Front Matter: Volume 8643

3D representation of digital signage improves its significance and rapid notification of important points. Real 3D display techniques such as volumetric 3D displays are effective for use of 3D for public signs because it provides not only binocular disparity but also motion parallax and other cues, which will give 3D impression even people with abnormal binocular vision. Our goal is to realize aerial 3D LED signs. We have specially designed and fabricated a reflective optical device to form an aerial image of LEDs with a wide field angle. The developed reflective optical device composed of crossed-mirror array (CMA). CMA contains dihedral corner reflectors at each aperture. After double reflection, light rays emitted from an LED will converge into the corresponding image point. The depth between LED lamps is represented in the same depth in the floating 3D image. Floating image of LEDs was formed in wide range of incident angle with a peak reflectance at 35 deg. The image size of focused beam (point spread function) agreed to the apparent aperture size.

We propose a novel real-time pickup and display of integral imaging system using only a lens array and a high speed charge coupled device (CCD). A simple lens array and a high speed CCD can capture 3D information of the object and a commercial liquid crystal (LC) display panel shows the elemental image in real-time. Reconstructed image is real and orthographic so that the observer can touch the 3D image. Furthermore, our system is free from pseudoscopic problem by adopting recent pixel mapping algorithm. This algorithm, based on image interweaving process, can also change the depth plane of the displayed 3D images in real-time. C++ programming is used for real-time capturing, image processing, and display. For real-time high quality 3D video generation, a high resolution and high frame rate CCD (AVT Prosilica GX2300C) and LC display panel (IBM 22inch 3840×2400) are used in proposed system. Proper simulation and experiment are presented to verify our proposed system. We expect that our research can be the basic technology for real-time 3D broadcasting and interactive 3D technology.

Recently liquid-based optical devices are emerging as attractive components in three-dimensional (3D) display for its compact structure and fast response time. Among them an electrowetting prism array is one of the promising 3D devices. It steers a beam, which enables to provide corresponding perspectives to observer. For high quality autostereoscopic 3D displays the important factors are the beam steering angle and the beam profile, the optical characteristics. In this paper, we propose a method to measure the optical characteristics of the liquid prism and show experimental results on our prototype electrowetting prism array, which consists of prisms with 200um by 200um size. A modified 4-f system is adopted for the proposed method. It provides two kinds of information of the optical characteristics of the liquid prism at the image plane and at the Fourier plane. First, the proposed measurement setup magnifies the image of the liquid micro prism array so that we can observe the status of the each prism array directly with bare eye and align a mask easily for selecting a prism to be examined at the image plane. Secondly, the steering angle can be calculated by measuring the displacement of the beam at the Fourier plane, where the angular profiles that have important information on the oilwater interface is observed precisely. The principle of the proposed method will be explained, and the measured optical characteristics from experimental results on the liquid prism we fabricated will be provided, which proves the validity of the measurement method.

A volume hologram recorded with a lens array is proposed as a transflective screen for Head Worn Display (HWD) systems. Design, fabrication as well as proof of concept are reported. Light from a projection system, with similar properties to one mounted on the side of an eyewear, is efficiently diffracted towards the eye with an angular spread given by the numerical aperture of the lenses forming the lens array. Using a dual-focus contact lens, high-resolution images can be added to the HWD user’s normal vision, as light from the surrounding environment is transmitted through the screen with low aberrations. This screen offers the possibility for small footprint and large field of view HWD’s.

To create holographic or volumetric displays, it is highly desirable to move from conventional imaging projection displays, where the light is filtered from a constant source towards flying spot, where the correct amount of light is generated for every pixel. The only light sources available for such an approach, which requires visible, high output power with a spatial resolution beyond conventional lamps, are lasers. When adding the market demands for high electro-optical conversion efficiency, direct electrical modulation capability, compactness, reliability and massproduction compliance, this leaves only semiconductor diode lasers. We present red-emitting tapered diode lasers (TPL) emitting a powerful, visible, nearly diffraction limited beam (M²1/e² < 1.5) and a single longitudinal mode, which are well suited for 3d holographic and volumetric imaging. The TPLs achieved an optical output power in excess of 500 mW in the wavelength range between 633 nm and 638 nm. The simultaneous inclusion of a distributed Bragg reflector (DBR) surface grating provides wavelength selectivity and hence a spectral purity with a width Δλ < 5 pm. These properties allow dense spectral multiplexing to achieve output powers of several watts, which would be required for 3d volumetric display applications.

There exists a growing demand for displays in wearable applications. Wearable displays have traditionally been state-ofthe- art flexible designs that are subsequently mounted onto clothing fabric. Ideally, such a design would itself be fabricintegrated. Recently, much attention has been placed on work involving the weaving of photonic bandgap and other optical fibers to create a true fabric based display. Little exists in the technical literature concerning knit-based fabric displays. In this research, a prototype 4-pixel emissive fabric display is demonstrated. Conductive silver-plated nylon fibers act as a cathode. The fibers are coated in poly-2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene (MEHPPV). When this layered structure is placed in contact with a separate metallic fiber (functions as an anode), a singlelayer PLED is formed. After drying and annealing, coated fibers are knit into a fabric matrix using a Shima Seiki SSG202SV automated knitting machine. The knit pattern itself provides a passive matrix addressing system similar to that of a more simple weave. Equivalent planar devices and single-pixel fiber structures are also fabricated. The resultant structures are all actuated, and current-voltage data is obtained for individual pixels using a source meter. Electroluminescence spectra are collected under tension using a UV-NIR spectrometer. The performance of the fiber devices is then compared to its planar analogues. Future directions for investigation are also proposed.

Microdisplay technology, the miniaturization and integration of small displays for various applications, is predominantly based on OLED and LCoS technologies. Silicon light emission from hot carrier electroluminescence has been shown to emit light visibly perceptible without the aid of any additional intensification, although the electrical to optical conversion efficiency is not as high as the technologies mentioned above. For some applications, this drawback may be traded off against the major cost advantage and superior integration opportunities offered by CMOS microdisplays using integrated silicon light sources. This work introduces an improved version of our previously published microdisplay by making use of new efficiency enhanced CMOS light emitting structures and an increased display resolution. Silicon hot carrier luminescence is often created when reverse biased pn-junctions enter the breakdown regime where impact ionization results in carrier transport across the junction. Avalanche breakdown is typically unwanted in modern CMOS processes. Design rules and process design are generally tailored to prevent breakdown, while the voltages associated with breakdown are too high to directly interact with the rest of the CMOS standard library. This work shows that it is possible to lower the operating voltage of CMOS light sources without compromising the optical output power. This results in more efficient light sources with improved interaction with other standard library components. This work proves that it is possible to create a reasonably high resolution microdisplay while integrating the active matrix controller and drivers on the same integrated circuit die without additional modifications, in a standard CMOS process.

Reverse-emulsion electrophoretic display (REED) technology is based on an electro-responsive ink comprised of self-assembled nanodroplets dispersed in a non-polar liquid. The dye-containing nanodroplets are selectively driven toward or away from the viewing plane by patterned electrodes that define distinct pixels. In this study, experimental measurements of relative luminance were conducted to determine how ink concentration affects display performance, especially with respect to image contrast and response time. The particle size distribution of the ink was determined by dynamic light scattering and corroborated by atomic force microscopy, with average size approximately 200 nm. Concentration levels of 100%, 50%, 37.5%, 25%, 18.8%, 12.5% were tested for luminance, and the highest contrast ratio was achieved at 25%. Ink concentration was observed to have little effect on switching time, with all cases reaching steady state within approximately 2 s. Spatial variability was measured by isolating 5 mm circular zones within each tested device, and the lowest variability in relative luminance was observed for 18.8% and 25% concentration levels. The experimental observations were compared to predicted behavior based on multiphysics simulation with diluted species transport and electrostatics. The experimental test devices exhibited behavior that was similar to the saturation effects predicted by simulation, accounting for steric effects.

State of the art LED pico-projectors using single-channeled optical layouts are always constricted by a trade-off between achievable flux and minimum system size. Furthermore, their limited depth of focus require additional mechanically moving components for focusing if variable projection distances are essential for their specific application. We present a novel microlens-array based LCD projector breaking these constraints of conventional LED illuminated systems, thus enabling a super compact, robust and bright module while offering new features for electronic focal distance control without additional mechanical components. While the short focal length of each contributing channel maintains a certain system slimness, the superposition of all individual projections on a screen done by image-preprocessing leads to dramatic flux enhancement without blurring effects. Starting with a description of the working principle of array projection we focus on key properties regarding depth of focus for examining novel image-preprocessing algorithms that enable for only software-controlled focal distance. Further improved program code enables sharp images even onto freeform screen geometries. The realized prototype utilizes a transmissive LCD microdisplay along with a monolithic array of 45 microlenses actively aligned to the top of the display coverglass. While the display is illuminated by a collimated white LED; each channel is assigned to one primary color by applying a color filter array buried below the microlenses to obtain a full color image on the screen. The displayed image content is controlled via PC by a novel software tool, whose correct operation is verified by experimental results.

Many kinds of head mount displays (HMDs) and head up displays (HUDs) have been appeared on the HMD / HUD early adaptor market. Many of them have become equipped with see-through capability and require dimming capability in response to ambient environmental conditions. We fabricated a high-speed liquid crystal (LC) variable attenuator using radially arranged electrodes and evaluated its basic characteristics.

At present, LED-based pico-projectors are in widespread use. However, with the requirement for compact size, the demand for laser-light-source-based pico-projectors is expected to increase in the near future. Furthermore, picoprojectors with 3D capabilities are desired. 3D projectors employ either an active shutter system or a passive shutter system. We have proposed a novel combined circular polarization switch for 3D laser pico-projectors with passive shutter glasses, which consists of a high speed ferroelectric liquid crystal (FLC) linear polarization switch and a multiorder quarter-wave plate using a nematic liquid crystal (NLC) for RGB color chromatic dispersion compensation. In this study, we present a design concept of the polarization switch and we demonstrate that it affords increased bandwidth compared to the achromatic compensation method using an FLC with low order compensation films. The adjustment for each RGB laser wavelength using an additional polymer film working in the target range of 445 – 640 nm is also indicated. By using this novel design, when the permissible crosstalk level is 0.5%, the available wavelength range broadens from 59% to 91% of the target range. In addition, we fabricate a prototype based on the design concept and evaluate its crosstalk and 3D performance, which are important parameters for a 3D projector, in combination with a MEMS system. The proposed switch can be placed in the path of a combined RGB laser beam, and it is suitable for both imager-based and scanning-MEMS-based systems because of its simple structure and compact design.

Flat panel displays are conventionally cooled by internal natural convection, which constrains the possible rate of heat transfer from the panel. On one hand, during the last few years, the power consumption and the related cooling requirement for 1080p displays have decreased mostly due to energy savings by the switch to LED backlighting and more efficient electronics. However, on the other hand, the required cooling rate recently started to increase with new directions in the industry such as 3D displays, and ultra-high-resolution displays (recent 4K announcements and planned introduction of 8K). In addition to these trends in display technology itself, there is also a trend to integrate consumer entertainment products into displays with the ultimate goal of designing a multifunction device replacing the TV, the media player, the PC, the game console and the sound system. Considering the increasing power requirement for higher fidelity in video processing, these multifunction devices tend to generate very high heat fluxes, which are impossible to dissipate with internal natural convection. In order to overcome this obstacle, instead of active cooling with forced convection that comes with drawbacks of noise, additional power consumption, and reduced reliability, a passive cooling system relying on external natural convection and radiation is proposed here. The proposed cooling system consists of a heat spreader flat heat pipe and aluminum plate-finned heat sink with anodized surfaces. For this system, the possible maximum heat dissipation rates from the standard size panels (in 26-70 inch range) are estimated by using our recently obtained heat transfer correlations for the natural convection from aluminum plate-finned heat sinks together with the surface-to-surface radiation. With the use of the proposed passive cooling system, the possibility of dissipating very high heat rates is demonstrated, hinting a promising green alternative to active cooling.

In this paper we present a mathematical model, its numerical simulations as well as preliminary experimental results used for the estimation of the true radiance value as well as the sub pixel position of a point targets that caused to saturation in the specific pixel at the detector where they appeared. The estimation is done by applying the model for the point spread function of the optics and by using the values of the neighbor and the non saturated pixels.

The performance of infrared imaging system is strongly affected by non-uniformity in infrared focal-plane arrays (FPA). In the classical scene-based nonuniformity correction (NUC) method, errors commonly occur resulting from local motion between two frames. In this paper, a novel scene-based NUC method is presented. This method calculates robust optical flow between two adjacent frames to get the velocity vector of each pixel in the current frame. In this way, corresponding to the pixel in the current frame, the location of the pixel in previous frame is known, and then these frames can be locally registered easily. Based on the assumption that any two detectors with the same scene would produce the same output value, minimize the mean square error between two local registered images to get the estimation of each detector’s gain and offset. With gain and offset parameters, nonuniformity of infrared imaging system can be corrected. One advantage of this scene-based NUC algorithm is that it can adapt to scene with local motion. The performance of the proposed algorithm is studied with infrared image sequences with simulated nonuniformity and infrared imagery with real nonuniformity. It shows that fixed-pattern noise is reduced efficiently even when the scene include local motion.

As a fine material widely used in solar cells, electrochromic devices and an excellent photocatalyst, Titanium dioxide (TiO2) has attracted more and more attention. There are many factors that affect the properties of TiO2 thin films including reaction temperature, reaction time and concentration. The influence of the pH of the precursor solution on the formation of TiO2 thin films, however, has not been studied thoroughly. Involved in the solution such as Hydrochloric acid (HCl) or urea ((NH2)2CO) reagent, the pH of the solution can be controlled by the ratio of both. During the experiment, which involves the hydrolysis reaction of Ti3+, changing the pH of the solution will affect the speed of the reaction rate and film thickness. Therefore, the pH of the solution affects the surface morphology of the TiO2 thin films. The growth of TiO2 with different pH shows unequable states. Through the observation and characterization of the experimental results, we can optimize the pH of the growth environment.

This investigation studies fringe field between laterally adjacent electrodes in a reverse-emulsion electrophoretic display (REED). The display consists of a nanodroplet ink and a porous matrix that serves as the "paper" between planar electrodes. One relative advantage of this type of electronic paper display is that it can be produced with lowcost materials and manufacturing processes. A concern for image resolution, however, is the fringe field effect that occurs in the gaps between neighboring electrodes. Ideally the dye-containing nanodroplets in the ink move in a direction that is strictly perpendicular to the opposing pairs of electrodes. However, nanodroplet saturation and potential gradients from neighboring electrodes may result in lateral displacement of the nanodroplets as well. Accordingly, this study examines how fringe field between neighboring electrodes is affected by lateral spacing and applied voltage. Transient and steady-state effects were studied by fabricating and testing devices that were patterned with different lateral spacing between electrodes, and switching under different voltage levels. Relative luminance was extracted from digital microscope images, captured in the vicinity between neighboring electrodes. Measurements were recorded for electrode spacing of 20 μm, 40 μm, 60 μm, and 80 μm with devices switched at ±1.5 V and ±2.5 V. Gradients in luminance overlapped at lateral distances below 60 μm, and became distinct for left and right electrodes spaced by at least 80 μm. Higher applied voltage resulted in steeper transition between light and dark states, but exhibited distortion at electrode edges.