Dispersive white-light spectral interferometry including the effect of thin-film for distance measurement

A spectral-domain white-light interferometric technique is used for measuring distances in a Michelson interferometer with a mirror represented by a thin-film structure (TFS) on a substrate. A fibre-optic spectrometer is employed for recording spectral interferograms that include wide wavelength range effects of dispersion in a cube beam splitter and multiple reflection within the TFS. Knowing the effective thickness of the beam splitter, its dispersion and parameters of the TFS and substrate, the positions of the second interferometer mirror are determined precisely by a least-squares fitting of the theoretical spectral interferograms to the recorded ones. We apply the technique to the beam splitter made of BK7 optical glass and to a uniform SiO₂ thin film on a silicon wafer. We compare the results of the processing that include and do not include the effect of the TFS.     

In situ calibration of a Michelson type, speckle-shearing interferometer: Wobbling mirror effect

In situ calibration of piezoelectric transducers in a phase stepping, Michelson type, speckle-shearing interferometer can be affected by mirror wobbling introduced by the transducers. When this happens, a modulation of the curves employed for calibration can be readily detected in imaging systems with large apertures. A calibration method that takes into account the modulation of these curves is, therefore, essential to insure the required regularity of the phase steps. A computer model of speckle-shearing interferometry is used to deal with piezoelectric non-linearities and mirror wobbling in the interferometer, and to show how the calibration curves are affected when both phenomena are present. Computer simulated and experimental results validate the calibration technique advanced here.     

Synthesis and reconstruction of computer generated holograms by a double pass technique on a twisted nematic-based liquid crystal spatial light modulator

Achieving phase only modulation from a spatial light modulator (SLM) is useful for many optical processing tasks. In this paper, we demonstrate a simple method of decoupling phase and amplitude modulation in a twisted nematic liquid crystal (TNLC) SLM using a double pass technique. A Jones calculus model is developed which matches our experimental data.     

Fourier transform profilometry based on composite structured light pattern

In Fourier transform profilometry (FTP), the zero frequency of the imaged patterns will influence the measurement range and precision. The π phase shifting technique is usually used to eliminate the zero order component, but this method requires the capture of two fringe patterns with a π phase difference between them, which will impede the real time application of the method. In this paper, a novel method is proposed, in which a composite structured light pattern is projected onto the object. The composite structured light pattern is formed by modulating two separate fringe patterns with a π phase difference along the orthogonal direction of the two distinct carrier frequencies. This method can eliminate the zero frequency by using only one fringe pattern. Experiments show that there is no decrease in the precision of this novel method compared with the traditional π phase shifting technique.     

干涉测量用半导体激光器驱动电源

设计了一种可调制的高稳定度半导体激光器驱动电路。该电路的直流稳定度高达1.5×10-5，输出电流在0～200mA内连续可调，长时间工作（12h以上）电流变化小于1μA；在直流基础上注入100kHz～300kHz的调制电流，其调制深度为0～100mA连续可调，可实现在激光干涉测量中对光波频率和光波强度的调制。将该电路驱动的光栅外腔半导体激光器和辅助温度控制电路应用于光干涉测量技术中，得到了功率稳定、波长单一的激光输出，解决了激光器的跳模现象，完成了对远距离微小振动（纳米量级）的测量。     

控制三维光场的纯相位衍射光学元件优化设计

为提高纯相位衍射光学元件的设计效果，实现高衍射效率的三维光场衍射传播控制，在原有GS迭代算法的基础上提出了新的相位加权迭代优化设计算法。此算法的特点是，建立多衍射输出平面迭代加权算法模型，并通过反馈各个设计输出平面在迭代计算过程中的设计误差，引入一定的相位动态加权整调策略，以达到更加优化的设计效果。以此算法设计一个纯相位衍射光学元件，将输入的高斯光束在距离输入面300mm～400mm内的每个平面上变换为2×2等强度光束阵列。通过对比实验发现此方法在原有算法基础上能进一步改善算法的收敛效果，提高整体设计质量，实现更加优化的运算。     

几周期余弦-高斯激光脉冲的时间重心

研究了几周期超短余弦-高斯脉冲的时间重心与绝对相位以及与余弦函数参量之间的关系．给出了几周期超短余弦-高斯脉冲时间重心的解析表达式和模拟图形．结果表明，余弦-高斯脉冲的时间重心随着绝对相位的变化而发生漂移，并且脉冲宽度对余弦-高斯脉冲时间重心的漂移量也有一定的影响．余弦函数的参量在一定取值范围内对余弦-高斯脉冲也有较大的影响，它可能导致几周期余弦-高斯脉冲的时间重心有较大的漂移．     

基于延时相关频谱的调制识别方法

以简单脉冲、线性调频、二项编码和频率编码信号为例,通过提取信号的延时相关频谱特征,对雷达信号的脉内调制特征进行了分析。在分析和提取了信号的延时相关频谱结构特征后,提出了一种基于延时相关频谱进行调制方式识别方法。仿真和试验结果表明:在低信噪比情况下,是一种较好的雷达脉内调制方式识别方法。     

利用SAR多目标回波估计多普勒参数

从回波中估计多普勒参数是合成孔径雷达运动补偿的关键。文中研究了多目标回波对参数估计的影响,从理论上推导了估计多普勒中心和调频率对回波的不同要求,并用两个指标举例分析了一段实测机载SAR数据,给出了实际应用中参数估计时选择回波的原则。     

A DCM‐Type Red‐Fluorescent Dopant for High‐Performance Organic Electroluminescent Devices

2‐(2‐tert‐Butyl‐6‐((E)‐2‐(2,6,6‐trimethyl‐2,4,5,6‐tetrahydro‐1H‐pyrrolo[3,2,1‐ij]quinolin‐8‐yl)vinyl)‐4H‐pyran‐4‐ylidene)malononitrile (DCQTB) is designed and synthesized in high yield for application as the red‐light‐emitting dopant in organic light‐emitting diodes (OLEDs). Compared with 4‐(dicyanomethylene)‐2‐tert‐butyl‐6‐(1,1,7,7,‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJTB), one of the most efficient red‐emitting dopants, DCQTB exhibits red‐shifted fluorescence but blue‐shifted absorption. The unique characteristics of DCQTB with respect to DCJTB are utilized to achieve a red OLED with improved color purity and luminous efficiency. As a result, the device that uses DCQTB as dopant, with the configuration: indium tin oxide (ITO)/N,N′‐bis(1‐naphthyl)‐N,N′‐diphenyl‐1,1′‐biphenyl‐4,4′‐diamine (NPB; 60 nm)/tris(8‐quinolinolato) aluminum (Alq₃):dopant (2.3 wt %) (7 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 12 nm)/Alq₃(45 nm)/LiF(0.3 nm):Al (300 nm), shows a larger maximum luminance (L_max = 6021 cd m^–2 at 17 V), higher maximum efficiency (η_max = 4.41 cd A^–1 at 11.5 V (235.5 cd m^–2)), and better chromaticity coordinates (Commission Internationale de l'Eclairage, CIE, (x,y) = (0.65,0.35)) than a DCJTB‐based device with the same structure (L_max = 3453 cd m^–2 at 15.5 V, η_max = 3.01 cd A^–1 at 10 V (17.69 cd m^–2), and CIE (x,y) = (0.62,0.38)). The possible reasons for the red‐shifted emission but blue‐shifted absorption of DCQTB relative to DCJTB are also discussed.