Interferometry optical

The determination of oil film thickness in elastohydrodynamic lubrication by optical interferometry is disclosed in a series of communications by Cameron and his co-workers [12, 13, 14, 15]. The principle of the method, as originally devised for the contact of a sphere against a flat plate, is illustrated in Fig. 6-7. A carefully made steel ball B, 2.54 cm in diameter, is cemented to a conical chuck C which is driven by a quill shaft S. A light spring seats the ball against a stationary con- 

The central region, corresponding to the area of dry contact, is dark because of the phase change of half a period due to reflection at the ball surface. The first dark ring corresponds to a film thickness t = X/2n. By measuring the radial coordinates of the rings for a succession of values for o, a topographical map of the ball surface can be constructed. 

Some points of experimental technique should be mentioned. The contact pressures under which the apparatus can be operated are increased by the use of diamond, which is mechanically stronger than glass, as the plate material. Furthermore, diamond has good thermal conductivity, so that heating of the contact zone as the experiment proceeds is easier to control. The average refractive index of the oil in the pressurized gap is computed from the Lorenz equation. 2-1 

Consider a cantilever with natural frequency coo and quality factor Q driven by an external excitation with frequency o). The ratio of the amplitude of the lever A relative to the maximum amplitude Aa is 

The dimensionless parameter a is introduced for convenience, which is almost always less than 1. The resonance frequeney too is related to the foree constant K through Eq. (15.3). The force gradient (in this operation mode usually negative) -dFJdz changes the resonance frequency too. 

The amplitude A in Eq. (15.5) changes. After a short amount of algebra, the relation between the force gradient and the amplitude reduction ratio a is 

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The advent of lasers allowed optical interferometry to become a useful and accurate technique to determine surface motion in shocked materials. The two most commonly used interferometric systems are the VISAR (Barker and Hollenbach, 1972) and the Fabry-Perot velocity interferometer (Johnson and Burgess, 1968 Durand et al., 1977). Both systems produce interference fringe shifts which are proportional to the Doppler shift of the laser light reflected from the moving specimen surface. Both can accommodate a speci-... 

Optical interferometry can be used to measure surface features without contact. Light reflected from the surface of interest interferes with light from an optically flat reference surface. Deviations in the fnnge pattern produced by the interference are related to differences in surface height. The interferometer can be moved to quantify the deviations. Lateral resolution is determined by the resolution of the magnification optics. If an imaging array is used, three-dimensional (3D) information can be provided. 

Doll, W. and Konczol, L. Micromechanics of Fracture under Static and Fatigue Loading Optical Interferometry of Crack Tip Craze Zones. Vol. 91/92, pp. 137 — 214. 

With diblock copolymers, similar behavior is also observed. One component is enriched at the surface and depending on miscibility and composition a surface-induced ordered lamellar structure normal to the surface may be formed. Recent investigations include poly (urethanes) [111], poly(methoxy poly (ethyleneglycol) methacrylate)/PS [112] and PS/PMMA [113, 114]. In particular the last case has been extensively studied by various techniques including XPS, SIMS, NR and optical interferometry. PS is enriched at the surface depending on blockcopolymer composition and temperature. A well ordered lamellar structure normal to the surface is found under favourable conditions. Another example is shown in Fig. 6 where the enrichment of poly(paramethylstyrene), PMS(H), in a thin film of a di-... 

The two limitations of optical interferometry, the one-quarter wavelength of light limit and the low resolution, have been addressed by using a combination of a fixedthickness spacer layer and spectral analysis of the reflected beam. The first of these overcomes the minimum film thickness that can normally be measured and the second addresses the limited resolution of conventional chromatic interferometry. 

Lubricating Films Using Wedged Spacer Layer Optical Interferometry, Proceedings, 14th Leeds-Lyon Symposium on Tribology, Interface Dynamics, Leeds, 1988, pp. 275-279. 

FIG. 9 Silver nanoparticles capped by 4-carboxythiophenol electrostatically adsorbed to positively charged octadecylamine monolayers, (a) Mass uptake versus number of layers at subphase pH 12 and pH 9 the inset shows the contact angle of water versus the number of layers, (b) Absorbance spectra as a function of the number of layers transferred (left), with the inset showing the plasmon absorbance at 460 nm versus the number of layers. Thickness versus number of layers as determined by optical interferometry is shown on the right. (Reprinted with permission from Ref. 103. Copyright 1996 American Chemical Society.)... 

Figure 34. Plots of x as a function of time for a typical experiment in heat-transfer salts at 168°C. (Reprinted from 0. Odawara, 1. Okada, and K. Kawamura, "Measurement of Thermal Diffusivity of HTS by Optical Interferometry," J. Chem. Eng. Data 22 222-225, Copyright 1977 American Chemical Society.)...

Gelikonov,V.G., Gelikonov, G.V., Ksenofontov, S.Yu., Kuranov, R.V., Morozov, A.N., Myakov, A.V, Turkin, A.A., Turchin, I.V. and Shabanov, D.V. (2003). New approaches in broadband fiber-optical interferometry for optical coherent tomography Radiophysics and Quantum Electronics 46 550-564. 

Many different methods have been developed for detecting the minute deflection of the cantilever (Sarid, 1991). In this. section, we present several important ones, including vacuum tunneling (Binnig, Quate, and Gerber, 1986), mechanical resonance (Diirig, Gimzewski, and Pohl 1986), optical interferometry (Martin et al., 1988 Erlandson et al., 1988), and optical beam deflection (Meyer and Amer, 1988). 

Deflection detection methods 317—323 detection limit 322 mechanical resonance 318 optical beam deflection 321 optical interferometry 319 vacuum tunneling 317 Density of states 23... 

BLM surface tensions have been determined by the application of an ultrasmall hydrostatic pressure to one side of the membrane and measuring the resultant curvature changes by optical interferometry (Fig. 61). Typical values of 0.2-Q.3 mNm 1 were obtained for y for glyceryl monooleate and phosphatidyl-serine BLMs [413]. 

The cantilever bending-technique requires a sensitive displacement detection such as a capacitance probe (Klokholm 1976, 1977), optical interferometry (Sontag and Tam 1986), a tunnelling tip (Wandass et al. 1988) or angular detection (e.g. laser beam deflection, Son-tag and Tam 1986 Trippel 1977 Tam and Schroeder 1988 Betz 1997 Sander et al. 1998). 

An increasingly important tool to determine the strain-induced anisotropy is MOKE (magneto-optical Kerr effect). In section 2 we mentioned already the calculations by Freeman et al. (1999). Experimentally, e.g. Ali and Watts (1999) (see also references therein) apply a bending device to induce strains in a controlled way, and determine the (local) curvature and the strains by optical interferometry or by direct measurement (stylus). The properties of the substrate are incorporated in a finite-element modelling calculation, thus allowing an absolute determination of the film properties. Compare also Stobiecki et al. (2000), who studied the strain induced anisotropy in FeB/Cu/FeB trilayers, using Kerr magnetometry (MOKE). 

A convenient technique for studying the crack tip craze propagation in amorphous polymers deals with optical interferometry. It has been applied to the examination of PMMA behaviour at various temperatures and crack speeds under conditions of stable propagation [44,45]. 

Piezoelectric Relaxation and Nonlinearity investigated by Optical Interferometry and Dynamic Press Technique... 

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