Showing papers on "Tilt (optics) published in 1983"

On the Structure of Tilt Grain Boundaries in Cubic Metals I. Symmetrical Tilt Boundaries

Abstract: The results of the study of symmetrical tilt boundaries, reported in the preceding part I, are generalized to asymmetrical tilt boundaries. A classification of tilt boundaries in cubic crystals is developed that reveals which boundaries to choose in order to study equilibrium faceting or intrinsic grain boundary dislocations (g.b.ds) accommodating a misorientation. Two series of atomistic studies of asymmetrical tilt boundary structures are presented based on this classification. The first is a study of long-period (27 ^ 97) [110] asymmetrical tilt boundaries in aluminium. The aims of this study are to investigate whether these boundaries are composed of fundamental structural elements, in the same way as was found in part I for symmetrical tilt boundaries, and to see if localized, distinct stress fields of edge g.b.ds exist throughout the misorientation range. With use of the results of this study, and the principle of continuity of boundary structure enunciated in part I, the boundary unit representation of a 27 — 1193 asymmetrical tilt boundary is derived as an example. It is generally found that the Burgers vectors of intrinsic secondary g.b.ds in tilt boundaries, based on favoured boundary reference structures, are non-primitive d.s.c. vectors. The reason for this is given and a simple formula is presented to derive the Burgers vectors of such dislocations for any favoured tilt boundary reference structure. It is pointed out that, in general, very low angle {0

Slant-tilt: The visual encoding of surface orientation

Abstract: A specific form for the internal representation of local surface orientation is proposed, which is similar to Gibson's (1950) "amount and direction of slant". Slant amount is usually quantifed by the angle ? between the surface normal and the line of sight (0°???90°). Slant direction corresponds to the direction of the gradient of distance from the viewer to the surface, and may be defined by the image direction ? to which the surface normal would project (0°???360°). Since the direction of slant is specified by the tilt of the projected surface normal, it is referred to as surface tilt (Stevens, 1979; Marr, 1982). The two degrees of freedom of orientation are therefore quantified by slant, an angle measured perpendicular to the image plane, and tilt, an angle measured in the image plane. The slanttilt form provides several computational advantages relative to some other proposals and is consistent with various psychological phenomena. Slant might be encoded by various means, e.g. by the cosine of the angle, by the tangent, or linearly by the angle itself. Experimental results are reported that suggest that slant is encoded by an internal parameter that varies linearly with slant angle, with resolution of roughly one part in 100. Thus we propose that surface orientation is encoded in human vision by two quantities, one varying linearly with slant angle, the other varying linearly with tilt angle.

Surface tilt (the direction of slant): a neglected psychophysical variable.

Abstract: Surface slant (the angle between the line of sight and the surface normal) is an important psychophysical variable. However, slant angle captures only one of the two degrees of freedom of surface orientation, the other being thedirection of slant. Slant direction, measured in the image plane, coincides with the direction of the gradient of distance from viewer to surface and, equivalently, with the direction the surface normal would point if projected onto the image plane. Since slant direction may be quantified by the tilt of the projected normal (which ranges over 360 deg in the frontal plane), it is referred to here assurface tilt. (Note that slant angle is measured perpendicular to the image plane, whereas tilt angle is measured in the image plane.) Compared with slant angle’s popularity as a psychophysical variable, the attention paid to surface tilt seems undeservedly scant. Experiments that demonstrate a technique for measuring apparent surface tilt are reported. The experimental stimuli were oblique crosses and parallelograms, which suggest oriented planes in 3-D. The apparent tilt of the plane might be probed by orienting a needle in 3-D so as to appear normal, projecting the normal onto the image plane, and measuring its direction (e.g., relative to the horizontal). It is shown to be preferable, however, to merely rotate a line segment in 2-D, superimposed on the display, until it appears normal to the perceived surface. The apparent surface tilt recorded in these experiments corresponded closely to that predicted by assuming the 3-D configurations consist of equal-length lines and perpendicular intersections.

Microscope stage assembly and control system

Abstract: A computerized stage assembly for a Scanning Electron Microscope including a support frame, a tilt frame pivotally coupled to the support frame, an X carriage engaged with the tilt frame for movement in an X direction, a Y carriage engaged with the X carriage for movement in a Y direction, and a pedestal carried by the Y carriage and capable of rotation around an axis substantially normal to both the X and Y directions. The tilt frame, X and Y carriages, and pedestal are moved by computer controlled step motors. The tilting and rotating of a specimen secured to the pedestal is non-eucentric, i.e. the axis of rotation or tilt is not necessarily through the point of inspection on the specimen. A method is disclosed for automatically returning an inspection point to the viewing field of the microscope after a non-eucentric rotation or tilt.

Dependence of the tilt angle on external forces for smectic-C and chiral smectic-C liquid crystals-measurement of the heat capacity of DOBAMBC

Abstract: A measurement of the specific heat of DOBAMBC is presented, and it is shown that a Landau expansion of the free-energy density with a sixth-order term is adequate to describe the measurement. The coefficients in the Landau expansion are estimated from this measurement. The dependence of the tilt angle on applied electric and magnetic fields is discussed for both smectic-C and chiral (ferroelectric) smectic-C liquid crystals. Numerical estimates of the Landau coefficients are used to show that the effect of external forces on the tilt angle is negligible except when being less than approximately 0.2 K from the transition to the smectic-A phase. The effect on the smectic-C-smectic-A phase-transition temperature is also discussed. Boundary effects can also affect the tilt angle, and an expression for the penetration depth of a boundary-induced disturbance is calculated. For thin, planar samples, a coupling between the two boundaries can induce a transition to the smectic-A phase. It is demonstrated ...

Article holding device

Abstract: A device for organizing papers, files and the like for use in a business environment or other similar situations has a base on which one or more tilt plates are located. The tilt plates are capable of being oriented with respect to the base in a tilting mode and in a locked mode. In the tilting mode the tilt plates rotate about a bottom edge to tilt forward and backward. In the locked mode, the tilt plates are fixed in a set orientation with respect to the base. The tilt plates are easily shifted between the tilt mode and the locked mode by simply sliding them sideways a short distance on the base. Tabs on the bottom of the tilt plate maintain the tilt plate on the base and interact with a stop and lock member on the base to determine which of the modes the tilt plate is in.

Inverted and noninverted lefthanders compared on the basis of motor performance and measures related to the act of writing

Abstract: Pen angles, tilt of writing page, head tilt, slant of writing, mirror writing, laterality quotients and familial sinistrality of inverted and noninverted lefthanded writers were measured. Subjects also performed two motor tests. Reliable differences were found only in terms of the pen angles and the tilt of the writing page, measures that define the groups in the first place. It was concluded that technical aspects of writing from the left to the right with the left hand and environmental pressures are important factors in the genesis of the inverted writing position in the lefthander.

Physiological and behavioral effects of tilt-induced body fluid shifts.

Abstract: This paper addresses the "fluid shift theory" of space motion sickness. The primary purpose of our research was the development of procedures to assess individual differences in response to rostral body fluid shifts on earth. Experiment I examined inner ear fluid pressure changes during head-down tilt in intact human beings. Tilt produced reliable changes. Differences among subjects and between ears within the same subject were observed. Experiment II examined auditory threshold changes during tilt. Tilt elicited increased auditory thresholds, suggesting that sensory depression may result from increased inner ear fluid pressure. Additional observations on rotation magnitude estimation during head-down tilt, which indicate that rostral fluid shifts may depress semicircular canal activity, are briefly described. The results of this research suggest that the inner ear pressure and auditory threshold shift procedures could be used to assess individual differences among astronauts prior to space flight. Results from the terrestrial observations could be related to reported incidence/severity of motion sickness in space and used to evaluate the fluid shift theory of space motion sickness.

Three-dimensional reconstruction of chromatin fibers.

Abstract: We have obtained tilt series of thin sections of chromatin fibers embedded in araldite-epon and stained with uranyl acetate. The tilt series contain between 12 and 18 micrographs, spanning tilt ran...

Vehicle mounted doppler radar system

Abstract: A Doppler radar system for mounting on a vehicle to sense the speed of movement of the vehicle and to provide an output proportional to the speed of the vehicle which is substantially free from errors due to the vibration and of the vehicle. A Janus configuration is also provided which also eliminates errors due to the angle of tilt of the vehicle.

Electronic compass with tilt compensation

Abstract: An electronic compass for land, sea or air vehicles comprises three magnetic sensors 4,5,6 arranged to be respectively responsive to orthogonal components of a magnetic field which includes the earth's magnetic field and a spurious magnetic field which is associated with the vehicle, for producing electrical signals corresponding to said components, tilt sensors 2,3 responsive to vehicle tilt with respect to the horizontal plane, data processor and storage means arranged to store signals derived from the sensors 4,5,6 as the vehicle is turned through a compass setting cycle, and signal processor means 18 to 28 responsive to electrical signals produced by the sensors 4,5,6 after the setting cycle has been completed and to the signals stored at 14 during the setting cycle, for providing compensated signals related to the bearing appertaining to the heading of the vehicle in which the effects of the spurious magnetic field are compensated for and further processor means 31,32 to which the compensated signals are applied and which is responsive to the tilt sensors 2,3 for modifying the compensated signals to produce output signals 33,34 appertaining to vehicle heading in which the effects of tilt are compensated for. A navigation system incorporating the compass can also monitor distance travelled or the vehicle velocity to derive the location of the vehicle.

Effects of chlorpromazine and promazine on the visual aftereffects of tilt and movement.

Abstract: The effects of chlorpromazine (CPZ) and promazine on the visual aftereffects of tilt and motion were measured. CPZ markedly reduced the strength of both aftereffects, while promazine produced a smaller and not always significant reduction. Control experiments suggested that the effects were produced in the central visual system rather than by several possible peripheral artefacts or by drowsiness. The effects are discussed with reference to the pharmacological activity of the drugs and their influence on the strength of inhibition in the visual cortex, both in normal subjects and in schizophrenic illness.

Liquid crystal devices with particular cholesteric pitch-cell thickness ratio

Abstract: A liquid crystal device comprises a layer of long pitch cholesteric liquid crystal material incorporating a pleochroic dye. The layer is contained between two cell walls surface treated to align liquid crystal molecules in a tilted homogeneous structure. The surface alignment and natural pitch of the cholesteric material are matched to provide a progressive molecular twist of between π and 2π, preferably about 3π/2, with a uniform tilt direction. The ratio natural pitch P divided by thickness d of the liquid crystal layer is arranged to lie between 0.5 and 1.0, with a value of d less than 20 μm. Both low tilt and high tilt surface alignment may be used separately or in combination. Polarizers may be used to enhance between ON and OFF states. The device has a sharp transmission/voltage characteristic which enables it to be used in large multiplex addressed matrix displays.

Tilt rod support for venetian blind assembly

Abstract: Tilt rod support adapted to be inserted into a venetian blind headrail to support a tilt rod directly or through the intermediary of a tape roll mounted on a tilt rod. The support has two vertical support portions having curved surfaces with each surface extending less than 180° of arc whereby a tape roll may be snapped into place between the vertical support portions. The tilt rod support includes flexible barbs and shoulders adapted to engage the sides of a route hole cut in a web of a headrail to lock the support in place in a headrail.

Transmission loss caused by an angular misalignment between two multimode fibers with arbitrary profile exponents.

Abstract: The coupling efficiency between two multimode fibers with an angular misalignment is calculated. For the practically interesting cases of parabolic and step-index profiles, closed-form expressions and simple approximations are derived. Furthermore a general loss formula for small tilt angles and arbitrary profile exponents is presented.

Aberrations Of Optical Systems With Large Tilts And Decentrations

Abstract: A computer program has been developed to analytically describe the first and third order properties of systems with large tilts and decentrations. The program describes the imagery through analytic formulae, in both the pupil and field variables, rather than by interpretation of ray trace data at sample points in the field. The first order properties of both the image and the pupil are described in terms of tilt, decentration, magnification, keystone distortion, and anamorphic distortion parameters. In computing these parameters, it is important to take into account the transferred components of the parameters, which are due to the first-order properties of the previous surfaces. The third order properties are computed by representing the surface aberration contributions as vector fields and summing them vectorially. The third order properties are described in terms of a coma field with a node displaced from the center of the image, a binodal astigmatism field, a trinodal distortion field, and a focal surface that is curved and displaced from the Gaussian image in both the transverse and longitudinal directions. The program is applied to several systems, and the results are compared to ray trace data. The interaction between large first order aberrations of intermediate images and pupils, and the third order properties of the image is discussed. Applications of the vector aberration field technique toward an automated design procedure are considered.

Effect of the degree and speed of tilt on the immediate heart rate reaction.

Abstract: The effect of the degree and speed of tilt on the immediate heart rate reaction measuring cardiac autonomic nerve function was evaluated in nine healthy subjects. The results showed that the tilt angle determined the immediate increase in heart rate. The increase in heart rate was maximal when a 90 degrees tilt was performed. After the immediate increase there was a transient decrease in heart rate after rapid tilts (2-5 s). A rapid 90 degrees tilt is preferred when automatic nerve function should be evaluated from the immediate heart rate response.

A high performance electron energy loss spectrometer for use with a dedicated STEM

Abstract: A uniform magnetic field spectrometer corrected for some second order aberrations has been designed and constructed. We demonstrate practical elimination of the focal plane tilt and two of the second order aperture aberrations. The spectrometer is capable of accepting absolute entrance semiangles of up to 7.8 mrad with a resolution better than 1/2 eV at 100 keV incident electron energies. With the addition of a weak octupole coil at the magnet entrance, a reduction in the limiting third order aberrations has been displayed.

Self-Referencing Wavefront Sensor

Abstract: A modified Smartt point-diffraction interferometer employing phase-shifting electronic phase measurement techniques is described. Special techniques making it possible for the interferometer to give good visibility interference fringes for a large range of input wavefront tilts are discussed. A trade-off between acceptable values of wavefront tilt and light efficiency is presented.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.