Showing papers on "Tilt (optics) published in 1979"

Early cardiovascular adaptation to simulated zero gravity.

Abstract: A study was conducted on five normal male volunteers (23-29 yr), under controlled conditions, to evaluate early adaptive responses to zero gravity. Specific objectives are (1) to characterize the hemodynamic, renal and hormonal responses to a central fluid shift, and (2) to compare data obtained during and after head-down tilt with corresponding data from actual space flight to validate tilt as a physiological model for simulation of zero gravity. Zero gravity is simulated by a 24-hr period of head-down tilt at 5 deg. The results suggest that hemodynamic adaptation occurs rapidly and is essentially accomplished by 6 hr, and that adaptation includes diuresis and reduction in blood volume. The validity of head-down tilt at 5 deg as an experimental model is established by comparing the results obtained with data from Apollo and Skylab astronauts on body fluid distributions and postflight responses to orthostatic and exercise stress.

Why the Molecules are Tilted in all Smectic A Phases, and How the Layer Thickness Can be Used to Measure Orientational Disorder*

Abstract: Even though the average molecular direction in smectic A phases is perpendicular to the smectic planes, most molecules in these phases have rather large tilt angles because the orientational order parameter S in all smectic A phases is significantly less than unity. This molecular tilt inherent to all A phases accounts for the observed differences between layer thickness d and molecular length l of four quite different compounds, without any need for assuming additional tilt, interdigitation, or kinking of chains. From the differences between d and l , S values from 0.78 to 0.84 are obtained, which yield average molecular tilt angles from 20° to 17°. It is predicted that all smectic A phases with monomolecular layers will follow the same pattern. The concept of “inherent tilt” should apply to all orthogonal smectic phases, thermotropic as well as lytropic.

The low-angle [011] tilt boundary in germanium I. High-resolution structure determination

Abstract: Pure tilt boundaries (θ = 0·5 to 5°) in germanium bicrystals with a [011] common axis have been studied with respect to the tilt angle, θ, and the grain-boundary plane. Structural detail is revealed at a 3 A level by multi-beam interference using both a 100 and a 500 keV electron microscope. At this scale great complexity arises from dislocation splitting. Four types of grain boundaries are encountered : they are formed with dislocations having 1/2[011] Burgers vector, but also with very uncommon Burgers vectors such as [111] (split into three Frank dislocations) or 1/2[211] (split into three partials). The type of grain boundary is determined by both the tilt angle and the grain-boundary plane.

Tilt Angle Determination of a Smectic C Phase by Field-Induced Freedericksz Transition and x ray Investigations

Abstract: A smectic C liquid crystal exhibiting positive dielectric anisotropy was oriented with the director parallel to the glass substrates. When an electric field was applied normal to the director direction a dielectric reorientation (Freedericksz transition) occurred. Dissolving a dichroic dye in the smectic C phase and applying an electric field, a guest host effect similar to nematic phases was observed. From the dielectric reorientation the tilt angle of the smectic C phase was determined at different temperatures. The tilt angles obtained by the electrooptical measurements agree sufficiently with the values measured by x ray investigations.

Determination of anchoring energies from surface tilt angle measurements in a nematic liquid crystal

Abstract: 2014 The anchoring energy of a nematic liquid crystal can be evaluated from measurements of the tilt angle at the boundary of its substrate. The equilibrium between surface and elastic energies determines the geometric structure of the distortion. For an obliquely evaporated SiO film, the energy value is about 10-3 erg/cm2. LE JOURNAL DE PHYSIQUE LETTR ES TOME 40, 15 MAI 1979, Classification Physics Abstracts 61.30 In previous articles [1], [2], we have shown that it is possible to determine liquid crystal tilt angles at the boundary of a substrate with great accuracy; we have also suggested the possibility of evaluating the anchoring energy. The purpose of this paper is to explain the theory of this effect and to give some experimental results. 1. Theoretical considerations. Consider a liquid crystal cell composed of two parallel glass plates separated by spacers of different thickness so as to form a small wedge (Fig. 1). With no external field, the equilibrium state is determined only by the elasticity of the nematic material and the anchoring at the boundary surfaces. From the elastic continuum theory of liquid crystals [3], [4], we can write the free energy density : (we assume the one-constant approximation : K = K11 = K2 2 K3 3, where K11, K2 2 and K3 3 represent the elastic constants corresponding to splay, (*) First reported at the 7th International Liquid Crystal Conference (Bordeaux, July 1978). ~ Fig. 1. Liquid crystal cell forming a small wedge : (~ and ~p 2 y represent the easy axis of the molecules ; ~i and 82 are the real tilt 1 ’ angles at the boundary surfaces. ) twist and bend distortions). The Euler-Lagrange . equation for minimization of the total bulk energy ’ is Laplace’s equation : If we assume that the rotation of the director is confined to the xOz plane, integration of (2) yields : Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyslet:019790040010021500 L-216 JOURNAL DE PHYSIQUE LETTRES where a is a constant representative of the bulk distortion in the nematic material (splay and bend). The balance of forces leads to the conditions : where i = (1 ; 2); Wsi is the energy corresponding to the liquid crystal orientation in the vicinity of the surface for z = zi. This energy, which is required to move the molecules by a small angle from their equilibrium position ~, can be expressed by the formula (5) : where Wi is then the anchoring energy relative to the boundary surface. The results of equation (5) may be admissible if we assume strong anchoring and small tilt angle variations around the equilibrium position. We shall see later the self-consistency of these assumptions. Now, we can write from (4) and (5) :

The Implications of the Diffuse-Cone Model for Smectic A and C Phases and A-C Phase Transitions

Abstract: The diffuse-cone model, developed on the basis of the existence of orientational disorder in smectic phases, is valid for all smectic A and C phases, and also, with appropriate modifications, for all other smectic phases. The fundamental angular parameter is not the optical tilt angle τ, but the preferred molecular tilt angle θm. This explains why τ does not follow the (TA-C-T)0.35 dependency predicted by De Gennes whereas θm does. The diffuse-cone model also explains why the tilt angle obtained from measurements of the smectic layer thickness will in general not be equal to τ, and thus invalidates arguments based on such differences which were used to support a particular structural model.

Survey apparatus and method employing canted tilt sensor

Abstract: A borehole mapping and navigational instrument which travels up and down in a well. The instrument includes a housing which supports at least a rate gyroscope, accelerometer, and an electric motor to rotate the accelerometer about an axis which is canted about the axis of the housing. Since the accelerometer is rotated, its tilt sensitive axis then effectively has components along the X and Y directions normal to the Z axis, whereby components along all three axis are provided.

Web guiding system

Abstract: A system for positioning a web of material as it enters and passes through a course for treating the web, as in a printing press, is disclosed. The edges of the web are scanned by infrared sensing devices which are connected by various electrical circuits to a tilt mechanism contacting the web, and both the scanning devices and the tilt mechanism may be synchronized, or manually controlled, to direct the web through the press. A broad diameter channel of infrared radiation is utilized in the scanners. The relationship of the web to its desired path and the correcting actions of the system may be continuously read in terms of actual deviation changes on a display panel. The tilt rollers and the scanners may be automatically centered on a fixed reference point in preparing the web for its course through the press. The system includes correlation of the tramming of the tilt rollers to continued position sensing of the web by the infrared scanners.

Geodetic tilt measurements along the San Andreas Fault in central California

Abstract: Changes in tilt have been measured by annual or semi-annual spirit level surveys of small-aperture (40 to 400 m) bench mark arrays located at borehole tiltmeter sites along the San Andreas Fault in California. Because there are six or more bench marks in most arrays, the tilt is overdetermined, and realistic estimates of uncertainties can be made. The large arrays (aperture 300 m) afford a precision (two standard deviations) of about 3 μrad in measuring tilt, and the measured tilt remains constant to within ±5 μrad over periods of up to 5 years. The small arrays (aperture 10 μrad) in tilt within periods on the order of a year, but the best tiltmeters exhibit a stability comparable to that obtained from surveys of the large-aperture bench mark arrays.

X-ray diffraction study of the structure of small-and large-angle [001] tilt boundaries in gold

Abstract: The structures of selected small- and large-angle [001] tilt boundaries in gold bicrystals were studied using X-ray diffraction techniques. All the boundaries examined gave rise to extra reflections. It was shown that these reflections could not result from (1) double diffraction, (2) surface diffraction or (3) diffraction of radiation with one-half or one-third of the characteristic CuKα wavelength and, therefore, must come from the grain boundary. The presence of these reflections is direct evidence for the periodic nature of all the grain boundaries studied. The grain boundary reflections were frequently split into pairs which are present on the high- and low-angle side of the tail of the f.c.c. reflection. This splitting was related to the presence of a small twist component superimposed on the tilt boundary. In general the low-angle reflections were observed to be higher intensity than the high-angle reflections. The analysis of these intensity observations indicates that the tilt-boundary s...

Mutual coherence function of a wave front corrected by zonal adaptive optics

Abstract: The mutual coherence function (MCF) of a wave propagated through atmospheric turbulence and corrected by zonal adaptive optics is derived for a segmented corrector with either piston only or piston with a local tilt fit. We begin with an intuitive approach which is based on replacing the outer scale of turbulence in the uncorrected MCF with a quantity proportional to the segment size. This approach is especially useful in deriving asymptotes. A rigorous approach provides the full curves, and reduces to a single curve for piston only and a single curve for piston with tilt, after proper parametrization. The effect of amplitude fluctuations is also considered, since scintillation limits the ultimate degree of correction as the segment size goes to zero. Although the analysis is for a segmented corrector, the results apply fairly well to continuous corrector with actuator spacing equal to d/√3, where d is the segment diameter.

Beam scanning-electrostatic

Abstract: A discussion of electrostatic scanning systems is given with respect to mechanical scanning, uniformity and current capabilities as they relate to ion implanters. Equations for the degradation of uniformity due to wafer tilt. misalignment and changing beam size are presented. Some commercial implantation scanning systems and related data are also presented along with a proposed high current electrostatic scanning system.

Imaging properties of off-axis parabolic mirrors.

Abstract: Geometric optics is used to find the shape of the image and the irradiance cast on a spherical target by a circular beam after reflection by a far off-axis paraboloidal mirror. For moderately large f/No. the image is found to be nearly circular with its center shifted slightly from the beam axis. However, the target irradiance can be highly asymmetric unless the beam intensity falls off rapidly with radius. An expansion in powers of inverse f/No. is used to obtain closed form expressions for the image shape and the target irradiance. Numerical studies are carried out for parameters relevant to the design of a laser fusion reactor. Limits are placed on allowable tilt errors by means of a naive analysis of ray aberrations. A useful formula is derived for the perturbed target irradiance under small tilt errors, based on a new expression for the caustic. These simple formulas allow one to carry out detailed design studies without recourse to ray tracing codes.

Determination of the standard deviation of height on a rough surface using interference microscopy

Abstract: When a rough surface is viewed in an interference microscope with tilt fringes introduced, the effect of the roughness is to reduce the average visibility of the tilt fringes. The relationship between the standard deviation of surface height and the average visibility of the tilt fringes is derived, and experimental results are presented of measurements made on ground glass surfaces using a Linnik interference microscope.

Device for adjusting an inclination angle of a tilt handle in a vehicle

Abstract: In a tilt handle, including a steering shaft, supported by a sleeve the lower end of which is pivotably provided so as to adjust an inclination angle of the tilt handle with relation to a car body, a device for adjusting the inclination angle of the tilt handle includes a stationary bracket, a movable bracket and spring means therebetween, the stationary bracket being positioned at a proper portion of the car body. The movable bracket is located at a suitable portion of the sleeve and is movable within the stationary bracket. The spring means is provided for energizing the sleeve to move upwardly.

Spatial analysis of tilt and gravity observations of Earth tides in western Europe

Abstract: Summary. Tidal gravity and tilt data are available with a great density in western Europe, so that local and regional variability of Earth tides are well documented. O1 and M2 are the most reliable waves and the relevant ocean loads are deduced from some cotidal charts and from Green's functions given by Farrell. The reliability of the charts is proved a posteriori by the convergence of O1 and M2 with respect to body tides for tilt and gravity. It is shown that a spatial trend of the gravimetric factor exists but cannot be analysed because of scatter in the data. For tilt tides the importance of the load due to the Bay of Biscay is emphasized; by considering tilt and strain powers, it is shown in a global approach that the noise is in favour of a local tilt-strain coupling, and it is proved that in each station a quantitative estimate of this phenomenon can be obtained by a statistical analysis derived from a theoretical scheme (King et al.) in as much as the ocean load is known with sufficient accuracy; an appraisal of the diminishing tilt factor is then deduced simultaneously.

Interaction of gravity and idiothetic course control in millipedes

Abstract: 1. If their walking plane is tilted, millipedes, in the dark, adopt a compromise course between the (“idiothetic”) tendency to continue going straight ahead and the (“allothetic”) tendency to walk uphill. This compromise direction is attained at about 30 cm of path length after the point of tilt and remains stable within the entire measured extent of about 130 cm, that is 20 to 30 times the animals' length. If the arena is set back into the horizontal after a 25 to 30 cm walk on the inclined plane the millipedes turn into a direction which is approximately equal to the initial one before the tilt. 2. If the animals had run through a bent passage before the tilt the result, at equilibrium, is as expected from a superposition of the two experiments. In the transient phase, the effect of gravity is delayed relative to that of the bent passage. 3. If the arena is tilted, when a millipede walks through a passage that prevents it from turning, and then set back horizontally, the animal turns toward the direction which had been uphill during the tilt. The amount of the turn depends on the direction and the time course of the preceding gravity influence, which acts as if processed by a “leaky” integrator. 4. In the inclined plane at equilibrium, the sine of the animal's deviation (α) from the projection of the vertical into the walking plane is, at first approximation, proportinal to the sine of the deviation (σ) from the animal's (self-adopted) idiothetic direction. More precisely, the pattern of equilibrium directions can be described by the additive superposition of two Fourier sine expansions with declining amplitudes $$\sum\limits_n {A_n \sin n\alpha + } \sum\limits_n {S_n \sin n\sigma = 0.}$$ 5. The courses observed at different angles of arena tilt (ϑ) can be best explained by assuming that the gravity influence is largely proportional to that component of the physical gravity vector which falls into the y-axis of the animal (g·sin α sinϑ, i.e. the “shear-component”), whereas the pressure-component (g·cosϑ) has no effect. 6. The results are discussed with respect to hypothetical underlying mechanisms, in comparison with the general properties of orientation systems, and in view of their methodological consequences.

Ski exercising apparatus

Abstract: An apparatus for providing exercises to enhance muscle tone and coordination especially adapted for skiing enthusiasts. The apparatus consists of a tilt swivel board upon which the user stands. The tilt swivel board is formed with a planar top surface and a substantially convex bottom surface. Elastic extensible springs are anchored at one end to the tilt swivel board and pass through a harness belt adapted to be attached about the user's waist. Handles are provided at the other end of the springs for grasping by the user while bending the knees. Thereafter, body weight shifts between the legs and arm movements similar to those during skiing cause the swivel board to tilt and rock thereby imparting body motions similar to those encountered during skiing.

Precise Optical Evaluation Using Phase Measuring Interferometric Techniques

Abstract: Fabrication of high quality optical surfaces requires both sensitive methods for measuring surface characteristics and delicate control of the fabrication process. Conventional metrology interferometers have been augmented with computer controlled interference phase measuring techniques to give greater accuracy and provide real-time data analysis. Key elements of a Phase Measuring Interferometer (PMI) system are a Twyman-Green interferometer; piezoelectric-driven reference mirror; image detector; and a minicomputer system with a graphic display, keyboard, and hard copier. Surface quality data is obtained by a direct measurement of intensity and computation of phase difference over an aperture containing a 32 x 32 element array. System functions include: isometric contour mapping at variable sensitivity, array subtraction, surface calibration, time averaging, determination of tilt and power over subapertures with respect to a clear aperture, and deconvolution of wavefront data to yield aberration coefficients. The system is being used to produce high-quality reflecting spheres, flats, mirrors, and refractive elements. A measurement uncertainty of <0.01A peak to valley and 0.001 Xrms has been achieved in the evaluation of a large spherical reflector.

Sandwich hologram interferometry. 5: Measurement of in-plane displacement and compensation for rigid body motion.

Abstract: Sandwich holography has been used for measurements of in-plane displacement of an object. The sign of the displacement is found by tilting the sandwich hologram during reconstruction. Fringes caused by in-plane rigid body motion can be compensated for, and local displacements evaluated. It is shown that an in-plane motion of more than 1 mm of the object placed at a distance of about 1 m from the plates can be compensated for and a local tilt of 1.5 × 10−3 degrees evaluated. A comparision between conventional evaluation and evaluation of sandwich holograms by measuring the tilt angle of the plates to calculate an object’s displacement is shown with a series of experiments.

Amplitude tilt correction apparatus

Abstract: Circuitry for detecting the spectral distribution of a signal that is phase indicative of a digital logic level and providing feedback signals for use in adjusting the signal amplitude of the spectrum to have a substantially zero slope over the relevant frequency bandwith. The correction is obtained by applying voltages to variable impedance pin diodes forming part of a tuned filter circuit.

Method of shadow printing exposure

Abstract: A method of pattern exposing an energy beam sensitive target surface to a particle beam by proximity printing, wherein mask alignment errors such as lateral deviations, skew and linear distortions are determined and are effectively corrected by scanning the mask area being transferred with a controllably tilted particle beam, the particle beam having a diameter which is small compared to the area of the mask being scanned. At each scan point the particle beam is controllably tilted in the same azimuth direction as the alignment error for that point and by a tilt angle (taken with respect to the normal direction of the target surface) which has a tangent equal to the product of the magnitude of the alignment error and the separation between the mask and target surface at that point.

Tilt compensating AGC

Abstract: A correcting bias is applied to the video signal from a hand-held optical character reader to compensate for horizontal tilt of the hand-held reader and also to increase the acceptability of photodiode arrays which are used in the reader and to correct uneven sensitivity of the photoelements in the photodiode arrays. The analog video is changed to a four bit video and this four bit video is processed to produce a tilt error signal indicative of magnitude and direction of the tilt. This tilt error signal is then applied back as a compensating factor in the four bit analog to digital converter to compensate for the tilt of the hand-held reader.