoded as computer generated holograms (CGHs) displayed in succession on an amplitude type spatial light modulator. The printer optical head extracts and demagnifies the beam with the 3-D object information from the beam diffracted by the modulator to produce a small size elemental hologram. This allows for mosaic delivery of exposures at primary colors with each elemental hologram acting as a single color channel. Computer generation of digital contents is accelerated by design of a phase-added stereogram approach based on partitioning of each CGH. Bright 3-D reconstruction with a motion parallax at saturated colors from holograms of test objects is presented. The holograms are printed on a silver-halide emulsion. The achieved high quality proves feasibility of recording analog color volume holograms from digital contents by mosaic delivery of the primary colors. Two quality enhancement approaches are proposed and tested.

We introduce a synchronization scheme of multiple displays with high-definition for real-time interaction. The system could provide 720p 3D resolution with help of plural projection units, and the images among the projection units should be synchronized for real-time interaction.

Holographic and two-dimensional displays can be combined at the angular spectrum domain to provide three-dimensional image near fovea and two-dimensional image for periphery. This scheme can resolve vergence-accommodation conflict of the near-eye display.

Interactive multi-plane display by using plural high-definition panels and transmissive dihedral corner reflector array plate was proposed. The observer could interact with floated multiple image planes.

International audience; The OSA Topical Meeting on Digital Holography and 3D Imaging (DH) was held 29 May to 1 June 2017 in Jeju Island, South Korea. Feature issues based on the DH meeting series have been released by Applied Optics (AO) since 2007. This year, AO and the Journal of the Optical Society of America A (JOSA A) jointly decided to have one such feature issue in each journal. This feature issue includes 33 papers in AO and 9 in JOSA A and covers a large range of topics, reflecting the rapidly expanding techniques and applications of digital holography and 3D imaging. The upcoming DH meeting (DH 2018) will be held 25–28 June 2018 in Orlando, Florida, USA, as part of the OSA Imaging and Applied Optics Congress.

The paper presents design and implementation of a color wavefront holographic printer which prints white light viewable holograms of three-dimensional (3D) objects from digital contents. Similarly to other holographic printers, the printed hologram is composed as a two-dimensional array of elemental volume holograms. In the proposed wavefront printer, the 3D information was encoded in computer generated holograms displayed in succession on an amplitude spatial light modulator. The light beam diffracted from the modulator was filtered to extract the beam coming from the object and demagnified to be recorded onto the holographic emulsion as a small size elemental hologram that made possible application of mosaic delivery of exposures at primary colors. As a result, each elemental hologram corresponded to a single color channel. A modified phase-added stereogram approach based on a hologram partitioning method was proposed to accelerate computer generation of digital contents. We achieved bright 3D reconstruction with a motion parallax at saturated colors from holograms of test objects that were printed on a silver-halide emulsion. Thus we proved experimentally feasibility of recording analog color volume holograms from digital contents by applying spatially separated exposures at primary colors to the elemental holograms.

The wavefront printer records a volume-reflection hologram as a two-dimensional array of elemental holograms from computer-generated holograms (CGHs) displayed on a spatial light modulator (SLM). The wavefront coming from the object is extracted by filtering in the spatial-frequency domain. This paper presents a method to improve color reproduction in a wavefront printer with spatial division of exposures at primary colors, by adaptive partitioning of the SLM in accordance with the color content encoded in the input CGHs, and by the controllable change of exposure times for the recording of primary colors. The method is verified with a color wavefront printer with demagnification of the object beam. The quality of reconstruction achieved by the proposed method proves its efficiency in eliminating the stripe artifacts that are superimposed on reconstructed images in conventional mosaic recording.

Holography is defined as a two-steps process of capture and reconstruction of the light wavefront scattered from three-dimensional (3D) objects. Capture of the wavefront is possible due to encoding of both amplitude and phase in the hologram as a result of interference of the light beam coming from the object and mutually coherent reference beam. Three-dimensional imaging provided by holography motivates development of digital holographic imaging methods based on computer generation of holograms as a holographic display or a holographic printer. The holographic printing technique relies on combining digital 3D object representation and encoding of the holographic data with recording of analog white light viewable reflection holograms. The paper considers 3D contents generation for a holographic stereogram printer and a wavefront printer as a means of analogue recording of specific artifacts which are complicated objects with regards to conventional analog holography restrictions.

The paper proposes encoding of directional information extracted from perspective images of 3D objects as phase holograms for holographic stereogram printing on a photoresist. Such printing allows for mass production of holograms.

A compact collimated display system using an aspherical screen with a concave mirror is proposed. As the collimated display can provide a long viewing distance for the observer, it is commonly used for personal virtual flight simulators. To deliver a collimated image, the conventional collimated display requires a large system, but by using an aspherical screen with a concave mirror, the system size can be diminished. In this paper, a method of designing the compact collimated display system is demonstrated with simulation and experiment results. Also, a floating display and a depth camera for detecting hand gestures were combined with the proposed system for interaction.

A tangible floating display that can provide different perspective views without special glasses being introduced. The proposed system can display perspective floating images in the space in front of the system with the help of concave mirrors. In order to avoid wearing special equipment to interact and deliver the sense of touch, the proposed system adopted an ultrasound focusing technology. For providing an immersive experience to the viewers, the proposed system consists of a tangible floating display system and a multiple-view imaging system for generating three lenticular displays in front of the users.

Zero-order and twin images are a serious obstacle in achieving a high-quality output in in-line digital holography (DH). They decrease the useful bandwidth of the off-axis DH. Over the years the twin image removal problem was approached both by instrumental and numerical means. The paper provides an extended survey of the proposed solutions with their pros and cons as a guide for further advance in this field. Processing of a single spatial carrier fringe pattern involves spatial filtering in the frequency domain, spatial phase-shifting (PS) or wavelet transform. A point source digital holographic microscopy (DHM), introduction of calibration measurements or various modifications of PS technique are instrumental solutions to the twin image problem for in-line DH. Numerical solutions to the same problem include iterative and non-iterative approaches, diffraction-based and inverse problem solutions, reconstruction of purely real or phase objects and of complex objects, reconstruction of plane and volume objects. Elimination only of the zero-order image relies on non-linear filtering or additional calibration measurements.

Evaluation of the effect of radial distortion for a holographic stereogram demands conducting an experiment which comprises rendering of a 3D obejc, acquisition of perspective images, rearrangement of the acquired images for hogel images and quality assessment of the observing image reconstructed from the holographic stereogram. We propose numerical implementation of this evaluation by a specially developed algorithm for modeling of all required steps. The modeling is done by using a numerical model of an optical engine for generation of radially distorted hogel images at various degrees of distortion. The distorted images are used to form the holographic stereogram and to make the numerically reconstructed images from the holographic stereogram which are observed by an observer at desired location. The reconstructed images are compared by using PSNR.

The paper is dedicated to SLM implementation of a sinusoidal phase grating for fringe projection profilometry with sinusoidal fringes. A low-contrast sinusoidal phase grating is capable of projecting focused sinusoidal fringes with satisfactory visibility in a large spatial region under coherent divergent illumination. The paper presents analysis of distortions in the projected fringes due to phase quantization when the phase grating is generated by a phase-only 8-bit SLM. We showed by simulation of propagation in the free space that the spread of intensity fluctuations of the projected fringes comprises 4–5 gray levels if an SLM with a 2π phase span is used and is much lower for an SLM with π/2 phase span. In addition, we proved that distortion due to the phase encoding of the grating complex amplitude can be modeled as gamma distortion with an invariable behavior in time at small values of the modulation parameter and removed by a proper correction of fringes after polyspectral analysis. The experiments we made with an 8-bit SLM of π/2 phase span confirmed the ability of this optical element to project sinusoidal fringes with a high spectral purity.

The in-line holography has obvious advantages especially in wider spatial bandwidth over the off-axis holography. However, a direct current (DC)-noise and an unwanted twin image should be separated or eliminated for a high quality reconstruction. Therefore, we introduce an effective Laplace operation-based numerical approach for DC-noise reduction in the in-line holography. The DC-noise in a holographic fringe pattern can be efficiently reduced by applying a second derivative operation while maintaining the two real and twin terms. For the performance evaluation, the proposed method is compared with the existing approaches, including the intensity average subtraction and frequency-domain filtering, which are generally used for the numerical holographic reconstruction. Experimental results show that the proposed method is numerically appropriate, and provides the high quality reconstruction for a digital holography. Therefore, we believe that the proposed scheme can be a useful tool for high quality reconstruction in the in-line holography.

In this paper, we describe social spatial mashup for information sharing in public space. The proposed social spatial mashup is based on RGB-D SLAM and creates a 3D feature map and allows users to locate information and contents in a 3D space. It thus allows users intuitively and spatially share information among users based on real objects and 3D space. We also implemented and tested the mashup method with Google Project Tango.

Development of display and its related technologies provides immersive visual experience with head-mounted-display (HMD). However, most available HMDs provide 3D perception only by stereopsis, lack of accommodation depth cues. Recently, holographic HMD (HHMD) arises as one viable option to resolve this problem because hologram is known to provide full set of depth cues including accommodation. Moreover, by virtue of increasing computational power, hologram synthesis from 3D object represented by point cloud can be calculated in real time even with rigorous Rayleigh-Sommerfeld diffraction formula. However, in HMD, rapid gaze change of the user requires much faster refresh rate, which means that much faster hologram synthesis is indispensable in HHMD. Because the visual acuity falls off in the visual periphery, we propose here to accelerate synthesizing hologram by differentiating density of point cloud projected on the screen. We classify the screen into multiple layers which are concentric circles with different radii, where the center is aligned with gaze of user. Layer with smaller radius is closer to the region of interest, hence, assigned with higher density of point cloud. Because the computation time is directly related to the number of points in point cloud, we can accelerate synthesizing hologram by lowering density of point cloud in the visual periphery. Cognitive study reveals that user cannot discriminate those degradation in the visual periphery if the parameters are properly designed. Prototype HHMD system will be provided for verifying the feasibility of our method, and detailed design scheme will be discussed.

The principle and implementation of a time angular multiplexing holographic display are presented. The object beam is extracted from a binary hologram on a DMD. The obtained 3D image shows an increased field of view.

Methods for generation of 3D contents for holographic displays and printers with focus on capture/display parameters adjustment are discussed. Input data for the generation process are captured by means of digital holography and profilometry/tomography or are acquired as multiple perspective images or are extracted from a computer graphic model. Article not available.

The layered display by using eight displays and half mirrors was proposed. Expressible depth range of the proposed method could be controllable with high precision stages and the number of voxels is 29.4Mpixels.

Design and implementation of a holographic wavefron printer with demagnification of the object beam is presented The printer prints a white light viewable color analo; hologram from a set of computer generated hologram displayed on an amplitude spatial-light modulator. W achieved bright 3D reconstruction with a motion parallax a saturated colors from holograms of test objects that wer printed on a silver-halide emulsion.

A compact wavelength multiplexing technique is proposed and experimentally investigated to improve the efficiency of a full-color holographic diffuser using photopolymer. The exposure responses of a monochromatic hologram and a three wavelength multiplexed hologram recorded in photopolymer film are presented. The time-scheduled exposure energies at wavelengths of 633, 532, and 473 nm were chosen to optimize the uniform diffraction efficiency of the wavelength multiplexed hologram. These three wavelength iterative sequences of exposures are applied to achieve a specific color balance for a multicolor holographic diffuser. The experimental results confirm that the fabrication method is well suited to the manufacture of holographic diffusers for full-color display applications.

The holographic wavefront printer decodes the wavefront coming from a three-dimensional object from a computer generated hologram displayed on a spatial light modulator. By recording this wavefront as an analog volume hologram this printing method is highly suitable for realistic color 3D imaging. We propose in the paper spatial partitioning of the spatial light modulator to perform mosaic delivery of exposures at primary colors for seamless reconstruction of a white light viewable color hologram. The method is verified for a 3 x 3 color partitioning scheme by a wavefront printer with demagnification of the light beam diffracted from the modulator. (C) 2015 Optical Society of America

A three-dimensional display using persistence of vision (POV) has its own benefits for natural image expression. Conventional POV display using light emitting diode (LED) array was connected with a high speed motor, so it could be possible to express curved-type two-dimensional display or volumetric three-dimensional display. However, it is necessary to consider interactive three-dimensional display. For example, this kind of volumetric display is hardly applied on interactive display since light emitting parts are placed in the center of a rotating screen. To provide a complementary effort to this need, we propose here a hologram-like interactive volumetric display using LED array type persistence of vision and a pair of parabolic mirrors. We build the volumetric POV display by using small size LED arrays. This POV display is located below a pair of parabolic mirrors so the mirrors make hologram-like volumetric POV images to be reimaged such as 4 f system of lenses. Several preliminary experiments will be provided for our proposed method.

Fast approximate digital hologram generation algorithm based on hologram partitioning and a single stage of the fast Fourier transform for each elemental hologram is proposed. Typical objective and subjective quality assessment confirms clear reconstruction comparable to that provided by the classical non-approximated algorithm.

Holographic-optical-element which has freely designed optical functionality can be printed out by holographic-wavefront-printer without the aid of any physical reference. We show that the printed holographic-optical-element can be successfully applied for see-through three-dimensional display.

Cataloged from PDF version of article. Three approaches for visualization of transparent micro-objects from holographic data using phase-only SLMs are described. The objects are silicon micro-lenses captured in the near infrared by means of digital holographic microscopy and a simulated weakly refracting 3D object with size in the micrometer range. In the first method, profilometric/tomographic data are retrieved from captured holograms and converted into a 3D point cloud which allows for computer generation of multi-view phase holograms using Rayleigh-Sommerfeld formulation. In the second method, the microlens is computationally placed in front of a textured object to simulate the image of the textured data as seen through the lens. In the third method, direct optical reconstruction of the micrometer object through a digital lens by modifying the phase with the Gerchberg-Saxton algorithm is achieved. © 2013 Optical Society of America.

We proposed a contents acquisition method based on a computer generated method for directional-view display. The proposed method can be incorporated in scalable directional-view display and integral imaging.

A conventional analog hologram displays highly realistic 3D images of objects. A holographic printer can record such a hologram onto a holographic emulsion from digital contents. Various holographic printers for recording a holographic stereogram, a fringe pattern or a wave-front have been developed for the recent two decades [1-4]. Multiple perspectives of the scene are used as contents for holographic stereogram recording, and an observer perceives a 3D object by binocular vision. However, the acquired perspectives have longitudinal magnification distortion caused by camera geometry that leads to the distorted 3D space representation over the displayed hologram. Thus the holographic stereogram may not be suitable for specific applications which require actual size display. The fringe printer records computer generated fringe patterns onto a holographic emulsion without any reference wave, and the printed hologram is a thin diffractive optical element which provides non-distorted 3D reconstruction but without color selectivity. The wave-front printing technique overcomes these drawbacks - longitudinal magnification distortion and lack of color selectivity – and makes a wave-front printer a desirable choice of a holographic printer. Two wave-front printers have been recently independently designed [1,2] and the aim of this paper is to analyze and compare their properties.

Fringe projection profilometry is a well-established method in optical metrology for capture of 3D objects [1]. The information is retrieved from the phase of the deformed fringe pattern formed by imaging the object onto a CCD camera after projection of a structured light pattern onto its surface. A variety of phase retrieval algorithms requires projection of sinusoidal fringes. Thin diffraction sinusoidal gratings under coherent illumination are a suitable choice for generation of good quality fringes focused in a large measurement volume [2]. The main drawback of coherent projection is the speckle noise. The lateral spacing of fringes produced by coherently illuminated sinusoidal grating does not depend on the wavelength. Thus, a light source with a wider spectrum can be used for reduction of the speckle noise in the fringe patterns recorded by the CCD camera provided the spatial coherence of the source is kept intact [3]. The aim of the present report is to prove speckle reduction in fringes projected with a sinusoidal phase grating (SPG) by using low coherent point light source with emphasis on LED illumination.