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Search Results: 1 - 10 of 5950 matches for " white-light interferometry "
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Teager-Kaiser Energy and Higher-Order Operators in White-Light Interference Microscopy for Surface Shape Measurement
Salzenstein Fabien,Montgomery Paul C,Montaner Denis,Boudraa Abdel-Ouahab
EURASIP Journal on Advances in Signal Processing , 2005,
Abstract: In white-light interference microscopy, measurement of surface shape generally requires peak extraction of the fringe function envelope. In this paper the Teager-Kaiser energy and higher-order energy operators are proposed for efficient extraction of the fringe envelope. These energy operators are compared in terms of precision, robustness to noise, and subsampling. Flexible energy operators, depending on order and lag parameters, can be obtained. Results show that smoothing and interpolation of envelope approximation using spline model performs better than Gaussian-based approach.
Recent developments in fiber optic spectral white-light interferometry
Yi Jiang,Wenhui Ding
Photonic Sensors , 2011, DOI: 10.1007/s13320-010-0014-z
Abstract: Recent developments in spectral white-light interferometry (WLI) are reviewed. Firstly, the techniques for obtaining optical spectrum are introduced. Secondly, some novel measurement techniques are reviewed, including the improved peak-to-peak WLI, improved wavelength-tracking WLI, Fourier transform WLI, and 3 × 3 coupler based WLI. Furthermore, a hybrid measurement for the intensity-type sensors, interferometric sensors, and fiber Bragg grating sensors is achieved. It is shown that these developments have assisted in the progress of WLI.
Measurement of the group refractive index of bulk material using white-light spectral interferometry

Zhang Shu-Na,Luo Zhen-Yue,Shen Wei-Dong,Liu Xu,Zhang Yue-Guang,

物理学报 , 2011,
Abstract: It is a radical but pressing problem to measure the group refractive index of dispersive material both accurately and rapidly in optical engineering field. In this paper, a white-light spectral interferometric system employing a fiber-optic spectrometer is developed for solving this problem. The system takes advantage of the characteristic of fiber-optic spectrometer which can get all the interferometric information by a single shot image without any mechanical scanning. Compared with the traditional windowed Fourier transform, a wavelet transform algorithm is used to directly extract the group delay rather than the phase from the interferogram. Therefore, the new method can provide a simple and fast solution, while still maintaining high accuracy. Based on this white-light Michelson interferometric system, fused silica and BK7 glass samples are measured respectively and the results agree well with the theoretical values over a broad spectral range. At the end of this paper, different mirror positions are used to verify the repeatability of our method.

科学通报(英文版) , 1992,
Experimental study on the chirped structure of the white-light continuum generation by femtosecond laser spectroscopy

Quan Dong-Hui,Liu Shi-Lin,Zhang Lei,Yang Jian,Wang Li,Yang Guo-Zhen,Weng Yu-Xiang,

中国物理 B , 2003,
Abstract: The chirped structure of the white-light continuum generation (WLCG) pulse produced by focusing 800nm laser pulse with a pulse duration of 150fs (FWHM: full-width-at-half-maximum) onto a 2.4 mm thick sapphire plate was investigated by the optical Kerr gate technique with normal hexane as the optical Kerr gate medium. The observed WLCG was positively chirped, the measured anti-Stokes spectrum of WLCG ranges from 449 to 580nm with a temporal span of 2.56ps. When using metal reflecting mirrors to eliminate the group velocity dispersion (GVD) effect, we found that a span of 1.3ps still remained, indicating that the chirped pulse cannot be accounted for simply by GVD of the pulse propagation in the dispersive media. Our results suggest that the light-induced refractive index change due to the third-order nonlinear optical effect leads to an additional positive group velocity dispersion, which contributes to an important portion of the observed temporal broadening of the chirped WLCG. In addition to using reflective optical elements instead of dispersive optical elements, an effective way of reducing the chirp is to minimize the optical path length of the WLCG medium.
Characterization of Fluoride Phosphors for Diode Pumped Solid-State Lighting Applications  [PDF]
Bommareddi Rami Reddy, Kristopher Liggins, Vernessa M. Edwards
Optics and Photonics Journal (OPJ) , 2018, DOI: 10.4236/opj.2018.88024
Abstract: Phosphor coated diodes are critical to the lighting industry. Rare-earth doped fluoride phosphors are characterized in this work. Spectroscopy and lifetime measurements of CaF2: Dy3+, LaF3: Eu3+ and Tb3+-doped LaF3 and CaF2 crystals were performed by irradiating the samples with 405 and 375 nm diode lasers. Chromaticity diagrams are developed from spectral measurements. Dy3+-doped CaF2 revealed bright white light emission having peaks at 492, 570 and 654 nm. The measured color coordinates are x = 0.322 and y = 0.340 for Dy3+-doped CaF2 and these values are close to those of sunlight and the coordinated color temperature is 6147 K, under 405 m laser excitation. Eu3+-doped LaF3 revealed twenty emission peaks in the visible wavelength region. The color coordinates measured for LaF3: Eu3+ are x = 0.283 and y = 0.293 under 405 nm diode laser excitation and the color temperature is 9557 K. Eu3+-doped LaF3 provides cool white-light, under 405 nm diode laser excitation. Tb3+-doped fluoride crystals revealed bright white light under low power diode laser excitation. The measured color coordinates for Tb3+-doped CaF2 are x = 0.329 and y = 0.558 and the color temperature is 7713 K. The color coordinates for LaF3: Tb3+ are x = 0.342 and y = 0.365 and the coordinated color temperature is 5370 K. These values are close to those of sunlight.
Fazendo imagens com um simples elemento difrativo ou refrativo: o axicon
Lunazzi, José Joaquín;Magalh?es, Daniel S. Ferreira;
Revista Brasileira de Ensino de Física , 2009, DOI: 10.1590/S1806-11172009000200013
Abstract: in this previously divulgated paper [1] we demonstrate that the light diffracted by a simple compact disc can be used to generate images with interesting basic attributes. we compare this attributes with the ones obtained with refractive elements. a compact disc acts as an axicon that generates a diffraction-free beam and, because the focused position of the image depends on the wavelength of the diffracted light, thus it can be useful as a spectral filter. the experiments are of easy reproduction, allowing the understanding of images that the students observe daily at school or at home.
Tricolor white emitting phosphor co-doped with Eu, Dy in SiO2 matrix
XiaoYun Hu,Jun Fan,DeKai Zhang,YiPing Ma,JinTao Bai,ZhaoYu Ren,Xun Hou
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0493-0
Abstract: A Eu, Dy co-doped SiO2 matrix, white emitting phosphor was prepared by the sol-gel technique. Strong red, green and blue emissions located at 618 nm, 573 nm and 400–550 nm were observed under UV laser excitation at room temperature. Such techniques as FT-IR and TGA-DSC were used to measure the microstructure of the luminescent material. The influence of the preparation techniques on the luminescence property of the Eu, Dy co-doped SiO2 matrix, such as anneal temperature, anneal time, dried atmosphere and the components of the matrix, was systematically studied, and the luminescence mechanism was interpreted. The red emission is the strongest when annealed at 750°C. However, blue emission appears when annealed at 700°C and is the intensest at 900°C. For the samples dried in vacuum, Eu3+ is more easily deoxidized to Eu2+ at lower temperatures, because the samples dried in the air compared with that dried in vacuum need higher temperature to form network structures. Only the SA and SAB matrix annealed at 850°C had blue emission in the four matrices (SA, SAB, SB, S) xerogel and the emission in the SAB matrix was stronger than that in the SA matrix. This may be due to the eutectic phase formed by the oxide boron, alkaline oxide and alumina in the SAB matrix, which constructs network structures and stabilizes the emission center and enhances the blue emission.
White-light emission of ZnO nanoparticles prepared by sol-gel method

Li Shi-Shuai,Zhang Zhong,Hang Jin-Zhao,Feng Xiu-Peng,Liu Ru-Xi,

中国物理 B , 2011,
Abstract: In:ZnO nanoparticles are prepared by the sol-gel process. The ratios of In/(Zn+In) are 0%, 5%, 8%, 10%, and 15%, respectively. Crystal phase structures and optoelectronic properties of these samples are characterized and the chromaticity coordinates of different samples are also calculated in CIE-XYZ colour system. The results show that preferred growth direction of ZnO changes from (002) plane to (001) plane and interplanar distance becomes shorter. When the doping amount of In is 5%, Zn atoms are completely replaced by In atoms. The resistivities of the samples first decrease, then increase afterwards with the increase of the amount of In. With the increase of In, the ultraviolet emission is redshifted and new peaks occur at 465 nm, 535 nm, and 630 nm. The sample with 10% indium has white-light emission. The band structures of samples with 0% and 12.5% indium are investigated by the first principle method. The mechanism of white emission is discussed from the viewpoint of additional energy levels.
Diffraction of white-light supercontinuum by femtosecond laser-induced transient grating in carbon bisulfide

Huang Li,Yang Yan-Qiang,Wang Ying-Hui,Zheng Zhi-Ren,Su Wen-Hui,

中国物理 B , 2010,
Abstract: Experiments on fs laser-induced transient grating (LITG) in carbon bisulfide (CS2) are carried out to explore the chirp characteristics of a white-light supercontinuum (SC) generated by a 800-nm, 160-fs laser pulse in a 4-mm thick Al2O3 crystal. Two orders of diffraction signals of SC by fs LITG in CS2 are observed, demonstrating that both the third-order process and the fifth-order process are present simultaneously. The experimental results also imply that the formation of an fs transient refractive-index grating in CS2 is mainly due to the electronic polarization process.
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