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91.
Measurement Accuracy in Phase-Shifting Point Diffraction Interferometer with Two Optical Fibers 总被引:1,自引:0,他引:1
Toshiaki Matsuura Satoru Okagaki Takaaki Nakamura Yasushi Oshikane Haruyuki Inoue Motohiro Nakano Toshihiko Kataoka 《Optical Review》2007,14(6):401-405
A phase-shifting point diffraction interferometer (PS/PDI) with point sources of two single mode optical fibers has been developed,
which will be appropriate for the surface figure measurement of large aperture optics on a sub-nanometer scale. To reduce
the measurement error factors, a fiber optic plate (FOP) is used as a projection plane for interference pattern. Errors caused
by imperfection of optical alignment, such as position of point sources and tilt of FOP, are minimized by analyzing the measured
phase data with an original method. Measurement accuracy in the PS/ PDI is estimated with the interference pattern produced
by the two optical fiber sources. If inhomogeneity of the FOP and a systematic error of the PS/PDI are eliminated, the measurement
accuracy of the present system is estimated to be less than 4nm P-V and 0.7nm rms, respectively, at a measurement wavelength
of 632.8 nm. 相似文献
92.
93.
94.
为了把量热法应用于远场激光强度时空分布测量,研究了基于热像仪靶面温度测量反演入射激光强度时空分布的重构理论。针对背光面两种不同边界条件(对流-辐射热流边界和恒定温度边界)推导出了由靶面温度分布反演激光束时空分布的重构表达式。获得的分析表达式对广泛的材料具有适用性。通过引入广义参量F0=α/L2,分别就F0》1和F0《1情况给出了重构近似表达式,并对满足F0》1条件的回推算法进行了数值模拟验证。数值结果表明,两种背光面边界条件下回推得到的激光束时空分布与原始激光束达到了很好的一致,但存在一与靶材傅里叶数相关的最小起始回推时间τ0。成果可用于强激光远场参量测量设备的研制。 相似文献
95.
基于彩色扫描仪的图像光谱重构 总被引:5,自引:0,他引:5
针对彩色扫描仪的特点,采用主元分析法(PCA)和反向传播(BP)人工神经网络(ANN)相结合的方法对图像光谱重构进行研究。选择IT8.7/2标准色卡作为训练样本,将该色卡中的另一组色靶作为检验样本以讨论不同网络结构以及不同主元数和训练样本数对光谱重构的影响,再以自然色系统(NCS)色卡为检验样本来分析不同种类的训练和检验样本与光谱重构性能的关系。实验结果表明,采用3-14-6网络结构和6个主元数是最佳选择,训练样本和扫描目标之间的一致性是基于彩色扫描仪图像光谱重构的关键所在。 相似文献
96.
基于Hilbert变换的相空间重建方法在HLS逐束团测量系统中的应用 总被引:1,自引:0,他引:1
引入基于Hilbert变换的相空间重建手段, 对合肥光源(HLS)逐束团测量系统采集的数据进行了全面的分析, 其中包括单个束流位置监测器(BPM)数据的相空间重建, 逐圈逐束团振荡相位信息、束团振荡模式信息、逐束团横向工作点(tune值)变换. 提出了新的分析束团tune值的手段, 提供传统方法无可比拟的更高的时间和频率分辨率. 还对不同模式的阻尼率进行了计算, 这为衡量逐束团反馈系统的效果提供了确实可靠的方法. 相似文献
97.
S.M. Driver 《Surface science》2007,601(2):510-517
We have used a novel fibre-optic low-energy electron diffraction (FO-LEED) instrument, capable of low flux measurements that minimise electron beam damage to surface overlayers, to study methanethiolate (CH3-S-) structural phases formed on Cu{1 1 1} at temperatures between 110 and 300 K. Three structural phases were seen: a (√3 × √3)R30° phase that forms at 110-140 K; a (4 × 4) phase which was observed transiently at 110 K; and a pseudo-{1 0 0} reconstructed phase which forms at room temperature. We discuss these in the context of previous studies of this system, and demonstrate the ability of the FO-LEED instrument to record high-quality LEED patterns and intensity data from a strongly beam-sensitive surface. 相似文献
98.
Several surface analysis techniques were combined to study the initial stages of oxidation of Cu(1 1 1) surfaces exposed to O2 at low pressure (<5 × 10−6 mbar) and room temperature. Scanning tunneling microscopy (STM) results show that the reactivity is governed by the restructuring of the Cu(1 1 1) surface. On the terraces, oxygen dissociative adsorption leads to the formation of isolated O adatoms and clusters weakly bound to the surface. The O adatoms are located in the fcc threefold hollow sites of the unrestructured terraces. Friedel oscillations with an amplitude lower than 5 pm have been measured around the adatoms. At step edges, surface restructuring is initiated and leads to the nucleation and growth of a two-dimensional disordered layer of oxide precursor. The electronic structure of this oxide layer is characterised by a band gap measured by scanning tunneling spectroscopy to be ∼1.5 eV wide. The growth of the oxide islands progresses by consumption of the upper metal terraces to form triangular indents. The extraction of the Cu atoms at this interface generates a preferential orientation of the interface along the close-packed directions of the metal. A second growth front corresponds to the step edges of the oxide islands and progresses above the lower metal terraces. This is where the excess Cu atoms extracted at the first growth front are incorporated. STM shows that the growing disordered oxide layer consists of units of hexagonal structure with a first nearest neighbour distance characteristic of a relaxed Cu-Cu distance (∼0.3 nm), consistent with local Cu2O(1 1 1)-like elements. Exposure at 300 °C is necessary to form an ordered two-dimensional layer of oxide precursor. It forms the so-called “29” superstructure assigned to a periodic distorted Cu2O(1 1 1)-like structure. 相似文献
99.
A simple, rigid pair-potential model is applied to investigate the dynamics of the (0 0 0 1) α-Al2O3 and α-Cr2O3 surfaces using the molecular dynamics technique. The simulations employ a two-stage equilibration process: in the first stage the simulation-cell size is determined via the constant-stress ensemble, and in the second stage the equilibration of the size-corrected simulation cell is continued in the canonical ensemble. The thermal expansion coefficients of bulk alumina and chromia are evaluated as a function of temperature. Furthermore, the surface relaxation and mean-square displacement of the atoms versus depth into the slab are calculated, and their behaviour in the surface region analysed in detail. The calculations show that even moderate temperatures (∼400 °C) give rise to displacements of the atoms at the surface which are similar to the lattice mismatch between α-alumina and chromia. This will help in the initial nucleation stage during thin film growth, and thus facilitate the deposition of α-Al2O3 on (0 0 0 1) α-Cr2O3 templates. 相似文献
100.
The morphology and structure of Pt deposited on a WSe2(0 0 0 1) van der Waals surface have been investigated by reflection high energy electron diffraction and scanning tunneling microscopy. At room temperature, the initial growth is characterized by the formation of three-dimensional fcc Pt islands with (1 1 1) orientation. In contrast, at higher temperatures of about 450 °C the formation of a novel chemically ordered Pt-Se alloy is observed. Based on the diffraction patterns, a tetragonal DO22-type structure of a Pt3Se compound is suggested. With increasing Pt thickness, this chemically ordered alloy disappears and an additional superstructure occurs, which is accompanied by the coalescence of the islands. The observed superstructure is attributed to a strong Se diffusion towards the growth surface, forming most likely a PtSe2 alloy with the CdI2-type layered structure on the top surface. Due to the lateral lattice mismatch between the Pt(1 1 1) layers and the PtSe2(1 1 1) top layer, a Moiré pattern with a period of 1.1 nm is created, which might be used as a long-range atomic pattern for further nanostructure growth. 相似文献