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While recent progress in holographic displays has shown that they are capable of displaying photorealistic 3D holograms in real time, the acquisition of high-quality real-world holograms has remained a missing piece regarding the realization of holographic streaming systems. Incoherent holographic cameras, which record holograms under daylight conditions, are suitable candidates for real-world acquisition, as they avoid the safety issue involved in the use of laser lights; however, they are hindered by severe noise due to the optical imperfections of such systems. In this work, we develop a deep learning-based incoherent holographic camera system that can deliver visually enhanced holograms in real time. A neural network filters the noise in the captured holograms, maintaining a complex-valued hologram format throughout the whole process. Enabled by the computational efficiency of the proposed filtering strategy, we demonstrate the first holographic streaming system integrating a holographic camera and a holographic display, with the aim of developing the ultimate holographic ecosystem of the future.

Incoherent digital holographic imaging method was presented with utilizing polarization-dependent self-interference effects obtained by cycloidal diffractive lens made by a quarter-wave retardation condition for providing enhanced imaging properties as well as compact module conditions.

We propose a holographic augmented reality system that can generate and reproduce an incoherent hologram. The augmented hologram consists of optically captured incoherent holograms and computer-generated holograms.

A voxel analysis technique of integral imaging system using self-interference incoherent digital holography is proposed, which can acquire the hologram in a condition of the incoherent light source. To find the exact position of the voxel and the expressible depth range of system, we use an autofocus algorithm that estimates the sharpness of numerically reconstructed holograms.

We propose a holographic stereogram synthesis method which uses holograms that are optically captured by self-interference incoherent digital holography (SIDH) based on a geometric phase lens. SIDH is a promising solution for hologram acquisition under low-coherence lighting condition. A mechanical scanning system is constructed to acquire multiple perspective holograms. Numerical simulations and experimental analyses conducted using high-resolution diffractive optical element demonstrate that the proposed method can produce a wide-viewing hologram which can realize realistic 3D scenarios with depth cues such as accommodation and motion parallax. The future objectives include the implementation of a multiple-camera system for holographic videos.

A floating 3D display with a dihedral corner reflector array (DCRA) is presented to improve space efficiency and eliminate ghost images. Floating displays using a DCRA have the space efficiency problem of having a system thickness equal to the height of the floating image and the problem of a ghost image interrupting the visibility of the floating display. The DCRA is analyzed to find the ghost image region. Based on the analysis, an off-axis integral floating display is placed outside the ghost image region to avoid the ghost image. To increase space efficiency, the optical path is folded using a mirror. In addition, the off-axis integral floating display is used to create a tilt angle for projecting the input image onto the DCRA in a proposed confined and narrow system to observe the complete 3D image. The effectiveness of the system was verified through simulations and experiments.

A bi-focal geometric phase (GP) lens can be used to improve the depth range of an integral floating display to form switchable depth planes. However, due to a chromatic aberration of a GP lens to form R/G/B sub-images at different locations, a color breaking of floated image can occur. In this paper, we propose a novel method to compensate that chromatic aberration by integrating R/G/B pixels at depths.

We propose an occlusion-capable near-eye display for augmented-reality. The combination of a transmissive dihedral corner reflector and a single digital micromirror device enables real scene occlusion by displayed virtual images in a compact form factor. © 2020 The Author(s)

Three-dimensional (3D) images reconstructed by integral imaging display are captured as a complex hologram using self-interference incoherent digital holography (SIDH) and analyzed for the volumetric image characteristics. The integrated images can present 3D perception through not only binocular disparity but also volumetric property, which is represented in forming a volume picture element, called ‘voxel’, and an important criterion to distinguish the integral imaging from the multiview 3D display. Since SIDH can record the complex hologram under incoherent lighting conditions, the SIDH camera system has the advantage to measure the voxel formed with the incoherent light fields. In this paper, we propose a technique to estimate and analyze the voxel characteristics of the integral imaging system such as the depth location and resolution. The captured holograms of the integrated images are numerically reconstructed by depth for the voxel analysis. The depth location of the integrated image can be calculated and obtained using the autofocus algorithms and the focus metrics values, which also show the modalities of depth resolution. The estimation method of this paper can be applied to the accurate and quantitative analysis of the volumetric characteristics of light field 3D displays.

Laser direct patterning (LDP) technology has attracted great attention due to its process simplification and environmental friendliness. It is replacing the existing photo-lithography technology. Infrared (IR) laser equipment also has advantages such as low cost and long duration, although it is difficult to implement fine line width compared to ultraviolet (UV) or excimer laser. Therefore, it is very important to realize 3-D patterning system based on cheap infrared laser system. In this paper, 3-D infrared laser direct patterning system was designed by introducing an etching process on Ag paste/ITO/PET flexible film. Such 3-D patterned Ag paste/ITO/PET flexible films showed feasibility and effectiveness of 3-D laser directional patterning technologies. Etch ratio of the fabricated Ag paste/ITO/PET flexible film after 3-D infrared laser direct patterning was then systematically investigated.

The two-dimensional transition-metal dichalcogenide semiconductor MoS2 has received extensive attention for decades because of its outstanding electrical and mechanical properties for next-generation devices. One weakness of MoS2, however, is that it shows only n-type conduction, revealing its limitations for homogeneous PN diodes and complementary inverters. Here, we introduce a charge-transfer method to modify the conduction property of MoS2 from n- to p-type. We initially deposited an n-type InGaZnO (IGZO) film on top of the MoS2 flake so that electron charges might be transferred from MoS2 to IGZO during air ambient annealing. As a result, electron charges were depleted in MoS2. Such charge depletion lowered the MoS2 Fermi level, which makes hole conduction favorable in MoS2 when optimum source/drain electrodes with a high work function are selected. Our IGZO-supported MoS2 flake field effect transistors (FETs) clearly display channel-type conversion from n- to p-channel in this way. Under short- and ...

In this study, a focus-free retinal projection display based on a Maxwellian view was implemented. The display was constructed using simple and cost-effective passive components, such as a retroreflector film, beam splitter, and a pinhole. As a part of the system, the pinhole and display serve as a pinhole projector, which projects images through a small exit pupil. The retroreflector film and the beam splitter form the conjugate image of the pinhole near an observer. By locating the center of the crystalline lens of an eye at the conjugate pinhole, the projected images are focused on the retina and are seldomly changed by the accommodative response of the lens. For the practical implementation of the system, a collimating lens was used as an imaging lens combined with a pinhole. The point spread function of the system was derived to theoretically demonstrate that the system exhibits focus-free features at accommodation distances of 0.25, 0.5, and 1 m. The experiments conducted to demonstrate the feasibility of the system are presented under the same accommodation condition as the analysis.

The condition for the integral floating display is analyzed and evaluated, which elicits the distinguished accommodation responses to different axial locations of targets. The analysis is carried out to derive condition which helps to devise such a system. And measurements of accommodation response from four subjects are conducted to confirm the agreements with the analytical results, by using the auto-refractometer. The two sample Kolmogorov–Smirnov test is applied to evaluate the measurement results qualitatively. The robust agreements between the analysis and the empirical results are observed. This research can be applied in the optimization of augmented reality or virtual reality devices to provide effective three-dimensional depth cues and relieve viewing discomforts.

The phase-shifting method is a simple and efficient approach to extract complex hologram information free of bias and twin-image noise. In this study, the geometric phase-shifting method is utilized for a self-interference incoherent digital holographic recording system based on the Michelson-type interferometer. The phase-shifting module consists of a horizontal polarizer, and two achromatic quarter-wave plates are employed inside the interferometer, replacing conventional phase-shifting devices, such as the piezo-actuated mirror. Since the phase-shifting amount of the introduced method herein is theoretical, regardless of the input wavelength, the simultaneous recording of step-wise phase-shifted interferograms for different color channels is available. Therefore, the multi-color hologram recording is achieved with fewer numbers of exposures. The demonstration of multi-color hologram recording and reconstruction are presented to validate the proposed idea.

A self-interference digital holographic camera with geometrical phase lens used as a passive-type common-path polarization selective wavefront modulator is proposed. A prototype is devised and the demonstration of self-interference is carried out. Since the geometrical phase lens is light weight, thin, transparent, and cost effective, the application toward the consumer level holographic camera capture system is expected.

We propose a focus-free retinal projection system, which is composed of a display device without coherent light, a pinhole, and a retroreflector film. By virtue of the retroreflector film as an image conjugator, a pinhole conjugate is formed as a small exit pupil at the center of eye pupil, which enables focus-free retinal imaging regardless of focal length of eye lens. This focus-free property of the proposed system addresses accommodation-vergence mismatch of three-dimensional augmented reality display system. We perform the experiments to prove the focus-free property of our proposed system.

The self-referencing interference incoherent digital holography system is presented. To capture the hologram, the geometrical phase lens is implemented inside the system, functioning as a common-path polarization dependent wavefront splitter and modulator.

Molybdenum disulfide (MoS2) nanosheet, one of two-dimensional (2D) semiconductors, has recently been regarded as a promising material to break through the limit of present semiconductors. With an apparent energy band gap, it certainly provides a high carrier mobility, superior subthreshold swing, and ON/OFF ratio in field-effect transistors (FETs). However, its potential in carrier mobility has still been depreciated since the field-effect mobilities have only been measured from metal–insulator–semiconductor (MIS) FETs, where the transport behavior of conducting carriers located at the insulator/MoS2 interface is unavoidably interfered by the interface traps and gate voltage. Moreover, thin MoS2 MISFETs have always shown large hysteresis with unpredictable negative threshold voltages. Here, we for the first time report MoS2-based metal semiconductor field-effect transistors (MESFETs) using NiOx Schottky electrode which makes van der Waals interface with MoS2. We thus expect that the maximum mobilities or ...

Although organic field-effect transistors (OFETs) have various advantages of lightweight, low-cost, mechanical flexibility, and nowadays even higher mobility than amorphous Si-based FET, stability issue under bias and ambient condition critically hinder its practical application. One of the most detrimental effects on organic layer comes from penetrated atmospheric species such as oxygen and water. To solve such degradation problems, several molecular engineering tactics are introduced: forming a kinetic barrier, lowering the level of molecule orbitals, and increasing the band gap. However, direct passivation of organic channels, the most promising strategy, has not been reported as often as other methods. Here, we resolved the ambient stability issues of p-type (heptazole)/or n-type (PTCDI-C13) OFETs and their bias-stability issues at once, using DNA-base small molecule guanine (C5H5N5O)/Al2O3 bilayer. The guanine protects the organic channels as buffer/and H getter layer between the channels and capping Al2O3, whereas the oxide capping resists ambient molecules. As a result, both p-type and n-type OFETs are simultaneously protected from gate-bias stress and 30 days-long ambient aging, finally demonstrating a highly stable, high-gain complementary-type logic inverter.

Two-dimensional (2D) molybdenum disulfide (MoS2) field-effect transistors (FETs) have been extensively studied, but most of the FETs with gate insulators have displayed negative threshold voltage values, which indicates the presence of interfacial traps both shallow and deep in energy level. Despite such interface trap issues, reports on trap densities in MoS2 are quite limited. Here, we probed top-gate MoS2 FETs with two- (2L), three- (3L), and four-layer (4L) MoS2/dielectric interfaces to quantify deep-level interface trap densities by photo-excited charge collection spectroscopy (PECCS), and reported the result that deep-level trap densities over 1012 cm−2 may exist in the interface and bulk MoS2 near the interface. Transfer curve hysteresis and PECCS measurements show that shallow traps and deep traps are not that different in density order from each other. We conclude that our PECCS analysis distinguishably provides valuable information on deep level interface/bulk trap densities in 2D-based FETs.

Enhanced analysis is performed to design a wedge projection system with a slab structure that increases the projected image size. The specification values of the system such as the length of the slab structure and the imaging region are calculated and investigated using an optical simulation tool. We also propose a split imaging region method to represent a large tiled scene using the thin wedge waveguide structure. Experiments are performed to verify the feasibility of the proposed method.

A pico-projector is a compact and mobile projector that has an infinite focus. We apply the pico-projector to a projection-type integral imaging system, which can expand the image depth to form multiple central depth planes. In a projection-type integral imaging system, the image flipping problem arises because the expanded elemental images pass through a lens array. To solve this problem, we propose the ray tracing of a pico-projector at a central depth plane and compensate the elemental image using a pixel-mapping process. Experiments to verify the proposed method are performed, and the results are presented.

Despite their huge impact on future electronics, two-dimensional (2D) dichalcogenide semiconductor (TMD) based transistors suffer from the hysteretic characteristics induced by the defect traps located at the dielectric/TMD channel interface. Here, we introduce a hydroxyl-group free organic dielectric divinyl-tetramethyldisiloxane-bis (benzocyclobutene) (BCB) between the channel and conventional SiO2 dielectric, to practically resolve such issues. Our results demonstrate that the electrical hysteresis in the n-channel MoS2 and p-channel MoTe2 transistors were significantly reduced to less than ∼20% of initial value after being treated with hydrophobic BCB dielectric while their mobilities increased by factor of two. Such improvements are certainly attributed to the use of the hydroxyl-group free organic dielectric, since high density interface traps are related to hydroxyl-groups located on hydrophilic SiO2. This concept of interface trap reduction is extended to stable low voltage operation in 2D MoTe2 FET with 30 nm BCB/10 nm Al2O3 bilayer dielectric, which operates well at 1 V. We conclude that the interface engineering employing the BCB dielectric offers practical benefits for the high performance and stable operation of TMD-based transistors brightening the future of 2D TMD electronics.

Self-interference digital holography (SIDH) is actively studied because the hologram acquisition under the incoherent illumination condition is available. The key component in this system is wavefront modulating optics, which modulates an incoming object wave into two different wavefront curvatures. In this Letter, the geometric-phase hologram lens is introduced in the SIDH system to perform as a polarization-sensitive wavefront modulator and a single-path beam splitter. This special optics has several features, such as high transparency, a modulation efficiency up to 99%, a thinness of a few millimeters, and a flat structure. The demonstration system is devised, and the numerical reconstruction results from an acquired complex hologram are presented.

We propose an improved projection-type integral imaging system using a three-dimensional (3D) screen consisting of a lens array and a retroreflector film in this paper. The projection-type integral imaging system suffers from the disadvantage of low-visibility images because of the inherently small exit pupil size of the projector. In order to resolve this problem, we adopt a 3D screen to avoid the demerits of a diffuser screen, such as off-screen image blur and loss of parallax. To determine the appropriate configuration of the 3D screen in the system, a simulation based on a ray transfer matrix analysis method was performed. The results show that the 3D screen should be located near the central depth plane of the integral imaging system, which leads to the conclusion that only the real mode is available for the proposed system. Experiments to verify this configuration and the feasibility of the proposed system were conducted using a system constructed with a real mode integral imaging system including a convex mirror array, which can fundamentally eliminate the pseudoscopic problem.

We propose the pickup system of integral imaging using the offset lens array (OLA), which is a useful optical component for both the pickup and display processes. The main purpose of our system is resolving the pseudoscopic image problem of integral imaging. Also, the flipped image of integral imaging that has the wrong perspective information can be removed by adding an external barrier in the display process. In this paper, the above properties are explained in detail, and the experimental results to verify the feasibility of the proposed system are presented. We are certain that our system can also be applied to other various pickup systems based on integral imaging.

We propose the method that suppresses the defocus noise optically in the Fresnel incoherent correlation holographic system using a pinhole-polarizer (PP), which is made by punching a pinhole on the linear polarizer. The system configuration of this suggestion is based on the original system with optical-sectioning capability, which is realized by presenting the phase-pinhole on the phase-only spatial light modulator. In our system, the phase-pinhole is replaced with a PP. The replaced component is no longer programmable yet provides an affordable, simple, and light-efficient system configuration. The feasibility of the system with the PP is analyzed and demonstrated.

This paper proposes a practical method to analyze the expressible depth range of an integral imaging system based on image blur at defocused depths, which is one of the most noticeable image degradations, caused by overlaps among voxels in both the real and focused mode. In order to obtain the preferably precise area of overlaps among voxels at each depth, display pixels are regarded as surface light sources in the process of voxel size calculation. As a criterion for determining the range, we determine the tolerable limit of the overlaps among voxels to be at least resolved from each other. Based on this principle, several mathematical expressions about the expressible depth range can be derived in both the real mode and focused mode, and their feasibilities are demonstrated by several experiments. The analyses are processed based on both wave optics and ray optics.

We developed volumetric 3D display by adopting liquid crystal based fast switching active optical shutter and polarization controller. This method can enhance the depth perception by projecting the clear depth images without blurring the image.

A 1D-2D hybrid complementary logic inverter comprising of ZnO nanowire and WSe2 nanosheet field-effect transistors (FETs) is fabricated on glass, which shows excellent static and dynamic electrical performances with a voltage gain of ≈60, sub-nanowatt power consumption, and at least 1 kHz inverting speed.

We demonstrate an inverter type nanodevice based on 2-dimensional semiconducting molybdenum disulfide (MoS2) nanoflakes. The inverter device was comprised of back-gate and top-gate field-effect transistors (FETs) which work respectively as a load and a driver for a logic inverter in the dark but switch their roles for photo-inverter operation. Our logic inverter shows a relatively high voltage gain of more than 12. When the back-gate FET controls the circuit as a driver to sensitively detect visible light using its open channel, the device effectively operates as a photo-inverter detecting visible photons. Our inverter based on top- and back-gate MoS2 FETs would be quite promising for both logic and photo-sensing applications due to its performance and simple device configuration as well.