This PDF file contains the front matter associated with SPIE Proceedings Volume 11709, including the Title Page, Copyright information and Table of Contents

Introduction to SPIE Photonics West OPTO conference 11709: Ultra-High-Definition Imaging Systems IV.

Japan Broadcasting Corporation (NHK) Science & Technology Research Laboratories (STRL) has long been consistently opening up new horizons for broadcasting. Its recent R&D on 8K ultra-high-definition television―the ultimate two-dimensional television―came to fruition as a regular satellite broadcasting service in Japan in December 2018, with 8K gradually penetrating media and other industries globally. The 8K specifications were determined based on psychophysical experiments to effectively produce an immersive and realistic experience with a two-dimensional screen. STRL is continuing to enhance user experiences. Aside from two-dimensional displays, today there are media devices such as head-mounted displays, augmented reality glasses, three-dimensional displays, and haptic devices. STRL is researching these devices to enhance their performance from the perspective of visual psychology and cognitive science. It is also developing three-dimensional information processing technologies and artificial intelligence aiming for new content presentations with new immersive devices. Conveying sensations other than sight and sound will create innovative sensory experiences that provide unprecedented immersion. A new media scheme that utilizes various delivery platforms such as broadcasting, the internet, and 5G is also being studied to produce new viewing experiences.

This paper describes a snapshot full- Stokes imager by two polarization cameras with linear micro-polarizer array which is aligned to 0, 45, 90 and 135° of azimuthal direction. A presentation highlights an imager for full Stokes parameters with retarder and two polarization cameras with calibration method for error of retarder to increase an accuracy. We also succeed to analyze a high definition polarization image by Stokes analysis in the Fourier domain although a polarization camera requires 2x2 pixels with linear micro-polarizer array in the space for one polarization analysis. We demonstrate same applications of bio-imaging using a differential interferometric microscope and some industrial applications by high-speed polarization camera.

Speckles, resultant to the randomized interference of coherent fields, are inherent in holographic displays. Speckle in holographic displays leads to low signal-to-ratio in the reconstructed holographic images and causes potential eye-safety issues. In this invited paper, recent works on speckle reduction in holographic displays either by modulating the light source module or by temporally multiplexing the computer generated holograms will be introduced.

Holographic three-dimensional (3D) display can reproduce the amplitude and phase of the wavefront, providing perfect reconstructions of real 3D scenes. The computer-generated hologram (CGH) for the 3D model is calculated by the layer-based angular-spectrum theory. The wavefront is encoded by the CGH which is uploaded on the phase-only spatial light modulator. In order to achieve holographic 3D display with the high-definition, the number of layers and the resolution of the 3D model are significantly important. In this work, the effects of the number of layers and the resolution on reconstruction quality are analyzed quantitatively, which provides a guidance for the design of holographic 3D display system. A high-definition 3D display system with a high-resolution 3D data module based on Kinect Azure is designed and built, realizing a high quality 3D display effect.

In polarization holography, the polarization information is recorded in the photopolymer material by interference, and the polarization state of the reconstructed wave can be calculated accurately by tensor method. Based on the guidance of tensor theory, this paper systematically analyzes the method of faithful reconstruction under any interference angle independent of exposure energy, and gives experimental verification under the condition of 40° interference angle. This conclusion is helpful to broaden our understanding of polarization holography based on tensor theory, and can be applied to the research of polarization multiplexing multi-channel holography.

The resolution of images is increasing year by year. High-definition images have a large amount of data so that high calculation cost is required for image processing. For example, when original data is restored from non-clear high-definition two dimensional coded images, it is necessary to improve the image quality. A volume holographic optical element works as a multiple lens for each pixel in an image so that spreading pixel patterns can be individually focused. Then, each pixel becomes clear and original data can be easily restored. However, it is difficult to analytically express the function of volume holographic optical elements. In our previous study, reconstructed images from a volume hologram, in which some data pages were recorded in multiple, were expressed by analytic function. The analytic function was called pixel amplitude function. In this study, the pixel amplitude function is used for an input image to a volume holographic optical element. Then, output image is analytically expressed.

The single-shot iterative Fourier transform algorithm as a common non-interferometric phase retrieval algorithm is very suitable for phase-modulated holographic data storage due to its fast, simple and stable properties. It retrieves the phase in the object domain iteratively from the intensity image in the Fourier domain captured by the detector. Because of the effects by complex noises of the experimental system, there is always an intensity image degradation which increases the phase decoding bit error rate. This paper proposed a denoising method based on end-to-end convolutional neural networks by learning the relationship between the captured intensity images and the simulation results to improve image quality significantly. Then the denoised intensity image was used in the phase retrieval. The experiment results showed that the bit error rate can be reduced by 6.7 times using the denoised image, which proved the feasibility of the neural network denoising method in the phase-modulated holographic data storage system.

In this talk, we will discuss a detailed study of the performance of organic photodiodes (OPDs) based on polymeric bulk heterojunctions. We will show that their performance is comparable with that of low-noise SiPDs in all metrics, except response time within the visible spectral range. Furthermore, OPDs present significant advantages over their inorganic counterparts since they can be fabricated on flexible substrates and their level of performance remains unprecedented even when their area is increased. Advantages of OPDs are further illustrated and quantified in a biometric monitoring application that uses ring-shaped, large-area, flexible OPDs, while maintaining low-noise SiPD-level performance. We will discuss how this remarkable performance arises from the selection of photoactive layer materials and by device-geometry optimization without charge-blocking layers.

The transport of intensity equation (TIE) has been widely applied to phase imaging. A variety of methods for solving the TIE have been proposed. One of the most popular methods is an FFT-based method, which is simple and fast. However, this method has a strict restriction that the intensity of the object is assumed to be uniform. Otherwise, the accuracy of phase retrieval results may drop significantly. The transport of phase equation (TPE) is an equation coupled with the TIE, and both are derived from the Helmholtz equation. Few works have studied the role of the TPE in 3D imaging. In this work, a non-iterative FFT-based TIE with TPE correction is proposed. The phases at the object plane and four defocused planes are first calculated by the TIE. Ideally, the object intensity and computed phases are supposed to satisfy both the TIE and TPE. But the non-uniformity of object intensity, as well as the use of finite differences of intensities in the calculation of longitudinal derivatives for the FFT-based TIE method, introduce errors in phase retrieval result. We show that by using the TPE, the local refractive index during propagation can be updated and used as a correction in the TIE. The TIE is solved once again using the updated refractive index, and shows reduction of errors. This proposed technique can be extended to amplitude and phase imaging. It also offers the advantage of yielding the unwrapped phase with good accuracy performance and can be potentially applied to medical high-definition 3D imaging, for cells, micro bubbles, etc.

Currently, we believe a prospective in-hospital combination of 8K ultra-high definition (UHD) image technology and a communication network built of 5G and graded-index plastic optical fibers (GIPOF) will be of great help to an advanced dynamic medical practice. In this paper, we report our prospect and the current state of the art of this integrated “8K plus 5G/GIPOF” hospital in terms of “how is it good?”, “where are we now?” and “where do we go from here?”

For image devices such as cameras and displays, it is difficult to obtain consistent color reproducibility due to individual manufacturer designs. We propose to improve the color reproducibility of medical images by using color charts. With the spread of COVID-19 infection, the need for telemedicine is increasing from the perspective of infection prevention. In addition, the digitization of medical images will progress in the future, and it is required that the color reproducibility of supervised data at the time of image acquisition be improved for learning / diagnosis assistance by AI. Colors in the specialized field of medical image processing are largely processed in non-standardized methods, raising many challenges in use cases where color is used for diagnostics. Smartphones are used in telemedicine, but color reproducibility may decrease due to differences in lighting as well as equipment, which may lead to a decrease in diagnostic accuracy. We have developed color charts and appropriate image processing algorithms for medical use cases. In the AI accuracy verification in pathological diagnosis, it was also confirmed that the AI diagnosis accuracy can be improved by performing image processing using a color chart.

The ever-growing demand for fast data transmission, including for high definition video, is an important challenge for communications. Visible light communication (VLC, also known as Li-Fi) in which visible light sources are used to send information is a promising approach to address aspects of this challenge. This talk will show how organic semiconductors can be used to make fast transmitters and receivers. In particular it will show how in spite of the low mobility of organic semiconductors, organic light-emitting diodes can be used as sources for data communication at over 1 Gbps.

In recent years, automotive gigabit and multigigabit Ethernet technology is expected to be applied in autonomous driving system and advanced driver assistance system. Step-index-type plastic optical fiber (SI-POF), graded-index-type glass optical fiber (GI-GOF), and graded-index-type plastic optical fiber (GI-POF) will be the transmission media for high bandwidth data transmission. In order to reserve smooth light coupling at in-line connections, flexible and low loss waveguide is required. In this presentation, we propose and demonstrate optical interconnection by light-induced self-written (LISW) waveguide using a soft gel resin. We performed simple fabrication of LISW waveguide using near infrared sensitive gel resin and high flexibility of waveguide under harsh environment of vibration. undefined In recent years, automotive gigabit and multigigabit Ethernet technology is expected to be applied in autonomous driving system and advanced driver assistance system. Step-index-type plastic optical fiber (SI-POF), graded-index-type glass optical fiber (GI-GOF), and graded-index-type plastic optical fiber (GI-POF) will be the transmission media for high bandwidth data transmission. In order to reserve smooth light coupling at in-line connections, flexible and low loss waveguide is required. In this presentation, we propose and demonstrate optical interconnection by light-induced self-written (LISW) waveguide using a soft gel resin. We performed simple fabrication of LISW waveguide using near infrared sensitive gel resin and high flexibility of waveguide under harsh environment of vibration.

Recently, Higher-resolution videos such as 4k8K are required in any fields and 5th generation of cellular networks, called 5G, is about to be installed. These trends need high-speed communication inside devices as well as intra devices. Most of all electrical companies is developing new gaming system of AR/VR or the other new products based on these technologies for consumer electronics. To meet the market demands, optical transmission using Optical Fiber has been developed and applied for connecting between devices, especially, Active Optical Cable (AOC) is focused on for the consumer electronics, which people can use easily such as a conventional copper cable. Then, Polymer optical waveguide is believed as the one of solutions to transmit optical signals inside devices. We have been developing Plastic Optical Fiber (POF) and Optical Flexible Printed Circuit (OFPC) from design of materials. Our new POF combines flexibility and high heat resistance. On the other hand, OFPC, which is combination of polymer waveguide and conventional FPC, can make the plug size of AOC smaller due to its unique coupling structure. Both of their characteristics can contribute to safety and usability of AOC. In this report, we describe the overview of our materials of POF and waveguide and their properties, then we introduce OPFC based on polymer optical waveguide.

A novel high-speed data transmission system comprising RJ45-connectored transceivers and SC-connectored POF (polymer or plastic optical fiber) cable has been examined, comparing with a glass optical fiber cable system and traditional copper ethernet cables. Polymer Optical Fiber and cables made of, offer high speed data transmission capability, yet very pliable and bendable. Graded-index (GI-) POF and cables appear as good substitutes of both copper wire/cables and glass fiber/cables in short-reach networks. In this paper, we will analyze data of comparison of technologies and demonstrate commercial feasibilities and deployments of RJ45-connectored GI-POF cable system for high speed 5G/6G, high-definition display, monitoring, imaging and other applications.

Ultra-high-definition applications will be one of the main drivers for emerging 5G communications. 5G supports higher data rate utilizing higher frequency bands than those in existing cellular systems. However, higher-frequency radio waves have higher directionalities, resulting in decreased indoor coverage. Therefore, radio-over-fiber (RoF) systems are needed for indoor distribution of wireless signals. Recently, we developed a graded-index plastic optical fiber (GI POF) that enables higher-quality RoF transmission than conventional multimode fibers for short-distance links (<100 m). The GI POF can reduce noise and distortion in RoF transmission through its strong mode coupling. Here, we demonstrate that the GI POF significantly increases fiber-misalignment tolerance in RoF transmission. The GI POF will realize do-it-yourself optical fiber connections for indoor applications.

The recent deployment of ultra-high definition (UHD) applications rapidly increases data traffic in communication networks including datacenter networks. In datacenters, a large number of parallel optical links with multi-fiber push-on (MPO) connectors are employed for high-speed inter-switch communications. However, it needs precise alignment to completely eliminate air gaps in MPO connectors, and the air gaps increase noise owing to optical reflection. Here, we demonstrate that graded-index plastic optical fibers (GI POFs) increase tolerance to the connector reflection for high-quality data transmission because of its intrinsic mode coupling. This feature of the GI POFs will be advantageous to MPO-connector-based interconnect for data center applications in the upcoming UHD era.

We have developed a 17.3-inch 8K wide color gamut in-plane switching LCD (IPS-LCD) with a polarized laser backlight. By applying a zero–zero-birefringence polymer, the polarized laser backlight emits polarized light with 88% polarization. We adapted the double light guide plate laser backlight to achieve uniform luminance. The developed IPS-LCD achieves a wide color gamut with high efficiency. The speckle problem was solved by applying an AC voltage to the laser diodes. In addition, the double light guide plates effectively suppress the speckle as the light is uniformly mixed in the light guide plate.

The holographic performance of photo-polymeric material PQ/PMMA is found to be largely determined by pre-polymerization modulation, such as stirring time and pre-polymerization temperature, during the material preparation process. In the current study, in order to determine the best stirring time during the pre-polymerization process, the influence of stirring time on the holographic properties of PQ/PMMA here is seriously analyzed. Experimental observations clearly indicate that, under the same baking conditions, the diffraction efficiency of PQ/PMMA increase initially with the stirring time but then decrease as the stirring time continue increases. When the stirring time is 75 min, the holographic performance of PQ/PMMA reaches its best in which the diffraction efficiency of the material can reach up to 49.3%. Current study here determines the optimal stirring time and pre-polymerization temperature during the pre-polymerization process, thus provide an effective guidance for further preparation of PQ/PMMA photo-polymer materials with excellent holographic properties.

Triple-zero-birefringence polymer (TZBP), where photoelastic birefringence, orientational birefringence, and the temperature dependency of orientational birefringence are suppressed to negligible levels, is required to achieve real-color display. Recently, we successfully synthesized TZBPs with excellent mechanical strength and high heat resistance by using alternating copolymers, which show nonlinear relationships between birefringence properties and the composition of polymers. Here, we propose the method to design TZBPs by utilizing alternating copolymers in ternary systems. Using this method, we can further improve the characteristics of the TZBP. The TZBPs based on the alternating copolymers will achieve real-color images not only for vehicle-mounted displays but also flexible displays.

Liquid-crystal displays and organic light-emitting diode displays cause a blackout problem or a color change problem, viewed through polarized sunglasses. The random depolarization film (RDF), a polymer film doped with calcite particles, improves both the problems of the displays and contributes to realizing real-color displays. However, RDF degrades sharpness of the displayed image owing to light scattering by the dopant particles. In this study, we achieve RDF that improves the image sharpness by utilizing directional forward scattering caused by micro-sized particles. In the conference, we will discuss the optimization of the dopant size in RDF for realizing real-color displays with the sharp image.

We present a wavelength coded volume holographic gratings (WC-VHGs) based dual wavelength fluorescence imaging system to simultaneously obtain two color fluorescence images of biological samples in one shot. The system utilizes wavelength coded recording technique based on Bragg degeneracy to generate the PQ-PMMA volume holographic gratings, which has high selectivity in both wavelength and angle. In order to improve the optical sectioning ability of the proposed system, we use HiLo image processing to suppress the out of focus signal. Experimental results demonstrate the imaging ability of the proposed system to observe multi-wavelength fluorescence images and HiLo images.

Quantitative differential phase contrast (qDPC) imaging is a specific technique for observing the transparent object. qDPC method adopts the structured-light illumination to provide the quantitative phase reconstruction, and it has lesser hardware requirement compared with other quantitative phase imaging (QPI) method. Conventionally, to achieve isotropic phase retrieval with better uniformity by utilizing qDPC system, it needs multiple measurements with different asymmetric illumination pattern along the transverse direction. However, it takes much more time to reconstruct the phase distribution while increasing the number of measurements. Therefore, here we applied the deep neural network (DNN) model for approaching isotropic phase retrieval and minimizing the acquisition time simultaneously. To achieve the isotropic phase distribution with less measurements, the U-net architecture was adopted in this study. The U-net model was utilized for converting the result from 1-axis qDPC method (the phase retrieval which has lesser measurements) to the result from 12-axis qDPC method (the phase retrieval which has more measurements to cover all the spatial frequency information in the spatial-frequency domain). For the model training stage, we prepared 5 different types of cells to provide sufficient training datasets. To evaluate the performance of our trained model, we prepared another 2 distinct types of cells referred as testing dataset. The results showed our model can recover the insufficient phase value in the sample. The morphology of cells can be analysis after applying our proposed DNN model.

In this study, we propose a method for reducing inter-pixel crosstalk noise using holographic optical elements, and confirm the reduction effect on 4×4 page data. Some experimental results are presented. undefined In this study, we propose a method for reducing inter-pixel crosstalk noise using holographic optical elements, and confirm the reduction effect on 4×4 page data. Some experimental results are presented.

In this study, we prepared a cylindrical wave diffractive optical element that diffracts color images using volume hologram technology to improve the performance and cost of HMDs.