Abstract: Curved integral imaging 3D display could provide enhanced 3D sense of immersion and wider viewing angle, and is gaining increasing interest among discerning users. In this work, large scale microlens arrays (MLAs) on flexible PMMA substrate were achieved based on screen printing method. Meanwhile, an inverted reflowing configuration as well as optimization of UV resin's viscosity and substrate's surface wettability were implemented to improved the numerical aperture (NA) of microlenses. The results showed that the NA values of MLAs could be increased effectively by adopting inverted reflowing manner with appropriate reflowing time. With decreasing the substrate's wettability, the NA values could be increased from 0.036 to 0.096, when the UV resin contact angles increased from 60.1° to 88.7°. For demonstration, the fabricated MLAs was combined to a curved 2D monitor to realize a 31-inch curved integral imaging 3D display system, exhibiting wider viewing angle than flat integral imaging 3D display system.

Abstract: A bionic-compound-eye structure (BCES), which is a substitute of a microlens array, is proposed to enhance the performance of integral imaging (II) 3D display systems. Hexagonal ocelli without gaps and barriers are predesigned to obtain a continuous image, high-resolution, and uniform parallax. A curved substrate is designed to enhance the viewing angle. In addition, ocelli are fused with the substrate to form a relief structure, BCES. When they are placed above a normal display, continuous and full-parallax 3D images with 150 µm effective resolution and a 28° horizontal, 22° vertical viewing angle could be achieved, about twice as much as that of normal systems. The weight of the BCES is 31 g, and the thickness of the whole system is 22 mm; thus, the BCES-based II (BCES-II) is very compact. In addition, this structure can be easily integrated into a cell phone or iPad for compact quasi-2D and 3D adjustable display.

Abstract: We propose mounting a downward-facing camera above the top end of a digital tablet pen. This creates a unique and practical viewing angle for capturing the pen-holding hand and the immediate surroundings which can include the other hand. The fabrication of a prototype device is described and the enabled interaction design space is explored, including dominant and non-dominant hand pose recognition, tablet grip detection, hand gestures, capturing physical content in the environment, and detecting users and pens. A deep learning computer vision pipeline is developed for classification, regression, and keypoint detection to enable these interactions. Example applications demonstrate usage scenarios and a qualitative user evaluation confirms the potential of the approach.

Abstract: One of the key properties of any binary is its viewing angle (i.e., inclination), $\theta_{\rm obs}$. In binary neutron star (BNS) mergers it is of special importance due to the role that it plays in the measurement of the Hubble constant, $H_0$. The opening angle of the jet that these mergers launch, $\theta_j$, is also of special interest. Following the detection of the first BNS merger, GW170817, there were numerous attempts to estimate these angles using the afterglow light curve, finding a wide range of values. Here we provide a simple formula for the ratio $\theta_{\rm obs}/\theta_j$ based on the afterglow light curve and show that this is the only quantity that can be determined from the light curve alone. Namely, it is impossible to determine each of the angles separately without additional information. Our result explains the inconsistency of the values found by the various studies of GW170817 that were largely driven by the different priors taken in each study. Among the additional information that can be used to estimate $\theta_{\rm obs}$ and $\theta_j$, the most useful is a VLBI measurement of the afterglow image superluminal motion. An alternative is an identification of the afterglow transition to the sub-relativistic phase. These observations are possible only for mergers observed at small viewing angles, whose afterglow is significantly brighter than the detector's threshold. We discuss the implications of these results to measurements of $H_0$ using GW observations. We show that while the viewing angle will be measured only in a small fraction of future BNS mergers, it can significantly reduce the uncertainty in $H_0$ in each one of these events, possibly to a level of 4-5\%. A minority of the mergers with high precision measurements of this kind may dominate in the future the precision in which $H_0$ will be measured using this method.

Abstract: Total and polarized radiances from above the ocean surface are measured by a state-of-the-art snapshot hyperspectral imager. A computer-controlled filter wheel is installed in front of the imager allowing for recording of division-of-time Stokes vector images from the ocean surface. This system, to the best of our knowledge, for the first time provided a capability of hyperspectral polarimetric multi-angular measurements of radiances from above the water surface. Several sets of measurements used in the analysis were acquired from ocean platforms and from shipborne observations. Measurements made by the imager are compared with simulations using a vector radiative transfer (VRT) code showing reasonable agreement. Analysis of pixel-to-pixel variability of the total and polarized above-water radiance for the viewing angles of 20°–60° in different wind conditions enable the estimation of uncertainties in measurements of these radiances in the polarized mode for the spectral range of 450–750 nm, thus setting requirements for the quality of polarized measurements. It is shown that there is a noticeable increase of above-water degree of linear polarization (DoLP) as a function of the viewing angle, which is due both to the larger DoLP of the light from the water body and the light reflected from the ocean surface. Results of measurements and VRT simulations are applied for the multi-angular retrieval of the ratio of beam attenuation coefficient (ctot) to absorption coefficient (atot) in addition to the other parameters such as absorption and backscattering coefficients retrieved from traditional unpolarized methods.

Abstract: This paper presents an integral three-dimensional (3D) display that efficiently enhances both the pixel densities and viewing angles of 3D images with parallel projection of elemental images. In the proposed method, ultra-high-definition (UHD) elemental images are projected and superimposed as parallel light rays from densely arranged compact UHD projectors onto a lens array. Three-dimensional images with enhanced pixel densities and viewing angles can be displayed by optimizing the projector positions and system design. The prototype yielded a horizontal pixel density of 63.5 ppi, approximately 97,000 pixels, and a viewing angle of approximately 30°, making it superior to previous integral 3D display systems.

Abstract: Gamma-ray burst (GRB) prompt emission is highly beamed, and understanding the jet geometry and beaming configuration can provide information on the poorly understood central engine and circum-burst environment. Prior to the advent of gravitational-wave astronomy, astronomers relied on observations of jet breaks in the multi-wavelength afterglow to determine the GRB opening angle, since the observer's viewing angle relative to the system cannot be determined from the electromagnetic data alone. Gravitational-wave observations, however, provide an independent measurement of the viewing angle. We describe a Bayesian method for determining the geometry of short GRBs using coincident electromagnetic and gravitational-wave observations. We demonstrate how an ensemble of multi-messenger detections can be used to measure the distributions of the jet energy, opening angle, Lorentz factor, and angular profile of short GRBs; we find that for a population of 100 such observations, we can constrain the mean of the opening angle distribution to within 10 degrees regardless of the angular emission profile. Conversely, the constraint on the energy distribution depends on the shape of the profile, which can be distinguished.

Abstract: Integral imaging three-dimensional (3D) display provides quasi-continuous viewpoints within a certain viewing angle. A single human eye can obtain several parallax images corresponding to the viewpoints. In this paper, we studied the effect of viewpoints received by a single human eye on the accommodation response when viewing the 3D image reconstructed by integral imaging 3D display. We analyzed the viewpoints distribution of an integral imaging 3D display and the correspondence relationship between the viewpoints and pixels information in elemental image array. In the experiment, the accommodation responses of human eyes when viewing the 3D image with different viewpoint quantities and dimensions are measured. The statistical results reveal that the more viewpoints received by a single human eye, the closer the accommodation response of the 3D image is to that of the real target. This tendency is obvious when the viewpoint quantity reduces from 10 × 10 to 6 × 6. For situations of 2 × 2 and 1 × 1 viewpoint, the accommodation response is unstable and different from the real target. When considering the viewpoint dimensions, two-dimensional viewpoints can provide a more natural accommodation response than one-dimensional viewpoints do. For the one-dimensional viewpoint situation, the horizontal arranged viewpoints and vertical arranged viewpoints have no statistical discrepancy.

Abstract: We have realized a new optical system to form multiple aerial images by use of thin optical components. The proposed optical system is based on aerial imaging by retro-reflection (AIRR). The aerial image formed by AIRR is visible over a wide viewing angle without using 3D glasses. In addition to AIRR, we have introduced a technique called infinity mirror in which a mirror and a half mirror are arranged in parallel to form multiple virtual images of a single light source. By combining AIRR and infinity mirror, multiple images are formed in mid-air. By placing a retro-reflector obliquely outside the infinity mirror, our proposed optics improves brightness of the aerial images by placing.

Abstract: We present multiwavelength modeling of the afterglow from the long gamma-ray burst GRB 160625B using Markov Chain Monte Carlo (MCMC) techniques of the afterglowpy Python package. GRB 160625B is an extremely bright burst with a rich set of observations spanning from radio to gamma-ray frequencies. These observations range from ~0.1 days to >1000 days, thus making this event extremely well-suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7-5.3 sigma) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 1.26 to 3.90 degrees, depending on jet shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of ~$10^{53}$ erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity, thus this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment.

Abstract: We present multiwavelength modeling of the afterglow from the long γ-ray burst (GRB) 160625B using Markov Chain Monte Carlo techniques of the afterglowpy Python package. GRB 160625B is an extremely bright burst with a rich set of observations spanning from radio to γ-ray frequencies. These observations range from ~0.1 days to >1000 days, thus making this event extremely well suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best-fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7σ–5.3σ) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 1fdg26 to 3fdg90, depending on jet-shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation a fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of ~1053 erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity; thus, this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment.

Abstract: The current efficiency and color purity of organic light-emitting diodes (OLEDs) can be easily improved by means of a microcavity structure, but this improvement is typically accompanied by a deterioration in the characteristics of viewing angle. To minimize the angular dependence of the color characteristics exhibited by these strong microcavity devices, we investigated the changes in the optical properties of the green OLED with a bottom resonant structure. This investigation was based on varying the hole transport layer and semitransparent anode thicknesses. The results of optical simulations revealed that the current efficiency and viewing angle characteristics can be simultaneously improved by adjusting the thickness of the two layers. Furthermore, optical simulations predicted that the angular color dependence could be limited to 0.019 in the International Commission on Illumination (CIE) 1976 coordinate system. This optimum condition yielded a current efficiency of ∼134 cd/A. To further reduce this color shift, a nanosized island array (NIA) was introduced through the dewetting process of cesium chloride. By employing NIAs, the color coordinate shift value was reduced to 0.016 in the CIE 1976 coordinate system, and a current efficiency of 130.7 cd/A was achieved.

Abstract: The essential improvements in the performance of light-diffusing materials for wide viewing angles in potential optoelectronic applications have attracted considerable attention. In this study, a simple and unprecedented strategy is proposed to simultaneously provide exceptional light scattering performance and high optical transparency for transparent optical thin films using hierarchical double-shell nanoparticles possessing a refractive index gradient on the nanoparticle surface. The hierarchical SiO2/TiO2/poly(methyl methacrylate) (PMMA) double-shell layered nanoparticles induce enhanced light scattering properties by their nanolayered gradient refractive index structure. Fourier transform infrared spectroscopy and scanning electron microscopy-energy-dispersive X-ray spectroscopy analyses show the successful formation of the multiple nanolayered structure of the double-shell nanoparticles. The synthesized SiO2/TiO2/PMMA nanoparticles with a diameter of 40 nm and a TiO2 layer thickness of 4.5 nm exhibit the highest diffuse reflectance of 87% in the visible region. An ultraviolet-light-cured optical film with an extremely low content of double-shell nanoparticles exhibits efficient light scattering characteristics while maintaining high optical transparency. This study provides a facile yet effective, scalable approach to improve the viewing angle performances of optoelectronic devices and paves the new way for further studies on the wide applications of light scattering phenomenon using optically active hierarchical nanoparticles with multiple refractive indices.

Abstract: A novel optical reverse mapping (ORM) method and an ORM criterion are proposed to evaluate the relevance between the directional backlight (DB) 3D light-field display system aberration and the crosstalk. Based on the ORM criterion, the space-division-multiplexed catadioptric integrated backlight (SCIB) and symmetrical triplet-compound lenticular array (triplet LA) are designed. The SCIB is composed of hybrid Fresnel integrated backlight unit (hybrid Fresnel unit) and space-division-multiplexed microprism unit (microprism unit). The hybrid Fresnel unit is used to provide the directional light, and the divergence angle is 2.4-degrees. The average uniformity of 83.02% is achieved. The microprism unit is used to modulate the directional light distribution into three predetermined directions to establish a 90-degree viewing area. Combined with SCIB, the triplet LA is used to suppress the aberrations and reduce the crosstalk. In the experiment, a DB 3D light-field display system based on SCIB and triplet LA is set up. The displayed light-field 3D image can be observed in a 90-degree viewing angle. Compared to the conventional DB 3D display system, the light-field 3D image is aberration-suppressed, and the SSIM values are improved from 0.8462 to 0.9618. Meanwhile, the crosstalk measurement results show that the average crosstalk is 3.49%. The minimum crosstalk is 2.31% and the maximum crosstalk is 4.52%. The crosstalk values in 90-degree are lower than 5%.

Abstract: A method to enhance the performance of an integral imaging system is demonstrated using the time-multiplexed convergent backlight technique. The backlight increases the space bandwidth of the integral imaging system. As a result, the resolution, depth of field, and viewing angle of the integral imaging system are increased simultaneously. The cross-talk noise is also decreased without using any optical barrier. One part of the added space bandwidth comes from the optimized illumination. The other part is converted from the time bandwidth of the system by time-multiplexing. The time-multiplexed convergent backlight modulates the direction of the backlight in time sequence to illuminate the elemental images. Then, the elemental images synthesize the 3D images using a microlens array. An elemental images rendering method using a conjugate pinhole camera and pinhole projector model is designed to dynamically match the illumination direction. The rendering method eliminates the distortion and maximizes the viewing angle and viewing zone. A field programmable gate array (FPGA)-based controller is used to manage and synchronize the time sequence of the backlight and the display devices. Using this technique, high-performance 3D images are realized. Comparison experiments of the integral imaging system using diffused backlight and convergent backlight are performed. The results show the effectiveness of the proposed technique.

Abstract: A transparent display allows us to see both the projection image displayed on it and the view behind it at the same time, which can be widely used in the car windshield, shop windows, and so on. To achieve the transparent display with the simple and easily available plasmonic nanoparticles, plasmonic Au-Ag nanoparticles with the strong scattering ability were used to achieve the objective of selectively scattering red, blue, and green light for the transparent screen in this work. Firstly, the optimized size parameters for these three color transparent displays were obtained theoretically. On the other hand, plasmonic nanoparticles used for the blue and green color transparence screen were reported in the previous experiments. Finally, a red color transparent display with the wide viewing angle was made based on the optimized Au nanoparticles experimentally.

Abstract: We investigate the angular field of view (AFOV) of a holographic image reconstructed from the digital Fresnel hologram in holographic display. The theoretical analysis clarifies that the AFOV of a holographic image is fundamentally determined by the hologram numerical aperture (HNA) other than a diffraction angle of pixel pitch of a pixelated modulator. This property is proved for various types of the digital holograms using a numerical simulation and optical experiments. The high-HNA hologram reconstructs the image with a high viewing angle, whereas the image contraction is inevitable due to the Nyquist sampling criterion in the hologram synthesis. We demonstrate the method for reconstructing the holographic image with a high viewing angle without image contraction.

Abstract: Using structural colors instead of pigment colors has many advantages, both environmentally and economically. However, the traditional process of eliminating structural iridescence often causes a decrease in color brightness and saturation. For a periodic optical structure having a refractive-index difference, it is necessary to pile up a certain number of layers to make the maximum reflectivity reach almost unity and obtain the minimal bandwidth. Therefore, the amorphization process inevitably leads to a decrease in the brightness and saturation of the structural color, as the short-range order domain is too small. In this paper, the concept of the polycrystallization process and corresponding method are introduced, by which a polycrystalline structure with an optimal grain size is built using silica nano-spheres. This structure guarantees the best brightness and saturation of the color at a low viewing angle, while eliminating the reflection of other colors at a high viewing angle. Subsequent graphene doping and superhydrophobic treatment enable the structural color to maintain its brilliant color for a long time even in an intensive harsh environment, such as on white substrates under high humidity conditions.

Abstract: A typical top-emitting organic light-emitting diode (OLED) has a strong microcavity effect because of the two reflective electrodes. The cavity effect causes a serious color shift with the viewing angles and restricts the organic layer thickness. To overcome these drawbacks, we design a multi-mode OLED structure with dual-dielectric spacer layers, which extend the cavity length by more than 10 times. This design completely eliminates the intrinsic cavity effect caused by the top and bottom boundaries and provides freedom for the organic layer thickness. We demonstrate these effects in a white multi-mode OLED using a white emitter, which shows a negligible angular chromaticity shift of Δuv = 0.006 from 0 to 70° and a Lambertian emission profile. The simple design and the perfect angular color profiles make the multi-mode OLED structure promising in large-area displays and solid-state lighting applications.

Abstract: Pedestrian detection based on Deep Convolutional Neural Networks (DCNNs) has made great stride in the last few years. Researchers have recently employed different DCNN-based techniques to detect pedestrian more accurately than before. In this paper, we propose a new Deep Model based on Changes in Camera Viewing Angle (DM-CCVA) to detect pedestrian. The proposed novel DM-CCVA is based on integrating a modified Single-Shot Detector (SSD) and a set of parallel Fast Region-based Convolutional Neural Networks (FRCNNs) to accurately detect pedestrian. The proposed deep architecture extracts initial candidate pedestrians using a modified SSD model, while utilizing five parallel Fast RCNNs to detect pedestrians in five different sets of camera viewing angles. We also propose a new training approach based on changes in camera viewing angle which searches the best Region of Interests (RoIs). Moreover, by exploiting a secure border in each initial candidate pedestrian, the proposed method both creates an Extended Region of Candidate Pedestrian (ERCP) and extracts multi-RoIs. It then selects a number of RoIs within the ERCP as detected pedestrians which satisfy few reasonable criteria. Comprehensive experimental results demonstrate that the proposed DM-CCVA is a highly effective method that achieves very competitive performance on two most popular pedestrian detection datasets: Caltech-USA and INRIA.

Abstract: We fabricated a high-density, large-scale magneto-optical (MO) light modulator array to investigate its performance for holographic display applications. The modulator comprised a magnetic nanowire for light modulation using MO Kerr effect and two hard magnets (HMs) to control the switching property of the nanowire. The magnetization direction of the designated pixels in the array was controlled by the external magnetic field, unlike a spatial light modulator, which drives arbitrary pixels with cell selection backplane transistors. Magnetization of the light modulators with HMs can be reversed using a smaller magnetic field compared with those without HMs; this enables the formation of magnetic patterns by switching only the magnetization direction of the nanowire with smaller switching field; the pattern thus obtained is predetermined and not arbitrary. A diffracted beam in a magnetic stripe pattern displayed on the array was observed as spot patterns, and their spot position was consistent with a diffraction angle of the stripe period. We fabricated a magnetic hologram using a 10 k × 10 k pixel array calculated by computer-generated holography and successfully reproduced a holographic three-dimensional image with a wide viewing angle.

Abstract: In integral photography (IP), it is difficult to obtain three-dimensional photographs with high spatial resolution, high angular resolution, and a wide viewing angle simultaneously. Thus, we proposed a dense parallax image acquisition method using single-pixel imaging. We confirmed that parallax images can be obtained depending on the position of the photodetector. By replacing the detector to each pixel of an image sensor, a two-dimensional image with different parallaxes in each pixel can be acquired. We demonstrated the reconstruction of dense parallax images according to the pixel position of the image sensor. This method is effective in addressing the trade-off among spatial resolution, angular resolution, and a viewing angle. It can also improve the image quality in IP.

Abstract: In this study, we present the comparison of device performance measurements for organic light emitting diodes using a spectroradiometer through the viewing angle and integrating sphere, widely used for device measurements. The mean calculation method using these results was applied to convert the spectroradiometer (under different viewing angles) data to match with the integrating sphere measurements. The conversion of the spectroradiometer based quantum efficiency and electroluminescence data from all different angular emission patterns was similar to that of the integrating sphere data within a reasonable range of deviation. As such, it is possible to reduce the recurring costs and required time between these two measurement techniques by bypassing the integrating sphere measurement.

Abstract: We present an optical set up that significantly reduces the ghost images appearing due to multiple reflections on both surfaces of the combiner (typically the windshield) of head-up display (HUD) systems. The method is based on an optimized polarization correcting optics attached to the HUD projector. For the quantitative investigation of the ghost images, we calculate the ghost image suppression ratio as a function of viewing direction using a custom algorithm based on ray tracing and Jones-vector formalism. We also present experimental results on the proposed configurations exhibiting very good agreement with calculation results. As a result, the ghost image free viewing area of polarization-type HUDs can be increased more than fourfold.