Showing papers on "Tilt (optics) published in 1980"

Solid and fluid phases in smectic layers with tilted molecules

Abstract: A recent theory of two-dimensional melting is applied to freely suspended liquid-crystal films with a tilt degree of freedom. As many as seven distinct phases are possible, including those we identify with smectic-$A$, -$B$, -$C$, and -$H$ liquid crystals. Some of these phases may survive when stacked to form bulk smectics.

Alignment of liquid crystals on obliquely evaporated silicon oxide films

Abstract: Liquid crystal alignment on thin films obliquely deposited by electron beam evaporation of SiO2 is reported Films deposited at a glancing angle of 5° give high tilt alignment ?45°, while increasing the deposition angle to 30° gives zero tilt alignment Scanning electron microscope (SEM) pictures relate surface topography to alignment The material and temperature dependence of tilt are reported The tilt is constant through the nematic‐smectic A transition

Investigations of tilt measurements using shallow borehole tiltmeters

Abstract: An array of shallow borehole tiltmeters has been operated at Pinon Flat Observatory since early in 1977. The data from this array are examined for coherence between the individual instruments and compared with the corresponding data from three 732-m laser strainmeters. In general, there is no significant coherence between the signals from the tiltmeters outside the microseismic and tidal bands even though they are spaced as closely as 10 m apart. Comparisons with the strain records show that the observed tilt noise power exceeds the strain noise power by 25-40 dB over the band from 0.000001 to 1 Hz. Analysis of the coherence estimates establishes the necessity for an unacceptably large (approximately 1000) array of instruments in order to determine the common tectonic signals. The observed secular tilt rates are from 40 to 450 times the observed secular strain rates for the same period. The theoretical noise power limit of the tilt transducer renders the instrument incapable of recording background noise at a quiet site over the band from 0.0001 to 0.1 Hz.

Real-Time Measurement of In-Plane Translation and Tilt by Electronic Speckle Correlation

Abstract: A new real-time method of measuring in-plane translation and tilt angle of diffusely reflecting surfaces is presented. We determine the speckle displacement induced by the translation and tilt from the peak position of the cross-correlation function of the outputs of a linear image sensor positioned in the speckle field. From experiments using a microcomputer system we obtained good agreement between theory and experiments for translation between -500 µm to +500 µm and also for tilt angle ranging from -0.3 deg to +0.3 deg. Several ways for extending the capabilities of the method are suggested.

CRT Housing support and rocking tilt apparatus

Abstract: For use with a display unit for a word processing system, apparatus is provided for support of the display unit to allow the operator to easily and quickly change the tilt angle of the display unit and retain the tilt angle after a change thereof. The support and rocking tilt apparatus is mounted to the base of the display unit and includes fore/aft retention by a spur gear form on the upper support unit and a rack gear form on the lower support unit, which co-locates the origin of the arc of the rocker, the center of gravity and the origin of the arc of the pitch diameter of the spur gear of the display unit through the tilt range. Rocker means associated with the gear forms provides side-to-side retention of the support and rocking tilt apparatus. Vertical retention apparatus is combined with a snubbing device, including a spring-loaded friction mechanism, which provides infinite actuation throughout the tilt range.

Lamp socket mounting and adjusting assembly

Abstract: A lamp socket mounting and adjusting assembly for an outdoor lighting luminaire in which the lamp socket is secured to an adjustable socket mounting plate which is variably positionable with respect to a socket mounting bracket to vary both the focal point and the focal tilt axis of the lamp. Separate sets of indicia on the socket mounting bracket indicate both the focal axis tilt and the focal point selected for the lamp.

Tilt steering of tandem wheeled or runner equipped vehicle

Abstract: This invention pertains to a novel approach toward steering of vehicles such as roller skates, skateboards, bicycles, motorcycles & etcetera where the wheels or runners of such vehicle are arranged in a tandem configuration and the steering achieved through sidewise tilt of the vehicle.

Development of the Crustal Tilt Observation Method Using Borehole-type Tiltmeters

Abstract: Continuous monitoring of the crustal tilt is one of the most effective approaches for the purpose of earthquake prediction. Drilling a borehole is not so expensive as construction of an underground vault, which is necessary for installation of water-tube tiltmeters and horizontal pendulum tiltmeters, and a borehole station is possible to be made even in a plain area. The National Research Center for Disaster Prevention has not only developed the boreholetype tiltmeter itself but has improved borehole drilling techniques and installation methods for the tiltmeter. The force-balanced pendulum tiltmeter developed for down-hole observation is installed at the bottom of the borehole of which the depth is about 100m. The measuring range is +2 x 10-4 radian, the resolution is 6 x 10-9 radian, and the long term drift is smaller than a few micro-radian per year after half a year since the installation. Clear records of the earth tides demonstrate the high quality of the instrument. Tilt changes of the order of micro-radian caused by precipitation are remarkable in the data of some stations. But, the crustal tilt observation by using borehole-type tiltmeters is expected to be very effective for detecting anomalous tilt changes of the order of 5 x 10-8 radian per day with a time constant of several hours to several tens of days.

Computer simulation of the structure and atomic vibration of the Σ=5 tilt boundary in aluminium

Abstract: The structure of the Sigma =5 tilt grain boundary in aluminium was simulated by molecular dynamics using the Morse potential. Two types of structure were obtained. The local density of states (LDS) of phonons was calculated by the recursion method developed by Haydock and colleagues. The Debye parameters ( theta D(n)) were found to be very small near the boundary plane and there were large mean atomic displacements in the direction perpendicular to the boundary plane.

Effect of off-vertical tilt and macular ablation on postrotatory nystagmus in the squirrel monkey

Abstract: The slow phase eye velocity (SPEV) and duration of post-rotatory nystagmus (PRN) were studied in squirrel monkeys (Saimiri sciureus) after a ramp speed rotation (0–200°/sec, with 1°/sec2 angular acceleration). When the results were compared between straight upright vertical rotation, 9° tilt rotation, and 18° tilt rotation, faster decay both in SPEV and in duration was found in the tilt rotation situations. Difference in nystagmic decay curves by tilting rotation axis could be from the convergence of macula-semicircular canal inputs. Subsequently bilateral macular ablation (two-stage) was performed. The difference in nystagmus decay curves between three different rotations was reduced; therefore, the change of gravity direction perceived through gravity receptors other than macular end organs was minimal and did not produce a difference in three different rotations.

Perception at the Blind Spot and Tilt Aftereffect

Abstract: Black and white stripes were used to induce a tilt aftereffect near the blind spot. Stripe fragments on either side of the blind spot were seen as being completed across the blind spot, but the magnitude of the tilt aftereffect they induced suggested that the perceptually "filled-in" portions of the stripes did not contribute to the aftereffect. So perceptually filled-in lines seem not to be fully potent percepts.

Camera Viewfinder Using Tilted Concave Mirror Erecting Elements

Abstract: The camera viewfinder would consist of a two-element objective lens, a field stop, a tilted concave mirror, an aperture stop, a second tilted concave mirror, and a two-element eyepiece. This forms a Z shaped configuration with the mirrors at the corners of the Z. The two mirrors, with the aperture stop midway between them, form a 1:1 telescopic erecting relay system. Two types of mirrors are studied: spherical and parabolic. The main problems encountered in the spherical mirror system are axial astigmatism and field tilt, both caused by the tilted mirrors. By using confocal, coaxial, decentered parabolic mirrors, with the aperture stop at the common focal point, the axial astigmatism can be eliminated; however, the field tilt problem is aggravated. By rotating the axis of the second parabolic mirror about the common focal point, the field tilt can be minimized, and the astigmatism in all beams eliminated. This last configuration is, however, plagued by distortion and coma. We conclude that none of these systems is satisfactory for image quality.

Accurate Optical Measurement of Small Tilt Angles in Thin Twisted Nematic Layers

Abstract: Liquid crystal (LC) molecules have a preferred orientation on a bounding surface. The angle, αo, that they form with the surface in the absence of applied fields is called the initial tilt angle and is an important measure of the liquid crystal-surface interaction.

A Graphic Approach To The Analysis Of Perturbed Optical Systems

Abstract: An analytical approach to determining the effects of tilts and decenters on an optical design has been developed. The work has been guided by the desire to provide rapid insight into the cause-and-effect relationship between a component perturbation and the degradation in some measure of image quality. This is done by providing a graphical display of the properties of aberration fields under the influence of tilt and decenter perturbations, and contour plots of the change in the RMS wavefront error or change in RMS spot size over the entire field.

Tilt compensating pendulum for seat mounted retractor

Abstract: A pendulum for a retractor to be mounted on a tiltable vehicle seat in which the pendulum cap is tiltable in the direction of seat tilt prior to actuation by a collision force.

Horizontal directionality estimation considering array tilt and noise field vertical arrival structure

Abstract: A new approach to undersea ambient noise field horizontal directionality estimation from towed line array data is presented. This new technique includes the effects of the three‐dimensional array response and the noise field vertical arrival structure during the estimation process. It is sufficiently general to include the angle of array tilt from the horizontal and does not require noise field stationarity as do most previous methods. The vertical dimension is included in the estimation process through a transformation of the noise field from a spherical coordinate system to a conical coordinate system of the array with an arbitrary tilt angle. The three‐dimensional pseudostationary noise field estimate ? (ϑ,φ) which results is then integrated over the vertical (φ) to obtain the horizontal directionality estimate ? (ϑ). The results indicate significant improvement in ? (ϑ) when the array tilt and noise vertical arrival structure are accounted for.

Directional two axis optical inclinometer

Abstract: An inclinometer which employs a laser light source with a transparent liq and a gas and the laws of optics to reflect the light source to a detector which provides signals for measuring the tilt angle and the direction of tilt from the local horizontal.

Lateral shear interferometer using twin three-beam holograms.

Abstract: A lateral shear interferometer using twin three-beam holograms is described. In the interferometer two first-order diffracted light beams from the first hologram play the role of a beam splitter; the second hologram eliminates the effect of tilt. This interferometer has two advantages over the single three-beam hologram lateral shear interferometer: (1) it can be used for small f/No. lens tests; (2) any small aberration of the optical system of the interferometer can be canceled by using the second hologram. In this paper, shearing interferograms of lens aberration, of refractive indices around a flame, and of spouting gas are demonstrated.

Aimable mounting apparatus

Abstract: A disc-shaped member-to-be-aimed is mounted for tilting about two mutually perpendicular tilt axes rotatable about a third and mutually perpendicular boresight axis that affords a conical field of view for the member in the presence of any asymmetry in its tilting about the tilt axis. A multi-gimbal assembly accommodates such multiple-axis movement freedom, and torque motors disposed in an axialwise direction at one side of the member-to-be-aimed affords radial compactness for the gimbal assembly.

Device Parameters And Optical Performance Of A Stacked Actuator Deformable Mirror

Abstract: A discrete-actuator, deformable mirror has been characterized for use in the infrared spectral region. This device, with a clear aperture diameter of nine inches, achieves a surface deformation of 8.5 μm at 1500 volts. Conformity of the reflective surface with a desired figure has been determined by interferometric analysis and residual error computation for focus, tip, tilt and two orders of astigmatism.

Overwater radar navigation system

Abstract: A system is provided for correcting the assumed orientation of the horizontal plane of an inertial navigation system on an aircraft, while it is flying over the ocean. The range from the aircraft to the ocean surface is measured along a boresight tilted at a small downward angle such as 6° to 12° from the horizontal, as by radar ranging, and the precise range and the precise tilt angle of the boresight with respect to the inertial or other horizontal is taken. The measured range is compared with an independently-derived range, and the difference is utilized to correct the assumed horizontal direction of the navigation system. The second range may be the range calculated on the basis of the downward tilt angle of the boresight from the assumed horizontal direction in the inertial navigation system, and the difference between the real and calculated ranges can be utilized to determine the error in the assumed horizontal direction of the inertial system.

Alignment Of A Full Aperture System Test Of A Cassegrain Telescope

Abstract: The misalignment of the secondary and primary mirrors, in a full aperture Cassegrain test, introduces coma and astigmatism into the wavefront. Equations were derived which relate the magnitude and orientations of these two aberrations to the tilt and decenter of one mirror with respect to the other when tested in an autocollimating mode. By determining the coma and astigmatism, introduced into the wavefront, using Zernike circle polynomial fitting techniques, the tilt and decenter correction can be computed which would optically align the secondary to primary. These alignment equations were verified by using a Space Telescope optical' formula, misaligning the secondary mirror, and calculating the resulting coma and astigmatism in the wavefront. The tilt and decenter, necessary to realign the two mirrors of the Space Telescope were calculated from the derived equations, and found to agree with the perturbed secondary mirror misalignment. An autocollimation test procedure will be described for obtaining the full aperture wavefront of a Cassegrain-type system, both on-axis and in the field.