Optical interferometry methods

It has been believed that the film shape in the elastohydrodynamic (EHD) conditions would be characterized by the parallel film at the centre of the contact area and the minimum film at the exit zone and the film thickness would become zero as the entrainment speed goes zero until recently. Dowson et al [1] presented the first exact solution for line EHD contacts by combination of the Reynolds equation and the elastic deformation equation of the bounding surfaces. Their numerical solutions indicated that the film profile was formed by the parallel film at the centre zone and die minimum film constriction at zone just before the exit zone and later such a profile was indicated experimentally by Crook [2], who measured the EHD film profile with a two disk apparatus by the electrical capacitance method. Gohar et al [3] showed EHD film shape in point contacts by the optical interferometry method. The film shape in the point contacts was also characterized by the parallel film and the horse shoe shaped constriction at the exist zone. Therefore, the two parameters of the... 

As a major branch of nanotribology. Thin Film Lubrication (TFL) has drawn great concerns. The lubricant him of TFL, which exists in ultra precision instruments or machines, usually ranges from a few to tens of nanometres thick under the condition of point or line contacts with heavy load, high temperature, low speed, and low viscosity lubricant. One of the problems of TFL study is to measure the him thickness quickly and accurately. The optical method for measuring the lubricant him thickness has been widely used for many years. Goher and Cameron [3] successfully used the technique of interferometry to measure elastohydrody-namic lubrication him in the range from 100 nm to 1 /rm in 1967. Now the optical interference method and Frustrated Total Reflection (FTR) technique can measure the him thickness of nm order. 

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... 

There are various surface techniques, eg., optical interferometry high frequency capacitance and resistance method, which demonstrate the build up of the physically and chemically reacted film during boundary lubrication in scuffing reactions (Anghel et al., 1997 Dowson et al., 1996 Smalley and Cameron, 1996). 

The Fourier transform method has been used to calculate the craze surface stress distribution from craze shapes obtained by means of optical interferometry — the craze shapes are the same in air and in toluene gas, only their sizes vary — the craze surface stress is almost constant along the craze boundary — the craze fibril volume fraction remains constant in air and in toluene gas over the whole velocity range, despite the fact that at low velocity in toluene gas the craze length reaches 4 times the length in air — the optical interference setup may give valuable information on the variations of craze fibril volume fraction, but not on its absolute numerical value. 

There is probably no fundamental technical progress to expect from optical interferometry. Only minor technical improvements may be made to enlarge the field of applicability of the method, using higher crack speeds, more sophisticated environments, etc. 

Surface Roughening/Recession. Two approaches to measurement of surface recession were explored. One method applied a classical form of optical interferometry to optically smooth samples of stone in an attempt to measure results after brief exposure of the surfaces to rain this approach was only partially successful and will be only... 

For calibration, the temperature at the sample location can be determined by visually observing the melting of salts of known melting temperatures. The salts that have proved to be most reliable for this purpose are NaCl (800.5 °C) and NaNOs (306.8 °C). The a-P phase transition in quartz (574°C) can be used as well. The laser interferometry method described above can be used to accurately pinpoint the transition in an optically perfect platelet of quartz. 

Photothermal detection has been accomplished in several ways mechanical or electrical thermometer (thermocouple), molecular thermometer, optical interferometry, photoacoustic (PA), thermal lens (TL), or the transient grating (TG) method. Although PA and TL detections are not included in this chapter, some of the experimental results of these methods are referred to in other sections, mostly for comparison purposes with the TG measurement. Characteristic features of these methods are presented in Section 1I.E. 

The method applied to measure the depth of the ablated area or the removed mass can also have an influence on the ablation parameters. If profilometric measurements (optical interferometry, mechanical stylus [34], or atomic force microscopy [35]) are used to calculate the ablation rate, a sharp ablation threshold can be defined. This is also supported by reflectivity [36] and acoustic measurements [37], In mass loss measurements, such as mass spectrometry or with a quartz crystal microbalance (QCM), the so-called Arrhenius tail [38] has been observed for certain conditions. The Arrhenius tail describes a region in the very low fluence range, where a linear increase of detected ablation products is observed, which is followed by a much faster increase, that coincides with removal rates of the profilometric measurements [39]. 

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 term Bio-CD has been coined to refer to platforms which utilize the immobihzation of biological samples on a (semi-)reflective CD or DVD surface [8]. The main optical detection method associated with Bio-CDs is spinning disc interferometry while Bio-CD platforms also utilize ODD technology as a common method for readout via the ODD pickup head. 

Various optical detection methods such as fluorescence, absorbance, interferometry, and scattering-based methods have successfully been applied to the LoaD platform in a broad range of biological application areas [2-6, 8-10]. Several techno-economic benefits such as cost-efficiency, noncontact interfacing, and assay... 

A wide range of techniques can be used to capture the surface roughness of a component using noncontact methods. Some of the more common instruments used to captore topographic data include confocal microscopy, laser triangulation, focus detection, and optical interferometry. A relatively recent branch of microscopy known as scanning probe microscopy (SPM) yields over 20 other instruments which are defined based on what probe-surface interaction they are monitoring. The SPM family is described in more detail elsewhere in this book and will be briefly mentioned in this article. 

Optical Interferometry. 2d ed. San Diego Academic Press, 2003. Overview of the basic theory of interferometry methods, including sections on laser interferometry. 

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