基于插值数浮动的MTF精确测量方法

采用刀口法测量成像系统调制传递函数(MTF)时,刀口装置与探测器矩阵夹角的准确测量是难点和关键点之一.针对这一问题,首先模拟刀口图像倾角对应的理论基准插值,研究了加载噪声情况下插值数浮动与线扩散函数(LSF)波动性变化以及MTF曲线衰减特性的定量关系;接着对实际X射线数字化成像系统获得的特定倾角下的刀口边缘图像进行了基于插值浮动的MTF测量,并将由其获得的MTF值与线对卡结果进行比较,证明了该方法用于成像系统MTF测量的有效性.结果表明:角度测量误差造成实际插值数偏离理想基准插值,导致LSF曲线光滑性变差,MTF衰减程度高于实际衰减.通过插值浮动方法,能够有效地避免角度测量误差引起的MTF测量的误差,降低角度测量的高精密性要求.     

CTP成像系统的MTF测量评价研究

分析了MTF测量的正弦光栅法和倾斜刃边法,总结了2种方法的优缺点,并分别用2种方法对一简单成像系统的MTF进行了测量,然后将结果与ISO标准进行了对比。结果表明,用倾斜刃边法测量不仅操作简单、易控制,测量结果也更精确。     

Estimation of point-spread functions and modulation-transfer functions of optical devices by statistical properties of randomly distributed surfaces

The point-spread function a(PSF) and the modulation-transfer function (MTF) are important tools to characterize the information transfer through optical devices. They give useful information about the resolution. Several methods have already been achieved to calculate the PSF and the MTF from theoretical aspects of wave propagation or from experimental results. I present a novel way of estimating these two functions. It deals with statistical considerations for a randomly distributed surface involving a statistical determination of the PSF and the MTF. Indeed, in this case the theoretical shape of the autocorrelation function of such surface profiles is known. It is a decaying exponential function α[exp(-β|x|)]. Comparingthe theoretical autocorrelation-function profile with the experimental one and deconvolving in Fourier space leads to an estimation of the MTF of the imaging device. Applying the inverse Fourier transform to the MTF involves the computation of the PSF, assuming that the latter has no imaginary part and is symmetrical. The two-dimensional images are regarded as an iteration of one-dimensional ones according to the orthogonal direction. The MTF's and PSF's are therefore one-dimensional. Different results are presented. The first result proceeds from investigation with scanning near-field microscopy and illustrates the method step by step. The tunneling effect is detected assuming that the information transfer is linear. The last result concerns an optical profilometer, and the influence of the microscope objective is studied.     

X-Ray Lithography Mask Metrology: Use of Transmitted Electrons in an SEM for Linewidth Measurement

X-ray masks present a measurement object that is different from most other objects used in semiconductor processing because the support membrane is, by design, x-ray transparent. This characteristic can be used as an advantage in electron beam-based x-ray mask metrology since, depending upon the incident electron beam energies, substrate composition and substrate thickness, the membrane can also be essentially electron transparent. The areas of the mask where the absorber structures are located are essentially x-ray opaque, as well as electron opaque. This paper shows that excellent contrast and signal-to-noise levels can be obtained using the transmitted-electron signal for mask metrology rather than the more commonly collected secondary electron signal. Monte Carlo modeling of the transmitted electron signal was used to support this work in order to determine the optimum detector position and characteristics, as well as in determining the location of the edge in the image profile. The comparison between the data from the theoretically-modeled electron beam interaction and actual experimental data were shown to agree extremely well, particularly with regard to the wall slope characteristics of the structure. Therefore, the theory can be used to identify the location of the edge of the absorber line for linewidth measurement. This work provides one approach to improved x-ray mask linewidth metrology and a more precise edge location algorithm for measurement of feature sizes on x-ray masks in commercial instrumentation. This work also represents an initial step toward the first SEM-based accurate linewidth measurement standard from NIST, as well as providing a viable metrology for linewidth measurement instruments of x-ray masks for the lithography community.     

Modulation transfer function measurement of sparse-array sensors using a self-calibrating fringe pattern

A simple method for the measurement of the pixel modulation transfer function (MTF) of sparse-array (extended MTF) sensors has been developed. We use a phase-shifting Twyman-Green interferometer to generate a series of single spatial-frequency fringe patterns incident on the sensor The resulting signal modulation is measured. We achieve self-calibration by restricting the measured spatial frequencies to multiples of the Nyquist frequency. The aliased patterns at these frequencies are unique and easily identifiable. Spatial frequencies of 480 cycles/mm are generated and measured. This frequency value is more than ten times that of the sensor sampling frequency. The expected MTF shape is obtained at multiples of the sampling frequency. At odd multiples of the Nyquist frequency, the MTF's are affected by the electronic bandwidth and cross talk in the charge-injection device sensor.     

利用CCD测定X射线增感屏的调制传递函数

本文论证了利用ＣＣＤ测定Ｘ射线胶片和增感屏调制传递函数和可行性，并给出了一种适用于ＣＣＤ测试数据的处理方法，对于同一种Ｘ射线胶片增感屏，分别给出了测微光密度计和ＣＣＤ两种测量数据及其误差分析，并用对几种不同增感屏和胶片性能做了评价，从实际应用中指出复ＣＣＤ探头测量调制传递函数的优越性。     

Modulation transfer function evaluation of linear solid-state x-ray-sensitive detectors using edge techniques

The exact determination of the modulation transfer function (MTF) of a physical system is a persistent problem. We present a practical method of measuring numerically the MTF of linear solid-state x-ray-sensitive detectors. The method is based on the use of edge techniques and allows us to obtain the MTF of a linear detector from its edge-spread function (ESF). ESF measurement techniques are discussed in detail, and calculation of the corresponding MTF's are shown.     

核查标准用于标准装置的有效控制

文章主要说明了应用核查标准对标准装置进行有效控制的原因、采用核查标准的具体方法和注意事项,并通过直流电阻箱标准装置说明对测量数据的定量分析,判定标准装置是否处于有效受控状态,长期运行的稳定性,此方法具有很好的推广应用价值。     

数字图像设备色度特征化建模软件研究

彩色图像在数字图像设备之间的传输和复制过程中,为保证其色彩还原的准确性和一致性,必须实施色彩管理,而色彩管理的核心技术之一就是对数字图像设备进行色度特征化.在研究了数字图像设备色度特征化的原理和方法的基础上,基于多项式回归法,建立了数字图像的设备色度值RGB与CIE标准颜色空间色度值CIE Lab之间的非线性关系;并通过Matlab软件编程,设计一种数字图像设备色度特征化的快速建模软件.实验结果表明,应用该软件可实现设备色度值RGB与标准颜色空间色度值CIE Lab的快速精确转换.     

Comparative analysis of techniques for measuring the modulation transfer functions of charge-coupled devices based on the generation of laser speckle

Two methods for measuring the modulation transfer function (MTF) of a charge-coupled device (CCD) that are based on the generation of laser speckle are analyzed and compared. The method based on a single-slit aperture is a quick method, although the measurements are limited to values of less than the Nyquist frequency of the device. The double-slit method permits the measurement of values of as much as some 1.8 times the Nyquist frequency, although it is a slower method because of the necessity to move the CCD. The difference between the MTF values obtained with the two methods is less than 0.1 in magnitude; the root-mean-square error between the two curves is 0.046 (4.6%).     

Simulation of Transient Response of Ir-TES for Position-Sensitive TES with Waveform Domain Multiplexing

We are developing a new x-ray microcalorimeter based on a superconducting transition edge sensor (TES) as an imaging sensor. Our measurement shows unique waveforms which we consider as an expression of thermal nonuniformity of TES films. This arises from the different thermal responses, so that response signal shapes would vary according to the position of the incident x-ray. This position dependency deteriorate the measured energy resolution, but with appropriate waveform analysis, this would be useful for imaging device. For more inspection, we have developed a simulation code which enables a dynamic simulation to obtain a transient response of the TES by finite differential method. Temperature and electric current distributions are calculated. As a result, we successfully obtained waveform signals. The calculated signal waveforms have similar characteristics to the measured signals. This simulation visualized the transition state of the device and will help to design better detector.      

投影机镜头的MTF实时检测系统

目前还没有标准的方法来检测投影机镜头的MTF,为此我们提出了一种基于图像分析的投影机镜头MTF实时测试系统.本系统使用CCD作为成像接收器,采用基于图像分析的方法,通过分析单个像素成像同时获得投影镜头子午和弧矢两个方向上的调制传递函数(MTF).阐述了整个测试系统的构造及理论框架,着重分析了系统参数标定的重要性以及如何正确地进行系统参数标定;全面分析了影响测试结果的因素以及如何正确快速地修正噪声的影响.检测了质量合格与质量不合格的投影机镜头,并将结果同设计值的进行比较,实验结果表明了本系统及其处理方法的有效性.     

Consideration on the Condenser for an Imaging Type Schwarzschild Soft X-ray Microscope

Abstract

Proposed is an imaging type Schwarzschild soft X-ray microscope including a condenser optimized for better imaging properties on the basis of Hopkins's theory. The condenser using grazing incidence reflective optics is found most suitable for a Schwarzschild objective. The modulation transfer function (MTF) for the microscope is calculated and it is shown that the MTF is improved with the light intensity distribution on the condenser pupil.     

Diffraction of transient horizontal shear waves by a running crack

An analysis of the diffraction of horizontally polarized shear waves of arbitrary profile by a finite crack extending uniformly is investigated. Transform techniques and a generalized Wiener-Hopf method are employed to solve the mixed boundary-value problem exactly from the instant the incident wave first strikes the crack until the diffracted wave reaches the opposite edge, is rediffracted, and then returns the original edge. The dynamic stress-intensity factors for an incident wave with a step function stress profile are obtained as functions of time, the angle of incidence and the speed of crack propagation. The effects of the aforementioned system parameters on the dynamic stress-intensity factors are shown graphically.     

Minutes of the 7th Session of the International Commission for Optics Held on May 2 and 4, 1966, at UNESCO,Paris, France

A simple MTF formula for the X-ray imaging process has been derived taking into account the size of the X-ray focus, off-focus radiation, scattered radiation from the object, and position of the imaged layer within the object. This formula has been confirmed experimentally using a lead test raster. It refers to an object model consisting of a variable depth object layer within a homogeneous water medium.     

Development and application of programs to measure modulation transfer function, noise power spectrum and detective quantum efficiency

This project aimed to produce programs to calculate the modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE) of digital X-ray systems, given a suitable digital image. The MTF was calculated using the edge technique and the NPS was calculated from a flat field image. Both programs require a suitably edited DICOM image as input. The DQE was then calculated from the output of MTF and NPS programs. This required data external to the DQE program to estimate the number of quanta per mm2 in the beam which formed the NPS image. All three programs run independent of each other on a PC and require no special software to be installed. Results for MTF, NPS and DQE for a Philips AC3 CR system are presented. In addition, the results for MTF from a Siemens Duo CT scanner with a specially designed PTFE edge are also shown.     

CMOS APS图像传感器的像质分析

使用标准CMOS制作工艺生产的有源像素传感器（APS）引起了广泛关注。为了确定CMOS APS成像系统设计的主要参数选择的正确性,以及能否满足要求或指标,需要对相机系统的像质进行分析。考虑到CMOS APS图像传感器与CCD的不同,在分析时计算了CMOS APS成像系统中的镜头、滤光片和焦平面的调制传递函数（MTF）,系统MTF曲线为各个部分MTF值之积。在系统截止频率范围内,利用MTF曲线所围面积的大小来评价系统的成像质量。在系统制造之前,用调制传递函数作为像质的评价方法,看其是否符合使用要求,是十分有价值的工作。     

台阶模糊边的X射线同轴相衬成像参数优化

采用图像衬度,信噪比,分辨率和探测器抽样数作为X射线同轴相衬成像质量的综合评价标准,针对具有广泛应用意义的台阶模糊边分布特征的物体,提出了参数优化方法并建立了优化流程.通过数值模拟的方式分别对具有广泛代表性的亚微米焦点源、激光驱动微米焦点源及同步辐射源3种X射线源下成像系统的相关参数进行了优化.结果表明,基于优化方法的优化流程很好地完成了3种X射线源的同轴相衬成像参数优化.可见,这种优化方法具有广泛的应用意义,在根据具体情况对方法进行简单修正的基础上,可以完成任意X射线源下对具有台阶模糊边分布特征物体的同轴相衬成像优化工作.     

A system for ultrasonic beacon-guidance of catheters and other minimally-invasive medical devices

Catheters and other interventional medical devices are presently guided by X-ray imaging, despite the advantages of ultrasound imaging over X-ray imaging in cost, safety, and availability. X-ray imaging is used because ultrasound reflects specularly from catheters and similar devices; their visibility is highly angle-dependent. With an omni-directional receiver mounted on a device, the receiver's location in the ultrasound image can be deduced from knowing which acoustic ray struck the receiver and the time from transmission of the imaging pulse to its reception by the receiver. This information is independent of specular reflection. The location of the device can then be indicated in the ultrasound image by an arrow pointing to the sensor, making possible ultrasound guidance of these devices. This paper describes the technical and practical considerations in the design and construction of the device-mounted receiver and associated electronics, and describes some clinical uses.