An improved ptychographical phase retrieval algorithm for diffractive imaging

The ptychographical iterative engine (or PIE) is a recently developed phase retrieval algorithm that employs a series of diffraction patterns recorded as a known illumination function is translated to a set of overlapping positions relative to a target sample. The technique has been demonstrated successfully at optical and X-ray wavelengths and has been shown to be robust to detector noise and to converge considerably faster than support-based phase retrieval methods. In this paper, the PIE is extended so that the requirement for an accurate model of the illumination function is removed.     

Mapping granular structure in the biological adhesive of Phragmatopoma californica using phase diverse coherent diffractive imaging

This paper demonstrates the application of the high sensitivity, low radiation dose imaging method recently presented as phase diverse coherent diffraction imaging, to the study of biological and other weakly scattering samples. The method is applied, using X-ray illumination, to quantitative imaging of the granular precursors of underwater adhesive produced by the marine sandcastle worm, Phragmatopoma californica. We are able to observe the internal structure of the adhesive precursors in a number of states.     

Extended ptychography in the transmission electron microscope: possibilities and limitations

The extended-ptychographical iterative engine (e-PIE) is a recently developed powerful phase retrieval algorithm which can be used to measure the phase transfer function of a specimen and overcome conventional lens resolution limits. The major improvement over PIE is the ability to reconstruct simultaneously both the object and illumination functions, robustness to noise and speed of convergence. The technique has proven to be successful at optical and X-ray wavelengths and we describe here experimental results in transmission electron microscopy supported by corresponding simulations. These simulations show the possibilities - even with strong phase objects - and limitations of ptychography; in particular issues arising from poorly-defined probe positions.     

长春光机所软X射线-极紫外波段光学研究

综述了我所软X射线-极紫外波段关键技术的研究进展。描述了软X射线-极紫外波段光源技术,研制了工作波段为6~22 nm的微流靶激光等离子体光源;介绍了光子计数成像探测器技术,研制出了有效直径为25 mm,等效像元分辨率为0.3 mm的极紫外波段探测器;开展了超光滑表面加工、检测技术的研究,研制了超光滑表面抛光机,加工出高面形精度的超光滑表面,面形精度为6 nm(RMS值),表面粗糙度达0.6 nm(RMS值);进行了软X射线-极紫外波段多层膜技术的研究,研制出13 nm处反射率为60%的多层膜反射镜,150 mm口径反射镜的反射率均匀性优于±2.5%;最后,讨论了软X射线-极紫外波段测量技术研究,研制出该波段反射率计,其测量范围为5~50 nm,光谱分辨率好于0.2 nm,测量重复性好于±1%。在上述关键技术研究基础上,研制出了极紫外波段成像仪和空间极紫外波段太阳望远镜,这些仪器在我国空间科学研究项目中发挥了作用。     

X射线衍射光学部件的制备及其光学性能表征

综述了国内外在纳米加工X射线衍射光学透镜方面的研究现状和最新进展。介绍了作者团队过去三年在这方面做的工作。针对衍射透镜关键技术,研发了具有大高宽比形貌的电子束光刻基础工艺;结合金电镀,提出了纳米尺度波带片的制造技术,并将该工艺成功扩展于分辨率板(Siemens star)和集成光栅型会聚透镜的研制。运用蒙特卡罗模拟和显影动力学,探索了电子束光刻技术所能够实现的最大高宽比以及造成这种限制的物理根源;成功研制了50~100nm的波带片透镜(其中,100nm波带片高宽比为16∶1)、50~300nm的分辨率测试板(其中,300nm测试板高宽比为10∶1)和200nm的会聚透镜(高宽比为10∶1)。对所研制的光学部件在同步辐射光源进行了实验表征。结果表明,100nm波带片聚焦斑尺寸为234nm,测试板和会聚透镜的光学特性与国外同样光学部件到达同等水平;会聚透镜辐照的均匀性为99%。最后,总结了近几年我国X射线衍射透镜的发展进度,指出了衍射光学部件光学性能发展的最大瓶颈是分辨率与衍射效率相互制约,提出了提高光学部件衍射效率的具体途径,给出了我国X射线衍射透镜技术的未来发展路线图。     

大型X射线光学仪器:单层镜和多层镜的制造与表征

150~500 mm长度的各种X射线光学元件可用于光束导引,光束调整,以及单色化。本文介绍了两种不同的大型X射线反射镜。第一种为单层反射镜,这种反射镜以2°掠入射角在软X射线区(50~200 eV)起全反射镜作用,可用于自由电子激光器,如德国汉堡的FLASH。第二种是多层镜,由于它的布喇格反射特性,适于作为反射镜以0.4~1°的入射角用于硬X射线区(20~50 keV),如层析光束线的同步辐射存储环中。两种反射镜都用最新物理汽相淀积法制备,并用磁控溅射来实现X射线光学应用所需要的优良光学品质。这一淀积工艺使不同批次的镀膜稳定性良好,有利于实际反射镜在优质衬底上的最后淀积。单层镜和多层镜在它们的相关能量范围内都有很高的反射率,表面粗糙度也很低,且在整个光学波长区这些特性表现均匀。文中所叙相关研究都是借助X射线反射计量(XRR)法,透射电子显微镜(TEM)、光学轮廓仪(OP),以及原子力显微镜(AFM)完成的。     

Repeatable and accurate assembly of X-ray foil optics

Repeatable and accurate assembly of thin, foil optics is crucial to meeting performance goals in optical systems such as grazing-incidence X-ray telescopes and diffractive lithography tools. Our previous work in proving key technologies for assembly has been motivated by the need to meet spectral resolution goals for the NASA Constellation-X mission. We report a new generation of technology that makes strides towards simulating actual telescope assembly conditions. Our technology is based on the use of micromachined silicon tooling that we call microcombs. Theoretical error budgeting and analytical models were applied to a mechanical design with an isolated metrology frame and high-resolution actuation with feedback. Experimental testing has yielded assembly results with sub-micron repeatability and accuracy. For complete foil reassembly, placement errors are approximately 0.3  m over a 140 mm× 100 mm× 0.4 mm foil. Accuracy of assembly in pitch and yaw are 0.34 and 2.01  m, respectively. This performance meets the 1  m telescope assembly accuracy goal with the exception of yaw accuracy, which is under continued development.     

Present Status of EUV Interferometer Development at the Research Center for Soft X-ray Microscopy

A new interferometer for extreme ultraviolet (EUV) radiation with a laser produced plasma (LPP) laboratory source is under construction. The LPP source is operated with a Sn solid rod target on which pulsed YAG laser is focused to produce high temperature plasma emitting EUV radiation. The source is equipped with a newly designed debris stopper protecting a condenser multilayer mirror from the particle debris of the target. The condenser mirror focuses the light onto an EUV beam - splitter to form transmitted and reflected paths for producing interference fringes of a sharing type. The optical configuration is of a common path based on a triangular path type with a focusing at the beam- splitter, which is enabled to produce fringes by a low coherence radiation with a standard optical quality beam - splitter. The fringes are recorded by an imaging plate with pixels as small as 25μm. The dynamic range of linearity in detection of the EUV light was found to be more than 10^4 with sensitivity of 10^4 photo ns/pixel, enough for the purpose of interferogram recording possibly with one laser shot.     

最小膜层厚度对X射线非周期多层膜光学性能的影响

选用能制备小周期的钨/硅(W/S i)作为膜层材料对,着重研究最小膜层厚度对X射线非周期多层膜光学性能的影响。基于矩阵法计算多层膜反射率和单纯形数值优化方法,设计了入射光子能量为8.0keV,掠入射角的宽度分别为0.85°~1.10°,1.40°~1.70°的X射线超反射镜。结合实际实验制备技术,考虑了W/S i两种膜层材料的最小成膜厚度,确定了膜堆中最小膜层厚度为0.5nm~1.0nm。通过改变最小膜层厚度的值,优化设计了上述条件下的非周期多层膜并对其光学性能进行比较。结果表明:同一个工作波长下,随着多层膜工作角度(掠入射)的增加,膜堆中膜层的厚度减小,最小膜层厚度对其光学性能的影响增加,其光学性能变差。     

Modelling the application of adaptive optics to wide-field microscope live imaging

Wide‐field fluorescence microscopy is an essential tool in modern cell biology. Unfortunately the image quality of fluorescence microscopes is often significantly degraded due to aberrations that occur under normal imaging conditions. In this article, we examine the use of adaptive optics technology to dynamically correct these problems to achieve close to ideal diffraction limited performance. Simultaneously, this technology also allows ultra‐rapid focusing without having to move either the stage or the objective lens. We perform optical simulations to demonstrate the degree of correction that can be achieved.     

In-situ deflectometic measurement of transparent optics in precision robotic polishing

In the ultra-precision manufacturing of large optics, industrial robots have the potential to become an intelligent and economical choice of surface polishing. However, the transport of the workpieces between the polishing platform and the measurement instrument seriously limits the manufacturing efficiency. Therefore, an in-situ measurement system based on the monoscopic deflectometry is developed to determine the form quality of the optical lenses during rough polishing. Stray light reflected from the lower surface of transparent lenses may degrade the measuring quality, thus an effective absolute phase retrieval algorithm is developed to decouple the superposed fringes associated with the upper and lower surfaces. Then, the form of the upper surface under polishing can be reconstructed to guide the subsequent polishing. Experimental results demonstrate that the accuracy of the method is comparable to that of the coordinate measuring machine, consequently the manufacturing efficiency and reliability of large optical workpieces can be greatly improved.     

X-ray microscopy: experimental results with the Göttingen X-ray microscope at the electron storage ring BESSY in Berlin

An X-ray microscope and X-ray microscopy experiments with biological specimens are described. The experiments have been performed with a resolution of about 0.05 μm using the synchrotron radiation of the electron storage ring BESSY.     

A method for correcting the effect of specimen drift on coherent diffractive imaging

Coherent diffractive imaging involves the inversion of a diffraction pattern to find the wave function at the exit-surface plane of the specimen. It is a promising technique for imaging, for example, nanoparticles with electrons and biological molecules with X-rays. If the illumination is not a plane wave of infinite extent, then a relative drift between the illumination and the object introduces errors into the diffraction pattern; an issue which is often overlooked. This may be of particular importance for applications with electron microscopes which use nanoscale probes. Here we show that beams which are uniform over a sufficiently large region can be used to pose a phase retrieval problem that is immune from specimen drift, provided suitable analysis of the diffraction data is undertaken. The method only applies to objects contained within a support that is smaller than a uniform region of the beam.     

非共轴掠入射X射线显微镜参数的误差分析

设计了一套由4个反射镜组成的非共轴掠入射X射线显微镜,分析了该系统的像差和成像质量。为了研制出高质量的设备,需要制定合理的加工和装配公差。研究了由于元件和结构参数(反射镜的半径,物距,掠入射角等)的误差而引起的高斯参数和像差的变化。首次用点列图和调制传递函数来定量评价图像质量降低的程度,并在此基础上制定了合理的加工和装配公差。在这些公差的约束下,研制成一套非共轴掠入射X射线显微镜,在激光引爆的惯性约束聚变的诊断实验中,用该系统获得了高质量的图像。     

Error analysis of the parameters for non-coaxial grazing X-ray microscope

A non-coaxial grazing X-ray microscope, consisting of four spherical mirrors, is designed for diagnosis of inertial confinement fusion (ICF). The aberrations and imaging quality of the microscope are analyzed. To acquire excellent imaging quality, suitable tolerances for manufacturing and assembling the microscope are necessary. This paper researches the changes of Gauss parameters and aberrations due to component and subsystem parameters (such as the radius of the mirror, angle between mirrors, grazing angle, object distance, etc.). Here, spot diagrams and modulation transfer function (MTF) are first adopted to quantitatively evaluate the imaging quality of the microscope. Suitable manufacturing tolerances of components and assembly tolerances of the system are established on the basis of the discussion and analysis. A set of non-coaxial grazing X-ray microscopes is manufactured based on the tolerances. In site tests of ICF, the images with high resolution are obtained by the microscope. __________ Translated from Optics and Precision Engineering, 2006, 14(1): 34–42 [译自: 光学精密工程]     

Quantitative X-ray imaging of labelled molecules in tissues and cells

Using cisplatin as a model system, we have been able to demonstrate the feasibility of studying the cellular and subcellular distribution of a labelled molecule containing a single atom of platinum per molecule in bone marrow. An X-ray imaging system consisting of a microcomputer, a 4pi system and a software package was interfaced with an electron microscope enabling the computer to control the beam movements as well as receive signals from the STEM and EDS X-ray detectors. X-ray imaging is useful for both tissue and samples in which the population of cells is not homogeneous. Imaging permits elemental distributions to be measured throughout the sample and not in just randomly selected areas as previously done in X-ray microanalysis. Images are created for not only the element labelling the molecule of interest but also other specified elements present.
Three types of maps for imaging labelled molecules are compared and discussed. When the original (collected) data are mapped, the elements of interest are obscured by the continuum. The maps calculated using an internal standard give a concentration distribution on the basis of volume (mmol L⁻¹ of packed cells). The maps calculated using the continuum normalization method according to Hall produces concentration distribution on the basis of mass (mmol kg⁻¹ dry weight). By recalculating using the 'Peak' or 'Hall' method the continuum problem is removed yielding quantitative images of the intracellular distribution of labelled molecules present in low concentrations.     

整体多毛细管X光透镜在扩展X射线吸收精细结构分析技术中的应用

为了将整体多毛细管X光透镜应用到扩展X射线吸收精细结构分析技术中,对整体多毛细管X光透镜的功率密度增益、光斑稳定性、高能滤波性质等进行了系统表征。通过实验可知,利用基于整体多毛细管X光透镜的扩展X射线吸收精细结构分析设备可对样品进行微区分析,其空间分辨为25 μm左右;利用整体多毛细管X光透镜会聚激光等离子体发出的X射线进行超快时间分辨扩展X射线吸收精细结构分析时,透镜的功率密度增益约为3 000。实验结果证明,整体多毛细管X光透镜可以改善扩展X射线吸收精细结构分析设备的性能。     

Multifunctional mini-computer program providing quantitative and digital X-ray microanalysis of cryosectioned biological tissue for the inexperienced analyst

A series of computer programs have been written for use in a multi-user resource center for biological microanalysis. They are tied together by a “Main Menu” program which acts as a traffic director and guides the investigator into whatever option is desired. These programs have been written with very clear instructions and interaction points. As a result, a complex handbook of options and responses is not required. Consquently, almost no training is required to use these programs as they are essentially self-explanatory. Extensive error checking has been included so that most errors are identified and corrections are requested without causing a program halt. Options available to the user provide for selected “region” analyses, elementally quantitative image analysis, and sorting of the resulting data files. A complete computer code printout is included in this report.     

Revisiting Bragg's X-ray microscope: scatter based optical transient grating detection of pulsed ionising radiation

Transient optical gratings for detecting ultrafast signals are routine for temporally resolved photochemical investigations. Many processes can contribute to the formation of such gratings; we indicate use of optically scattering centres that can be formed with highly variable latencies in different materials and devices using ionising radiation. Coherent light scattered by these centres can form the short-wavelength-to-optical-wavelength, incoherent-to-coherent basis of a Bragg X-ray microscope, with inherent scope for optical phasing. Depending on the dynamics of the medium chosen, the way is open to both ultrafast pulsed and integrating measurements. For experiments employing brief pulses, we discuss high-dynamic-range short-wavelength diffraction measurements with real-time optical reconstructions. Applications to optical real-time X-ray phase-retrieval are considered.