Showing papers on "Tilt (optics) published in 2008"

The Three-dimensional Evolution of Buoyant Magnetic Flux Tubes in a Model Solar Convective Envelope

Abstract: We present a set of three-dimensional spherical shell anelastic MHD simulations of the buoyant rise of magnetic flux tubes from the base of the convection zone to a depth of 16 Mm below the photosphere. It is found that when a twisted flux tube arches upward due to buoyancy, it rotates out of the plane and thus produces a tilt at the apex. Our simulations show that for tubes with the twist rate that is necessary for a cohesive rise, the twist-induced tilt dominates that caused by the Coriolis force, and furthermore, the twist-induced tilt is of the wrong direction (opposite to the observational Joy's law) if the twist is left-handed (right-handed) in the northern (southern) hemisphere, following the observed hemispheric preference of the sign of the active region twist. It is found that in order for the emerging tube to show the correct tilt direction (consistent with observations), the initial twist rate of the flux tube needs to be less than half of that needed for a cohesive rise. Under such conditions, severe flux loss is found during the rise. We also found that due to the asymmetric stretching of the rising tube by the Coriolis force, a field strength asymmetry develops, with the field in the leading leg (leading in the direction of rotation) of the Ω-shaped emerging tube being stronger than the field in the following leg, which results in a more compact morphology in the leading polarity of the emerging active region.

Disk drive comprising slanted line servo bursts having a varying tilt angle

Abstract: A disk drive is disclosed comprising a disk having servo data defining a plurality of servo tracks. The servo data comprises a preamble comprising a varying length across a radius of the disk, and a plurality of slanted line servo bursts recorded at a tilt angle with respect to the preamble. The tilt angle varies across the radius of the disk commensurate with the varying length of the preamble. A position error signal (PES) is generated in response to a phase difference when reading the preamble and the slanted line servo bursts.

Correction for non‐perpendicularity of beam and tilt axis in tomographic reconstructions with the IMOD package

Abstract: A correction for non-perpendicularity between the beam axis and the tilt axis in electron tomographic tilt series has been implemented in the IMOD software package and its value and limitations have been explored. Correction for this effect can provide a significant improvement in the alignment error and the reconstruction quality in some cases. However, when the projection model being fit includes an anisotropic shrinkage (i.e. stretch) in the plane of the specimen, adding a variable for the beam tilt does not produce a lower alignment error; it is thus not possible to distinguish between the effects of stretch and beam tilt. Test reconstructions indicate that an alignment solution that includes stretch will adequately correct for the effects of a beam tilt. For specimens subject to deformation under the beam, an alignment solution that accounts for stretch is preferable to one that accounts for beam tilt instead, provided that the markers used for alignment are sufficiently well distributed. Otherwise, a correction for beam tilt should be used.

Tilt menu: using the 3D orientation information of pen devices to extend the selection capability of pen-based user interfaces

Abstract: We present a new technique called 'Tilt Menu' for better extending selection capabilities of pen-based interfaces. The Tilt Menu is implemented by using 3D orientation information of pen devices while performing selection tasks. The Tilt Menu has the potential to aid traditional one-handed techniques as it simultaneously generates the secondary input (e.g., a command or parameter selection) while drawing/interacting with a pen tip without having to use the second hand or another device. We conduct two experiments to explore the performance of the Tilt Menu. In the first experiment, we analyze the effect of parameters of the Tilt Menu, such as the menu size and orientation of the item, on its usability. Results of the first experiment suggest some design guidelines for the Tilt Menu. In the second experiment, the Tilt Menu is compared to two types of techniques while performing connect-the-dot tasks using freeform drawing mechanism. Results of the second experiment show that the Tilt Menu perform better in comparison to the Tool Palette, and is as good as the Toolglass.

Tilt of emerging bipolar magnetic regions on the sun

Abstract: Magnetic fields emerging from the Sun's interior carry information about the physical processes of magnetic field generation and transport in the convection zone. A statistical analysis of variations of the tilt angle of bipolar magnetic regions during the emergence, observed from SOHO MDI, shows that the systematic tilt with respect to the equator (Joy's law) is established by the middle of the emergence period. This suggests that the tilt is most likely generated below the surface. However, the data do not show evidence of a dependence of the tilt angle on the amount of flux or a relaxation of the bipolar orientation toward the east-west direction, in contrast to the predictions of the rising magnetic flux rope theories.

Patellar tilt: the physical examination correlates with MR imaging.

Abstract: Patella malalignment is a recognized cause of knee pain, tilt being one of its more common forms Although patellar tilt has been described both on the physical examination and on computerized imaging, to date the correlation between the two has not been established A strong correlation would strengthen the value of each Moreover, in situations where tilt cannot be clinically assessed (eg obesity), CT or MR imaging could be an adequate substitute for the clinical determination of tilt We propose to correlate the physical examination with the magnetic resonance examination by way of an MR Tilt Angle This angle is measured in a manner similar to the assessment of tilt on the physical examination, in that a line is drawn across the medial and lateral borders of the patella and referenced off the posterior femoral condyles Most tilt angles use the slope of the lateral facet as a measure of tilt These tilt angles paradoxically diminish as patellar tilt increases , a potential source of confusion In this study, we use an MRI tilt angle that increases in the same direction as the actual tilt, which is more intuitive We examined 30 patients with tilt and 51 patients without tilt Patients with significant tilt on the physical examination can be expected to have an MRI Tilt Angle that is 10 degrees or greater whereas an angle of less than 10 degrees is associated with the absence of significant tilt on the physical examination This MRI Tilt Angle fills the need for an easy, objective, intuitive measure of tilt and is an excellent adjunct to the physical examination

Tracking solar collector assembly

Abstract: A tracking solar collector module assembly comprises a frame and a solar collector. The frame has a polar-equatorial orientable tilt axis. The solar collector is mounted to the frame and has a circumferential edge. The circumferential edge has a first edge portion substantially directed in a polar and westerly direction and a second edge portion substantially directed in a polar and easterly direction. The first edge portion and the second edge portion are at least substantially on opposite sides of the tilt axis. The first edge portion and second edge portion define an average included angle of 40° to 120°.

A spatio-temporally compensated acousto-optic scanner for two-photon microscopy providing large field of view.

Abstract: Acousto-optic deflectors (AOD) are promising ultrafast scanners for non-linear microscopy. Their use has been limited until now by their small scanning range and by the spatial and temporal dispersions of the laser beam going through the deflectors. We show that the use of AOD of large aperture (13mm) compared to standard deflectors allows accessing much larger field of view while minimizing spatio-temporal distortions. An acousto-optic modulator (AOM) placed at distance of the AOD is used to compensate spatial and temporal dispersions. Fine tuning of the AOM-AOD setup using a frequency-resolved optical gating (GRENOUILLE) allows elimination of pulse front tilt whereas spatial chirp is minimized thanks to the large aperture AOD.

On The Origin of the Blue Tilt in Extragalactic Globular Cluster Systems

Abstract: Some early-type galaxies show a correlation between color and integrated magnitude among the brighter metal-poor globular clusters (GCs). This phenomenon, known as the blue tilt, implies a mass-metallicity relationship among these clusters. In this paper we show that self-enrichment in GCs can explain several aspects of the blue tilt, and discuss predictions of this scenario.

Temperature-insensitive fiber Bragg grating tilt sensor

Abstract: A temperature-insensitive optical fiber tilt sensor is presented. The sensor scheme uses a prestrained fiber Bragg grating to sense the strain, which depends on the tilt angle. To compensate for the temperature effect, materials that have different linear thermal expansion behaviors are used for implementation of the sensor body. The differentiation in the linear thermal expansion would then cause a counter effect to the original temperature effect. Experimental tests show an accuracy of ±0.167° in tilt angle measurement. A temperature stability better than ±0.33° over the temperature range from 27 °C to 75 °C is demonstrated. The resolution 0.0067° in tilt angle measurement is achieved by using our preliminary sensor with a dimension of 16×5×5 cm3.

Changes in crystalline lens radii of curvature and lens tilt and decentration during dynamic accommodation in rhesus monkeys

Abstract: Dynamic changes in crystalline lens radii of curvature and lens tilt and decentration were measured during centrally stimulated accommodation in four iridectomized eyes of two adolescent rhesus monkeys. Phakometry measurements were performed dynamically using a custom-built, video-based, Purkinje-image instrument. Lens anterior and posterior radii were calculated from reflections of paired light sources from the ocular surfaces (Purkinje images PI, PIII, and PIV). Lens tilt and decentration were calculated assuming linearity between Purkinje image positions, eye rotation, lens tilt, and decentration. Because the monkey eyes were iridectomized, Purkinje images were referred to the mid-point of the double first Purkinje image (PI). Mean unaccommodated values of anterior and posterior lens radii of curvature were 11.11 +/- 1.58 mm and -6.64 +/- 0.62 mm, respectively, and these decreased relatively linearly with accommodation in all eyes, at a rate of 0.48 +/- 0.14 mm/D and 0.17 +/- 0.03 mm/D for anterior and posterior lens surfaces, respectively. Tilt and decentration did not change significantly with accommodation except for tilt around the horizontal axis, which changed at a rate of 0.147 +/- 0.25 deg/D. These results are important to fully characterize accommodation in rhesus monkeys.

Frequency-Selective Coding of Translation and Tilt in Macaque Cerebellar Nodulus and Uvula

Abstract: Spatial orientation depends critically on the brain's ability to segregate linear acceleration signals arising from otolith afferents into estimates of self-motion and orientation relative to gravity In the absence of visual information, this ability is known to deteriorate at low frequencies The cerebellar nodulus/uvula (NU) has been shown to participate in this computation, although its exact role remains unclear Here, we show that NU simple spike (SS) responses also exhibit a frequency dependent selectivity to self-motion (translation) and spatial orientation (tilt) At 05 Hz, Purkinje cells encode three-dimensional translation and only weakly modulate during pitch and roll tilt (04 ± 005 spikes/s/°/s) But this ability to selectively signal translation over tilt is compromised at lower frequencies, such that at 005 Hz tilt response gains average 20 ± 03 spikes/s/°/s We show that such frequency-dependent properties are attributable to an incomplete cancellation of otolith-driven SS responses during tilt by a canal-driven signal coding angular position with a sensitivity of 39 ± 03 spikes/s/° This incomplete cancellation is brought about because otolith-driven SS responses are also partially integrated, thus encoding combinations of linear velocity and acceleration These results are consistent with the notion that NU SS modulation represents an internal neural representation of similar frequency dependencies seen in behavior

Structural Setting of the Northeastern Biga Peninsula (Turkey) from Tilt Derivatives of Gravity Gradient Tensors and Magnitude of Horizontal Gravity Components

Abstract: The tilt derivatives (or angles) are determined using the gravity gradient tensors (GGT) from two horizontal components (Gx, Gy) and vertical component (Gz), and the magnitude of the horizontal components (MHC). We show that the tilt derivatives from GGT and MHC are highly suitable for mapping linear geological structures or edges of target geology. The results obtained from theoretical data, with and without random noise, have been analyzed in this study. The tilt derivatives from GGT and MHC allow imaging the horizontal boundaries of gravity sources with a high resolution and show an improvement performance as edge detectors since they are ultra sensitive for detecting source boundaries.

Projection image display apparatus

Abstract: A projection image display apparatus includes a lens unit into which light modulated in accordance with an image signal is entered, a first reflecting mirror having a reflecting surface into which the light passing through the lens unit is entered and by which the light is converged, a second reflecting mirror for reflecting the light reflected by the first reflecting mirror, and a mirror actuator for changing a tilt angle of the second reflecting mirror with respect to the light.

Body-tilt and visual verticality perception during multiple cycles of roll rotation.

Abstract: To assess the effects of degrading canal cues for dynamic spatial orientation in human observers, we tested how judgments about visual-line orientation in space (subjective visual vertical task, SVV) and estimates of instantaneous body tilt (subjective body-tilt task, SBT) develop in the course of three cycles of constant-velocity roll rotation. These abilities were tested across the entire tilt range in separate experiments. For comparison, we also obtained SVV data during static roll tilt. We found that as tilt increased, dynamic SVV responses became strongly biased toward the head pole of the body axis (A-effect), as if body tilt was underestimated. However, on entering the range of near-inverse tilts, SVV responses adopted a bimodal pattern, alternating between A-effects (biased toward head-pole) and E-effects (biased toward feet-pole). Apart from an onset effect, this tilt-dependent pattern of systematic SVV errors repeated itself in subsequent rotation cycles with little sign of worsening performance. Static SVV responses were qualitatively similar and consistent with previous reports but showed smaller A-effects. By contrast, dynamic SBT errors were small and unimodal, indicating that errors in visual-verticality estimates were not caused by errors in body-tilt estimation. We discuss these results in terms of predictions from a canal-otolith interaction model extended with a leaky integrator and an egocentric bias mechanism. We conclude that the egocentric-bias mechanism becomes more manifest during constant velocity roll-rotation and that perceptual errors due to incorrect disambiguation of the otolith signal are small despite the decay of canal signals.

Stitching of off-axis sub-aperture null measurements of an aspheric surface

Abstract: Optical testing of a large convex aspheric surface, such as the secondary of a Ritchey-Chretien telescope, can be performed with a Fizeau interferometer that utilizes subapertur e aspheric reference plates, each providing a null test of a subaperture of the larger mirror. The subaperture data can be combined or stitched together to create a map of the full surface. The region of the secondary mirror surface under test in each sub-aperture is an off-axis segment of the parent aspheric surface, therefore, the Fizeau reference requires a non-axi-symmetric aspheric surface to match it. Misalignment of the Fizeau reference relative to the parent in each sub-aperture will then result in aberrations in the measurements other than the ordinary terms of piston and tilt. When stitching sub-aperture measurements together, the apparent aberrations due to the null lens misalignment need to be fitted and subtracted. This paper presents an algorithm to perform this particular type of stitching. Keywords: optical testing, stitching, aspheric optics

Effects of contact geometry on pull-off force measurements with a colloidal probe.

Abstract: This paper examines the effects of contact geometry on the pull-off (adhesion) force between a glass sphere (colloidal probe) and a silicon wafer in an environment with controlled relative humidity. An atomic force microscope is used to measure the pull-off force between the colloidal probe and the sample mounted at different tilt angles. The results show that the measured pull-off force is very sensitive to the tilt angle. Through the use of a newly developed direct scanning method, the exact contact geometry is determined for the zero-tilt angle case. The obtained digital image is then rotated to determine the contact geometry for the cases with other tilt angles. A detailed examination of the contact geometry, along with a magnitude analysis of the capillary force, suggests that the adhesion is most likely dominated by the capillary force from the meniscus formed between the probe and the sample. The strong dependence of the adhesion on the tilt angle may result from the change of meniscus dimensions associated with the probe-sample separation, which in turn is controlled by the highest peak on the probe sphere. Our observation emphasizes the combined role of microsurface shape near the contact and nanoroughness within the contact in determining the colloidal probe pull-off force and also microadhesion force in general.

Modeling Spatio-Temporal Dynamics of Optimum Tilt Angles for Solar Collectors in Turkey

Abstract: Quantifying spatial and temporal variations in optimal tilt angle of a solar collector relative to a horizontal position assists in maximizing its performance for energy collection depending on changes in time and space. In this study, optimal tilt angles were quantified for solar collectors based on the monthly global and diffuse solar radiation on a horizontal surface across Turkey. The dataset of monthly average daily global solar radiation was obtained from 158 places, and monthly diffuse radiation data were estimated using an empirical model in the related literature. Our results showed that high tilt angles during the autumn (September to November) and winter (December to February) and low tilt angles during the summer (March to August) enabled the solar collector surface to absorb the maximum amount of solar radiation. Monthly optimum tilt angles were estimated devising a sinusoidal function of latitude and day of the year, and their validation resulted in a high R2 value of 98.8%, with root mean square error (RMSE) of 2.06°.

Newly Structured Double Excited Two-Degree-of-Freedom Motor for Security Camera

Abstract: This paper proposes a newly structured double excited two-degree-of-freedom (DOF) motor with tilt/pan motion to use in a security camera. For applications in active vision, a tilt/pan mechanism should be accurate, fast, small, inexpensive, and have low power requirements. We have designed a new type of motor meeting these requirements, which incorporates both tilt and pan into a single, two-degree-of-freedom device. The focus of the research is to design the improved 2-DOF motor which can eliminate the drawbacks as manufacturing, complicated control, and difficulty in lamination in conventional model. Additionally, to effectively improve the torque characteristic, the main pole pitch and the auxiliary pole shape are determined by the pan motion and the tilt motion, respectively. The validity of proposed structure will be shown in the computer simulation of the newly structured double excited 2-DOF motor for security cameras.

Medical device and medical instrument alignment

Abstract: Systems and methods for orienting a medical instrument relative to at least a portion of a medical device include a first tilt detector associated with the medical instrument and a second tilt detector associated with the medical device. The first tilt detector may be within an orientation device that is coupled to or separate from the medical instrument. The tilt detectors generate signals that may be used to determine the relative orientation between at least a portion of the medical device and medical instrument. For example, in some embodiments, the signals may be used to determine whether the orientations of the portion of the medical device and the medical instrument substantially match.

Single drive variable azimuth and beam tilt antenna for wireless network

Abstract: An antenna array employing a combined azimuth and elevation beam angle adjustment electromechanical system is disclosed. The system employs a dual purpose remotely controllable actuator. The actuator is used to adjust azimuth angle of the antenna array and radiation beam tilt of the same. An antenna array employing a combined azimuth, beamwidth and elevation beam angle adjustment electromechanical system is also disclosed.

The influence of beam position and swimming direction on fish target strength

Abstract: Henderson, M. J., Horne, J. K., and Towler, R. H. 2007. The influence of beam position and swimming direction on fish target strength. - ICES Journal of Marine Science, 65: 226-237.Fish orientation is consistently identified as a major influence on fish target strength (TS). Generally, orientation is defined as the tilt angle of the fish with respect to the acoustic transducer, whereas a more accurate definition includes tilt, roll, and yaw. Thus far, the influences of roll and yaw on fish TS have only been examined cursorily. We used in situ single-target data to create fish tracks, to estimate fish tilt and yaw, and correlated these estimates with TS. The results show that tilt, yaw, and beam position have a significant influence on fish TS. To investigate further how yaw and beam position affect TS, we calculated the expected backscatter from each fish within simulated fish aggregations using a backscatter model. The TS of individual fish at 38 and 120 kHz varied by as much as 11 and 19 dB with changes in yaw and beam position. Altering the fish’s tilt, yaw, and beam position resulted in TS differences of 14 and 26 dB at 38 and 120 kHz, respectively. Orientation had a minimal influence on an aggregation’s average TS if the aggregation had a variable tilt-angle distribution and was dispersed throughout the acoustic beam.

Interaural self-motion linear velocity thresholds are shifted by roll vection

Abstract: The otolith organs respond equivalently to changes in gravitational force due to head tilt and to changes in inertial force due to linear acceleration. It has been shown that the central nervous system (CNS) uses internal models of the laws of physics to distinguish tilt from translation. Models with these internal models predict that illusory tilt, if large enough, will be accompanied by an illusion of linear motion. To investigate this prediction, we measured interaural, self-motion, direction-detection thresholds in darkness and with roll optokinetic stimulation. Each lateral translation consisted of a single cycle of sinusoidal acceleration, after which subjects indicated whether they translated to the left or right. We found that the interaural direction-detection threshold measured during clockwise and counterclockwise optokinetic stimulation shifted in opposite directions relative to thresholds in darkness. Using a generalized linear model, we determined that this finding was statistically significant (P < 0.005) and is consistent with the prediction that illusory tilt should be accompanied by a non-zero neural estimate of linear velocity that, if large enough (supra-threshold), contributes to translation perception.

Device mount with selectively positionable tilt axis

Abstract: A mounting system for an electronic display device includes a display interface having an interface member presenting a display mounting surface and a tilt head assembly defining a substantially horizontal tilt axis oriented generally parallel with, and spaced apart from, the display mounting surface. The tilt head assembly includes a control mechanism for selectively shifting the tilt axis between a first location spaced apart a first distance from the display mounting surface and a second location spaced apart a second distance from the display mounting surface, wherein the second distance is greater than the first distance.

Flight test results of automatic tilt control for small scaled tilt rotor aircraft

Abstract: A small scaled flight model of the tilt rotor aircraft for the Smart UAV Program at KARI(Korea Aerospace Research Institute) has been developed and tested. Since the flight characteristics of a tilt rotor aircraft are new to KARI, the scaled model was used as a test bed to evaluate the flight control algorithm for the full scale smart UAV. The flight test of the small scaled model was performed after various ground tests including tethered hover test. The control laws in initial phase consist of rate SAS feedbacks, control surface mixers, a rotor governor and a manual tilt command path. A rate feedback SCAS control law was used in order to evaluate the flight characteristics of the tilt rotor aircraft. As the flight test proceeds, an attitude SCAS was added because the attitude of aircraft was not clearly recognized due to the small size and fast speed of the aircraft. The first full conversion to a fixed wing mode was made through the manual tilt command by the external pilot. And then the automatic conversion was successfully performed by speed hold command in compliance with a pre-defined conversion corridor. Several problems unexpected were found during flight tests including oscillation of long period mode near helicopter mode, a delayed response to the altitude command and etc. The flight test results of the small scaled tilt rotor aircraft using an automatic tilt control is described in this paper and the solutions of the problems noticed in the flight test are presented.

Optimal Light Beams and Mirror Shapes for Future LIGO Interferometers

Abstract: We report the results of a recent search for the lowest value of thermal noise that can be achieved in LIGO by changing the shape of mirrors, while fixing the mirror radius and maintaining a low diffractional loss. The result of this minimization is a beam with thermal noise a factor of 2.32 (in power) lower than previously considered Mesa Beams and a factor of 5.45 (in power) lower than the Gaussian beams employed in the current baseline design. Mirrors that confine these beams have been found to be roughly conical in shape, with an average slope approximately equal to the mirror radius divided by arm length, and with mild corrections varying at the Fresnel scale. Such a mirror system, if built, would impact the sensitivity of LIGO, increasing the event rate of observing gravitational waves in the frequency range of maximum sensitivity roughly by a factor of 3 compared to an Advanced LIGO using Mesa beams (assuming all other noises remain unchanged). We discuss the resulting beam and mirror properties and study requirements on mirror tilt, displacement, and figure error, in order for this beam to be used in LIGO detectors.

Alignment tool for directional antennas

Abstract: A tool and method for aligning directional antennas quickly and accurately in azimuth, tilt and roll. The tool includes a housing, mounting brackets for securing the tool to an antenna, a data storage device including predetermined alignment information, a GPS system for measuring azimuth, and inclinometers for measuring tilt and roll. The tool also includes displays for displaying the measured values of the azimuth, tilt, and roll relative to the predetermined parameters. As a result, a user can easily align an antennas based on the azimuth, tilt, and roll information measured and displayed by the tool.

Computer-readable storage medium having stored therein information processing program and information processing apparatus

Abstract: A controller includes imaging means for capturing predetermined imaging targets and acceleration detecting means for detecting an acceleration applied to an input device. Based on a tilt which is related to images, included in a captured image captured by the imaging means, of the imaging targets and which is included in the captured image, a game apparatus calculates, as a first tilt, a tilt of the controller which is related to a rotation around an axis of a capturing direction of the imaging means. Further, based on the acceleration detected by the acceleration detecting means, the game apparatus calculates, as a second tilt, a tilt which is related to a rotation around an axis of a direction different from the capturing direction. The game apparatus executes a predetermined process using the first tilt and the second tilt as an orientation of the controller.