Equivalent edge currents for arbitrary aspects of observation

Explicit expressions for equivalent edge currents are derived for an arbitrary local wedge angle and arbitrary directions of illumination and observation. Thereby the method of equivalent currents (MEC) is completed as a practically applicable theory of the electromagnetic high-frequency diffraction by edges. The derivation is based on an asymptotic relationship between the surface radiation integral of the physical theory of diffraction (PTD) and the line radiation integral of MEC, and the resulting expressions are deduced from the exact solutions of the canonical wedge problem.     

Equivalent currents for a ring discontinuity

Based on the geometrical theory of diffraction, equivalent filamentary currents are derived for a linear element of a surface singularity for general incidence and polarization. The currents are used to obtain an analytical expression for the bistatic field diffracted by a ring singularity, valid within the caustic region as well as at wide angles.     

Time-domain equivalent edge currents for transient scattering

Time-domain equivalent edge currents (TD-EEC) are developed for the transient scattering analysis. The development is based an the Fourier inversion of frequency domain equivalent edge current expressions. The time-domain diffracted fields are expressed in terms of a contour integral along the diffracting edges for any arbitrary input pulse shape, thereby yielding finite results at the caustics of diffracted rays. The approach also eliminates the need for the evaluation of a convolution integral in the time domain geometrical theory of diffraction (GTD) analysis. The results are compared with the first order GTD results for the transient scattering analysis for a circular disk     

New concept for applying edge line phase-shifting masks to arbitrary mask layouts

This paper explains the principle of a method which avoids printing of phantom resist lines due to undesired intensity minima appearing on Cr-less edge line phase-shifting masks. The method combines principles of grey-tone lithography and attenuated phase-shifting masks to give, what we call, a Cr-Less Attenuated Phase-shifting mask (CLAP). Rules for generating a CLAP design and a paradigm setup of a CLAP mask are presented. The capabilities and possible limitations of the CLAP method based on simulated results for a standard wafer stepper setup using the SOLID lithography simulator are being assessed.     

Equivalent currents for an aperture in an impedance surface

Expressions of equivalent magnetic and electric currents for an aperture in an impedance surface is derived in a self-consistent manner. Each equivalent current consists of the combination of the tangential electric and magnetic fields in the aperture, and is placed in front of the original aperture where the surface is extended to close the aperture. The result is particularly useful for problems involving apertures in an impedance ground plane     

Equivalent circuit of dipole antenna of arbitrary length

The purpose of this letter is to derive an equivalent circuit for a dipole of any length and to compare the input impedance versus frequency of the resulting equivalent circuit with published analytical and experimental data     

射线数字探测器灵敏度校正的等效能谱法

由于平板探测器对有无试件射线能谱响应的灵敏度不同,致使利用射线透照成像对试件投影估计的对比度降低,影响了对细节的可检出性。通过分析射线成像检测的数理模型,提出等效能谱透照成像方法,对探测器灵敏度进行校正。利用无缺陷的高密度材料等被检试件,进行背景成像,实现在有无试件情况下的探测等效能谱成像。与常规校正法对焊接板进行实验对比研究结果表明,等效能谱法增强了成像的可视化效果,通过像质计灵敏度实验,其对比度灵敏度提高了20-40灰度级;提高了检测中诸如未焊透和裂纹等微小细节的可检出性。     

线激光传感器的边缘偏差修正方法

为了修正线激光传感器在轮廓测量中的边缘偏差,提出了一种边缘偏差修正方法。该方法通过分析边缘偏差的主要误差来源,建立一种基于曼哈顿距离和切比雪夫距离的混合去噪模型,实现杂散噪声的滤除;采用最小二乘法对线激光轮廓测量误差模型进行补偿。为了验证该方法的有效性,以量块的标称尺寸作为评价指标进行测量校准实验。实验结果表明:该修正方法对杂散噪声的滤除效果显著;其中,未经补偿的尺寸测量误差为0.43 mm,经修正方法补偿后的尺寸测量误差最小达0.04 mm,比前者降低了一个数量级。因此,该方法可有效修正边缘偏差,提高线激光传感器的轮廓测量精度。