Display Surface Research Articles

Recent developments in the in‐situ measurement of sediment geoacoustic properties

The latest version of the in‐situ sediment acoustic measurement system (ISSAMS) allows direct, in‐situ measurement of sediment geoacoustic properties. Geoacoustic probes, which are mounted on a rigid frame, are inserted into the sediment hydraulically. The entire operation is controlled and monitored in real‐time from the surface. Data is collected and processed by a wet‐side computer and transmitted to the surface for waveform display and analysis. Video cameras both monitor insertion of probes and provide preliminary indication of sediment type. A seabird CTD is used to measure bottom water temperature, salinity, and sound speed. Sediment compressional wave velocity and attenuation are measured over pathlengths of 40 to 110 cm and at depths of between 0 to 50 cm below the sediment–water interface. Pulsed sine waves are transmitted at 58‐kHz and time delays and voltages are used to determine values of velocity and attenuation between identical radial‐poled ceramic cylinders (two transmit and two receive). Shear wave velocity and attenuation are measured using a similar pulse technique. Bimorph bender elements mounted in flexible silicone rubber mounts and driven at 100 to 2000 Hz to generate shear waves. Values of sediment geoacoustic properties from muddy sediments of Eckernförde Bay, Baltic Sea and carbonate sediments of the Florida Keys presented used to illustrate the operation and utility of the new system.

Preparation of amorphous BaTiO3 thin films on indium tin oxide-coated soda lime glass by metalorganic chemical vapor deposition

Metalorganic chemical vapor deposition of BaTiO3 thin films on indium tin oxide–coated soda lime glass substrate in the temperature range between 400 and 550 °C was investigated to produce an insulating layer with high breakdown voltage and a smooth surface for electroluminescence display. In order to prevent the diffusion of sodium ions toward the indium tin oxide layer and BaTiO3 insulating layer, the deposition temperature should not be higher than 500 °C. X-ray diffraction patterns showed that the BaTiO3 thin film deposited at 400 °C was amorphous. The stoichiometry of the films was identified by Auger electron spectroscopy. Scanning electron microscopy results suggested that BaTiO3 thin films deposited at 400 °C had smooth surfaces without defects such as pinholes and clusters, but surface flatness decreased at the deposition temperature of 550 °C. The dielectric constant was 12.9. The breakdown voltage determined from current–voltage measurements was as large as 2×106 V/cm.

Amorphous Silicon Electronics

The progressive miniaturization of electronics is familiar to everyone; computing power that used to occupy a room can now be put onto a single integrated circuit. Miniaturization is admirable when size is not relevent to the electronic function, but there are plenty of devices in which a large physical size is essential. Many of these concern information technology, examples being the computer display, printer, and fax machine. Communication with the electronic world is primarily visual and operates at a large format typified by a document. In this rapidly advancing field, we are eagerly awaiting desktop interactive display surfaces that can input as well as display information, document readers, truly portable computers, electronic vision and—the oldest dream of all—the television that hangs on the wall. Realization of these hopes requires a set of technologies that permit bigger rather than smaller electronic systems, and amorphous silicon is helping to make this happen.

Visibility of Transmissive Liquid Crystal Displays under Dynamic Lighting Conditions

Liquid crystal displays maintain superior contrast under bright sunlight conditions compared with cathode-ray tube displays. This attribute, along with reduced weight, volume, and power requirements, make liquid crystal displays especially desirable for use in vehicular applications. The present experiment was designed to determine the luminance requirements for transmissive liquid crystal displays viewed under a wide range of lighting conditions typical of many vehicular environments. Both the ambient illumination incident on the display surface and the forward-field-of-view adaptation luminance were parametrically manipulated. The visual task involved speeded spatial discrimination responses for detection of the gap in a modified Landolt-C acuity target. The results indicate that under the worst lighting conditions tested, a display luminance of approximately 180 cd/m2 yielded asymptotic spatial discrimination performance. The results have been incorporated into a predictive visual performance model for spatial discrimination tasks, which describes the present data well and represents a first step toward a device-independent model of display visibility.

A practical approach to calculating luminance contrast on a CRT

Luminance contrast is the basis of text legibility, and maintaining luminance contrast is essential for any color selection algorithm. In principle, it can be calculated precisely on a sufficiently well-calibrated display surface, but calibration is very expensive. Consequently, most current systems deal with contrast using heuristics. However, the usual CRT setup puts the display surface into a state that is relatively predictable. Luminance values can be estimated based on this state, and these luminance values have been used to calculate contrast using the Michelson definition. This paper proposes a method for determining the contrast of colored areas displayed on a CRT. It uses a contrast metric that is in wide use in visual psychophysics and shows that the metric can be approximated reasonably without display measurement, as long as it is possible to assume that the CRT has been adjusted according to usual CRT setup standards.

Visualization and analysis of acoustic scattering from elastic objects, on the surface and in the far field.

In typical structural acoustic scattering problems, the surface pressure and normal velocity on the object are determined as well as the far-field pressure or target strength. These functions may be obtained by computation or measurement, and each may be a function of the surface coordinates as well as the direction and time or frequency characteristics of the incident wave. They are typically stored as a multidimensional array of (possibly complex) numbers. Modern visualization techniques greatly aid the analysis and understanding of these large data sets. An efficient architecture and relevant algorithms have been developed for this purpose using commercially available software and a typical workstation. A top-down approach to understanding and analyzing these data sets will be described. This includes spatial, spectral, and statistical processing of the fundamental data. The appropriate use of color, spatial coordinates of the display surface, and time animation will be illustrated with viewgraphs and videotape examples. [Work supported by the Defense Advanced Research Projects Agency (DARPA).]

Exocentric Judgements in Real Environments and Stereoscopic Displays

Spatial direction errors during interpretation of perspective images, such as 3D map displays, may originate from misjudgment of the orientation of the viewing direction used to make the display. One source of these errors could be perceptual evidence of the display surface. Two experiments are reported in which the same judgement exocentric task was presented, but the cues to the picture surface were reduced or eliminated by presenting the task as a stereoscopic, virtual image or by a geometrically matched physical model. A theory developed to model exocentric direction errors on perspective displays has been fitted to the data from these two experiments. The parameters estimated from the fit in both experiments indicate that the subjects may be more correctly estimating the viewing direction than in ordinary perspective displays. Consequently, in some real world or stereo viewing conditions, errors in estimating the viewing direction are not likely to dominate exocentric direction errors.

Color Coding and Size Enhancements of Switch Symbol Critical Features

The purpose of these two studies was to evaluate recognition performance of symbols on programmable switches using different critical feature enhancement techniques. Based on previous studies, it was assumed that subjects were processing the meaning of the symbols at a holistic level. Enhancing a critical feature (the specific part of the symbol which makes it most identifiable) was proposed as a method for creating a more unique symbol, thereby improving recognition performance. Color coding and size enhancement of the critical feature were evaluated to determine if either technique improved symbol recognition performance. In the first study the size enhancement was between 60–75% in total number of pixels for the critical feature. The amount of size enhancement was limited by the display surface area. In the second study, a new method of size enhancement was utilized whereby the longest axis of the critical feature was increased by 0.10 of an inch. In this study, there was no display surface constraint. In both studies color coding of the critical feature was also evaluated. The results of the first study indicated that only the color coding technique was significant. In the second study, both color coding and size enhancement were significant. It was concluded that in the first study the way in which the size enhancement was applied to the critical feature (an increase in total surface area) was not sufficient to achieve a unique symbol, so it did not improve the subject's recognition ability; however, in the second study, size enhancing the longest axis was sufficient to result in a performance payoff.

The EH101 Electronic Instrument Systems

This paper describes the background to the introduction of an electronic instrument system on the Anglo-Italian EH101 helicopter. The demanded flexibility to accommodate the display needs of several roles leading logically to the adoption of full colour multi-purpose display surfaces and the drive to achieve maximum commonality between military and civil variants is discussed. The configurations arrived at for both variants are described together with the operating philosophy and display formats developed during an ongoing simulator program. The paper also deals with a detailed description of the hardware implementation of the EIS including the fully integrated systems architecture and details of the symbol generators (SGs), display units (DUs) and display mode selectors (DMSs). Emphasis is placed on the robust integrity characteristics and reversionary switching philosophy of the system.

Evaluation of visual display surfaces by real users early in the design stage

Groups of non-computer scientists were tested to evaluate the potential of an as yet non-existent interactive terminal with a screen diagonal of one meter. A simulated large image terminal provided limited realistic interactions using software developed to give close proximity to the predicted visual effect. Subjective responses from 101 subjects were elicited from a questionnaire designed to evaluate specific aspects of the “terminal” in use. From this data, two types of screen (lenticular and plain) and two types of interaction devices (touch and remote pointer) were analyzed experimentally using a two-way factorial design. Potential end-users provided positive feedback concerning future use of the Large Image Terminal. Building a realistic mock-up revealed screen contaminations which would not have been discovered until a much later stage. Although statistical analysis of screen evaluations was equivocal, the questionnaire was sufficiently penetrating to separate the positive and negative features. This methodology was invaluable in guiding the design process.

Illusions: Can Change of Vantage Point and Invariant Impressions Remove Deception?

This article reports on three experiments in viewing illusions held at different slants to the line of sight. In Experiment 1, we used six geometrical illusions and found that they were illusory when viewed with the line of sight normal to the display surface and that the illusion was dispelled when the figures were viewed from glancing angles. In Experiment 2, questions were put to the viewer about the real state of affairs in two of the illusions in Experiment 1. Viewers who suffered from the illusion from one vantage point and who had the illusory effect dispelled from the other vantage point were unable to discern the correct state of affairs. Experiment 3 found that aspects of shape in a geometrical illusion could be accurately discerned by viewers given a set of vantage points spaced 360' around the figure.

Rotation algorithm artifacts in stereoscopic images

We examine the effect of using rotations for generation of the left- and right-eye perspective views of a stereoscopic image. We show that this approach to stereoscopic display of perspective views results in vertical parallax between the left- and right-eye views and we present an analytic expression that characterizes this parallax in terms of the center of rotation, the location of the image plane, and the angle of rotation. We also derive an analytic expression that shows that the rotation of the perspective views results in a semicylindrical stereo window with center at approximately (0, 0, P12) and radius R/2, where R is the distance from the center of rotation to the center of projection. When this semicylindrical window is mapped to a flat display surface, relative depth relationships can be distorted.

A Method of Stereoptically Simulating Manifolds of Three-Dimensional Objects Using Only a Single Display Pattern: A Shape-Depth-Texture Invariance

A means of conceptualizing and generating visual displays that are "self-stereoptic manifolds" is described. First, single patterns that can replace pairs of stereograms to produce illusions of depth are defined and an example is shown. Patterns such as these produce illusory three-dimensional objects hanging in space before or behind the display surface. It is further demonstrated geometrically that such a display actually has three-dimensional information embedded in it peculiar to each of a family, or manifold, of objects that can be experienced one at a time. Each object of the family appears when the viewer looks in space where it "exists." The others remain invisible unless their locations are fixated. If any member of a specific manifold of three-dimensional illusory objects is physically duplicated as a real object and textured in the same way that the illusory object appeared to be, then this new real object will, in turn, generate an illusion of each of the other objects of the manifold when the observer fixates in space where each "exist." Also, if then the viewer looks where the original display previously was, the newly constructed object will disappear and the display will reappear. The geometry and the advantages and disadvantages in relation to a stereoptic pair are discussed.

Naturalistic Observation of Adjustable VDT Stand Usage

Ergonomists have long recommended user adjustable furniture for office workers. A majority of the recommendations have been based upon anthropometric models of economically “correct” postures. Research validation of these proposals is sparse, and those that have been conducted are predominantly laboratory oriented. This research observed the use of adjustable furniture in a field setting. Three questions were addressed: 1) what are the preferred settings when the equipment has been used for a length of time?; 2) do people change the settings?; and 3) how do these measures relate to anthropometric data? The offices of 91 workers were measured covertly. Twenty one offices were measured once, 41 twice, and 29 three times. All the offices had an adjustable VDT stand with independent height and angle adjustments for both the keyboard and display. Seat height had a mean and standard deviation of 20.0 and 0.85 inches. The height of the home row of the keyboard had a mean of 29.1 and a standard deviation of 1.2 inches. For the display surface the mean and standard deviation were 29.7 and 1.3 inches. In terms of repeated measures, 62.9% of the chair heights, 57.1 % of the keyboard heights, and 91.4% of the display heights did not change. Of the observed changes, 90% were between 0.25 in and 0.75 inches. None of the observed heights correlated well with stature, seated eye height, or popliteal length. One correlation was 0.32, all others were less than 0.20. The results are similar to other published data in that the measured settings are much higher than anthropometric models would predict. More significantly, they do not match the new ANSI guideline nor the proposed CSA guideline for adjustable furniture. This suggests that the ergonomic theories behind these recommendations need to be modified to more closely reflect actual use products.

Factors affecting the detection of signals in simulated FTI displays

A number of experiments are described which investigate the effect of various display parameters on the visibility of signal lines using computer generated simulations of frequency-time-intensity displays. A signal detection theory analysis of the data was used to disambiguate the perceptual effect of a given display parameter from its effect on the display surface signal-to-noise ratio (SNR). It was found that changes in the luminance characteristics of the display (such as the number of grey levels and the type of grey scale) affected signal visibility, but only because of their effect on the SNR. On the other hand, two spatial display parameters (pixel width and display/signal height) had additional perceptual effects. The practical implications of the findings for display technology are discussed.

Concurrent motion in infant event perception

Infant sensitivity to motion relationships specifying certain complex events, such as a person walking, has recently been demonstrated, but the perceptual principles underlying early event perception are not well understood. Retinal motion toward a common point (concurrent motion) specifies translation in depth to adult perceivers in the absence of conflicting information ( Börjesson & von Hofsten, 1973). We tested this principle of event perception with 28 16-week-old infants. One group was habituated in a dark room to a concurrent motion: three points of light moving in a frontoparallel plane toward and away from a central point (not seen). After habituation, the room was illuminated, and looking time was tested to alternate presentations of two displays. In one display (depth motion), three lights were attached to a triangle actually moving in depth; in the other display (surface motion), the three lights moved visibly along the surface of a fronto-parallel stationary triangle. If concurrent motion, in the absence of conflicting information, specifies motion in depth to infants, they were expected to look longer after habituation at the surface motion display. A control group tested infants' relative interest in the two test displays with no prior habituation period. Control-group infants marginally preferred the depth movement display. The habituation group responded three times as much to the surface motion display, suggesting that motion in depth had been perceived during habituation. Specification of motion in depth by concurrency of relative proximal stimulus motions seems to be an operative principle in infants' perception; moreover, at least some principles of early event perception are unrelated to person perception or biological motion. The relation of these results to recent findings in infant object perception is discussed.

Quantitative Evaluation of Perspective and Stereoscopic Displays in Three-Axis Manual Tracking Tasks

Optimal presentation of three-dimensional information on a two-dimensional display screen requires careful design of the projection to the display surface. Monoscopic perspective projection alone is usually not sufficient to represent three-dimensional spatial information. It can, however, be improved by the adjustment of perspective parameters and by geometric visual enhancements such as reference lines and a background grid. Stereoscopic display is another method of providing three-dimensional information to the human operator. Two experiments are performed with three-axis manual tracking tasks. The first experiment investigates the effects of perspective parameters on tracking performance. The second experiment investigates the effects of visual enhancements for both monoscopic and stereoscopic displays. Results indicate that, though stereoscopic displays do generally permit superior tracking performance, monoscopic displays can allow equivalent performance when they are defined with optimal perspective parameters and provided with adequate visual enhancements.

Colour contrast calculations for displays viewed in illumination

A procedure is described to assist the display designer to assess the role of luminance and chrominance in determining the ability of a displayed colour to withstand the effects of ambient illumination. Plots are produced for primary and complementary colours displayed on a colour cathode-ray tube to exemplify how to predict the contrast that exists between each colour and the achromatic background due to the display surface and the contrasts which exist when colours are overlaid. Although the example is for a cathoderay tube the procedure can be applied to other types of display technology and can be used to evaluate hypothetical designs prior to development.

Underlying Behavioral Parameters of the Operation of Touch-Input Devices: Biases, Models, and Feedback

Touch-entry devices have exhibited a number of advantages in relatively low-resolution applications. Requirements for high-resolution input must, however, take into account the inherent biases and limitations of the operator. In this study performance biases in the use of an infrared touch-input device were examined with the input (display) surface at various declinations. A general bias to touch low and to the right of targets was found, the low bias increasing with increasing display declination. Attempts to reduce bias error through simple models based upon earlier trials were more effective when derived from individual performances rather than populational behavior (averages). Handedness effects on performance were also found. Training is discussed as a viable alternative, along with preliminary training results.

Working with occam: a program for generating display images

It is assumed that a host processor computes the corner coordinates of surfaces and outputs these sequentially, in ranked order, to the components described in an OCCAM program. The data is precomputed and stored in a sequential file. A scheduler controls the activity of a number of zone management processors (ZMPs), all running in parallel, and a special memory buffer. Each ZMP handles only one surface at a time. A processor can pick up a new surface for display when the previous surface has been completed. Only one ZMP can write into a given raster scanline at one time. Others may be writing into the same column of other lines at the same time. Hidden surface elimination is achieved by processing the surfaces in an order ranked on distance from the viewing point. This ranking is done in the host processor. The ranked data is held on a file, which is read sequentially in 512 byte blocks. This data has been previously computed and stored as a sequence of double-byte integers in the required order for a series of picture frames, one frame per 512 byte block. The occam implementation on the Apple II europlus running under UCSD version 4 is very slow. It is postulated that an implementation using separate occam professor hardware units for each appropriate process would run in real time. There is considerable communication between the processors. The activity of each processor is generally sequential and all the processors run in parallel. Comments are made about some of the problems and advantages of programming in occam in an appendix.