共查询到20条相似文献,搜索用时 31 毫秒
1.
脉冲激光光热失调技术 总被引:4,自引:0,他引:4
将脉冲激光作为加热光引入光热失调测量技术中,提出了脉冲激光光热失调测量技术,介绍了其基本原理,分析了脉冲激光光热失调测量技术用于测量光学薄膜微弱吸收的可行性.实验以532 nm的高反射光学薄膜为样品,采用波长为632.8 nm的探测光,研究了脉冲激光光热失调技术信号振幅的时间特性以及最大信号幅值与样品表面加热光能量密度、加热光斑与探测光斑相对位置的变化关系.研究结果表明,光热信号随时间先增大后减小,而随表面加热光能量密度的提高而增大,当样品表面加热和探测光斑重合时光热信号最大. 相似文献
2.
《Infrared physics》1990,30(2):181-186
Photoacoustic spectra of kaolinite obtained with a step-scan FT-IR spectrometer are examined with respect to signal saturation and phase. At low modulation frequency, saturation facilitates observation of several weak bands; background intensity and saturation are reduced by recording the interferogram in quadrature, rather than in phase, with the excitation. Higher modulation frequency data can be improved qualitatively be calculating the difference between the quadrature and in-phase spectra. 相似文献
3.
本文从理论上分析了脉冲光热谱中波长效应。讨论了波长调谐对脉冲光热光谱信号的峰值和时间特性的影响。 相似文献
4.
B. Li 《The European physical journal. Special topics》2008,153(1):395-400
A flatly topped circular beam (“top-hat beam”) is
employed as the excitation beam for photothermal deflection and surface
thermal lens techniques. The Fresnel diffraction model is applied to
describe the photothermal signals. The theoretical comparison between a
Gaussian beam and a top-hat beam excited photothermal signal amplitudes
shows that the use of the top-hat beam excitation improves the measurement
sensitivity of the photothermal techniques. Experimental results for both
photothermal deflection and surface thermal lens are presented. The
potential applications of the top-hat beam excited photothermal techniques
are highlighted. 相似文献
5.
Eric Y.Jiang Forrest J. Weesener 《光散射学报》2005,17(3):315-317
pacc:0765Thispaperdemonstratesthreevibrational spectroscopictechniquesandtheirapplicationsin characterizationofspatiallyheterogamousmateri als,namelystep-scanphasemodulationFTIR photoacousticspectroscopy(S2MPAS),visible(confocal)Ramanmicroscopy(CRM)andF… 相似文献
6.
7.
An analysis and experimental data of the time-dependent response of an all-fiber ring resonator in which the ring is illuminated by a phase modulated input beam are presented. The resonator is operated as a high-resolution optical-scanning spectrometer. Since the resolution limit is a function of the finesse and cavity-loop length, we will show that it is not possible to design a high-resolution ring resonator that will not produce a distorted output signal when the phase modulation rate is comparable to the response time of the ring. 相似文献
8.
The effect of the laser source spotsize on the
measurement sensitivity of layered system using photothermal radiometry (PTR)
technique is presented. The beam size effect on the PTR measurement
sensitivity is theoretically examined and experimentally demonstrated using
a carbo-nitrided C1018 steel sample. The experimental results using a
focused beam and an expanded beam for a carbo-nitrided C1018 sample
validated the theoretical prediction, according to which the expanded beam
showed a much larger magnitude change (contrast) in both amplitude and phase
than results with a focused beam. 相似文献
9.
《Infrared physics》1989,29(1):87-100
The two common methods of phase correction, namely interferogram symmetrization and the Mertz multiplicative procedure, are examined with respect to photoacoustic Fourier Transform Infrared data in this paper. Although the symmetrization method is widely thought to be superior, the present study has shown that the results of the two procedures are generally in good agreement, provided that a sufficient amount of information is used in either calculation. This conclusion holds for both mid- and far-infrared interferograms recorded with rapid-scan operation, and for MIR interferograms measured with step-scan operation. 相似文献
10.
本文给出了聚焦激光束加热时脉冲光热偏光谱的理论,考虑了加热束传输特性和探测束有限尺寸的影响,比较了各种理论模型及其适用范围,并对紧聚焦激光束加执焊脉冲光热偏转光谱的各项结构参数进行了优化。 相似文献
11.
This paper presents a new approach to the theory and technique of ultrasonic transducer arrays, which makes it possible to obtain their directional beam patterns for receiving broadband acoustical signals.The general formulae were derived for the beam pattern of the array, and as an example the beam patterns of the end-fire array have been computed and plotted, for signals of different correlation function.For experimental verification of the theory the simple processor solution is proposed. This technique is based on spatial/temporal signal processing for beamforming of the directional response of an end-fire array. 相似文献
12.
James A. Harrington 《Fiber and Integrated Optics》2013,32(3):211-227
Abstract An analysis and experimental data of the time-dependent response of an all-fiber ring resonator in which the ring is illuminated by a phase modulated input beam are presented. The resonator is operated as a high-resolution optical-scanning spectrometer. Since the resolution limit is a function of the finesse and cavity-loop length, we will show that it is not possible to design a high-resolution ring resonator that will not produce a distorted output signal when the phase modulation rate is comparable to the response time of the ring. 相似文献
13.
Drawing on interferometry and Fourier analysis, this paper describes the use of a two-beam thermal lens technique for measuring thermo-optical properties in optical materials. The procedure consists of yield interference patterns deformed by a localized photothermal effect. The photothermal phase shift is locally induced by the pump beam focused on a tested sample located on an on-axis probe beam, which is the first arm of a Mach-Zehnder interferometer. The plane where the effect is localized is imaged onto a CCD camera. Then two interferograms are recorded: one without effect and the other one with the induced photothermal phase. Fourier analysis performed on these interferograms allow us to plot the thermal lens map and, therefore, to estimate thermo-optic constant of Malachite Green in water solution. The method is applied to measure low linear absorptions of a diluted sample of Rhodamine B in water solution at 633 nm, showing that the proposed technique allows to measure photothermal phase shift as low as 3.1 mrad at 8 mW of input power in diluted materials. 相似文献
14.
15.
A simple experimental method of eliminating zero-order diffraction in the reconstructed image of off-axis digital holography is presented. Holographic diffraction grating acting as a beam splitter, an off-axis holography system is formed. The holograms of object with different recording parameters are obtained by adjusting the reflecting mirror in the recording optical system to vary the incidence orientation of the object beam in CCD to introduce a phase shift. The zero-order image can be eliminated by numerically processing the holograms of object with different recording parameters. The theoretical analyses have been done in detail and the experimental results are also given. The zero-order image eliminated, the area of reconstructed image increases remarkably, the image quality can then be significantly improved and the better resolution obtained. The experimental results show that the method presented in this paper is feasible, simple in optical system and easy in operation and data processing. 相似文献
16.
A distance-scan method to determine the distance between the probe beam and sample, which is not easily measured exactly, in photothermal deflection (PD) was reported, with which the distance and thermal diffusivity of the deflecting medium can be simultaneously measured. Probe beam size effect (PBSE) on PD phase signal was quantitatively analyzed to clearly show its physical meaning. The measured distance was experimentally verified as correct and reliable, and the measured thermal diffusivities of N2 and CO2 are in good agreement with the literature values. They could not be precisely measured by phase signal without considering the PBSE. 相似文献
17.
调制激光作用牙齿组织发生散射形成光子密度波, 而由于光热效应产生热波, 基于一维介质辐射传输漫射近似方程与一维热传导方程建立了调制激光作用牙齿组织半透明混合介质的一维热波数学模型. 利用该模型仿真分析了牙齿龋损特性参数(牙釉质龋损层光吸收系数、散射系数、热扩散系数及龋损深度)对光热辐射动态响应特性的影响与规律. 利用红外探测器(HgCdTe, 2–12 μm)记录808 nm半导体激光激发牙齿组织产生的热波信号, 由锁相放大器计算热波信号的幅值与相位. 通过频率扫描试验获得了牙齿组织的光热动态响应, 利用多参数最佳统计拟合方法得到了牙齿组织特性参数. 结果表明光热辐射测量对牙齿组织不均匀性和龋损特性均具有较高敏感性与特异性. 相似文献
18.
Jyotsna Ravi S. Lekshmi K.P.R. Nair T.M.A Rasheed 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,83(2):193-202
A modified amplitude method to analyze the photothermal probe beam deflection signal for the determination of low thermal diffusivity values of materials is proposed. This simple theoretical model, which is an extension of the amplitude method proposed by Quelin et al., takes into account the dependence of the photothermal signal on the height of the probe beam above the sample surface which affects mirage measurements when the thermal diffusivity of the coupling medium is greater than that of the sample. The present work is similar to the modification to the phase method proposed by Bertolotti et al. for determination of low thermal diffusivity. The method can be applied irrespective of whether the sample is optically transparent or optically opaque and is independent of thickness. 相似文献
19.
20.
研制了上海光源同步辐射空间干涉仪,用于储存环束团横向截面尺寸及发射度的精确测量。对干涉仪工艺设计中的光路参数、关键设备选型、数据处理方法及数据采集处理软件结构进行了分析讨论。结合束流实验完成了系统调试及运行参数优化,结果表明,CCD增益系数与曝光时间设置对测量精度有显著影响,增益系数设为0 dB,曝光时间设为200 ms时,随机测量误差可控制在μm量级。对上海光源储存环横向束斑尺寸进行了精确测量,结果表明:空间相干度曲线近似为高斯分布,可以采用单一空间频率的相干度测量值进行快速束斑尺寸计算;水平束斑尺寸实测值为52.4 μm,与理论值预期值53.0 μm相比,差异小于2%;系统测量误差约为5.5%,主要误差来源为相干度随机测量误差。 相似文献