Liquid-crystal color light valve

A multilayer color display device employs two kinds of liquid-crystal films, One is a field-effect nematic liquid crystal; the other comprises a mixture of cholesteric and nematic liquid crystals that have the same function as circular polarizers used in place of crossed polarizers. Three colors (red, green, and blue) can be modulated independently by changing three voltages.     

新型多畴扭曲向列相液晶显示器

提出在像素电极下方放置凸起物,获得具有宽视角特性的多畴扭曲向列相液晶显示器。该模式比传统的多畴TN模式摩擦过程少,工艺过程简单。在这种液晶显示器中,初始状态(未加电)时,分子排列结构和普通单畴TN模式相同,在加电压状态时,由于凸起物的存在,液晶分子沿着4个不同的方向排列形成多畴区域。文中运用专业液晶模拟软件模拟,对该液晶显示器的电光特性进行研究,结果表明,该液晶显示器具有宽视角、色散小及色彩还原性较好的特性。     

利用单块硅酸铋晶体同时测量交流电压和电流

设计并实验实现了利用单块硅酸铋(Bi12SiO20,BSO)晶体同时测量交流电压和电流的传感方案,其光学传感单元仅由起偏器、BSO 晶体和检偏器组成。BSO 晶体兼有Pockels 电光效应和Faraday磁光效应,在起偏器和检偏器的主透光方向互相平行或互相垂直的情况下,输出光信号中同时包含被测电压和电流传感信号,其中电压传感信号为被测电压的倍频信号,而电流传感信号则与被测电流同频率,因而可以利用电子滤波器从光电检测信号中分离出电压与电流传感信号,从而实现电压和电流的同时测量。利用一块尺寸为6.04.02.9 mm3 的BSO 晶体,实验实现了6 A、200 V 范围内工频电流与电压的同时测量。     

Liquid crystal electrography: Electric field mapping and detection of peak electric field strength in AlGaN/GaN high electron mobility transistors

The liquid crystal mixture E7, based on cyanobiphenyl, has been successfully employed to map electric field strength and distribution in AlGaN/GaN high electron mobility transistors. Using a transmitted light image through crossed polarizers the optical response of the liquid crystal deposited onto the surface of the devices was recorded as a function of source–drain bias, V_ds. At a critical voltage of 4 V the preferred direction of orientation of the long axes of the liquid crystal molecules in the drain access region aligned with one of the polarizers resulting in reduced transmitted light intensity. This indicates that at this electric field strength molecule orientation in most of the liquid crystal film is dominated by the electric field effect rather than the influence of surface anchoring. The experimental results were compared to device simulations. Electric field strength above the surface at V_ds = 4 V was simulated to reach or exceed 0.006 MV/cm. This electric field is consistent with the field expected for E7 to overcome internal elastic energy. This result illustrates the usefulness of liquid crystals to directly determine and map electric fields in electronic devices, including small electric field strengths.     

A dual color basis tunable color EL device employing ZnS:Tb,F/ZnS:Mn stacked phosphor layers with color filters

A tunable color thin-film electroluminescent (EL) device having a stacked structure of ZnS:Tb, F/ZnS:Mn with red and green colored filters was developed. The obtained red and green emissions have high enough luminance to be considered as a practical tunable color display panel, though the color tone of the green emission approaches yellow-green. It was confirmed that varying the color between red and green can be easily done by changing the filters and applied voltage. This device should be useful for a wide variety of applications in such fields as active information display systems     

Fiber loop polarizers using a fused taper coupler

All-fiber polarizers using a fused taper coupler are presented. The polarizers are fabricated by constructing a fiber loop joining the output ports of a fused taper coupler. Input light splits into two linearly polarized modes which are reflected and transmitted by the polarizers, respectively. The transmitted and the reflected lights become linearly polarized. The demonstrated polarizer shows an extinction ratio of -20.0 dB     

Characteristics of a 12-domain MVA-LCD

A multi-domain (12-domain) vertical alignment liquid crystal display (MVA-LCD) device is proposed and its electro-optic characteristics evaluated through a 3-D simulator. The MVA-LCD exhibits advantages in wide viewing angle, high transmittance, fast response time, and small color shift when a pair of wide view crossed circular polarizers is employed. Potential applications of this MVA-LCD for high quality LCD TVs and computer monitors are emphasized.     

基于单片机便携式颜色自适应识别电路的设计

为解决电致变色器件的颜色变化受外界环境颜色控制的问题,设计了一种基于单片机的便携式颜色自适应识别电路。与传统颜色识别电路相比较,该电路利用数字式的颜色传感器来获取外界环境颜色,产生的数字颜色信号易于单片机进行处理。在电路中,下位机部分主要负责获取电致变色器件变色参数及控制电致变色器件的颜色变化;而上位机部分主要负责把下位机获取的电致变色器件变色参数进行电压到颜色的曲线拟合,并通过蓝牙通信把拟合曲线参数传递给下位机。结果表明,该电路能自动根据环境颜色提供-4～4 V范围步进为0.1 V的电压来驱动电致变色器件的颜色显示,与传统的颜色识别电路设计相比,识别的精度和速度都得到了明显改善。     

各向异性PDLC散射膜的特性研究

采用摩擦表面取向层的方法制备了有光学各向异性结构的ＰＤＬＣ膜。研究了液晶盒的厚度、摩擦强度,以及在紫外光诱导相分离过程中的光照强度对ＰＤＬＣ膜的光学各向异性程度和电光特性的影响。对ＰＤＬＣ的光学各向异性进行了研究,并给出了要获得低阈值电压、高各向异性的聚合物分散液晶各向异性膜的盒厚、摩擦强度以及光照度等条件。被取向后的ＰＤＬＣ各向异性膜可被用来作为具有很好光电特性的电可调散射式偏振片。     

Highly contrasted and stable electrochromic device based on well-matched viologen and triphenylamine

An electrochromic device (ECD) can change color absorption when subjected to an appropriate voltage. Such a device includes three components: a working electrode, a counter electrode and an electrolyte. Compatibility of these three components is important for ECD’s stability. In this study, two novel compatible electrochromic materials, cathodic 1-(9-hexyl-9H-carbazole)-1′-(propylphosphonic acid)-4,4′-bipyridilium dichloride and anodic (4-(diphenylamino)phenyl)methylphosphonic acid were designed, synthesized and fabricated into electrochromic electrodes using a chemisorption method. We characterized the electrochromic performance of these two electrodes, including the degree of color change, color changing voltage and charge capacity; the results indicated that they matched each other very well. An electrochromic device fabricated using these two electrodes, as expected, exhibited rapid, vivid color changes and proved highly stable for up to 100,000 cycles.     

The Effects of Multiple CW Interferers

When two or more CW transmitters create an electromagnetic field to which a susceptible device is exposed, the possibility that damage or performance degradation will result may, under certain circumstances, be increased by the effects of occasional phase coincidence among the transmitters. If they move into and out of phase fairly slowly, then, over finite tihe intervals of significant duration, the effective value of the combined voltage at a given point in the device can considerably exceed the long-term effective (rms) value. In this paper, an upper bound is placed on this short-term effective voltage for situations where the transmitted waveforms are sinusoidal and the susceptible device can be modeled as part of a linear circuit. It is shown that, if the separate contributions of the N transmitters have similar amplitudes and their frequencies are close together, the short-term effective value can occasionally exceed the rms value by 10 log, N dB or more for a significant time interval. In some cases, this difference might be enough to cause the device's threshold of damage or performance degradation to be exceeded.     

Time dependence of soliton formation in planar cells of nematic liquid crystals

Spatial optical solitons can be observed in bulk nematic-liquid-crystal cells with an entrance window and a bias voltage applied over the cell to enhance the optical nonlinear effect of laser-induced molecular reorientation. The soliton-induced waveguide is observed in transmission by use of a second light source and crossed polarizers. This setup allows us to investigate the time dependence of the molecular reorientation that sustains the soliton-like beam propagation. Results from a numerical simulation are in good agreement with the experimental results, which confirms the validity of our model.     

引入悬浮栅对有机薄膜晶体管的阈值电压进行调整

The structure of organic thin film transistors (OTFTs) is optimized by introducing floating gate into the gate dielectric to reduce the threshold voltage of OTFTs in this article. Then the optimized device is simulated and the results of the simulation show the threshold voltage of optimized device is reduced by about 10 V. The reduction of the threshold voltage is helpful and useful for the application of OTFTs in many areas. In addition, this way to reduce threshold voltage of OTFT is compatible with traditional silicon technology and can be used in manufacture.     

Threshold voltage adjustment of organic thin film transistor by introducing a polysilicon floating gate

The structure of organic thin film transistors (OTFTs) is optimized by introducing a floating gate into the gate dielectric to reduce the threshold voltage of OTFTs. Then the optimized device is simulated, and the simulation results show that the threshold voltage of optimized device is reduced by about 10 V. The reduction of the threshold voltage is helpful and useful for the application of OTFTs in many areas. In addition, this way of reducing the threshold voltage of OTFT is compatible with traditional silicon technology and can be used in manufacturing.     

Novel scattering and color converting substrates for simple-structured white organic light-emitting diodes

Organic light-emitting diodes (OLEDs) have shown great success in the display applications recently. However, the applications of OLEDs in lighting are still limited due to their complex device structures. Here, we developed a novel phosphor doped glass substrate with both high scattering and excellent color conversion capability to greatly simplify the device structures of white organic light-emitting diodes (WOLEDs). A simple-structured WOLED comprising a blue OLED and the scattering fluorescent substrate was demonstrated to realize high quality white light for lighting applications. The WOLED exhibits a turn-on voltage of 2.7 V, a maximum power efficiency of 29.8 lm/W, an external quantum efficiency (EQE) of 14.2%, a color rendering index (CRI) of 86, and a correlated color-temperature (CCT) of 3900 K. The low turn-on voltage can be attributed to the single emissive layer structure used in the WOLED. The high power efficiency as well as the high EQE are due to both the high color conversion efficiency and the high scattering capability of the fluorescent substrate. In addition, the WOLED is favorable for high-quality solid-state lighting in our daily life due to its high color rendering ability along with an adequate CCT CC.     

Programmable memory cell using quantum confined Stark effect in multi-quantum well heterojunction bipolar transistor

A three terminal bistable programmable memory cell which can be read either optically or electrically is proposed and demonstrated. The device is based on using Stark effect of the excitonic transitions in a multi-quantum well base region of a heterojunction bipolar transistor. The single device can be flipped (and held) from low transmittance (high voltage) to high transmittance (low voltage) state and vice versa by a varying base current signal.<>     

A liquid-crystal display panel using polarizers as panel substrates

A liquid-crystal display (LCD) using polarizers as the panel substrates is investigated. The optical properties of TN LCD's using biaxially drawn polyester films and uniaxially drawn polyester films are evaluated. As a result, the latter films are selected as supporting films of the polarizers. Since both uniaxially drawn polyester films and LC molecules are optically anisotropic, interference colors may result due to birefringence. Also, as these polyester films are thermally anisotropic, warping of the LCD panel may occur after heat treatment. The influence of the arrangement of the polarizers on the optical and thermal properties of the LCD is discussed and the most suitable structure is determined. The developed plastic LCD is 0.5 mm in thickness and has better optical characteristics than those of a conventional LCD using glass substrates.     

A High-Speed Measurement Method for Reflective Liquid Crystal Cells Using a Liquid Crystal Polarization-Converting Device

We propose a novel measurement method for determining cell parameters, such as a cell thickness and twist angle in reflective liquid crystal (LC) cells, by using a unique polarization-converting device prepared with a circularly and homogeneously aligned LC (CH-LC) cell. The light intensity distributions from the reflective LC cell transmitted twice through the CH-LC cell are measured by a charge-coupled device array camera. Cell thickness can be derived by using coordinate values of local minimum spot in the spatial light intensity distribution measured at one wavelength, where the pretilt angle is assumed to be the designed value. Both cell thickness and twist angle can also be determined by two local minimum positions of the light intensity at two different wavelengths and the effects of a quarter-wave plate are discussed     

无序的混合排列型ECB—LCD的研究

为了改善常规的ＥＣＢ的显示品质，采用不摩擦技术制备无序的混合排列型ＥＣＢ液晶盒，分析了它的电光特性和视角特性。无序的混合排列型ＥＣＢ液晶盒是多畴的结构，并具有很多向错，但人的肉眼却识别不出。无序的混合排列型ＥＣＢ器件具有三色峰值电压分离较好、工作电压低、视角在整个平面内具有方位角对称性的特点。     

AC-driven,color- and brightness-tunable organic light-emitting diodes constructed from an electron only device

In this paper, a color- and brightness-tunable organic light-emitting diode (OLED) is reported. This OLED was realized by inserting a charge generation layer into an electron only device to form an n-i-p-i-n structure. It is shown that, by changing the polarity of applied voltage, only the p-i-n junction operated under positive bias can emit light and, by applying an AC voltage, emission from both junctions was realized. It is also shown that, by using a combination of blue- and red-emiting layers in two p-i-n junctions, both the color and brightness of the resulting white OLED can be tuned independently by changing the positive and negative amplitudes of the AC voltage.