Maximizing electro‐optic performances in the fringe‐field switching liquid crystal mode with negative dielectric anisotropic liquid crystal

The fringe‐field switching (FFS) mode that uses liquid crystals (LCs) with negative dielectric anisotropy is used in high‐resolution FFS liquid crystal display owing to its higher transmittance over positive LC, although its response time becomes slow and operating voltage (V_op) becomes high. In the device, reduction of the cell gap is required to achieve fast response time, which results in increase in V_op in general. In this paper, we propose the FFS mode with electrode width 1 µm and distance between the electrodes 1.5 µm. In such an electrode structure, V_op decreases with decreasing cell gap to 2 µm so that a proper V_op, high LC's light efficiency of 90%, a high color temperature, and a fast response time less than 10 ms, can be achieved, which maximizes electro‐optic performance of the FFS mode.     

Fast‐response liquid‐crystal displays using crossed fringe fields

Abstract— A fast‐response and wide‐view liquid‐crystal display (LCD) using the crossed fringe‐field‐switching (CFFS) mode is proposed, where the fringe‐field electrodes exist on both the top and bottom substrates. The bottom fringe field is used to turn on the LC directors and the top fringe field is used to assist in the LC decay process. The decay time is reduced by ～2× compared to that of the conventional FFS mode between the full bright and dark states, and more than a 2× improvement is obtained for other gray‐scale transitions. This CFFS mode also preserves the wide‐view characteristics as the conventional FFS mode. Its applications to LCD TVs and monitors for reducing image blur are addressed.     

Electro‐optical characteristics of ion‐beam‐aligned FFS‐LCDs on diamond‐like‐carbon thin film

Abstract— A fringe‐field‐switching (FFS) mode cell having LC alignment has been developed by using a non‐rubbing method, a ion‐beam‐alignment method on a‐C:H thin film, to analyze the electro‐optical characteristics of this cell. The suitable inorganic thin film for FFS‐LCDs and the alignment capabilities of nematic liquid crystal (NLC) have been studied. An excellent voltage‐transmittance (V‐T) and response‐time curve for the ion‐beam‐aligned FFS‐LCDs were observed using oblique ion‐beam exposure on DLC thin films.     

A submillisecond‐response liquid crystal for color sequential projection displays

We report a new LC with low viscosity and high clearing point (T_c ~102 °C) for color‐sequential projection displays. Using a 1.95‐µm mixed‐mode twisted nematic cell, the averaged gray‐to‐gray response time is less than 1 ms, which is ~3.6× faster than the current state of the art. Such a mixed‐mode twisted nematic liquid‐crystal‐on‐silicon can be used for near‐to‐eye wearable projection displays and head‐up displays in vehicles.     

Analysis of the dependence of optical response time of liquid‐crystal displays on the viewing direction

Abstract— The optical response time of liquid‐crystal displays (LCDs) has recently been observed to be dependent on the viewing direction. For the vertically aligned LC mode, response time increased as the viewing angle increased when the final state is the zero gray level of the minimum luminance. This change in response time is analyzed to relate to the deformation of the normalized luminance curve of LCDs for different viewing directions. The dependency trends of the optical response time for the oblique direction can be estimated from the temporal luminance measurement data along the normal direction and the normalized luminance curve for oblique viewing directions.     

Ultra‐FFS TFT‐LCD with super image quality,fast response time,and strong pressure‐resistant characteristics

Fringe‐field‐switching (FFS) devices using liquid‐crystal (LC) with a negative dielectric anisotropy exhibit high transmittance and wide viewing angle simultaneously. Recently, we have developed an “Ultra‐FFS” thin‐film‐transistor (TFT) LCD using LC with a positive dielectric anisotropy that exhibits high transmittance, is color‐shift free, has a high‐contrast ratio in a wide range, experiences no crosstalk and has a fast response time of 25 msec. In this paper, the device concept is discussed, and, in addition, the pressure‐resistant characteristics of the devices compared with that of the twisted‐nematic (TN) LCD is discussed.     

High‐transmittance in‐plane‐switching liquid‐crystal displays using a positive‐dielectric‐anisotropy liquid crystal

Abstract— The in‐plane‐switching (IPS) mode exhibits an inherently wide viewing angle and has been widely used for liquid‐crystal‐display (LCD) TVs. However, its transmittance is limited to ～76% compared to that of a twisted‐nematic (TN) cell if a positive‐dielectric‐anisotropy LC is employed. A special electrode configuration that fuses the switching mechanism of the conventional IPS and the fringe‐field switching (FFS) to boost the transmittance to ～90% using a positive LC has been developed. The new mode exhibits an equally wide viewing angle as the IPS and FFS modes.     

High‐performance OCB‐mode field‐sequential‐color LCD

Abstract— Optically compensated bend (OCB) mode is a promising technology for future high‐quality display devices due to its wide viewing angle without gray‐scale inversion and color shift, fast response time, high contrast ratio, and wide temperature range. This paper summarizes the developments of the OCB mode and the optical performance of OCB‐mode field‐sequential‐color LCD.     

高精度光学自动检测仪快速对焦方法研究

为提高光学自动检测设备中自动对焦的准确性、快速性和稳定性,提出一种新型的高精度快速自动对焦技术方案.该系统利用光学三角法测距原理将汇聚到工作台上的激光光斑成像在CCD上,再利用光斑灰阶的变化实现精密对焦.实验结果表明:显微镜重复对焦精度可以达到0.1 μm,对焦时间小于200 ms,满足工业光学检测系统中实际应用的需要...     

The application of a light guiding flexible tubular waveguide in evanescent wave absorption optical sensing

A light guiding flexible fused silica (FFS) capillary has been used in designing evanescent wave (EW) absorption based chemical sensors. The FFS capillary is similar to a conventional silica optical fiber in that it can guide light in the wavelength region from UV to near infrared, but different from a conventional optical fiber in that it is a tubular waveguide. The inner surface of the FFS capillary is fused silica, which was coated with a reagent doped polymer in order to design an optical fiber chemical sensor. The FFS capillary has a cladding layer plus a protection polymer coating on its outside surface. The cladding layer ensured the capability of the FFS capillary for guiding light. The protection coating increases the FFS capillary's mechanical strength and makes it robust in practical applications. This makes the FFS capillary very useful in designing an EW based optical chemical sensor of a long path length. Techniques for activating the inner surface of an FFS capillary, coating the inner surface of the capillary with a polymer, connecting the coated capillary to a light source and a photodetector, and delivering a sample through the capillary have been developed in this work. Three optical sensors for sensing Cu(II), toluene in water samples and ammonia in a gas sample have been fabricated and tested. Preliminary test results obtained in this work illustrate the feasibility of fabricating highly sensitive EW absorption based chemical sensors with the light guiding FFS capillary.     

隐式路由协议的一种转发节点快速选择算法

针对已有隐式路由协议转发节点选择算法效率不高的缺点，提出了一种基于IEEE 802.11 DCF机制的转发节点快速选择算法（FFS）．该算法让候选转发节点根据自己的转发优先级退避相应的时隙后发送CTS帧，并在多个候选节点发生冲突时随机选择退避时隙值，从而快速高效地唯一确定转发节点．仿真结果表明，FFS算法在能效、时延、分组到达率等网络性能指标上优于已有算法．     

Characterization of flexible reflective liquid‐crystal cells

Abstract— We consider peculiarities in testing flexible reflective liquid‐crystal (LC) cells. Several new methods for measuring optical retardation of filled reflective LC cells on plastic substrates are proposed. Cases when the plastic is anisotropic and the LC cell consists of either one or two internal polarizers are studied. The majority of proposed methods can be applied for transmissive LC cells as well as for measuring twist angle.     

Local dimming light‐guiding plate type backlight system using alignment‐controlled polymer‐dispersed liquid crystals

A new technology which enables a local brightness control according to the displayed images has been expected in the thin and lightweight backlight systems to improve a contrast ratio and power consumption of the liquid crystal displays (LCDs). In this paper, we have proposed a novel local‐dimming backlight system using alignment‐controlled polymer‐dispersed liquid crystals as a light‐guiding plate and investigated the forming conditions of polymer‐dispersed liquid crystals to achieve both a high‐luminance ratio and a fast response speed. As a result, we found that a luminance ratio and response speed of the backlight system can be improved by using bifunctional LC monomer materials and forming fine and rigid polymer network in the LCs, and achieved high luminance ratio of 16:1 and fast response time less than 0.5 ms. In addition, we fabricated the twisted nematic‐mode LCD using the local dimming light‐guiding plate‐type backlight based on this design, and successfully realized eight times higher contrast ratio than that of the traditional twisted nematic‐mode LCD.     

High‐speed nonchiral‐smectic‐C liquid‐crystal modes for display applications

Abstract— Three nonchiral‐smectic‐C (NSC) liquid‐crystal (LC) modes having fast‐response and wide‐viewing characteristics applicable for next‐generation LCDs are described. In the NSC LC modes, fast analog optical modulation is achieved by means of a coupling with an external electric field in a dielectrically driving scheme. The fast response results intrinsically from no interlayer interferences during molecular rotation in the layered structure of the NSC LC. Moreover, the self‐formation of two domains and the in‐plane variations of the optic axis produce the wide‐viewing properties. A step‐wise temperature annealing process is employed for a stable and well‐aligned smectic layer structure in a time‐efficient manner.     

A silicon‐chip‐based light valve with reflective twisted‐nematic mode for high‐definition projectors

Crystalline‐silicon‐chip‐based reflective light valves are suitable for realizing high definition and bright liquid‐crystal projectors. We have developed an XGA (1025 × 769 pixels) silicon‐chip‐based light valve with a diagonal display area of 2.54 cm (1 in.). The reflective twisted‐nematic mode was examined by using the Jones matrix method as a display mode, and the normally white reflective twisted‐nematic mode was selected. This mode is suitable for a narrow cell gap, and a fast response time can be expected. In addition, the driving voltage of this mode is low and has good chromaticity with small retardation. The cell gap of the light valve is 2 μm. The cell gap support is made using spacer posts formed on the silicon chip with a photodefinable resin. The response time is 12 msec, including both rise and fall times. The contrast ratio is more than 1000 at 5 Vrms.     

基于传输补偿算法的光纤通信设计研究与仿真

研究光纤通信问题,提高通信的效率。针对光信号在传输过程中,不同的频率成分或模式成分因传播速度不同而相互散开,使传输的信号脉冲发生畸变,从而限制了光纤的传输效率,很难保证信息传播的高效性的问题。提出基于激光通信设备的光纤通信优化方案。通过激光能量补偿和偏振模色散补偿算法,校正了光纤通信过程中由于能量损耗和偏振模色散导致的通讯误差,从而能够快速、准确的使用激光通信设备在光纤通信中高效传输数据。实验证明,该算法能够补偿光纤通信中,色散导致的传递误差,取得了较好的效果,为光纤通信优化设计提供了依据。     

Interference and ion effects in the electro‐optical response of PDNLC films

Abstract— We have considered the interference in polymer‐dispersed nematic liquid‐crystal (PDNLC) films caused by the superposition of light beams that pass through and between the LC droplets. The relative phase retardation of the beams depends on the applied voltage, and, as a consequence, interference oscillations can occur at transmittance‐voltage curves. Typical forms of the curves for composite films with various structures are presented. Interference oscillations were revealed not only in the static electro‐optical characteristics but in the dynamic ones also. For PDLC films based on commercially available components produced without thorough purification, the combination of interference and ionic effects is observed in the dynamics of the optical response. The relaxation of transmittance due to the depolarization ionic field is presented, depending on droplet size, temperature, pulse duration, and the concentration of the ionic admixture.     

面向函数型数据的快速特征选择方法*

函数型数据的特征选择是从庞大的函数信息中选出那些相关性小、代表性强的少部分特征,以简化后期分类器的计算,提高泛化能力.由于特征选择方法用于函数数据分类效果并不理想,文中提出面向函数型数据的结合主成分分析法和最小凸包法的快速特征选择(FFS)方法,可以快速获得稳定的特征子集.此外,考虑到特征之间可能存在相关性,将FFS的结果作为其它方法的初始特征子集,故融合FFS与条件互信息方法.在UCR数据集上的实验证明FFS的有效性,并通过对比实验给出在不同时间代价和分类精度需求下的方法选择策略.     

A fast‐switching OCB‐mode LCD for high‐quality display applications

Abstract— Optically compensated bend (OCB) mode is a promising technology, due to its wide range of viewing angles without gray‐scale inversion or color shift, fast response, high contrast ratio, and wide temperature range. This paper summarizes the fundamental characteristics of OCB mode and discusses the development of field‐sequential‐color displays and 3‐D displays for future high‐quality display applications.     

Facilitation of reaction times with GAP paradigm: comparison of manual and saccadic responses

Manual and saccadic reaction times (RTs) were measured to peripheral target onsets. Previous researchers reported marked decrement in saccadic latencies when the central fixation mark offset preceded the target onset by a short interval (a gap paradigm). The first experiment ascertained whether a similar RT facilitation would occur with a manual RT task. It was found that, in line with previous studies, a majority of saccades was less than 150 ms when a gap of 200 ms was inserted between the fixation offset and the target onset. These short latency saccades were executed virtually without error. Manual RTs were also facilitated, but the amount of facilitation was modest, and it was bargained for at the expense of increased errors.

To compare these two response modes under the gap paradigm, two additional experiments were conducted. First, to check the possibility that the facilitation of manual RTs was due to the prolonged experience with the gap paradigm, 36 naive subjects were recruited, and their manual RTs were measured under one of two gap durations (100 or 200 ms). Both gap durations were successful in bringing about RT facilitation, suggesting that naive subjects could utilize the gap paradigm to speed up their responses. The gap durations of 100 and 200 ms were equally effective in the facilitation of RTs.

In the final experiment, three subjects were observed in manual and saccadic RT tasks under 13 gap-overlap intervals (— 1000 to + 1000ms, of which a negative sign indicates a delayed fixation mark offset relative to target onset or overlap condition). Both saccadic and manual RTs were shortened in the gap range 100-300 ms, while they were increased under the short (less than 300 ms) overlap condition. These effects were more conspicuous for the saccade. Prolonged fixation mark presentation (overlaps of more than 500 ms) caused delayed response initiations only for the saccade.