Indirect measurement of the intensity of incident light by the light transmission fluctuation method

The light transmission fluctuation method is a simple and useful method for in situ and in-line measurement of particle size and concentration. To accomplish the measurement, it is necessary to know the intensity of incident light or background signal I(0). However, measuring I(0) during in-line applications is hard. In this Letter, an algorithm is proposed to indirectly measure I(0) based on the variation of transmitted light signals. Experiments have been carried out to verify the algorithm and the maximum deviation between premeasured I(0) and indirectly measured I(0)' is less than 2.5%.     

Laser fluctuation studies in intensity dependent absorption of light

The interaction of a laser with an intensity-dependent absorber has been analysed for discrete regions of operations of the laser. It is shown that the beam is thermally defocused due to absorption for the values of intensity under consideration. The fluctuation properties have been analysed by evaluating 〈I〉,〈I ²〉 and 〈(ΔI)²〉/〈I〉².     

Novel correction method for X-ray beam energy fluctuation of high energy DR system with a linear detector

A high energy digital radiography (DR) testing system has generated diverse scientific and technological interest in the field of industrial non-destructive testing. However, due to the limitations of manufacturing technology for accelerators, an energy fluctuation of the X-ray beam exists and leads to bright and dark streak artifacts in the DR image. Here we report the utilization of a new software-based method to correct the fluctuation artifacts. The correction method is performed using a high pass filtering operation to extract the high frequency information that reflects the X-ray beam energy fluctuation, and then subtracting it from the original image. Our experimental results show that this method is able to rule out the artifacts effectively and is readily implemented on a practical scanning system.     

Effects of cross-correlated noises on the intensity fluctuation of the single-mode laser system

A single-mode laser model with cross-correlated additive and multiplicative noise terms is considered, and the effects of correlation between noises on the relaxation time and the intensity correlation function are studied. Using the projection operator method and taking into account the effects of the memory kernels of the intensity correlation function, the analytic expressions for the relaxation time and the correlation function are derived. Based on numerical computations, it is found that the self-correlation time and the cross-correlation time have the same effects on the single-mode laser system.     

Error correcting coding-theory for structured light illumination systems

Intensity discrete structured light illumination systems project a series of projection patterns for the estimation of the absolute fringe order using only the temporal grey-level sequence at each pixel. This work proposes the use of error-correcting codes for pixel-wise correction of measurement errors. The use of an error correcting code is advantageous in many ways: it allows reducing the effect of random intensity noise, it corrects outliners near the border of the fringe commonly present when using intensity discrete patterns, and it provides a robustness in case of severe measurement errors (even for burst errors where whole frames are lost). The latter aspect is particular interesting in environments with varying ambient light as well as in critical safety applications as e.g. monitoring of deformations of components in nuclear power plants, where a high reliability is ensured even in case of short measurement disruptions. A special form of burst errors is the so-called salt and pepper noise, which can largely be removed with error correcting codes using only the information of a given pixel. The performance of this technique is evaluated using both simulations and experiments.     

光压缩态的相位涨落

本文对光场压缩态的相位涨落进行了计算,得出(△cos(?))~2和(△sin(?))~2的表达式.压缩分量的涨落与相位涨落同时压缩.     

K-F系统中的波前相位调制与光强调制的转换

研究在由一薄片Ｋｅｒｒ 介质与一块二维反馈镜组成的非线性光学系统中光波前相位与光强的转换过程。根据基尔霍夫衍射定理,导出了单一模式以及小畸变近似条件下多个模式的相位－ 光强转换关系的方程。结果证明：通过衍射,入射波前相位各阶Ｚｅｒｎｉｋｅ 模式成分的大小转换为反馈光光强的非线性调制。     

All-optical method for maintaining a fixed intensity level of a light signal in optical computation

In data and image processing the role of optics is already well established. Due to inherent parallelism the optical systems run faster than its electronic counterparts. Optical nonlinear material can be used as a successful optical switch. The primary requirement for proper functioning of such nonlinear material based logic devices is a fixed intensity level of the optical signal against a specific logic state. In this communication, the authors propose a new concept to obtain a fixed intensity level of optical signal against a specific logic state for data processing. The scheme may extend a tremendous application not only to the area of all-optical computation, but also to optical communication process.     

一种新颖的智能眼镜光学系统设计方法

提出采用Fresnel微结构的曲面波导微投影光学系统眼镜设计思想,理论分析了所提光学系统的成像原理,给出了光学设计方法,并运用该方法设计了一套样机,曲面波导板近眼表面(即前表面)曲率半径为140.0 mm,后表面曲率半径为143.5 mm,中心厚度为1.7 mm,材料选PMMA (即有机玻璃),微型显示器选0.23″硅基OLED显示屏,分辨率640×480(象素),出瞳直径选为8 mm,眼点距约为18 mm,视场角9.6°(H)×7.2°(V),调制传递函数(MTF)在空间分辨率30 lp/mm时,中心视场MTF接近0.45,全视场大于0.2。从而验证了该方法的可行性。     

基于~(252)Cf中子源自相关分析的核事件死时间测量与修正方法

基于所研制的252Cf中子源频域测量系统,针对核探测系统的死时间使核事件丢失这一问题,利用自相关分析,研究了一种核探测系统死时间测量与修正的方法。试验测量结果表明:采用自相关图谱,可以直接获得高速频谱测量系统的死时间为40 ns,既方便又快捷,且测量精度高,达到了ns级,优于国外文献报道的类似核武器识别测量系统的死时间20μs。     

微光电视成像系统表征方法

在分析微光电视成像系统的基础上,提出了适用于微光电视成像系统仿真所用的微光场景图像数据的要求及生成方法;针对第二代近贴聚焦系统和第三代像增强系统,建立了微光电视成像系统的能量增益理论模型;引入３维噪声理论模型表征了微光成像系统的噪声;最后,提出了微光电视图像噪声抑制算法的评价方法。仿真结果表明：经微光系统传递后,图像中的高频信息变模糊,加入噪声后,信噪比降低;而经过5帧平均算法后的图像质量明显改善,对比度增加。     

Harmonic method for measuring and correcting amplitude functions in the circular accelerator

Free oscillations of particles in the ring’s focusing system with a variable gradient are described by the amplitude function (beta function) and the phase function. The gradient perturbation leads to distortions in these functions. Beta-function distortions reduce the ring acceptance, especially if the working point on the betatron frequency is close to the half-integer resonance. A new method for calculating the current in the windings of correcting quadrupole lenses is presented. The idea of this method consists of the excitation of the closed orbit distortions with the dipole magnet. A comparison of the measured values of these orbits in the pickup with calculated values for the ideal gradients presents the opportunity to calculate the resonant harmonics of the beta-function distortions and then adjust them using quadrupole correctors. The algorithm of the method and the preliminary results of applying it to the SIS 100 synchrotron are given.     

利用线谱起伏实现目标测距

常见水中目标辐射噪声的线谱会随目标运动而出现强弱起伏。不同号简正波之间的干涉是目标声强随距离起伏的主要原因,利用简正波水平波数差和波导不变量之间的关系,推导了不同线谱随距离变化起伏的理论关系式。基于此关系式,提出利用两条或多条线谱声强起伏进行声源测距的方法。针对两条线谱起伏测距方法存在的旁瓣问题,解释其形成原因,并提出用多条线谱声强起伏抑制旁瓣。数值仿真验证了方法的可行性,利用多条线谱声强起伏测距的方法可有效抑制旁瓣。海试数据分析表明,当连续谱部分非常微弱无法有效测距时,利用多条线谱声强起伏测距的方法仍能稳定的估计渔船目标距离,估计距离的平均相对误差为12%。     

Design considerations for SERS detection in colloidal solution: reduce spectral intensity fluctuation

The intensity fluctuation of surface‐enhanced Raman scattering (SERS) has seriously hampered its practical applications. The previous studies that involved SERS intensity fluctuation mostly focus on the assembled substrates or single molecule and single nanoparticle but have few attention on colloidal solutions containing numerous molecules and/or nanoparticles. Here, we studied the time‐elapsed SERS spectra of three different analytes in colloidal solution. Their peak intensities fluctuated simultaneously and uniformly throughout the acquisition process and had no correlation with their wavenumber wandering. Gravity‐induced inhomogeneous distributions of Ag nanocubes in solution led to the spatial and temporal variations of peak intensities, which could be reduced by altering the integration time, particle concentration, and solvent viscosity and density. Furthermore, the dissimilar interactions between analytes and Ag nanocubes showed non‐detectable influence over their intensity fluctuations. This investigation gives out the significant guidance for SERS detection in colloidal solution. Copyright © 2015 John Wiley & Sons, Ltd.     

子孔径拼接中系统误差的修正方法

为了提高大口径光学元件子孔径拼接测量的检测精度,提出一种平面绝对测量技术,修正子孔径拼接过程中产生的系统误差。利用改进的三面互检法获得参考平面的面形数据,采用这些测量数据构建基于Zernike多项式的参考面面形误差修正波面,在拼接过程中运用误差修正波面对获得的子孔径测量数据进行实时修正,并与全口径直接测量结果进行对比,结果PV（peak value,PV,峰谷值）误差从0.072 1 减少到0.028 6 。结果表明该方法有效减少了参考平面系统误差对拼接测量精度的影响,提高了大口径光学元件的检测精度。     

使用位置环的惯性稳定系统中陀螺漂移误差软件修正方法

针对使用位置环的惯性稳定系统中存在因陀螺固有温度漂移特性引起的系统跟随位置误差,首先提出一种软件修正方法,给出此软件修正方法的理论基础及软件修正的具体实现过程,最后对此修正方法进行了实验验证。实验结果表明：在没有振动的情况下,修正程序能将漂移完全校正,效果良好;在存在振动的情况下,修正程序也能较好地校正漂移,但校正后存在1个或2个码值的误差。     

线性啁啾高斯脉冲堆积中的强度起伏频率

基于谱分析方法系统研究了多个线性啁啾高斯脉冲堆积的强度起伏频率。首先基于傅里叶变换方法分别分析并模拟了两路和多路线性啁啾高斯脉冲堆积,讨论了等幅度、等延迟多路线性啁啾高斯脉冲堆积的情况下,起伏频率与初始高斯脉冲的数目与啁啾系数、时间延迟和脉冲宽度的关系,并简要分析了多路线性啁啾高斯脉冲堆积的一般情况。结果表明,在堆积脉冲的强度谱中存在一系列分立的频率边带,这些频率边带对强度起伏有贡献。高频的频率边带由于幅度交叠的部分较少,所以对强度起伏贡献较少。强度起伏频率随初始啁啾高斯脉冲啁啾系数和时间延迟的增大而增大,随脉冲宽度的减小而增大。