We propose a chiral-nematic liquid crystal (CN-LC) device that reflects the infrared light, where the planar
state is transparent over the entire visible wavelengths and the focal conic state scatters the light
achromatically. The proposed CN-LC device can be operated at a low voltage because of the long pitch. A
liquid crystal display (LCD) switchable between reflective and transmissive modes can be realized by
stacking a CN-LC layer and a nematic LC layer.
We propose a fast switching method for a homogeneous-aligned liquid crystal (LC) cell using 3-terminal
electrode structure. LCs are vertical-aligned momentarily before they are in-plane switched to show a bright
state, by which LCs are in a transient state rather than the stable state. The turn-on can be faster, whereas LCs
start to relax along the rubbing direction so that the relaxation is optically hidden. The turn-off time of about
0.6 ms could be obtained. Experimental results show that fast gray-to-gray response as well as turn-on and
turn-off can be achieved by using the proposed switching method.
The common feature of bistable liquid crystal displays (LCDs) is the existence of the two stable states without an
external field. In the bistable chiral splay nematic (BCSN) mode, the splay and π twist states are used for the two stable
states. The BCSN mode is a potential candidate of bistable modes, because it can be operated not only as a storage
device, but also as a monostable device with a fast response time in the same panel. The transition between two memory
states of the BCSN LCD is strongly coupled with the strength of applied electric fields. In this paper, we investigated the
bistable property by calculating the bistable curves and the correlation between the horizontal electric fields strength. To
realize the gray scale of BCSN LCD, We also propose a grid electrode structure with the varying-space between
electrodes which causes the varying strength of the horizontal electric fields. The selective transitions by the electrode
structure are demonstrated in this paper.
A novel method for switching the viewing-angle of a liquid crystal display is proposed by using a polymernetworked
liquid crystal cell in combination with a collimated backlight system. The bright state for a wide
viewing-angle is obtained aligning liquid crystals randomly in polymer-networked structure, which diffuses a
collimated backlight. The liquid crystals homogeneous-aligned by in-plane switching are operated as the
bright state for a narrow viewing-angle since a collimated backlight passes through the liquid crystal layer
intactly. It is demonstrated experimentally that the viewing-angle can be controlled omni-directionally
without an additional panel or an additional backlight system.
We propose an optical configuration of a twisted-nematic liquid crystal (TNLC) device driven by an in-plane electric
field for a single-cellgap transflective display. The dark state of the reflective part is realized by a nematic liquid crystal
layer with the twisted angle of 63.6° and the retardation of 194 nm, while a quarter-wave plate is inserted for the dark
state of the transmissive part. Wavelength dispersion of the TNLC layer is suppressed by introducing a half-wave plate,
whose optimum angle is found by using the Muller matrix method. Different directions of electric fields rotate liquid
crystals to 15° for the bright state of the reflective part, but to -30° for that of the transmissive part. With the proposed
configuration, we can realize a single-gamma transflective display in single cellgap structure without any in-cell
retardation layers. By fabricating a 2.0" qCIF+ (176×RGB×220) prototype panel, we demonstrated both high
reflection/transmission and single gamma of the proposed configuration.
The influence of charge injection on efficiency and operating voltage of organic light emitting device was investigated. Using UV-treated and un-treated ITO substrates, organic light emitting diodes were fabricated as we vary the thickness of LiF layer as the electron injection layer. The operating voltages and efficiencies were measured. When ITO surface is UV treated, operating voltage was decreased for all ranges of LiF thickness. By inserting a LiF thin layer with thickness of 5~10 Å lower operating voltages and higher power efficiencies were achieved. For a thicker LiF layer, power efficiency was decreased rapidly for UV treated ITO because of insulating properties of LiF. On the other hand, for untreated ITO - higher hole injection barrier, it was kept relatively high value up to the range of 20Å of due to the charge balance.
Two different configurations of transflective liquid crystal displays (LCDs) using multi-domain method will be presented. One is composed of hybrid-aligned nematic mode in the reflective region and parallel-rubbed vertically aligned mode in the transmissive region. In order to make the reflective and transmissive regions in the same pixel independent, an Ar+ ion-beam alignment method is used. The other multi-domain transflective LCD, where vertically aligned mode is applied, has patterned metal electrodes on one substrate. In this mode, the device can be designed with single driving circuit and single cell gap. These transflective LCDs show excellent performance in reflectance and transmittance characteristics, viewing angle property, and contrast ratio.
A wavelet transform is efficient for multiresolution signal
analysis. Difference-of-Gaussian (DOG) wavelets belong to a particular
class of wavelets that extract the information of a specific frequency
range in an image. Different DOG wavelets are produced by simple diffusion
and subtraction processes by using diffusion network. We propose
an optoelectronic DOG wavelet transform system using the point
spread function of the combined system, which is similar to the Gaussian
function. The experimental results show that the proposed system has
potential applications to the systems that require DOG wavelet transforms
in real time.
In this paper we investigate a feasibility of an opto-electronic implementation of the diffusion neural network for contour detection. The diffusion neural network performs the Gaussian operation efficiently by the diffusion process. We apply this in producing the DOG (Difference of two Gaussian) functions, which can detect the intensity changes of the different spatial frequency components in an image. In the diffusion neural network each neuron has four connections with the four nearest neighbor neurons and a self-decay loop for a 2D image, and the connection weights are fixed-valued. Therefore the diffusion neural network is simpler and more efficient than LOG masking method in hardware or optical implementation. We implement the diffusion neural network opto-electronically using the point spread function of a spatial light modulator. This system is composed of a spatial light modulator, a 2D image sensor array, and a computer. The processing time of the system is very fast. Therefore the system has a potential applicability to the system that requires a real time processing of an image.
In this paper we report the fabrication of a planar optical waveguide lens on a Y-cut LiNbO3 substrate by Ti-indiffusion and Ti-indiffused proton-exchange (TIPE). LiNbO3 planar waveguides are fabricated and refractive indices of the waveguides are measured. Based on the measured indices, planar waveguide lenses are designed and fabricated. The measured focal point and spot size of the fabricated lens are in good agreement with those of the designed lens.
In this paper we report a method of designing integrated-mirror etalons for photonic switching without time-consuming numerical calculation. It consists of the following two-step process: (1) find the minimum reflectance to obtain the maximum allowable linewidth of an etalon, and (2) find the number of the quarter-wave layers in each mirror of the etalon to obtain the reflectance given by step 1. The condition for maximum transmission in an integrated-mirror etalon is also derived. Under this condition we can achieve the required linewidth with the minimum number of quarter-wave layers.
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