共查询到20条相似文献,搜索用时 31 毫秒
1.
All-fiber digital heterodyne interferometry is a laser metrology technique employing pseudo-random codes phase modulated onto
an optical carrier signal. In this heterodyne interferometer system, the optical signal includes signal reflected and transmitted
from the sample, respectively. Compared with the conventional heterodyne interferometry, this enhanced optical system has
much higher measurement sensitivity, and can distinguish the signal which reflected from the front and the rear surface of
the sample. Analysis and simulation for the digital heterodyne interferometry are presented. It takes approximately 4 s to
scan the whole surface with the diameter of 300 mm. The thickness profile of the sample is obtained in the experiment. The
discussion about the experiment is given finally. 相似文献
2.
This paper proposes an optical method for measuring small displacements using the surface plasmon resonance (SPR) heterodyne interferometry. A heterodyne light beam reflected by a mirror passes through a hemisphere glass and then enters into a surface plasmon resonance apparatus at the resonant angle. A small displacement of the mirror will introduce a phase-difference variation between p- and s-polarizations of the light emerging from the SPR apparatus. The phase-difference variation can be precisely measured with the heterodyne interferometric technique, and the associated displacement can be estimated. The feasibility of this method was verified by experiment, and the displacement measurement resolution of about 1.4 nm over a traveling range of 6 μm was achieved. Our method of measurement has the merits of both common-path interferometry and heterodyne interferometry. 相似文献
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Shearing speckle pattern interferometry is a full-field speckle interferometric technique used to determine surface displacement derivatives. In this paper, a new measurement system of real-time heterodyne shearography interferometry is presented. This system combined with heterodyne measurement, shearography interferometry and time domain signal processing technology can dynamically detect the out-of-plane displacement gradient. The principles and system arrangement are described. Using the Jones matrix, the mathematical expression of light intensity distribution passing through this system is deduced. A preliminary experiment was performed to demonstrate the performance of this new device, and simulations were conducted using the finite element method. Comparison of results shows that quantitative measurement of the displacement derivative has been achieved. 相似文献
6.
With analog scanning, time-domain low-coherence interferometry lacks precise depth information, and optical carrier generation demands a linear scanning speed. Full-field heterodyne low-coherence interferometry that uses a logarithmic complementary metal-oxide semiconductor camera, acousto-optic modulation, and digital depth stepping is reported, with which random regions of interest, lateral and axial, can be accessed. Furthermore, nanometer profilometry is possible through heterodyne phase retrieval of the interference signal. The approach demonstrates inexpensive yet high-precision functional machine vision offering true digital random access in three dimensions. 相似文献
7.
If the incident angle of a light beam on the boundary surface between the thin metal film of a surface plasmon resonance (SPR) apparatus and a test medium is equal to or very near the resonant angle, then the phase difference between the p- and s-polarizations of the reflected light is related to the associated physical parameter. The phase difference can be measured accurately with heterodyne interferometry. If the relationship between the phase difference and the associated physical parameter is specified, then the associated physical parameter can be estimated from the phase difference data. This method has the benefits of both common-path interferometry and heterodyne interferometry, such as simple structure, high stability, high resolution, easy operation, and rapid real-time measurement. 相似文献
8.
光电极值法是光学薄膜厚度监测的常用方法,该方法在镀膜前引用块状材料的折射率设计膜系。而在实际镀制过程中,用于镀制光学薄膜的材料折射率会发生改变,从而给膜厚的监控带来误差。为了避免折射率变化的影响,采用外差干涉法测量折射率,将实际测得的薄膜折射率应用光电极值法监控薄膜的设计,从而减少了因材料折射率的变化引起的误差。以750nm截止滤光片的镀制为被测对象进行了实验,对制备的滤光片透射率光谱曲线进行了比较。结果表明,实际的透射率曲线与设计的透射率曲线吻合较好,两次实验曲线平均吻合度均在98%以上,系统稳定性很好,从而说明结合外差干涉法的光电极值监控法可以很好地克服折射率变化引起的误差。 相似文献
9.
Optical coherence tomography (OCT) is a novel imaging modality based on low-coherence interferometry. This paper summarizes some of our latest work on the development of OCT where we have taken two approaches. In the first approach we have developed a phase-drift-suppression method for stable heterodyne detection in the presence of phase fluctuations. In the second approach we have concentrated on the development of two-dimensional heterodyne detection techniques for real-time imaging. A novel detection scheme has been proposed, which enables parallel heterodyne detection with a commercially available imager such as a charge-coupled-device camera. Meanwhile, a non-scanning OCT system configuration based on off-axis interferometry is being studied. Using a newly developed angular-dispersion imaging scheme, we show that the axial reflectance profile in OCT measurement can be detected instantaneously with a sensor array. 相似文献
10.
This paper proposes a simple method for measuring the concentration of solutions based on the phase difference of internal reflection polarization angle and circularly polarized heterodyne interferometry. For a circularly polarized heterodyne light beam incident on the boundary surface between a hemispherical prism and a test solution, the reflected light passes through a properly oriented analyzer for interference. The phase difference between s- and p-polarized light is sensitive to the solution concentration when the incident angle equals the internal reflection polarization angle. Based on these effects, the resulting phase difference makes it possible to analyze the concentration of solution through heterodyne interferometry. The experiments in this study confirm the feasibility of this method, which provides the advantages of simple installation, ease of operation, and high accuracy. 相似文献
11.
The book describes modern methods of receiving laser signals, viz., by interferometry, by nonlinear optics, by laser amplification, and by heterodyne mixing. The theory of these methods is considered as applied to the problem of laser radars. Investigated in detail are features such as the resolving power of interferometry and nonlinear-optics method, the efficiency of parametric conversion of laser signals, the sensitivity of laser amplifiers, and problems of optimal heterodyne detection. Methods of speckle interferometry and adaptive optics are described. The book is aimed at a large circle of scientists and engineers active in the problem of recording of laser signals, as well as to students in advanced courses of the corresponding specialties.N. D. Ustinov — General Editor.Translated from Metody Obrabotki Opticheskikh Polei v Lazernoi Lokatsii, pp. 3–269, 1983. 相似文献
12.
A novel method of optical coherent tomography—spectral heterodyne tomography—is proposed. Spectral heterodyne tomography is based on parallel heterodyne detection of a multitude of frequencies of the light backscattered by an object under study. The result of this detection is a spectral distribution of the amplitude and phase of the scattered radiation. Subsequent numerical processing allows one to find the distribution of scattering centers over the depth corresponding to the point of entrance of the incident light. The proposed method is potentially characterized by a higher efficiency as compared with the most successful approach to optical coherence tomography, based on heterodyne scanning interferometry. 相似文献
13.
应用共路外差干涉法分析了牛顿望远镜的偏振特性。根据菲涅耳定律求出了入射光s-偏光和p-偏光入射到望远镜各点的反射率公式。给出了共路外差干涉法测量牛顿望远镜偏振特性的实验装置原理图。采用632.8nm的外差光源,分析了牛顿望远镜对s-偏光和p-偏光反射系数、相位差以及对入射光偏振度的影响,根据入射角度的不同绘制了相应的变化曲线。结果表明:镀有铝膜的牛顿望远镜对入射光偏振特性影响较小,s-偏光和p-偏光反射系数相差不到0.01,偏振度变化不超过0.07,适用于激光遥感偏振成像的接收系统。 相似文献
14.
This work proposes a simple measurement technique based on the optical activity of cholesteric liquid crystal (CLC) and circular common-path heterodyne interferometry for measuring small wavelength differences. A circularly polarized heterodyne light passes through a CLC cell and an analyzer, generating an interference signal. When the CLC cell is properly chosen with a circular regime, it has strong optical activity. Accordingly, the phase difference between the left and right circular light of the interference signal depends strongly on the wavelength. As the wavelength changes, variations of the phase difference can be accurately detected by heterodyne interferometry. Substituting the variation of phase difference into specially derived equations, the wavelength variations can be estimated accurately. The feasibility of this method, which is applicable when the wavelength is larger than the product of the pitch and the refractive index of the CLC cell, was demonstrated; it provides the advantages of simple installation, ease of operation, and high accuracy. 相似文献
15.
Shinn-Fwu Wang 《Optics and Lasers in Engineering》2009,47(10):1039-1043
In this paper, an optical fiber sensor based on multiple total internal reflections (MTIRs) in heterodyne interferometry is proposed. With the optical fiber sensor the phase shift difference due to the multiple total internal reflections effect between the p- and s-polarizations is measured by using heterodyne interferometry. Substituting the phase shift difference into Fresnel's equations, the refractive index for the tested medium can be calculated. The resolution of the sensor can reach 1.6×10?6 refractive index unit (RIU). The optical fiber sensor could be valuable for chemical, biological and biochemical sensing. It has some merits, such as, high resolution and stability, high sensitivity, high resolution and real-time measurement. 相似文献
16.
Russell B. Pillers Banmali S. Rawat 《International Journal of Infrared and Millimeter Waves》1996,17(11):1809-1820
The nonlinearity of a frequency-ramped single-mode laser source to be used in optical heterodyne interferometry has been investigated. The analysis is based on mode-hopping due to variation in injection current, temperature and mismatch reflections. 相似文献
17.
Two-frequency interferometry for small displacement measurements is examined from a practical point of view. A laser beam that is modulated sinusoidally in intensity by an acousto-optic Bragg cell provides signal and reference optical waves to produce dynamic interference. The output signal of a photodetector receiving the interference is composed of optical homodyne and heterodyne components. The heterodyne component carries a vibrational displacement to be detected on its amplitude. A sinusoidal vibration amplitude is measured down to 0.5 nm. 相似文献
18.
A novel grating-generated scan correlation interferometry approach using a heterodyne technique for real-time signal processing is demonstrated. The characterization of reflections from a sample and detection of a femtosecond four-pulse train are presented as applications of the method. 相似文献
19.
D-type fiber biosensor based on surface-plasmon resonance technology and heterodyne interferometry 总被引:1,自引:0,他引:1
A D-type fiber biosensor based on surface-plasmon resonance (SPR) technology and heterodyne interferometry is presented. The sensing device is a single-mode optical fiber in which half the core is polished away and a thin-film layer of gold is deposited. We measure the phase-difference variations instead of the light intensity as in traditional SPR techniques. Therefore the accuracy and resolution of our method are very high. Its sensitivity can reach 2 x 10(-6) refractive-index units. The sensor has some merits, e.g., tunable high sensitivity, small size, lower cost, smaller sample volume, and suitability for in vivo testing. This novel method of a D-type fiber biosensor based on SPR technology and heterodyne interferometry is valuable for chemical, biological, and biochemical sensing, and the novel method of D-type fiber biosensing is a feasible means of study. 相似文献
20.
In this paper, an optical heterodyne interferometric detection model with a frequency-ramped laser diode (LD) has been analyzed. The effect of the nonlinearity of the LD source on the optical heterodyne interferometry has been investigated in two different ways, which are the power-distortion Fourier series analysis and the harmonic distortion analysis. The general formulation between the tangent of the tested phase and the interference fringe have been presented with the analysis of the beat signal in the frequency domain by each methodology. The numerical results of these formulations have been presented. 相似文献