Optimization of a-Si:H-based three-terminal three-color detectors

Three-terminal three-color n-SiC:H/a-Si:H-based TCO/PINIP/TCO/PIN/metal detectors are presented. Assemblies having different surface roughness of transparent conducting oxide (TCO) layers are compared with regard to the external steady-state characteristics and transient behavior. The roughness of the sputtered TCO surface can be modified by an etching treatment. With the selection of smooth or textured TCO surfaces, the wave propagation of light within the device is controlled. This design technique can be exploited to optimize the color separation and improve the reproducibility of spectral responsivities in the assemblies. The examined assemblies exhibit very selective spectral responsivity for the fundamental chromatic components (red-green-blue) and a linear photocurrent-generation rate relationship over more than five orders of magnitude of illumination intensity. Since the color detection of blue and green light is performed in the PINIP structure by bias switching, the transient current response of the PINIP structures is investigated. A reciprocal relationship between the delay time and illumination intensity is established. An optimum operation region for the switching voltages is determined with regard to the quality of color separation, dynamic range, and transient behavior     

Accurate Measurement and Characterization of Organic Solar Cells

Methods to accurately measure the current–voltage characteristics of organic solar cells under standard reporting conditions are presented. Four types of organic test cells and two types of silicon reference cells (unfiltered and with a KG5 color filter) are selected to calculate spectral‐mismatch factors for different test‐cell/reference‐cell combinations. The test devices include both polymer/fullerene‐based bulk‐heterojunction solar cells and small‐molecule‐based heterojunction solar cells. The spectral responsivities of test cells are measured as per American Society for Testing and Materials Standard E1021, and their dependence on light‐bias intensity is reported. The current–voltage curves are measured under 100 mW cm^–2 standard AM 1.5 G (AM: air mass) spectrum (International Electrotechnical Commission 69094‐1) generated from a source set with a reference cell and corrected for spectral error.     

Study of the color detection of a-Si:H by transient response in thevisible range

A new technique of color detection based on time-resolved charge collection during transient response measurement using a hydrogenated amorphous silicon detector has been proposed and experimentally demonstrated. The method based on the material intrinsic wavelength-filtering properties is implemented in color sensing by transient response of a detector to a combination of basic color light and voltage pulse. Resulting transient responses under different illumination and bias voltage conditions confirm considerable accuracy of proposed method. In particular, the best agreement of measured and calculated transient response curves has been obtained by using the spectral response of all three primary colors in calculations. It was observed that the presence of blue light drastically reduces the transient response to a chromatic light illumination. Finally, a voltage pulse influence to the basic colors transient response was found     

Coordinated underwater dark channel prior for artifact removal of challenging image enhancement

When dehazing underwater images, the patch-by-patch dark channel prior (DCP) method is frequently used. After the DCP-based processing, there are still some drawbacks, such as patch artifacts, and these artifacts will seriously affect the subjective quality of some challenging images. To remove the patch artifacts from the DCP-guided enhancement mechanism, this paper proposes a coordinated underwater dark channel prior (CUDCP) method. The proposed method considers the characteristics of the red-green-blue channels with different attenuation situations, and thus the attenuation ratios of the red-green-blue channels are adaptively coordinated in diverse images. The requirement for color restoration is then assessed by an evaluation criterion, and the color restoration is carried out by using the compensated gray world (CGW) theory, which further coordinates the intensity of various red-green-blue channels. Our method next applies a patch-division average filter in accordance with the sub-patch classification. On the typical dataset, the enhanced images of our CUDCP method have higher average underwater image quality measure (UIQM) scores (about 2.274 8) when compared with the original images and those of some state-of-the-art enhancement methods, while the computational cost of CUDCP (about 88.618 8 s) is slightly higher than that of the original DCP (about 87.493 8 s). The experimental results demonstrate that in comparison to state-of-the-art enhancement methods, the proposed method can significantly reduce patch artifacts in challenging image enhancement, while maintaining the objective quality of such underwater images, and also enhancing their subjective quality at a reasonable computational cost.     

Large Area Flat—screen Liquid Crystal Television（continued 1）

A modular flat-screen liquid crystal television display is described .The picture elements of the modules may be emissive ,reflective or transmissive .The flat-screen liquid crystal television also comprised of an electrical control circuit capable of categorizing incoming television picture signals corresponding to the modules in the array and directing the electrical signals to the drive circuits of each module according to the portion of the television picture to be reproduced by the picture elements of that module.The picture elements are preferably formed in a light modulating film composed of a liquid crystal dispersion in a polymeric binder.A color display was also produced by placing a patterned red-green-blue filter adjacent the active matrix so that each picture element could also be coordinated with the color components of a color video signal.     

Large Area Flat—screen Liquid Crystal Television

A modular flat-screen liquid crystal television display is described.The picture elements of the modules may be emissive ,reflective or transmissive .The flat-screen liquid crystal television also comprised of an electrical control circuit capable of categorizing incoming television picture signals corresponding to the modules in the array and directing the electrical signals to the drive circuits of each module according to the portion of the television picture to be reproduced by the picture elements of that module.The picture elements are preferably formed in a light modulating film composed of a liquid crystal dispersion in a polymeric binder.A color display was also produced by placing a patterned red-green-blue filter adjacent the active matrix so that each picture element could also be coordinated with the color components of a color video signal.     

Color characterization of large area polymer image sensors

Large area image sensors made with semiconducting polymers are demonstrated to have true-color resolution (24-bits). The red, green and blue color primaries are achieved by coupling a set of color filters with the polymer sensor; the color-sensing pixels are fabricated from a single polymer with photoresponse that covers the visible spectral range from 400 to 700 nm. A process for recovering the image from the pixelated photocurrent data is developed; the image recovery process is general and applicable to image arrays with power-law light intensity dependence and with finite pixel dark current. Large size, true-color images were processed by scanning with a linear array of polymer photodiodes.     

A feedback-control model of human vision

In order for the human retina to achieve its very wide operating range (one billion to one in light intensity), high accuracy of spectral discrimination (the eye can distinguish among at least 10 million different shades of object color), constancy of object color, and uniform field of color perception, it appears necessary that the retinal receptors incorporate the following feedback-control processes: time-average feedback, spatial-average feedback, and automatic gain control. Time-average feedback would adapt each receptor to the time-average light it receives; spatial-average feedback would modify the signal from each receptor as a function of a weighted spatial-average of the receptor signals throughout the retina; and automatic gain control would keep the sensitivity of each receptor constant regardless of the adaptation conditions. This paper presents a model of a retinal receptor which incorporates these feedback control processes, and which appears to be consistent with physiological and psychological evidence.     

数字微镜Hadamard变换光谱仪光谱反演矩阵标定及实验

国内外对DMD空间光调制的Hadamard变换成像光谱仪做了大量的理论研究和实验验证,但这项技术的研究还不够成熟,很多问题需要进一步的研究。在这种光谱仪中每个像素点色散光谱的编码矩阵互不相同。通过比较激光编码图像灰度值的变化并结合S矩阵元素的变化规律,提出了一种光谱反演矩阵的标定方法。以七阶左移循环S矩阵为例设计编码模板,通过两组成像实验对光谱反演结果进行了验证。在第一组实验中,将一束激光波长为632.8 nm激光导入光谱仪中,光谱仪的光谱响应范围为550~680 nm,632.8 nm在第五个波段范围626~644 nm之内理论上只有波段范围为626~644 nm的第五幅光谱图像是明亮的,其余的图像没有能量分布,实际的实验结果与理论上的分析相吻合。在第二组实验中,让光谱仪对一个彩色蝴蝶模型进行成像,在反演后得到的光谱图像上提取两个测试点的光谱曲线,与用辐射度计提取的光谱特性曲线进行对比分析,实验结果表明反演所得的光谱曲线与辐射度提取的光谱特性曲线基本一致。两组光谱反演的实验结果验证了所提出的光谱反演矩阵标定方法的有效性。     

通过圆偏振光提高飞秒激光诱导击穿光谱的发射强度

激光诱导击穿光谱(LIBS)是一种快速、实时的元素成分分析技术。为了提高LIBS的灵敏度,人们已经提出多种方法来提高LIBS的光谱强度。本文采用飞秒脉冲激光烧蚀黄铜产生LIBS,对比了圆偏振和线偏振下LIBS光谱的强度,结果发现圆偏振下的光谱强度比线偏振下的强,光谱强度大约提高了15%。采用飞秒激光照射金属时,金属内部的自由电子吸收光子的能量。在线偏振飞秒激光场中,电子在脉冲的每个光学周期中经历交替的加速和减速;而圆偏振飞秒激光可以连续加速电子,因此电子可以获得更高的能量,这使得圆偏振飞秒激光产生的光谱强度不同于线偏振飞秒激光产生的光谱强度,圆偏振激光有助于改善飞秒LIBS信号的强度。     

A Paper-Based Wearable Photodetector for Simultaneous UV Intensity and Dosage Measurement

Photodetectors, which convert the light signal into other forms of signal, have been under the spotlight of research for many years because they are widely applied in monitoring, communication, and imaging. Most of the currently available photodetectors can output electrical signals to indicate the transient light intensity, while some display color change to reveal the absorbed light dosage. However, there is no device that can tell the transient light intensity and accumulated light dosage at the same time. Here, a paper-based wearable photodetector that can simultaneously measure transient light intensity and accumulated light dosage is reported. The phosphomolybdic acid/citric acid system, whose color change can be observed by the naked eye, is designed as the photochromic material to combine with photodetective materials (using 2D Sr₂Nb₃O₁₀ and ZnO nanoparticle as examples) on paper. Such paper-based photodetector fully utilizes natural hygroscopicity and softness of paper, showing decent flexibility. Its optoelectronic signal remains stable even after 1000 cycles of bending. To the best of one's knowledge, this is the first photodetector that can tell light intensity and dosage simultaneously. This work introduces a new type of wearable photodetector by structure design and material selection, shedding light on more novel works for convenient and practical photodetection.     

多碱光电阴极膜厚对阴极灵敏度的影响研究

叙述了多碱光电阴极光谱反射的特点,测量了超二代微光像增强器多碱光电阴极的光谱反射曲线,分析了光谱响应曲线产生干涉加强峰和干涉减弱峰的原因,比较了不同膜层厚度多碱阴极光谱反射曲线的区别。根据能量守恒定律,利用实测的多碱光电阴极光谱反射率和光谱透过率,计算出多碱光电阴极的光谱吸收曲线,通过研究不同厚度多碱阴极的光谱吸收,发现多碱光电阴极膜层厚度加厚并不会提高其对所有波段光吸收率的特点。厚度增加只会增加短波和长波的光吸收率,但中波的光吸收率不会增加反而下降,这是由于受到光谱反射的影响。阴极膜层的厚度既影响光谱反射和光谱透过,又会影响光谱吸收,因此也影响多碱阴极的光谱响应,所以多碱光电阴极的膜层厚度是影响多碱光电阴极灵敏度的一个关键参数。实践证明,转移式技术制作的多碱光电阴极膜层厚度也存在一个最佳值,超过这一最佳厚度,阴极的灵敏度不增反降,这是因为红外光谱响应增加不多,但中波光谱响应下降很多。所以对转移式多碱光电阴极而言,实践证明当膜层厚度达到最佳厚度时,膜层呈现淡红色,在制作过程中要控制好阴极膜层的厚度,这样才可能获得较高的阴极灵敏度。     

Transient behavior of optimized nipiin three-color detectors

The detection of the fundamental components of the visible light (blue, green, red) is realized with a multispectral photodiode based on amorphous silicon. The preferential carrier collection region of this two-terminal device shifts upon changing the applied bias voltage, which leads to a color sensitivity. Structures with controlled bandgap and mobility-lifetime product exhibit a dynamic behavior above 95 dB. Three linearly independent spectral response curves can be extracted to generate a RGB-(red-green-blue)-signal. Bias voltage switching experiments under different monochromatic illumination conditions are carried out to investigate the time-dependent behavior. Furthermore, in order to improve the understanding of the photocurrent transients, we have characterized the voltage-dependent capacitance behavior, Thus, a Simulation Program with Integrated Circuit Emphasis (SPICE) model including the capacitance-voltage (CV) data has been developed, which describes the transient behavior of the detector. The simulations are in good agreement with the experimental data and allow an interpretation of the transient photocurrent response after bias voltage switching. Based on these results, optimization criteria to improve the transient behavior are discussed     

A study of efficiency and accuracy in the transformation from RGBto CIELAB color space

The perceptually uniform color space CIELAB (Commission Internationale de l'Eclairage) is useful for image analysis, particularly in applications involving color acceptability decision making; however, the transformation of an entire red-green-blue (RGB) color image is very time consuming. Various techniques are investigated for approximating the nonlinear function, and their performance in terms of speed and accuracy is assessed. This article arises from a project that aims to use video cameras to monitor the color of manufactured products.     

梯度掺杂GaN光电阴极的光谱响应测试与分析

用光谱响应测试仪得到了反射式梯度掺杂GaN光电阴极在激活和衰减过程中的光谱响应曲线,发现此曲线不断发生变化。在激活过程中光谱响应不断提高,且长波响应提高较快;衰减过程中光谱响应不断下降,长波响应下降得更快。结果表明：光谱响应曲线的变化与光电阴极高能光电子的逸出有关。GaN光电阴极发射的电子能量分布随入射光子能量升高而向高能端偏移,阴极表面势垒形状的变化对低能光激发电子的影响更大,导致光谱响应曲线随入射光波长改变而产生了不同的变化。     

Robust Periocular Recognition by Fusing Sparse Representations of Color and Geometry Information

In this paper, we propose a re-weighted elastic net (REN) model for biometric recognition. The new model is applied to data separated into geometric and color spatial components. The geometric information is extracted using a fast cartoon - texture decomposition model based on a dual formulation of the total variation norm allowing us to carry information about the overall geometry of images. Color components are defined using linear and nonlinear color spaces, namely the red-green-blue (RGB), chromaticity-brightness (CB) and hue-saturation-value (HSV). Next, according to a Bayesian fusion-scheme, sparse representations for classification purposes are obtained. The scheme is numerically solved using a gradient projection (GP) algorithm. In the empirical validation of the proposed model, we have chosen the periocular region, which is an emerging trait known for its robustness against low quality data. Our results were obtained in the publicly available FRGC and UBIRIS.v2 data sets and show consistent improvements in recognition effectiveness when compared to related state-of-the-art techniques.     

Effect of illumination wavelength and intensity on minority-carrier diffusion length of EFG silicon ribbon solar cells

Local spectral photoresponses of the edge-defined film-fed growth technique (EFG) ribbon solar cells were measured as a function of the bias light wavelength and intensity. The minority-carrier diffusion length estimated from the spectral response measurement of the short-circuit current (JSc) was found to increase semilogarithmically with the intensity at various bias light wavelengths, and to increase with the bias fight wavelength for the constant intensity in the position with a medium diffusion length (≃20 µm). In the position with a longer (≃89 µm) or shorter (≃7 µm) diffusion length, the bias light wavelength, however, had a smaller influence on the diffusion length. The effect of the bias light wavelength and intensity on the diffusion length is theoretically explained by a model of filling deep traps by photo-injected minority carriers.     

Characterization of the chirp and intensity modulation propertiesof an SOA-MZI wavelength converter

Wavelength converters based on cross-phase modulation in semiconductor optical amplifiers (SOAs) in the arms of a Mach-Zehnder interferometer (MZI) provide a key network element for reconfigurable optical networks that incorporate wavelength routing. For system design purposes, the properties of the intensity and phase (chirp) modulation of the wavelength-converted signal for an SOA-MZI wavelength converter are important. In this paper, the small-signal α parameter, which characterizes the converter chirp, and the conversion frequency response are characterized experimentally for an integrated all-active SOA-MZI wavelength converter. For both co- and counterpropagating signals, the variation of the a parameter along the interference and conversion curves is considered in detail. Three optical modulators with quite different chirp properties are used to generate the modulated input signal to the wavelength converter. The results demonstrate that the chirp of the wavelength-converted signal is primarily determined by the device properties and the intensity of the modulated input signal. The a parameter of the wavelength-converted signal is negative for noninverting operation and positive for inverting operation. An important contribution of the paper is the detailed assessment of this key device characteristic. The experimental characterization of the wavelength converter is incorporated into a device model that can be used to obtain the pulse response. Calculated and measured results for the time dependence of the intensity and chirp of the wavelength-converted signal are in good agreement. The conversion frequency response for the intensity modulation is also measured along the conversion curve. The 3-dB bandwidth is found to be generally about 8-10 GHz     

消光强扰动的相位载波解调算法

激光语音探测是一种非接触远距离信息获取技术,具有灵敏度高、探测距离远、抗干扰等优点被广泛应用。但是,在目标物的后向光散射特性的影响下,该技术探测性能受到机位角度、目标材料、表面粗糙度影响,严重者有效信号将湮灭到噪声里致使系统探测失效。针对此,结合传统的微分交叉相乘解调（PGC-DCM）算法,开展归一化自相除相位载波解调算法研究,解决目标物后向光散射特性差异所带来的光强扰动问题。首先,建立消光强扰动算法数学模型,利用LabView构建仿真模型,通过该模型进行新算法的频谱响应与消光强能力的仿真分析,发现该算法可实现对干涉信号中B值,一倍频G、二倍频H以及一阶贝塞尔函数J₁和二阶贝塞尔函数J₂影响的消除;其次,针对不同光强度B值,进行了PGC-DCM和新算法性能对比分析,结果表明新算法可以解调出语音信号,在弱光环境下,优势更加明显;而PGC-DCM解调方法在光强度较小情况下时(例如B=0.5 mW),语音信号湮灭,无法还原出信号;最后,建立了远距离光强扰动抑制实验系统,进行了光强扰动消除能力实验。实验结果表明:该算法在探测光功率为10、20、30、40 mW条件下,系统解调输出语音信号幅度一致,消除了光强不同对信号探测的影响。