Showing papers on "Tilt (optics) published in 1972"

Displacement Measurement from Double-exposure Laser Photographs

Abstract: Surface displacement can be measured by recording a double-exposure photograph of the laser-illuminated object, followed by optical processing of the recorded speckle-pattern image. The analysis can either be on a point-by-point basis, or by a spatial filtering technique which resolves the motion in any desired direction orthogonal to the line of sight. The limits within which the technique may be used to measure lateral translations and rotations of the surface are examined theoretically and experimentally, and the effect of lens aberrations and surface scattering properties are discussed. Surface tilt may also be measured by recording a defocused double exposure image and analysing its optical transform. The photographic techniques described can be extended to measuring surface vibration, by recording a single ‘time-averaged’ exposure and examining the modified optical transform fringe pattern.

Contrast and size variables and the tilt after-effect.

Abstract: The relationship between the contrast and bar width of adapting and test gratings in the determination of the magnitude of the tilt after-effect was explored. When the contrast of adapting and test gratings is varied concomitantly over four levels, the magnitude of the tilt after-effect does not change. When the contrast of the adapting grating is higher than the test grating, the magnitude of the after-effect is increased and when its contrast is lower than the test grating, the magnitude of the after-effect is decreased. When the bar width of the test grating is narrower or broader than that of the adapting grating, the magnitude of the after-effect does not change. The implications of these results for a neurophysiological explanation of the tilt after-effect are discussed.

Grain boundary kinking in f.c.c. bi-crystals

Abstract: Grain boundaries formed in bi-crystals with a common [001] tilt axis and the (100) planes symmetrically disposed by certain non-coincidence rotations have been observed to kink. This kinking results in the boundary being composed of connected straight segments rather than taking a straight path between the pinned end points. The segments are not randomly oriented with respect to the path of minimum length and can be associated with boundar}’ paths of short periodicity.

Magnetic fluid level detector and vibration transducer

Abstract: A level detector and vibration transducer employing a magnetic fluid sensing element to measure tilt and vibration. The level detector and vibration transducer is used to measure tilt about an axis in a nominally horizontal plane. The device can also be used to monitor vibration along any specified axis. This is accomplished by mounting the transducer along the specified axis and subjecting the transducer to successive vibratory forces for successive displacements of the magnetic fluid in the vial. The moving system (or sensor) consists of a vial partially filled with a magnetic fluid encompassed by a linear variable differential transformer pickoff. When the magnetic fluid is equally distributed in the vial, there is equal coupling between the two magnetic field coils and the output voltage is zero. A slight tilt will displace more of the magnetic fluid to one side and will unbalance the magnetic field causing an A.C. voltage to exist between the two pickoff coils. The amplitude of the A.C. voltage is proportional to the amount of tilt and the phase is proportional to the direction of tilt.

The effect of variation of frame shape on the angular function of the rod-and-frame illusion

Abstract: The angular function of the rod-and-frame illusion was studied under conditions of variation in frame shape. The results support predictions arising from the hypothesis that as a frame is varied in tilt, vertical settings of a rod will be in error in the direction of the major frame axis closest to true vertical.

Tilt errors and precipitation effects in trivane measurements of turbulent fluxes over open water

Abstract: For 390 ten-minute samples of turbulent flux, made with a trivane above a lake, the vertical alignment is determined within 0.1 ° through azimuth-dependent averaging. One degree of instrumental misalignment is found to produce an average tilt error of 9 ± 4% for momentum flux, and 4 ± 2% for heat flux. The tilt error in the vertical momentum flux depends mainly ons u/u*, and cannot be much diminished with impunity by high-pass pre-filtering of the turbulence signals. The effects of rain on trivane measurements of vertical velocity are shown to be negligible at high wind speeds, and adaptable to correction in any case. The normalized vertical velocity variance,s w/u*, appears to be proportional to the square root ofz/L for unstable stratification. For a wind speed range of 2 to 15 m s−1, the eddy correlation stresses measured at 4- and 8-m heights can be reasonably well estimated by using a constant drag coefficientC d=1.3 X 10-3, while cup anemometer profile measurements give an overestimate of eddy stress at high wind speeds. A good stress estimate is also obtained from the elevation variance; it is suggested that trivane measurement of this variance might be made from a mobile platform, e.g., a moderately stabilized spar buoy.

Perception of verticality on a modified portable Rod-and frame Test.

Abstract: 563 boys from Grades 7 to 11 were tested on a modified version of the portable Rod-and-frame Test (RFT). The absolute sum of RFT errors decreased progressively from Grade 7 through Grade 11 and correlated with Ss' age (p < .001). About 90% of the total variance of these scores was accounted for by errors in the direction of the tilt of the frame. Errors toward tilt of frame decreased with increasing age, whereas the proportion of errors against the tilt of frame showed an opposite trend. Trials with the frame left off 0° produced a higher absolute sum of RFT errors and larger errors toward tilt of frame than the right-tilt trials. These findings were discussed within a developmental framework and related to studies on the effect of the frame.

Tilt limit detecting apparatus

Abstract: A tilt limit detecting device which utilizes a bubble level containing a prescribed amount of opaque fluid and a photodector arrangement transverse to the longitudinal axis of the bubble level. The photodector arrangement includes a pair of light source-photocell combinations the first of which is normally positioned at the center of the bubble in the level position while the second combination is spaced a distance Y from the first, such that the distance Y is less than the bubble length X. The opaque fluid acts as a shutter interposed between the light source-photocell combinations, so that with the connection of suitable electronic circuitry to the photocells angular tilts in excess of the allowable limit, which generally equals X/2 in radians, are detected as well as the particular direction, clockwise or counter clockwise, identified.

Behavior of Grain Boundaries Near the Melting Point

Abstract: The absolute grain boundary energies of {011} tilt boundaries in bismuth at a temperature very near the melting point were measured over the range of misorientations 0.5° to 14.5°. A study of the structure of these boundaries was extended as far as 27°. The results at small tilt angles (θ≤6°) can be described accurately in terms of a heterophase dislocation model. This model also correctly predicts the grain boundary energies of [001] tilt boundaries in copper near the melting point, again for tilt angles less than about 6°. The heterophase dislocation model is unique, inasmuch as it permits the calculation of absolute grain boundary energies in terms of usually available thermodynamic and elastic quantities and a simple macroscopic parameter related to the boundary structure. In addition, the theory provides a basis for interpreting the structural transition observed in bismuth tilt boundaries at intermediate misorientations (θ=15°). Finally, the failure of current theories to predict the correct energy-misorientation dependence over a wide range of misorientations is ascribed to linear and nonlinear interactions among the misfit dislocations—interactions which increase rapidly in importance for misorientations above about 5°. For a quantitative description of the energetic behavior of higher angle grain boundaries than are treated at present, a theory which accounts for such interactions appears to be required.

The constancy of object orientation: effects of target inclination.

Abstract: The constancy of object orientation was investigated by tilting S backwards at angles of 0°, 25°, 50°, or 75° in the median plane in order to match a line target, previously presented with S upright. The orientation of the target was either 0° (vertical), 30° or 60° (top toward S). The task entailed the perception of target orientation relative to the direction of gravity, hence S's body tilt had to be taken into account. Ss showed nearly perfect constancy in all conditions, however line tilt was a significant factor. Errors in matching the target orientation did not vary with body tilt although errors in apparent body orientation yielded a negatively accelerated function of body tilt. Several paradigms representing orientation constancy were discussed.

Adjustments of visual tilt as a function of age

Abstract: Using a psychophysical method of adjustment, 175 Ss, ranging in age from 3 to 20 years, made four adjustments each of a luminous line to subjective vertical, horizontal, and 45-deg tilts in the dark. There were no significant differences in mean errors of adjustment to the vertical and horizontal over the ages tested. There were significant differences in intra-S variability of adjustment to the horizontal and vertical, with the greatest improvement occurring before age 10. Older children and adults produced significantly larger mean errors of adjustment to the 45-deg tilt than did the younger children; but the variability of settings by younger children was very high, indicating that they did not discriminate the 45-deg tilt more accurately than the older groups. The intra-S variability at all ages showed that adjustment was more accurate to the horizontal and vertical than to the 45-deg tilt.

Mutual coupling in linear dipole arrays

Abstract: A Hallen's type integral equation is formulated for the current distribution on a dipole which can assume an arbitrary tilt angle in an infinite periodic phased array. The active impedance of the dipole is calculated for various combinations of spacing, tilt angle, scan angle, and frequency.

Remote reading tilt encoder

Abstract: A pair of tilt encoders are mounted at right angles to one another. In one embodiment, each encoder comprises a pendulum connected to vary the resistance of a potentiometer as a function of the tilt angle of the pendulum. Each of the potentiometers are connected to a circuit which produces an output tilt resolution signal comprising an analog ramp function upon which is superimposed a single pulse. The time from the beginning of the ramp to the leading edge of the superimposed pulse is indicative of the tilt angle of one of the encoders while the time from the leading edge of the pulse to the end of the ramp is indicative of the tilt angle of the other encoder.

Lack of directional specificity in tilt aftereffect induced with moving contours

Abstract: Eight Ss were required to set a grating to vertical following exposure to a tilted grating. Aftereffect was measured with both gratings stationary, with one grating stationary and the other moving, or with both gratings moving either in the same or in opposite directions. The mean tilt aftereffect did not vary among these conditions. The results are discussed with reference to explanations of visual tilt aftereffect that have been offered in terms of selective suppression of spatially tuned feature detectors.

Image quality in telescopes with image motion compensation by secondary mirror control.

Abstract: Image motion compensation by servocontrolled tilt of the secondary mirror is applied in a 40-cm diam f/7.5 Cassegrainian balloon-borne telescope. A tilted-aplanatic configuration is used, i.e., the mirrors are aspherized to render the stabilized image free of third-order coma. A spatial resolution of 2 sec of arc is maintained in the presence of pointing errors up to 10 min of arc. The most important remaining aberrations are third-order astigmatism and fifth-order spherical aberration. For the latter, a general expression is presented that can also be applied to other two-mirror telescopes.

Structure of a Coincidence and Near‐Coincidence Tilt Boundary in Gold

Abstract: The structure of tilt grain boundaries formed by a rotation of 60° and 30° about a 〈111〉 axis has been examined by transmission electron microscopy. In specimens containing 30° boundaries, low‐angle dislocation arrays with a tilt angle of 2.2° are commonly observed. This is attributed to the presence of a coincidence site lattice relation at 27.8°.

Headlight control system

Abstract: A system for controlling the tilting of the headlights on a vehicle. In one embodiment the tilting of the headlights is adjusted to compensate for sagging of the rear of the vehicle. In another embodiment means is provided for controlling the tilting of single filament headlights so that a ''''high tilt'''' or ''''low tilt'''' beam aim can be selectively achieved.

Type head tilt and rotating mechanism

Abstract: A tilt bridge for a type carrier carries unitarily rotatable thereon a type carrier and a gear, and such gear is in constant engagement with another gear at an axis location whereabout the tilt bridge is required to tilt. The gear on the tilt bridge has freedom for tilting movement about said axis location in respect to the other gear and is in constant mesh therewith for receiving therefrom rotary type-selective movements for the type carrier. The tilt and rotate axes are mounted on a swingable support whereby the carrier may be swung to print.

Adaptation of stereo vertical as a function of prolonged body tilt in the sagittal plane

Abstract: Adaptation of stereo vertical as a function of prolonged body tilt in the sagittal plane

Some results of calibrating CG-2 gravimeters (sharpe) by the tilt method

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