Electronic holographic displays precisely reconstruct the wavefront of object light and have attracted considerable attention for Virtual Reality (VR) and Augmented Reality (AR) applications. To achieve a high-quality holographic display with a wide field of view, it is necessary to reduce the pixel pitch of a spatial light modulator (SLM) to about 1 μm. We have achieved a precise control of Liquid Crystal (LC) alignment in 1 μm pitch pixels by exploiting the anisotropy of pixel space due to the lattice-shaped dielectric walls. In this paper, we have investigated the effect of LC-SLM structure on the image quality of electric holographic displays. As a result, we clarified that the image quality of phase-modulation type holographic displays does not degrade even when the number of gray levels is four or more and established a simple pixel structure that allows independent control of 1 μm pitch pixels and high image quality.
One-dimensional 1-μm-pitch light modulation was achieved experimentally using a liquid crystal (LC) device for wide viewing-zone angle holographic displays. When the pixel pitch of the LC device is 1 μm, individual pixel driving is extremely difficult due to electric field leakage and penetration of the elastic force of the LC from adjacent pixels. To overcome these problems, a dielectric shield wall structure is suggested, with dielectric walls between pixels. An LC cell with a dielectric shield wall structure was fabricated using nanoimprint technology; the individuality of the light modulation and diffraction pattern produced by the LC cell was evaluated. Our results showed that the dielectric shield wall structure achieved individual 1-μm-pitch light modulation and a diffraction angle of 19 deg at a wavelength of 633 nm. The remaining layer of the dielectric resin, which is surplus dielectric resin under the dielectric walls produced by the nanoimprint procedure, should be reduced as it tends to increase the driving voltage and electric field leakage from adjacent pixels.
We focused on several technical approaches to flexible liquid crystal (LC) display in this report. We have been
developing flexible displays using plastic film substrates based on polymer-dispersed LC technology with molecular
alignment control. In our representative devices, molecular-aligned polymer walls keep plastic-substrate gap constant
without LC alignment disorder, and aligned polymer networks create monostable switching of fast-response ferroelectric
LC (FLC) for grayscale capability. In the fabrication process, a high-viscosity FLC/monomer solution was printed,
sandwiched and pressed between plastic substrates. Then the polymer walls and networks were sequentially formed
based on photo-polymerization-induced phase separation in the nematic phase by two exposure processes of patterned
and uniform ultraviolet light. The two flexible backlight films of direct illumination and light-guide methods using small
three-primary-color light-emitting diodes were fabricated to obtain high-visibility display images. The fabricated flexible
FLC panels were driven by external transistor arrays, internal organic thin film transistor (TFT) arrays, and poly-Si TFT
arrays. We achieved full-color moving-image displays using the flexible FLC panel and the flexible backlight film based
on field-sequential-color driving technique. Otherwise, for backlight-free flexible LC displays, flexible reflective devices
of twisted guest-host nematic LC and cholesteric LC were discussed with molecular-aligned polymer walls. Singlesubstrate
device structure and fabrication method using self-standing polymer-stabilized nematic LC film and polymer
ceiling layer were also proposed for obtaining LC devices with excellent flexibility.
We have been developing a novel-structure ferroelectric liquid crystal (FLC) device containing micropolymers for roll-up screen displays. We studied bending-iteration tolerance of a flexible FLC device containing polymer-fiber networks and lattice-shaped walls. Although conventional bistable FLC devices have the disadvantage of fragile smectic layer structures, the polymer walls fasten two flexible thin plastic substrates and keep the FLC layer thickness constant even when the device is bent. Otherwise, the anchoring of the molecular-aligned polymer networks enables FLC to obtain monostable molecular switching. We first examined mechanical stability of smectic layers in monostable FLC devices by shearing two substrates. It was found that the monostable FLC device shows good tolerance without generating alignment defects, in comparison with the bistable FLC device. We then formed a flexible device of a size of 100mm x 100mm by utilizing two-step photopolymerization-induced phase separation of an FLC/monomer solution film coated by a flexographic printing method. As a result, the 2-μm-thick cured composite film supported the two 100-μm-thick plastic substrates. We repeatedly bended it at a minimum curvature radius of 20mm in period time of 20s. As a result, its microscopic texture and electrooptic effect were not changed even after bending of 1000 times. The spatial uniformity of the flexible device was kept for more than 10000-times bending.
We have developed a ferroelectric liquid crystal device with a novel structure containing a polymer fiber network for flexible lightweight displays using thin plastic substrates. The aligned polymer fibers of sub-micrometers -diameter were formed under ultraviolet light irradiation in a heated nematic- phase solution consisting of liquid crystal and monofunctional acrylate monomer. The rigid polymer network was found to adhere to the two plastic substrates, and the uniform liquid crystal alignment provided a contrast ratio of 100:1 for a monomer concentration of 20 wt%. This device achieves a continuous grayscale capability as a result of change in the spatial distribution of small liquid crystal domains, and also exhibits a fast response time of 80 microsecond(s) due to high-purity separation of polymer and liquid crystal materials. It therefore has attractive features for flexible moving-image display applications.
A novel 3D camera named Axi-vision camera was developed. IT can acquire both color and distance information of objects. An intensity-modulated light illuminates objects and the camera with an ultra-fast shutter captures the light reflected from the scene. The distance information is obtained from two images of the same scene taken under linearly increasing and decreasing illuminations. The camera does not require scanning, multiple camera units, or complicated computations. It is possible to acquire distance information for each pixel of a TV image at real time. The operational features and technical specifications of the camera were investigated. The application to TV program production, such as replacing the image of an object at a particular distance by another, was demonstrated. A new 3D display system is also proposed, developed and demonstrated.
The polymer-dispersed liquid crystal (PDLC) films of the optically addressed light valves in the high-definition television (HDTV) projection display described here can modulate unpolarized light with high spatial resolution as well as with a high optical efficiency based on the light scattering effect. A PDLC film suitable for use in HDTV projection display was developed by evaluating the microscopic spatial light modulation and polymer-network morphological properties of test films prepared using various curing conditions for photopolymerization-induced phase separation. Films produced under optimum curing conditions have a fine polymer-network structure appropriate for films used in the light valves of a HDTV projection display. Our prototype full-color HDTV projection display using three PDLC light valves provides a resolution of 850 TV lines, a brightness greater than 1800 ANSI lumens, and a maximum contrast ratio of 100:1.
There is hopefully expected a projection display using spatial light modulators (SLMs) converting a faint input-image into a brilliant output-image. A conventional liquid crystal SLM loses more than 50% of a reading light in polarizer. To solve this problem, we developed a new SLM consisting of polymer-dispersed liquid crystal (PDLC) and Bi12SiO20 photoconductive layers. This SLM needs no polarizer, because it lets a reading light pass or scatter depending on whether a writing light is incident upon the photoconductive layer. We calculated the dependence of the resolution of the device on the several parameters including thickness, dielectric constants and conductivities of the dielectric mirror and PDLC layer by using a new electrical image method. A high-definition SLM with limiting resolution (36 - 50 lp/mm) was fabricated by stacking the optimized mirror and PDLC layer. In cooperating the device into a Schlieren optical system consisting of an LC panel as an input image source and a 1 kW Xenon lamp as a projection light source, we performed high-contrast green image projection with a total luminous flux of 1500 lumen.
We describe the polymer-dispersed liquid crystal light valve (PDLCLV) using a polymer-dispersed liquid crystal (PDLC) film and a Bi12SiO20 (BSO) photoconductive crystal. The PDLCLV has many features suitable for large screen displays, such as no polarizer requirement, a high transmittance (72 to 78%) and high extinction ratio (146:1 to 178:1) in the entire visible wavelength, short rise/decay times (3/5 to 14/15 ms), and a high resolution (34 lp/mm). We discuss the light scattering and modulation characteristics of the PDLC film; photoconductive characteristics of the BSO crystal; and the design, fabrication method, and optical input/output characteristics of the PDLCLV. We also describe the configuration and image display characteristics of a monochrome projection-type display consisting of the PDLCLV as an image converter, an active matrix liquid crystal panel with thin film transistors as an image source, and a 1-kW xenon arc lamp as a reading light source.
This paper describes the polymer-dispersed liquid crystal light valve (PDLCLV) using a polymer-dispersed liquid crystal (PDLC) film and a photoconductive crystal. Bi12SiO20 (BSO) and its application to projection displays. The PDLCLV has many features suitable for large screen displays, including no requirement of polarizers, high transmittance, and high-speed response. We discuss the light scattering and modulation characteristics of the PDLC film, photoconductive characteristics of the BSO crystal, and the design, fabrication and optical input/output characteristics of the PDLCLV. We also describe the configuration of a monochrome projection display consisting of the PDLCLV as an image converter and a liquid crystal panel with thin film transistors as an image source and its image display characteristics.
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