Showing papers on "Tilt (optics) published in 1993"

Scanning probe microscope

Abstract: A scanning probe microscope having numerous advantages is disclosed. Respective scanning force and scanning tunneling probes are removably mounted in the head using kinematic mounting techniques so that they may be substituted for one another without the need to adjust the cantilever deflection sensor. A linear position-sensitive photodetector in the deflection sensor eliminates further the need for adjustments. A motorized, non-stacked x,y coarse movement stage is kinematically positioned with respect to the base and features a minimized mechanical loop to reduce thermal and vibrational effects on the position of the sample. A z coarse movement stage positions the head kinematically with respect to the base and includes a motorized drive means which allows the height, tilt and pitch of the probe to be adjusted. The scanner includes x,y and z sample position detectors which provide an accurate measurement of the position of the sample with respect to the probe. The z position detector provides an output which is exclusive of sample tilt and which may be used as an output of the scanning probe microscope. The outputs of the x,y and z position detectors may also be connected in feedback loops with the controller to improve the performance of the scanning probe microscope.

Radiographic analysis of patellar tilt

Abstract: We describe the radiographic measurement of the angle of tilt of the patella and relate it to malalignment of the extensor mechanism. The tilt angle is defined as the angle subtended by a line joining the medial and lateral edges of the patella and the horizontal. The radiograph (Merchant type) is taken with the foot pointing up, the lower edge of the film parallel to the ground, and the knee at 30 degrees flexion. The mean tilt angle of a group of patients with signs and symptoms suggesting patellofemoral malalignment was 12 degrees (+/- 6 degrees); in a similar group of control subjects it was 2 degrees (+/- 2 degrees) (p < 0.01). Tilting of 5 degrees was taken to be the limit of normal. For the detection of patellar malalignment, the tilt angle was almost as specific as the congruence angle (92% v 99%) but more sensitive (85% v 25%) and more accurate (89% v 62%).

Sourceless orientation sensor

Abstract: A sourceless orientation sensor having an azimuthal sensor which determines the azimuthal orientation relative to a planetary magnetic field, and a tilt sensor which determines the direction and magnitude of the displacement from vertical using the planetary gravitational field. The tilt sensor includes a transparent gas and a transparent viscous fluid in a spherical shell, a light emitting diode (LED) mounted at the top of the shell, and four photodetectors mounted at the bottom of the shell. As the tilt sensor is rotated the path of the light cone emanating from the LED and refracting at the gas/fluid interface is altered, thereby altering the intensity of light incident on the photodetectors. The magnitude of the light incident on the photodetectors is processed to provide the tilt angles. A thin transparent disk floats at the gas/fluid interface to damp surface waves caused by reorientation of the device. A time sequence of orientations of the sensor may be interpreted to provided a gesture sensing device.

Stylus tilt detection apparatus for communication with a remote digitizing display

Abstract: An architecture is disclosed for improved tilt detection for a radiative pickup stylus. The architecture includes a contact sensing mechanism and a coaxial conductor assembly which provides both position measurement and tilt sensing measurement features. By using the contact sensor to establish a calibration for the position and tilt detection elements, an improved, highly accurate position and tilt sensing capability is provided for radiative pickup stylus for a digitizing display.

Femtosecond pulse front tilt caused by angular dispersion

Abstract: Femtosecond pulse fronts suffer a time delay across the beam when propagating through diffraction gratings or dispersive prisms. A general relation was found describing the tilt angle γ of the pulse front as, tanγ=λde/dλ where de/dλ is the angular dispersion of the grating or prism and λ is the central wavelength of the pulse. The expression is valid for any spectral device having angular dispersion (e.g., Fabry-Perot interferometer, Lummer-Gehrcke plate, and Michelson echelon). The tilt angle is shown to have a close relation to the classical uncertainty principle.

Sedimentation of particles in polymer solutions

Abstract: In this paper, we present detailed and systematic experimental results on the sedimentation of solid particles in aqueous solutions of polyox and polyacrylamide, and in solutions of polyox in glycerin and water. The tilt angles of long cylinders and flat plates falling in these viscoelastic liquids were measured. The effects of particle length, particle weight, particle shape, liquid properties and liquid temperature were determined. In some experiments, the cylinders fall under gravity in a bed with closely spaced walls. No matter how or where a cylinder is released the axis of the cylinder centres itself between the close walls and falls steadily at a fixed angle of tilt with the horizontal. A discussion of tilt angle may be framed in terms of competition between viscous effects, viscoelastic effects and inertia. When inertia is small, viscoelasticity dominates and the particles settle with their broadside parallel or nearly parallel to the direction of fall. Normal stresses acting at the corners of rectangular plates and squared-off cylinders with flat ends cause shape tilting from the vertical. Cylinders with round ends and cone ends tilt much less in the regime of slow flow. Shape tilting is smaller and is caused by a different mechanism to tilting due to inertia. When inertia is large the particles settle with their broadside perpendicular to the direction of fall. The tilt angle varies continuously from 90° when viscoelasticity dominates to 0° when inertia dominates. The balance between inertia and viscoelasticity was controlled by systematic variation of the weight of the particles and the composition and temperature of the solution. Particles will turn broadside-on when the inertia forces are larger than viscous and viscoelastic forces. This orientation occurred when the Reynolds number Re was greater than some number not much greater than one in any case, and less than 0.1 in Newtonian liquids and very dilute solutions. In principle, a long particle will eventually turn its broadside perpendicular to the stream in a Newtonian liquid for any Re > 0, but in a viscoelastic liquid this turning cannot occur unless Re > 1. Another condition for inertial tilting is that the elastic length λU should be longer than the viscous length ν/U where U is the terminal velocity, ν is the kinematic viscosity and λ = ν/c2 is a relaxation time where c is the shear wave speed measured with the shear wave speed meter (Joseph 1990). The condition M = U/c > 1 is provisionally interpreted as a hyperbolic transition of solutions of the vorticity equation analogous to transonic flow. Strong departure of the tilt angle from θ = 90° begins at about M = 1 and ends with θ = 0° when 1 < M < 4.

Adjustable athletic training system

Abstract: An athletic training system includes a position processor which can be mounted on the head of an athlete by means of, for example, a head band. The position processor includes a sensor in the form of two tilt sensors mounted at right angles to each other. The direction of tilt is sampled by a microprocessor as output voltages from the sensors for further processing. Software of the microprocessor processes the sensed directions by filtering and hysterisis algorithms in order to eliminate rapid changes of state of the switches of the sensor due to sporadic movement caused by the motion of the athlete. The positional information is conveyed to the athlete as a pattern of lights and tones. Proper and improper head positions are indicated for a plurality of directions of tilt. The training system is user controllable by means of rotary switches to adjust, among other things, the level of sensitivity of the system. The system can also self-center by adjusting all sampled directions by a sampled reference value.

Laser beam survey instrument having a tiltable laser beam axis and tilt detectors

Abstract: According to the present invention, fixed tilt detectors are fixed in planes crossing perpendicularly to each other of shaft center of a laser projector, and tilting tilt detectors are mounted on a plate, which is tiltable with respect to shaft center of the laser projector. The laser projector is leveled in such manner that the fixed tilt detectors indicate horizontal direction or tilting tilt detectors aligned with the fixed tilt detectors indicate horizontal direction, and horizontal reference plane is obtained. The tilting tilt detectors are tilted with the fixed tilt detectors as reference, and the laser projector is leveled so that the tilted tilting tilt detectors indicate horizontal direction, and reference plane tilted at an arbitrary angle is obtained.

Transverse spectral filtering and Mellin transform techniques applied to the effect of outer scale on tilt and tilt anisoplanatism

Abstract: The process of setting up problems of wave propagation through turbulence and reducing the expressions to integrals is typically lengthy. Furthermore, to yield useful results the integrals must be evaluated numerically, except for the simplest problems. Here procedures are given for quickly writing an integral expression and easily evaluating it analytically, yielding a series solution that requires only a few terms to yield accurate results. The solution can also be expressed as a finite sum of generalized hypergeometric functions. The approach uses the Rytov approximation and filter functions in the spatial domain to express quantities of interest such as Zernike modes and effects of anisoplanatism for single or counterpropagating or copropagating plane or spherical waves in integral form. The integrals are readily evaluated with Mellin transforms. We illustrate the technique by deriving the tilt jitter of a single wave and the jitter between two waves with outer-scale effects present. It is shown that outer scale has a significant effect on tilt even for large outer-scale sizes. The effect of outer scale on tilt anisoplanatism is less pronounced.

Angle measurements of the distal radius: a cadaver study

Abstract: The quality of reduction of distal radius fractures is assessed mainly by degree of restoration of radial angle and palmar tilt. This cadaver study investigates the effects of forearm rotation of these measurements. A 5° rotational change produces a 1.6° change in palmar tilt on the conventional lateral view and a 1.0° change on the 15° lateral view. Lateral radiographs could be rotated 15°–30° and still be considered acceptable. Therefore, rotation may produce up to a 4.0° (15° lateral view) or 6.4° (conventional lateral view) change in measured palmar tilt. To provide clearer measuring landmarks and minimize error due to rotation, we recommend obtaining the 15° lateral view routinely in fractures with significant dorsal angulation. We also studied the interobserver variability of different surgeons assessing radial angle and palmar tilt. The mean standard deviation between surgeons was 3.2° for radial angle, 3.6° for conventional lateral palmar tilt, and 2.1° for 15° lateral palmar tilt.

The growth of fault-bounded tilt blocks

Abstract: A series of uniformly tilted fault-bounded blocks is a common feature in actively extending regions, such as the Basin and Range province. If the tilted blocks were produced by rigid “domino-style” rotation, one would predict large voids at either end of a series of these blocks. Using tilt data and a simple flexural calculation, we suggest that much of the apparent rigid behavior could also be produced by internal block deformation. In our model of normal fault growth, isostatic/elastic uplift of the footwall is coupled with hanging wall downdrop within the region between faults, resulting in the appearance of a tilted rigid block. We present tilt data sampled at varying distances from several block-defining faults within the northeast Basin and Range province. Tilt measurements between a series of 30-km spaced block-defining faults are found to be uniform, while tilts between more widely spaced faults exhibit a pattern of tilt that diminishes to zero in less than 30 km. Using a simple flexural calculation for internal block deformation, we show that for this region the patterns of tilt are consistent with a flexural length scale of ∼8–12 km and deflections of 2–4 km. These estimates are compatible with both the lower limit to seismicity and basin depth determined from earthquake and seismic reflection studies.

Liquid-level gauging

Abstract: An ultrasonic liquid level gauging sensor has a transducer at the lower end of a tube that is filled with liquid to the same height as liquid outside the tube. The sensor has an axial rod extending along the tube and supporting several calibration reflectors. The rod enables the sensor to be used at high tilt angles.

Four-way levelling mechanism for off-road vehicle

Abstract: A four way tilt mechanism (15) for maintaining the super-structure (14) of an off road vehicle generally horizontal while the vehicle is working on uneven terrain is disclosed. The tilt mechanism is very robust and provides independent adjustment of the angle of tilt relative to each of two pivot axes (16, 17). The tilt mechanism (15) incorporates a spherical bearing (37) mounted on a shaft (38) perpen-dicular to the longitudinal pivot axis (16) of the tilt mechanism to eliminate end-play in the joint which forms the longitudinal pivot axis. The longitudinal and transverse pivot axes (16, 17) preferably lie in the same plane so that many of the the forces which are trans-ferred from the superstructure (14) of the vehicle through the tilt mechansim (15) to the chassis (13) of the vehicle cannot cause a torque on the components of the tilt mechanism.

Correlation between surface and bulk orientations of liquid crystals on rubbed polymer surfaces: Odd-even effects of polymer spacer units.

Abstract: Using surface optical second-harmonic generation, we have determined the molecular tilt angle and the in-plane orientational order of the liquid-crystal molecules 4'-n-octyl-4-cyanobiphenyl (8CB) on a series of polyimide surfaces. The polyimides differ in the length of the flexible spacers in between neighboring aromatic cores. Using birefringence measurements, we obtained the bulk tilt angle of liquid-crystal cells having the same series of surfaces. The surface molecular tilt angle, the in-plane orientational ordering near the surface, and the bulk tilt angle all exhibit an odd-even effect related to the odd or even number of spacer units in the polyimides. The results are explained by the fact that polyimide surfaces with even numbers of spacer units are smoother and capable of inducing higher surface ordering in the 8CB surface layer. The orientational order at the surface is shown to be intimately correlated with the bulk tilt angle.

Comment on molecular dynamics simulations of monolayers of fluorinated amphiphiles

Abstract: We report the results of new molecular dynamics simulations of liquid‐supported monolayers of perfluorinated and partially fluorinated amphiphiles such as F(CF2)11COOH and F(CF2)10CH2COOH. The new simulations include a representation of the superhelical structure of the perfluoroalkane portion of the amphiphile chain in the intramolecular potential energy; in addition, the calculation of the collective tilt angle of the monolayer is improved to include the effect of the azimuthal distribution of individual molecular tilt angles. The results of the simulations are in agreement with the available experimental data. In particular, the packing structure and the observed breakup of the homogeneous ordered monolayer into ordered islands with the same collective tilt of the molecules are correctly predicted as are the very small collective tilt angles. These new results remove the discrepancy between predicted and observed collective tilt angles reported in our previous papers [J. Chem. Phys. 96, 1352, 4735 (1992)].

Optical information recording and reproducing device

Abstract: PROBLEM TO BE SOLVED: To reduce the degradation in the quality of recording and reproducing signals caused by the tilt between optical beams and an optical information recording medium in an optical information recording and reproducing device. SOLUTION: The device conducts a recording and a reproducing of an optical information recording medium having a transparent protective layer. The device is provided with a tilt detecting device 15, an off-track adding device 12, a determination means which determines an optimum direction to deviate the center of an optical spot from the center of the information track of the medium against the tilt between optical beams and the medium, a means, which makes the amount of deviation into a fixed value, and a means, in which the medium is divided into a few areas and a tilt detecting function is activated every time an area varies during a recording and a reproducing. By conducting a scanning while the center of the optical spot on the medium is deviated from the center of the information track of the medium, the quality degradation of the recording and reproducing signals caused by the tilt of the recording surface of the medium is reduced.

Correlation between surface and bulk orientations of liquid crystals on rubbed polymer surfaces : odd-even effects of polymer spacer units

Abstract: Using surface optical second-harmonic generation, we have determined the molecular tilt angle and the in-plane orientational order of the liquid-crystal molecules 4'-n-octyl-4-cyanobiphenyl (8CB) on a series of polyimide surfaces. The polyimides differ in the length of the flexible spacers in between neighboring aromatic cores. Using birefringence measurements, we obtained the bulk tilt angle of liquid-crystal cells having the same series of surfaces. The surface molecular tilt angle, the in-plane orientational ordering near the surface, and the bulk tilt angle all exhibit an odd-even effect related to the odd or even number of spacer units in the polyimides

Tip-tilt compensation : resolution limits for ground-based telescopes using laser guide star adaptive optics

Abstract: The angular resolution of long-exposure images from ground-based telescopes equipped with laser guide star adaptive optics systems is fundamentally limited by the the accuracy with which the tip-tilt aberrations introduced by the atmosphere can be corrected. Assuming that a natural star is used as the tilt reference, the residual error due to tilt anisoplanatism can significantly degrade the long-exposure resolution even if the tilt reference star is separated from the object being imaged by a small angle. Given the observed distribution of stars in the sky, the need to find a tilt reference star quite close to the object restricts the fraction of the sky over which long-exposure images with diffraction limited resolution can be obtained. In this paper, the authors present a comprehensive performance analysis of tip-tilt compensation systems that use a natural star as a tilt reference, taking into account properties of the atmosphere and of the Galactic stellar populations, and optimizing over the system operating parameters to determine the fundamental limits to the long-exposure resolution. Their results show that for a ten meter telescope on Mauna Kea, if the image of the tilt reference star is uncorrected, about half the sky can be imaged in the Vmore » band with long-exposure resolution less than 60 milli-arc-seconds (mas), while if the image of the tilt reference star is fully corrected, about half the sky can be imaged in the V band with long-exposure resolution less than 16 mas. Furthermore, V band images long-exposure resolution of less than 16 mas may be obtained with a ten meter telescope on Mauna Kea for unresolved objects brighter than magnitude 22 that are fully corrected by a laser guide star adaptive optics system. This level of resolution represents about 70% of the diffraction limit of a ten meter telescope in the V band and is more than a factor of 45 better than the median seeing in the V band on Mauna Kea.« less

Prediction of the heliospheric current sheet tilt: 1992 – 1996

Abstract: Heliospheric current sheet tilt evolves systematically over the solar cycle. Here we show that this evolution is different than the sunspot cycle and that tilt for the period 1992-1996 can be predicted using persistence. That is, the tilt over the coming cycle will be the same as for the past cycle. The Ulysses spacecraft has passed Jupiter and is moving out of the plane of the ecliptic, so we use the prediction of the changing heliospheric current sheet tilt to predict that Ulysses will pass beyond the envelope, or maximum latitude, of the heliospheric current sheet in November 1993.

Automatic tip angle control

Abstract: An off-highway vehicle having an earth moving implement has a tilt function associated with the implement For example, a bulldozer has a tilt function associated with the bulldozer blade The vehicle has a processor adapted to receive a position signal from a position sensor associated with the tilt function of the implement The operator engages a switch to activate an automatic tilt function A selector switch is provided so that the operator can select between a plurality of pre-set blade angles The selector switch outputs a target position signal associated with a pre-set angle to the processor The processor automatically calculates a command signal for the tilt function based on the difference between the position signal and the target position signal The processor issues the command signal to the tilt function causing the tilt function to move the implement to the pre-set angle associated with the switch position

Traveling inspection robot system

Abstract: In a traveling inspection robot system, two carriages are each provided with one pair of guide rollers for guiding the travel in the vertical direction and two pairs of side rollers for guiding the travel in the horizontal direction. The two pairs of side rollers are arranged such that one pair locates on each of the front and rear sides of the pair of guide rollers as viewed in the direction of advance. The two carriages are interconnected by a coupling plate through parallel steering shafts, and a sprocket and a motor for driving the sprocket are provided as travel driving device on one carriage for giving a traction force to a transversely central portion of the upper inner surface of the monorail. An antenna and a current collector are provided on the other carriage. A control circuit unit and a span and tilt mechanism are attached to the coupling plate with a sensor unit mounted to the span and tilt mechanism. A swing motor and a tilt motor in the span and tilt mechanism are arranged in respective dead spaces created when the span and tilt mechanism swings and tilts. A chain, a trolley line and an antenna line are laid and wired on the upper inner surface of the monorail. With such an arrangement, the degree of freedom in rail design can be increased, the robot and the monorail can be both made small in size, and therefore the applicable range of the traveling inspection robot can be enlarged.

Profile stabilization of tilt mode in a field‐reversed configuration

Abstract: The possibility of stabilizing the tilt mode in field‐reversed configurations without resorting to explicit kinetic effects such as large ion orbits is investigated. Various pressure profiles, P(Ψ), are chosen, including ‘‘hollow’’ profiles, where current is strongly peaked near the separatrix. Numerical equilibria are used as input for an initial value simulation, which uses an extended magnetohydrodynamic (MHD) model that includes viscous and Hall terms. Tilt stability is found for specific hollow profiles when accompanied by high values of separatrix beta, βsep. The stable profiles also have moderate to large elongation, racetrack separatrix shape, and lower values of s, average ratio of Larmor radius to device radius. The stability is unaffected by changes in viscosity, but the neglect of the Hall term does cause stable results to become marginal or unstable. Implications for interpretation of recent experiments are discussed.

Alkylene Polyimides for Aligning Nematic Liquid Crystals: Anomalous Odd-Even Effect in Tilt Bias Angles as a Function of Chain Length of Alkylenes

Abstract: Measurements of tilt bias angles of a nematic liquid crystal were carried out, by using several alkylene polyimides synthesized from 3,3′,4,4′-biphenyltetracarboxylic dianhydrides and diamines with different chain lengths as alignment layers. The tilt bias angle dependence on the alkylene chain length of polyimides shows an anomalous odd-even effect. Small tilt bias angles, less than one degree, were observed with odd-number alkylene chain lengths. Relatively high tilt bias angles, however, were observed with even-number lengths. We have made an attempt to explain this effect from X-ray diffraction and scanning electron microscope measurements and molecular mechanics calculations of the polyimides with alkylene chain. As a result, this odd-even effect of the tilt bias angle is due to the difference of surface structures between alkylene polyimides with odd alkylene lengths and those with even ones.

Molecular tilt direction in a slightly tilted homeotropic aligned liquid crystal cell

Abstract: The influence of hardness and topology of substrate surface on the pretilt angle were investigated for a slightly tilted homeotropic alignment achieved by the rubbing technique. On a soft surface, the grooves are produced which align in the same direction as the rubbing direction while the liquid crystal molecules tilt in the direction opposite to the rubbing direction. On a hard surface, no grooves are observed and the molecules tilt in the same direction as the rubbing direction. These results were applied to the fabrication of a two‐domain vertically aligned nematic liquid crystal display.

Magnetic structure near (310) tilt boundaries in iron.

Abstract: The layer Korringa-Kohn-Rostoker method has been used to investigate the electronic and magnetic structure of an isolated, symmetric Σ5 Fe (310) tilt boundary The calculation shows an enhancement of the local magnetic moment at the grain boundary, which decays away rapidly from the region of the interface The magnitude and form of the enhancement is similar to that found near iron surfaces from recent tight-binding calculations

Tilt steering system

Abstract: In a tilt steering system, rockable teeth engage with or disengage from fixed teeth as a tilt lever is rotated. At the same time, a tilt bolt and a tilt nut are tightened or loosened. When the teeth engage each other, the tilt bolt and the tilt nut are tightened so that a fixed bracket is pressed against both sides of a vertically shifting bracket.

Method for testing an optical window with a small wedge angle

Abstract: The invention provides a technique for eliminating "ripple" or ghost fringes from a wavefront transmitted by an optical window with a very small wedge angle, distortions in the wavefront being measured by an interferometer. A collimated beam produced by the interferometer is transmitted through the optical window, which is tilted so as to prevent direct reflections from entering a detector of the interferometer. The beam transmitted through the window is reflected by a return flat back through the window and transmitted to the detector. The return flat is tilted slightly in the direction of or opposite to the direction of tilt of the window, causing the re-incident angle of the returned ray to be different from the original incident angle of the collimated beam. This causes the multiple reflections within the window to be different and to be out of phase. The ghost fringes are cancelled by appropriately tilting the return flat.

Axial tilt angles of active regions and their polarity separations

Abstract: Sunspot group and magnetic (plage) data are examined to search for a relationship between the tilt angles of active regions and the separations of their leading and following portions. A relationship is found in the sense that larger positive tilt angles are associated with larger polarity separations. This is the direction predicted by recent theoretical work (D'Silva and Choudhuri, 1992). The explanation for this appears to be that smaller surface polarity separations lead to larger magnetic tension forces, which diminish the effect of the Coriolis force that acts to twist rising flux tubes.

Wavefront error estimation derived from observation of arbitrary unknown extended scenes

Abstract: An extended scene wavefront sensing apparatus and procedure that separates (deconvolves) scene effects from wavefront errors of an optical or similar system. The present wavefront sensing apparatus and procedure uses a point source wavefront slope sensor in scene scanning mode and estimates wavefront errors by using a cross-correlation or cross-coherence procedure that operates on the outputs of the point source wavefront slope sensor. A signal processing procedure employed by the point source wavefront slope sensor provides output signals corresponding to wavefront slopes at forward optics pupil locations geometrically projected to the location of the transmission and reflection measurement plane detector pairs. During the scanning process, each of the detector pairs (equivalent to a subaperture) measures the effects of the local unchanging wavefront error in the forward optical system and temporal variations due to the scanning scene. By cross correlating or cross-cohering each detector pair's temporal difference with differences from selected reference detector pairs, the scene induced variations in the measurement are eliminated, thereby leaving the stationary wavefront error component of the measurement. The lead/lag time in the temporal differences output between detector pairs and reference detector pairs are then used to estimate the wavefront slope differences between equivalent subapertures. The wavefront slope differences are used in a reconstructor to generate wavefront errors or wavefront slope errors, except for an unobservable global tilt.