Spot Displacement Research Articles

201 半導体レーザーによる高感度傾斜角検出器の検出精度の向上に関する研究(計測)(オーガナイズドセッション(a)材料力学・材料強度に関する新展開)

A high-sensitive tiltmeter which consists of a simple optical system with a laser diode and a quadrant photo diode detects a minute crustal movement as the angle of tilt. In this system, slight misaligment of the optical system emerges as skewness of the laser spot. In order to reduce this skewness, we changed reflectors from the surface of hydrargyrum to a mirror placed on the viscoid liquid. We experimentally evaluated a change of the sensitivity as a function of direction of the laser spot displacement. The experimental results show the improvement in the skewness of a laser spot. This system contains 4.3×10^<-7> [rad] accuracy for detecting the tilt angle.

Point pattern matching in the analysis of two-dimensional gel electropherograms.

In the automation of proteome analysis, matching of two-dimensional (2-D) electropherograms represents a bottleneck in the process. Here we present a point pattern recognition approach to the matching of spots in 2-D electropherograms. The algorithm is based on a comparison of spot neighborhoods, converted to point patterns between reference and compared gels. The neighborhood was characterized by a syntactic descriptor which minimized the influence of spot displacements. A combined criterion utilizing the similarity of point patterns and a metric definition of position similarity was derived. The efficiency and accuracy of the algorithm was tested on a set of 69 gels with different levels of similarity. For a typical gel the accuracy of matching was higher than 98% and the number of correctly identified spots was higher than 95%.

Measurement of Action Potential-Induced Presynaptic Calcium Domains at a Cultured Neuromuscular Junction

Spatially localized Ca(2+) domains are thought to play a key role in action potential (AP)-evoked neurotransmitter release at fast synapses. We used a stage-scan confocal spot-detection method and the low-affinity Ca(2+) indicator Oregon Green 488 BAPTA-5N to study the spatiotemporal profile of presynaptic AP-induced Ca(2+) domains. Families of scanned AP-induced fluorescence transients were detected from spot locations separated by 200-300 nm, within the vicinity of Ca(2+) entry sites. Typically, the largest transient in a particular scan peaked within approximately 1 msec and decayed with rapid (tau(1) of 1.7 msec) and slow components (tau(2) of 16 msec, tau(3) of 78 msec). As the spot was incrementally displaced, transients progressively exhibited a slowing in their time-to-peak and a loss of the fast decay component. Three-dimensional graphs of fluorescence versus time and spot displacement revealed the presence of AP-induced fluorescence domains that dissipated within approximately 7 msec. The size of fluorescence domains were estimated from the full-width at half-maximum of gaussian fits to isochronal DeltaF/F plots and ranged from 0.6 to 3.0 micrometer, with a mean +/- SD of 1.6 +/- 0.6 micrometer. Model simulations of a localized Ca(2+) entry site predicted the major features of the fluorescence transients and suggested that, within approximately 1 msec of the initiation of the Ca(2+) current, both the fluorescence domain and the underlying Ca(2+) domain do not extend significantly beyond the site of entry. Consistent with this prediction, the intracellular addition of EGTA (up to 2 mM) accelerated the decay of the measured transients but did not affect the domain size.

Fluid surface imaging using microlens arrays

The paper describes a new technique for measuring surface slopes at the air–water interface. A microlens array is employed to optically sample the fluid surface at a large number of measurement points in parallel. The focal plane image of the lenslet array is recorded by a standard video camera, generating a data set of typically 4000 candidate samples for each video frame. The displacement of the focal spots is analyzed using a cross-correlation technique augmented by a topological identification algorithm which makes use of the hexagonal structure of the lenslet array. Surface height profiles are computed by integrating the surface slope field.

Acoustical imaging by time reversal

For the last few years, time-reversal techniques have been proved to be efficient for defect detection in materials without a priori knowledge on the defect. In the case of an extended target, an iterative time-reversal experiment allows focusing on the most reflective point of the defect. At this time, it was not possible to obtain an image of the defect after detection. Using PASS (phased array simulation software, developed in the laboratory), the time-reversal sequence is first iterated in order to be able to focus through a cylindrical interface separating a fluid and a solid. Then, the series of temporal signals is used in conjunction with time-delay laws, thus yielding spatial micro-angulations of the focused beam. Finally, the software is used to compute the back-scattered field due to several extended defects. After calibrating the focal spot displacement with the considered microangulation time delay law, it is shown how this technique allows one to obtain an image of the different defects in the material, even though the standard time-reversal method is only able to focus on the most reflective one. Starting from these numerical results, an experimental validation will start soon.

Structure and dynamics of high-current arc cathode spots in vacuum

Experiments are reported on the number and displacement velocity of arc spots on CuCr and Cu cathodes in the current range 40 - 1500 A. The spot number was found to increase linearly with current. The average current per resolvable spot amounted to for CuCr and for Cu. For times after ignition random spot displacement R was observed, having mean square values of for Cu and for CuCr. The Cu spots showed brightness fluctuations with intervals of . Because of this obvious dynamics, the theoretical models of the spot plasma must be time-dependent. A self-consistent theoretical description of Cu and Cr plasmas is given, yielding the cathode temperature, plasma density, electric field strength, current density and plasma velocity in the time range 10 ns to 3 ms.

A new method for tensile testing of thin films

A new method for tensile testing of thin films is presented. The strain is measured directly on the unsupported thin film from the displacement of laser spots diffracted from a thin grating applied to its surface by photolithography. The diffraction grating is two-dimensional, allowing strain measurement both along and transverse to the tensile direction. In principle, Young’s modulus, Poisson’s ratio, and the yield stress of a thin film can be determined. Cu, Ag, and Ni thin films with strong ⟨111⟩ texture were tested. The measured Young moduli agreed with those measured on bulk crystals, but the measured Poisson ratios were consistently low, most likely due to slight transverse folding of the film that developed during the test. The yield stresses of the evaporated Cu and Ag thin films agreed well with an extrapolation of the Hall-Petch relation found for bulk materials. Ni thin films are known to deviate from a bulk Ni Hall–Petch relation for submicron grain sizes, and sputtered Ni films show much higher yield stresses than electrodeposited or vapor-deposited films of similar grain size. Our sputtered Ni films had higher yield stresses than other sputtered films from the literature.

The Elastic Moduli of Silver Thin Films Measured with a New Microtensile Tester

ABSTRACTA new design for a thin film microtensile tester is presented. The strain is measured directly on the free-standing thin film from the displacement of laser spots diffracted from a thin grating applied to its surface by photolithography. The diffraction grating is two-dimensional, allowing strain measurement both along and transverse to the tensile direction. In principle, both Young's modulus and Poisson's ratio of a thin film can be determined. Ag thin films with strong &lt;111&gt; texture were tested. The measured Young moduli agreed with those measured on bulk crystals, but the measured Poisson ratios were low, most likely due to slight transverse folding of the film that developed during the test.

Deviation from icosahedral symmetry in rapidly solidified Al6Cu(Li, Mg)3icosahedral phase

Abstract Deviations from perfect icosahedral m35 point-group symmetry in icosahedral particles in rapidly solidified Al-3Cu-l·5Li-lMg and Al-3Cu-l·5Li-lMg-0·1Zr have been investigated experimentally by a combination of conventional and high-resolution transmission electron microscopy. The as-rapidly-solidified icosahedral particles are nearly spherical and are typically 0·1–0·2 um in diameter. Four types of deviation from perfect icosahedral symmetry are observed: (1) Dark-field images show speckled contrast on a scale of approximately 20–50nm. (2) Selected-area electron diffraction patterns show elongation and radial and circumferential displacement of individual diffraction spots, with the degree of distortion varying from one particle to another, and from one place to another, on a scale of about 100 nm inside a given particle. Unusual triangularly shaped electron diffraction spots from whole icosahedral particles result from superimposed local spot distortions. (3) High-resolution images show displaci...

Wavelength-independent integrated focus sensor using a reflection twin micro-Fresnel lens

A compact focus sensor constructed with thin film components such as a reflection twin micro-Fresnel lens and a photodetector is proposed. This sensor has a folded optical path and is insensitive to wavelength shift. Theoretical analysis indicates that the optical performance of reflection Fresnel lenses can be improved in comparison with a conventional transmission micro-Fresnel lens. The reflection twin Fresnel lens was fabricated using electron-beam lithography and exhibited diffraction-limited focusing performance with high (71%) efficiency. It was demonstrated that the focus sensor had excellent spot displacement characteristics in agreement with theoretical results, and a focus error signal was detected. This focus sensor could be useful for the optical head of an optical disk system.

Auger electron spectroscopy–electron energy-loss spectroscopy–low-energy electron diffraction study of a V6C5(100) surface

The surface properties of (100) oriented substoichiometric vanadium carbide V6C5 was examined by electron spectroscopy and low-energy electron diffraction (LEED) observation. The electron energy-loss spectroscopy (EELS) spectra for a clean surface of the crystal showed similar features to those of a TiC(100) except for the loss region of less than 10 eV. In the LEED experiment, however, rather complicated patterns appeared contrary to the case of TiC(100), which indicated only fundamental lattice structure. The displacement of LEED spots with the energy variation of primary electron suggested that the surface was formed with two different kinds of facet planes. The carbides in general are inactive against common gases, while reactive particles such as oxygen interact with these materials. The irradiation of atomic hydrogen onto the specimen, however, causes no significant changes either in the compositional ratio of vanadium versus carbon or in LEED patterns. In the EELS spectra, by atomic hydrogen irradiation, the 3-eV loss peak disappeared, while a new peak near the 10-eV loss peak appeared, suggesting that atomic hydrogen could interact with this surface.

Unusual arrangement of the inclinations of lattice planes and Ψ splitting

The X-ray stress measurements method has been most widely used to obtain the residual stresses after samples had been subjected to friction, turning, grinding etc. There is one problem, however: the stresses obtained when the incident X-rays are in the working direction are different from those obtained when the incident X-rays are in the opposite direction to the working direction, even if the other geometrical conditions between the incident X-rays and the specimen are the same (Ψ splitting). Transmission electron diffraction patterns of very-fined-grained (less than 200 nm) oxygen-free high conductivity copper which had been repeatedly subjected to unidirectional friction showed unidirectional spot displacements. This suggests that the inclinations of the lattice planes were arranged in an unusual way; this could be one cause of Ψ splitting. This concept is completely different from those already reported, which attribute Ψ splitting to the residual stresses which have a component normal to the worked surface or to the phase stress in the affected layer.

Regulatory effect of dopamine on spatial properties of horizontal cells in carp retina

Three types of light-induced response (L-, RG-, and YRB -type S-potentials) recorded from isolated retinas of the carp (Cyprinus carpio) were identified by their spectral response and later by morphological localization of the recording sites marked with an intracellular Lucifer Yellow (LY). Horizontal cells in a given layer, generating one of the above response types, are electrically coupled via gap junctions, so that the injected LY normally diffused to several neighboring cells. The spatial property of the three types of responses was examined by enlarging the diameter of a light spot (0.25 to 4.0 mm) and displacing the spot (0.5 mm diameter) along a straight 4-mm line which passed over the recording point at the middle. In normal retinas, the half-decay distance of response amplitude with spot displacement was shorter in the order of L-, RG-, and YRB -type responses, and correspondingly the dye diffusion area was narrower in the same order of cells. Dopamine (DA; 10 to 20 microM), applied to the vitreous fluid beneath the isolated retina, altered the spatial property of all types of responses by increasing the amplitude of responses to central spots and decreasing that of those to distant spots, and it restricted the intracellular LY to single injected cells. In contrast, in retinas from which DA interplexiform cells had been deprived by prior destruction with a neurotoxin, 6-hydroxydopamine, the amplitude of responses became smaller while the half-decay distance was longer by 1.1- to 1.6-fold, depending upon the cell type, and the dye diffusion area in all types of cells became wider by 2-fold as compared to those in normal retinas.(ABSTRACT TRUNCATED AT 250 WORDS)

Random walk of cathode arc spots in vacuum

The cathode spot movement of a vacuum arc with Al, Cd, Mo and Cu cathodes was investigated. Provided external disturbances are absent the cathode spot was found to move at random. The two-dimensional distributions of spot displacements can be described by a Rayleigh function. From the experimental data the average distances between cathode craters were deduced, leading to values of 2-3 times the crater diameter. Crater formation times, derived from the random walk data, were used to calculate the erosion rates of the metals listed. Good agreement was found between these data and earlier experimental results of cathode erosion rates and ion flows.

Beam alignment tests for therapy accelerators

Beam spot displacement, collimator asymmetry, and movement of either collimator or gantry rotational axis can cause misalignment of the X ray beam from a therapy accelerator. A test method, sensitive to all the above problems, consists of double-exposing a film, located at the isocenter, for two gantry positions, 180° apart. Opposite halves of the field are blocked for each exposure. A lateral shift of one half with respect to the other indicates the presence of one of the problems mentioned above. Additional tests are described, each of which is sensitive to only one of the problems and capable of quantifying the error.

Gaging By Remote Image Tracking

A method is described for performing noncontact optical gaging of complex parts in a production environment. The operational concept of the system, known as Gaging by Remote Image Tracking, relies upon an optical triangulation technique. A spot of light is projected from a gage head onto the surface of the part being gaged; an image of this spot is focused on the center of a tracking photodetector, mounted within the gage head. If the part is translated in a direction perpendicular to the projection axis, the focus spot on the surface of the photodetector will move as the surface curvature of the part changes. As a result of this movement, voltage signals are generated which provide: (1) a measure of the spot displacement on the photodetector, and (2) a signal for driving the optical head in a direction which recenters the image spot on the photodetector. The first signal, with appropriate scaling, provides virtually an instantaneous measure of the dimensional change of the part. The second signal is used to drive the system to a known distance from the part (system null). By monitoring the motion of the entire system with a linear encoder and adding this measurement to the instantaneous measure of surface curvature, the result is a fast, noncontact optical gaging system with large dynamic range.

Erosion Craters and Arc Cathode Spots in Vacuum

AbstractThe development of erosion craters on clean, smooth cathodes in UHV has been investigated with a time resolution of nanoseconds (current range 10–200 A). Furthermore, crater size erosion rate and velocity of spot displacement have been measured in dependence on current and surface conditions. The relevance of the results for different cathode spot models is discussed in detail. From the measurements the following conclusions are drawn.The craters are caused by the action of the discharge pressure on the molten metal within a spot. The spots move in a random manner in elementary steps of a crater radius with time constants of the order of 10−8 s. The main reason for the movement is the formation of micropoints at crater boundaries. Droplets and contaminations induce jumps of more than a crater radius. The impact of droplets causes considerable deformations of the cathode surface. Nanosecond pulse breakdowns and quasi‐stationary arcs result in values of crater size, spot velocity and erosion rate that are comparable within an order of magnitude.These results support a non‐stationary spot model that describes the cathode spot as a sequence of surface explosions.

Beam wander in a turbulent medium: An application of Ehrenfest’s theorem

Beam wander of a finite optical beam propagating in a turbulent medium is investigated theoretically. Using the optical analog of Ehrenfest’s theorem, it is shown that the centroid of a finite beam propagates as a paraxial ray in a certain effective refractive index that depends on the irradiance profile of the beam. Ray statistics in the effective refractive index are studied for arbitrary irradiance profiles and new results are obtained for the variance of spot displacement and beam angle of arrival. These results are then applied to the particular cases of focused and collimated gaussian beams in atmospheric turbulence with a modified Von Karman power spectrum to yield the functional dependence of spot dancing and angle-of-arrival statistics on the inner and outer scales of turbulence and on the Fresnel number for focused gaussian beams.

Etude de la rotation rétrograde, en 4 jours, de la couche extérieure nuageuse de Vénus

We review briefly photographic as well as spectrographic observations which have allowed us to prove and confirm the retrograde rotation of about 4 days of the external cloud layer of Venus. Certain configurations visible in ultraviolet light—in particular two spots having the shape of a horizontal Y—seem permanent, and we can establish their cartography. But the observations suggest that highlying clouds cover these configurations from time to time. An examination of the displacement of the equatorial spots during time intervals of several hours furnishes an instantaneous synodic rotation period somewhat larger than 4 days for the permanent spots. The synodic period is shorter for the variable spots. The observations of the periodic return, at the subsolar point, of the equatorial Y shaped configurations, suggest that the mean rotation period of these spots is remarkably constant and almost equal to 4 days. This period increases considerably when the spot latitudes are greater than ±6°. Ephemerides have been calculated for the years to come.

Sputtering Experiments with 1–5-keV Ar+ Ions. Displacement of Ejection Pattern Spots

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