Showing papers on "Tilt (optics) published in 2005"

Pelvic tilt makes acetabular cup navigation inaccurate

Abstract: Background Modern navigation techniques allow precise positioning of the acetabular cup relative to the anterior pelvic plane. Variations in pelvic tilt will affect the resulting spatial orientation of the cup.Methods We measured pelvic tilt in 30 volunteers with an inclinometer combined with an ultrasonographic position measurement system. A mathematical algorithm was developed to calculate the resulting cup position measured on standard radiographs, depending on pelvic tilt.Results Average pelvic tilt at rest was −4° in the lying position and −8° in the standing position, and ranged from −27° to +3°. Pelvic reclination of 1° will lead to functional anteversion of the cup of approximately 0.7°.Interpretation Pelvic tilt makes navigation systems referring to the anterior plane inaccurate.

Generating the curvature perturbation at the end of inflation

Abstract: The dominant contribution to the primordial curvature perturbation may be generated at the end of inflation. Taking the end of inflation to be sudden, formulae are presented for the spectrum, spectral tilt and non-Gaussianity. They are evaluated for a minimal extension of the original hybrid inflation model.

Generating the curvature perturbation at the end of inflation

Abstract: The dominant contribution to the primordial curvature perturbation may be generated at the end of inflation. Taking the end of inflation to be sudden, formulas are presented for the spectrum, spectral tilt and non-gaussianity. They are evaluated for a minimal extension of the original hybrid inflation model.

Mobile terminal apparatus

Abstract: A mobile terminal apparatus 1 uses an acceleration sensor as a tilt angle sensor 24 , and realizes various applications based on this detection result. A processing unit 10 counts the number of steps of a human based on acceleration components of low frequency detected by the tilt angle sensor that detects the acceleration components. At that time, the acceleration component of an axis among three axes which most approximates a gravity axis is mainly used. A viewpoint relative to a three-dimensional object or a three-dimensional space displayed on a display unit 36 is moved. By effectively utilizing the detection result of the tilt angle sensor, it is possible to realize a mobile terminal apparatus 1 featuring greater usefulness.

Relative angle determinable stitching interferometry for hard x-ray reflective optics

Abstract: Metrology plays an important role in surface figuring with subnanometer accuracy. We have developed relative angle determinable stitching interferometry for the surface figuring of elliptical mirrors, in order to realize hard x-ray nanofocusing. In a stitching system, stitching angles are determined not by the general method using a common area between neighboring shots, but by the new method using the mirror’s tilt angles measured at times when profile data are acquired. The high measurement accuracy of approximately 4nm (peak-to-valley) was achieved in the measurement of a cylindrical surface having the same curvature as the elliptically designed shape to enable hard x-ray nanofocusing.

Tilted ghost inflation

Abstract: In a ghost inflationary scenario, we study the observational consequences of a tilt in the potential of the ghost condensate. We show how the presence of a tilt tends to make contact between the natural predictions of ghost inflation and the ones of slow roll inflation. In the case of positive tilt, we are able to build an inflationary model in which the Hubble constant H is growing with time. We compute the amplitude and the tilt of the two-point function, as well as the three-point function, for both cases of positive and negative tilt. We find that a good fraction of the parameter space of the model is within experimental reach.

Inductive tilt sensor with magnets and magnetic fluid

Abstract: The paper presents a new type of tilt inductive sensor using four magnets and a magnetic fluid. The determination of the sensor sensibility is performed with theoretical predictions based on the potential magnetic energy function of the assembly constituted by two repulsion magnets. This energy function is experimentally determined. The sensor sensibility varies in conformity to a power law depending on the initial distance between two repulsion magnets. The sensor supplies a signal proportional with the tilt.

Method and apparatus for optimizing speakerphone performance based on tilt angle

Abstract: According to the present invention, a tilt sensor is used to determine the tilt angle of a speakerphone and the surface on which it rests. This information is used to optimize both the receive and transmit signals for the chosen tilt angle. The information can also be used to adjust performance of any beamformer(s) where the speakerphone incorporates a microphone array or loudspeaker array. In one embodiment, vibrational data is provided by the tilt sensor for enhancing the receive signal and acoustic echo cancellation.

Pyramid sensor for segmented mirror alignment.

Abstract: We report what is to our knowledge the first laboratory experiment that shows the use of a pyramid wavefront sensor to cophase and align segmented mirrors having three degrees of freedom per segment, i.e., piston, tip, and tilt. In the laboratory the iterative alignment procedure reached a wavefront residual error of about 10 nm. The residual error was equally distributed between piston, tip, and tilt. These results demonstrate that the pyramid can successfully simultaneously sense the piston, tip, and tilt of a segmented mirror. This last feature makes this technique very attractive in phasing and aligning astronomical segmented telescopes such as extremely large telescopes currently under extensive studies.

Electrical resistance of low-angle tilt grain boundaries in acceptor-doped SrTiO3 as a function of misorientation angle

Abstract: The transport of charge across symmetrical low-angle [001] tilt grain boundaries in Fe-doped SrTiO3 was examined. Grain boundary resistances were obtained from impedance spectroscopy measurements on bicrystals with misorientation angles θ=2.3°, 5.4°, and 7.8° as a function of temperature and oxygen partial pressure. By comparing these data with values predicted from a double Schottky-barrier model, we show that the resistance of a low-angle tilt grain boundary in acceptor-doped SrTiO3 is correlated with its dislocation content, but in a nontrivial manner.

Determination of mechanical and electronic shifts for pinhole SPECT using a single point source

Abstract: The effects of uncompensated electronic and mechanical shifts may compromise the resolution of pinhole single photon emission computed tomography. The resolution degradation due to uncompensated shifts is estimated through simulated data. A method for determining the transverse mechanical and axial electronic shifts is described and evaluated. This method assumes that the tilt of the detector and the radius of rotation (ROR) are previously determined using another method. When this assumption is made, it is possible to determine the rest of the calibration parameters using a single point source. A method that determines the electronic and mechanical shifts as well as the tilt has been previously described; this method requires three point sources. It may be reasonable in most circumstances to calibrate tilt much less frequently than the mechanical shifts since the tilt is a property of the scanner whereas the mechanical shift may change every time the collimator is replaced. An alternative method for determining the ROR may also be used. Lastly, we take the view that the transverse electronic shift and the focal length change slowly and find these parameters independently.

Tilt recorded by a portable broadband seismograph: The 2003 eruption of Anatahan Volcano, Mariana Islands

Abstract: [1] The horizontal components of broadband seismographs are highly sensitive to tilt, suggesting that commonly deployed portable broadband seismic sensors may record important tilt information associated with volcanic eruptions. We report on a tilt episode that coincides with the first historical eruption of Anatahan volcano on May 10, 2003. The tilt was recorded by a Strekheisen STS-2 seismograph deployed in an underground insulated chamber 7 km west of the active vent. An ultra-long period signal with a dominant period of several hours was recorded on the E-W component beginning at 06:20 GMT on May 10, which coincides with the onset of continuous volcano-tectonic (VT) seismicity and is one hour prior to the eruption time estimated by the Volcanic Ash Advisory Center. The signal is much smaller on the N-S component and absent on the vertical component, suggesting it results from tilt that is approximately radial with respect to the active vent. An estimate of tilt as a function of time is recovered by deconvolving the record to acceleration and dividing by the acceleration of gravity. The record indicates an initial episode of tilt downward away from the volcanic center from 06:20–09:30 GMT, which we interpret as inflation of the shallow volcanic source. The tilt reverses, recording deflation, from 09:30 until 17:50, after which the tilt signal becomes insignificant. The inflation corresponds to a period of numerous VT events, whereas fewer events were recorded during the deflation episode, and the VT events subsequently resumed after the end of the deflationary tilt. The maximum tilt of 2 microradians can be used to estimate the volume of the source inflation (∼2 million m3), assuming a simple Mogi source model. These calculations are consistent with other estimates of source volume if reasonable source depths are assumed. Examination of broadband records of other eruptions may disclose further previously unrecognized tilt signals.

Relationship between Trendelenburg tilt and internal jugular vein diameter.

Abstract: Objectives: To evaluate the relationship between Trendelenburg tilt and internal jugular vein (IJV) diameter, and to examine any cumulative effects of tilt on the IJV diameter. Methods: Using a tilt table, healthy volunteers were randomised to Trendelenburg tilts of 10°, 15°, 20°, 25°, and 30°. Ultrasound was used to measure and record the lateral diameter of the right IJV at the level of the cricoid cartilage. Following each reading the table was returned to the supine position. Balanced randomisation was used to assess cumulative tilt effects. Results: A total of 20 healthy volunteers were recruited (10 men, 10 women). Mean supine IJV diameter was 13.5 mm (95% CI 12.8 to 14.1) and was significantly greater at 10° (15.5 mm, 95% CI 14.9 to 16.1). There was no significant difference between 10° and greater angles of tilt. The effect of the previous angle of tilt did not prove to be statistically significant. Conclusion: Increasing the degree of Trendelenburg tilt increases the lateral diameter of the IJV. Even a 10° tilt is effective. The cumulative effect of tilt (that is, the effect of the previous angle) is not significant. Ultrasound guided cannulation is ideal, but in its absence Trendelenburg tilt will increase IJV diameter and improve the chance of successful cannulation. While 25° achieved optimum distension, this may not be practical and may be detrimental (for example, risk of raised intracranial pressure).

Experimental research on a novel fiber-optic cantilever-type inclinometer

Abstract: Experimental setup for tilt measurement and a novel signal detection method for demodulation of fiber Bragg grating (FBG) wavelength shift are proposed. Being attached, respectively, on the upper and lower surface of only one single pendulum-type cantilever element, only a couple of matched FBGs are used for both tilt angle sensing and wavelength shift signal demodulating. So the received light power will change due to the split of the two reflected spectra of FBGs, which corresponds to the tilt angle. In addition, the cross-sensitivity effect of FBG-based sensors will be solved automatically due to a differential signal process method. Experimental results indicate the measurement accuracy is about ± 0.03°, and measurement resolution is estimated to be about 0.002°.

Automatic digging and loading system for a work machine

Abstract: An automatic loading control system for loading a work implement of a work machine with material from a pile may include a lift sensor configured to monitor a lift actuator and communicate a lift signal. The system may also include a tilt sensor configured to monitor a tilt actuator and communicate a tilt signal. A speed sensor may be configured to communicate a speed signal indicative of a speed of the work machine. A control module may be configured to receive the lift signal, the tilt signal, and the speed signal and generate a signal to control a rim-pull based on at least one of a lift velocity of the lift actuator, a tilt velocity of the tilt actuator, and a work machine velocity to facilitate movement of the work implement through the pile.

Mach-Zehnder interferometer for piston and tip-tilt sensing in segmented telescopes: theory and analytical treatment.

Abstract: A study is presented of a Mach-Zehnder interferometer for the measurement of phasing errors of the type found in segmented telescopes. We show that with a pinhole much larger than the Airy disk and an optical path difference between the arms equal to a quarter of the wavelength, the interferometric signal is related to the second derivative of the wave front. In this condition the signal is produced mostly by the segmentation errors and is marginally sensitive to other aberrations including atmospheric turbulence. The signal has distinguishable symmetric and antisymmetric properties that are related to segment aberrations. We suggest using the antisymmetric component of the signal to retrieve piston, tip, and tilt. The symmetric component of the signal serves as an estimate of the measurement error. In this way we proceed with a study of the errors associated with the misalignment of the interferometer, the segment edge imperfections, and the nonaveraged atmospheric perturbations. The entire study is performed on a theoretical basis, and numerical simulations are used to cross check the analytical results.

Absense of slow transients, and the effect of imperfect vertical alignment, in turbulent Rayleigh-Benard convection

Abstract: We report experimental results for the influence of a tilt angle beta relative to gravity on turbulent Rayleigh-Benard convection of cylindrical samples. The measurements were made at Rayleigh numbers R up to 10^11 with two samples of height L equal to the diameter D (aspect ratio Gamma = D/L = 1). The fluid was water with a Prandtl number sigma = 4.38. In contrast to the experiences reported by Chilla et. al. (2004) for a similar sample but with Gamma = 0.5 (D = 0.5 and L = 1.0 m), we found no long relaxation times. For R = 9.4 times 10^10 we measured the Nusselt number N as a function of tilt angle beta and obtained a small beta dependence about a factor of 50 smaller than the result found by Chilla et. al. (2004) for their Gamma = 0.5 sample. We measured side-wall temperatures at eight equally spaced azimuthal locations on the horizontal mid-plane of the sample and used their cross-correlation functions to find the turn-over time of the large-scale circulation (LSC). The resulting Reynolds numbers R_e^cc were found to increase with beta. An important conclusion is that the increase of R_e^cc with beta of the LSC does not significantly influence the heat transport. Over the range 10^9 < R < 10^11 the enhancement of R_e^cc at constant beta due to the tilt could be described by a power law of R with an exponent of -1/6, consistent with a simple model that balances the additional buoyancy due to the tilt angle by the shear stress across the boundary layers. Even a small tilt angle dramatically suppressed the azimuthal meandering and the sudden reorientations characteristic of the LSC in a sample with beta = 0. The azimuthal mean of the temperature at the horizontal mid-plane within our resolution was independent of beta.

Beam wander effects on the scintillation index of a focused beam

Abstract: First-order weak-fluctuation Rytov theory predicts that the longitudinal (on-axis) scintillation component of an untracked focused beam projected along a horizontal path will become significantly smaller as the size of the transmitter aperture increases. At the same time, the radial component near the diffractive edge of the beam is predicted to increase without bound. The results of recent computer simulations are at odds with this behavior, and we believe that this discrepancy is due to the fact that Rytov theory does not correctly account for the effects of beam wander. We present a theoretical structure that accurately describes far-field irradiance fluctuations caused by uncorrected tilt jitter. This new theory is validated by demonstrating excellent agreement between the predicted scintillation index and computer code results for both tracked and untracked beams. For many applications of practical interest, such as free-space optical communications, a good understanding of the time-average Strehl ratio is also essential; simulation results for this parameter are presented and shown to be in good agreement with theory.

Investigation on the traceability of three dimensional scanning electron microscope measurements based on the stereo-pair technique

Abstract: An investigation was carried out concerning the traceability of dimensional measurements performed with the scanning electron microscope (SEM) using reconstruction of surface topography through stereo-photogrammetry. A theoretical description of the effects that the main instrumental variables and measurement parameters have on the reconstruction accuracy of any point on the surface of the object being imaged was undertaken. This description was based on the model function introduced by Piazzesi adapted for eucentrically tilted stereo-pairs. An analysis of the sensitivity coefficients for the vertical elevation model has identified the most important instrumental variables and measurement parameters to be the tilt angle and the magnification calibration. An equation describing the theoretically determined uncertainty of the vertical elevation was produced. An experimental investigation was carried out involving: (i) magnification calibration using a steel scale with 50 μm pitch at low magnifications, and a 2D calibration grating with 2.120 μm pitch at high magnifications; (ii) tilt angle calibration by laser interferometry; (iii) vertical elevation calibration using gauge-block steps; (iv) calibration in the vertical plane using two ISO 5436 type C roughness standards. Results from magnification calibration and tilt angle measurement were used for calculating the theoretical uncertainty on the vertical elevation. Experimental deviations measured on gauge-block steps showed slightly bigger values than those calculated from the theoretical model. Lateral measurement on the reconstructed three-dimensional topography of the type C roughness standards showed good agreement with the nominal profile wavelength values.

Charged particle beam device

Abstract: PROBLEM TO BE SOLVED: To provide a charged-particle-beam system capable of minimizing the vibration of a sample generated by floor vibration or sound SOLUTION: A vertical part of a tilt table is formed of a material, having a longitudinal elasticity coefficient larger than that of a horizontal part of the tilt table In addition, the vertical part of the tilt table is formed of the material, having specific gravity larger than that of the horizontal part of the tilt table COPYRIGHT: (C)2005,JPO&NCIPI

Shear Layers and Aperture Effects for Aero-Optics

Abstract: *† ‡ This paper examines the effect of a finite aperture on wavefronts, especially with regard to aero-optic distortions from a shear layer. When the net deflection of a beam is corrected in real time to bring a beam on target, a common practice in optic applications even if no other corrections are performed, this removal of the off-target tilt and the finite aperture of the beam act as a spatial filter. This restricts the tip-tilt correction and the wavefront correction to separate frequency ranges, causing the rms magnitude of the remaining distortion to be corrected to vary with aperture size. It has also been found that for a shear layer, aperture size is a key factor in scaling the severity of optical distortions, and it is likely to be a key component in scaling other types of optically-aberrating flows.

Nature of the transition between two modes of external space perception in tilted subjects.

Abstract: A striking feature of visual verticality estimates in the dark is undercompensation for lateral body tilt. Earlier studies and models suggest that this so-called Aubert (A) effect increases gradually to around 130° tilt and then decays smoothly on approaching the inverted position. By contrast, we recently found an abrupt transition toward errors of opposite sign (E effect) when body tilt exceeded 135°. The present study was undertaken to clarify the nature of this transition. We tested the subjective visual vertical in stationary roll-tilted human subjects using various rotation paradigms and testing methods. Cluster analysis identified two clearly separate response modes (A or E effect), present in all conditions, which dominated in different but overlapping tilt ranges. Within the overlap zone, the subjective vertical appeared bistable on repeated testing with responses in both categories. The tilt range where bistability occurred depended on the direction of the preceding rotation (hysteresis). The overlap zone shifted to a smaller tilt angle when testing was preceded by a rotation through the inverted position, compared with short opposite rotations from upright. We discuss the possibility that the A-E transition reflects a reference shift from compensating line settings for the head deviation from upright to basing them on the tilt deviation of the feet from upright. In this scenario, both the A and the E effect reflect tilt undercompensation. To explain the hysteresis and the bistability, we propose that the transition is triggered when perceived body tilt, a signal with known noise and hysteresis properties, crosses a fixed threshold.

The influence of tilt angle on the acoustic target strength of the Japanese common squid (Todarodes pacificus)

Abstract: To measure the influence of changes in tilt angle on the acoustic target strength (TS) of the Japanese common squid (Todarodes pacificus), we conducted a series of experiments to estimate TS in relation to tilt angle and swimming angle. Swimming angle was measured in a seawater tank using two infrared, underwater cameras under dark conditions. Ex situ measurements of TS in relation to tilt angle on live specimens using a fishhook and cage method were then conducted at 38 and 120 kHz; mantle length (ML) ranged from 21 to 27 cm (mean 24.75 cm). For the more precise TS measurement with tilt angle, another set of ex situ TS measurements relative to tilt angle was made at 38 and 120 kHz on tethered, anesthetized specimens in seawater. The mean swimming angle was � 17.7( (G12.7( s.d.). The mean TS varied from � 48.6 to � 44.6 dB and was relatively higher at 120 kHz than at 38 kHz, in the order of 0.7 and 2.5 dB. The empirical relationship between TS (dB) and ML (cm) is given by TS Z 20 log10(ML) � 75.4 (rZ 0.81) at 38 kHz or TSZ 20 log10(ML) � 73.5 (r Z 0.64) at 120 kHz. Based on the tethered method for the anesthetized squid, the mean standardized TS values (b20) were found to be highly correlated with the tilt angle, and the resultant fitted equations for b20 were expressed as: b20Z � 73.3C 0.48!q C 0.0122!q 2 C 0.00016! q 3 for 38 kHz and b20Z � 72.6C 0.53! qC 0.0134!q 2 C 0.00014!q 3 for 120 kHz, where q is the negative tilt angle in degrees. The mean TS based on the measurements using live squid was higher than that of tethered measurements, i.e., 2.6 dB at 38 kHz and 4.0 dB at 120 kHz. The higher mean TS in the ex situ measurements for the live squid can be explained by the influence of the low tilt angle on the overall TS data. The results can be used to understand the influence of tilt angle on the TS of Todarodes pacificus and thus improve the accuracy of biomass estimates.

The Origin of High Optical Tilt in a Homologous Series of Fluorinated Antiferroelectric Liquid Crystals

Abstract: The compounds from the fluorinated nF6B (n = 1,2,3,4,5,6,7) homologous series were investigated by means of optical, electrooptical, refractometrical, dielectric, densytometric, X-ray and IR spectroscopy methods. For some compounds being a subject of investigations a computer simulation of molecular properties were done. In our opinion high value of optical tilt Θo angle in comparison with a tilt angle obtained from X-ray measurements can be interpreted in terms of de Vries model of SmA* phases as well as of dimers creation process.

Reduction of anisotropic image resolution in transmission electron microtomography by use of quadrangular prism-shaped section.

Abstract: A quadrangular prism specimen (a 'prism-shaped' section) was observed in three-dimension (3-D) by transmission electron microtomography (TEMT) over as wide a tilt range as possible. Two types of specimens were prepared for the TEMT experiments: (i) a prism-shaped section of a block copolymer nanostructure, whose cross section was 200 nm on each side and (ii) a conventional ultrathin section having the same thickness (approximately 200 nm) as the prism-shaped section. Image quality of the projections taken at high tilt angles, e.g. 60 degrees, of the prism-shaped section was considerably better than that of the ultrathin section. This was because the path length of electron beam of the prism-shaped section was shorter (and hence the transmission was higher) than that of the ultrathin section at the same tilt angle. Thus, although the projections of the ultrathin section at the tilt angle larger than approximately 40 degrees did not effectively contribute to the 3-D reconstruction, those of the prism-shaped section at very high tilt angles, e.g. +/-75 degrees, can still be used for the 3-D reconstruction. Three orthogonal cross-sectional views of the 3-D reconstruction were extensively compared between the two sections. It was found that (i) the image contrast of the 3-D reconstruction was significantly enhanced and (ii) an elongation of structural object due to limitation of the angular range in the electron tomography was considerably reduced using the prism-shaped section.