VDU Screen Research Articles

On the preferred viewing distances to screen and document at VDU workplaces

Abstract Previous research has shown that during work at visual display units (VDUb) most subjects prefer viewing distances greater than 50 cm. The present study investigates whether this is also true in those VDU tasks that require the subjects to shift their gaze frequently between the VDU screen and a paper document. In a laboratory VDU task two conditions were compared: one in which both screen and document were located at the same viewing distance of 50 cm (as recommended in most ergonomic guidelines) and another in which the distance to the document was 50 cm and the distance to the screen was 70 cm. Gaze shifts between screen and document were made every 2 s. Visual strain of 20 subjects aged 19-51 years was estimated with a questionnaire. Contrary to expectation, visual strain was not greater when the viewing distances to screen and document differed. Thus, the dynamic load on accommodation and convergence due to the different viewing distances (50 and 70 cm) did not produce stronger visual strain...

Talking with JIMMY: using electronic publications in higher education

Electronic publishing (EP) is taken to mean the collection, storage, manipulation and distribution of information held in electronic form, and consumed via a computer VDU screen. EP and computer‐mediated communication (CMC) systems are potentially powerful educational tools offering advantages like amplifying teacher and student input, encouraging a resource‐based, transactional approach to learning, providing experience of computer‐supported cooperative working (CSCW), and enhancing students' feedback and self‐monitoring. ‘JIMMY’, an electronic publishing and communication environment on a Vax minicomputer at Queen Margaret College, Edinburgh, and its use by arts, business and health care students and staff, is described. Work in progress includes providing remote access from clinical placement sites and evaluating the use of CMC for information management education.

Legibility of video display units during off-angle viewing

Abstract This research examined how off-angle or oblique viewing of a VDU screen and the physical location of a message on the screen influenced message legibility. Eight trained subjects viewed five-character long common words, number strings, and alphanumeric messages presented at 15 different combinations of oblique viewing angle and location of message on the VDU screen for 2–5 seconds. It was found that common words and number strings showed little overall loss in legibility except when oblique viewing angle exceeded ± 32°. Alphanumeric messages were found to have a significantly lower legibility than the common words and number strings. It was recommended that for best overall legibility of the three types of messages studied here, that oblique viewing angles be less than ± 32°. Predictor equations were also developed to aid in predicting loss of accuracy based on the type of message and physical features of the viewing task.

Use of slow phosphors to eliminate flicker in VDUs with bright background

Area and border types of flicker on bright-background VDU screens and their suppression are discussed. Results of measurements of critical flicker fusion frequency and border flicker for fast and slow phosphors are compared. It is shown that the use of slow phosphors does help to eliminate flicker, but problems still remain in relation to scrolling and low phosphor efficiency.

Analysis of saccadic eye movements with a microcomputer

This analysis of saccadic eye movements has found use in clinical diagnosis. Saccades are induced by a microcomputer-controlled TV stimulator and are recorded by electro-occulography. The analysis algorithm detects saccades by the velocity profile of eye position and then computes the principal saccadic parameters, peak velocity and amplitude. In addition, the saccades are presented on the VDU screen, together with the computed results of the analysis; they may be edited if necessary. The programs have been implemented in Pascal and Assember languages.

Alerts

A press notice from the City of Westminster reports that a phone‐for‐the‐deaf service is being tested in Marylebone Public Library. From the Library the deaf person rings an operator at the Royal National Institute for the Deaf and, via a keyboard and VDU screen, indicates who they would like to telephone. When the call is made by the RNID operator the deaf person can speak to the distant end but replies are received by the operator, who, using a similar keyboard, types them back to the Marylebone Library. This is public provision of an already available system whereby deaf people, with a £200 keyboard adapter and their own domestic TV set, can have help from RNID in making telephone calls. It is said that deaf people much prefer this system to merely asking a friend to make the call for them because they feel they are “not bothering anyone”, the operator being somewhere else and therefore “out of sight, out of mind”. Deaf people not familiar with the equipment will receive instruction from Marylebone Library staff.

Studying depth cues in a three-dimensional computer graphics workstation

A Three-Dimensional Interactive Graphics Workstation has been constructed within the Human-Computer Interface Research Unit. The principal accomplishment of this workstation has been to provide a tool enabling a user to interact with a computer-generated image perceived in three dimensions. This image is perceived by workstation users to exist in free space forward of a VDU screen. A pilot experiment has been conducted where subjects interact both with a simple model of a cube and a three-dimensional computer-generated representation of the cube. The results indicate a significant positive correlation between performances using the cube model and the 3-D representation.

Digitized images: what type of grey scale should one use?

One of the issues faced by engineers when designing a system which records an external event and represents it in the form of a digitized image on VDU screen is which type of grey scale to use. An experiment is described which compares, in a simulated digitized image, the effect of a linear and a logarithmic grey scale on the detectability of a straight-line signal embedded in visual noise. It was found that both bright and dark signals were detected more easily with the linear scale. A signal detection theory analysis was carried out to compare human performance with that of an 'ideal' observer who performed the detection task with a filter spatially matched to the signal. It was found that the model of performance for this ideal observer accounted well for the results provided the assumption of a linear transformation of luminance was made. The analysis showed that the superiority of the linear over the logarithmic grey scale was simply due to the higher signal-to-noise ratio of the signals in the former.

A computer program for repetitive strain gauge rosette analysis

A system is described with which the signals from a strain gauge rosette can be used to compute principal stresses and their orientation, the results being plotted on a VDU screen and updated continuously.

VTUTIN: a full screen gel management editor.

Large DNA sequences are now routinely sequenced by the cloning of randomly generated fragments into single-stranded DNA phage vectors (the 'shotgun' method). Various programs exist for computerized assembly of such fragments, including the phases of data entry, homology searching and gel-management/editing. Many gel-management editors are rudimentary in nature, using either line-editing techniques or using unnatural displays or command systems. Others are available only on restricted types of computer system. The program VTUTIN makes full screen editing along the lines of modern text editors available for the complex data type of sets of sequence gels and their consensus. Not only are the data displayed on the VDU screen in a natural manner, but VTUTIN has also been written to model the command system of a well-established text editor (PDP-11 KED or VAX/VMS EDT) to simplify editor use and learning. VTUTIN has been written in Pascal in a modular form so that wide-spread portability is facilitated. VTUTIN is currently implemented to work on VT-100 type terminals although the modularity of the code should allow straightforward conversion for other terminal types and should also permit simple alteration to model any other text editor.

Skylink self-service ticketing terminal: design and ergonomics

Abstract Within the next few years, most airlines worldwide will be adopting sophisticated self-service automated systems to enable staff to cope with the predicted increase in airline travel. NCR's new Skylink terminal, designed by Douglas Kelley Associates (DKA), London, is a highly flexible self-service passenger system that can handle flight inquiries, make reservations through the airline's central computer, electronically debit payment for tickets and print and issue tickets. It can also function as a check-in and boarding terminal, providing passes and baggage tags. This case study paper outlines the many unique factors pertinent to self-service sales terminals. It wilt then plot the development work undertaken by DKA in conjunction with the NCR Corporation in achieving practical results applicable for installations worldwide. Particular attention will be devoted to the airline ticketing and check-in terminals emphasizing the vital importance for ergonomic considerations to be integrated into the engineering and appearance design activities from the beginning. Physical factors of ergonomic concern are carefully illustrated together with the more abstract psychological aspects of anxiety and privacy. The customer interface by means of VDU screen expression is also discussed and specially programmed computer graphics dialogues shown to illustrate its importance. Other aspects of environmental installation, queueing practices, media replenishment, etc., are included. A future overview of such systems is explained showing its adaptation to hotel checking-in, car rental control as well as to variations of ticketing, from travel agents to executive offices of the future.

Visual Fatigue and Saccadic Eye Movement Parameters

It has been suggested by Bahill and Stark (1975) that visual fatigue can be identified by changes in some of the saccadic eye movement parameters. These include increases in the frequency of occurrence of glissades and overlapping saccades and reductions in the peak velocity and duration of saccades. In their study, fatigue was induced by the same step tracking task that was used to evaluate the changes in saccadic parameters. However, there is evidence that subjects experience extreme feelings of fatigue while performing such a task and that somehow the task is unnatural. The present study was designed to assess whether there are any differences in the various saccadic parameters obtained while subjects perform a step tracking task and a cognitive task involving the comparison of number strings. Both tasks were presented on a VDU screen. The second objective was to establish whether there are any changes in the parameters for either task as a result of prolonged performance. The results showed no major differences in the saccadic eye movements between the two tasks and no consistent changes resulting from prolonged performance.

Measurement of contrast enhancement in VDU screens

Contrast enhancement has been measured on three different VDUs with each of four different enhancement filters. The contrast enhancement filters are of different types — circular polarizing, mesh, neutral isotropically absorbing, and spectrally selective isotropic absorbing. For situations where the contrast reduction is caused by near-specular reflection of ambient light, the circular polarizing filter is considerably more effective than the others. For situations where the contrast reduction is caused by non-specular reflection of ambient light, the filters were all about equally effective. Thus, in an average situation where contrast of the unfiltered VDU image is reduced by both near-specular and non-specular reflections, it would be expected that the circular polarizer would enhance contrast to a noticeably greater extent than the other filters. Resolution was also measured through each of the filters which had been tested for contrast enhancement. The mesh filter noticeably degraded resolution, whereas the circular polarizer and the isotropically absorbing filters did not.

True ergonomic design for users: More than just furniture

Ergonomics extends beyond the seating and physical characteristics of a VDU screen to cover issues relating to the design of the job being performed at the terminal and the type of software employed. Recognition of the importance of the user interface will lead to decreased error rates, increased productivity and lower absenteeism levels.

A device for spatial, temporal and contrast resolution measurement using a VDU screen

This paper describes a recently designed electronic eye-test device. It measures spatial, temporal and contrast resolution by means of test pictures presented on a VDU screen. The subject responds using a keyboard. The tests are fully automatic and therefore easily applied in large scale test set-ups.

Frame repetition rate for flicker-free viewing of bright VDU screens

Frame repetition rate for flicker-free viewing of bright VDU screens

Influence of vdu screen brightness on the visibility of reflected images

The problem of reflection from vdu screens is considered. The variation of contrast with screen luminance is described, and data from psychological tests are used to find acceptable values of these quantities. The results put the case for the black-on-white vdu screen.

A microcomputer-based quantum mechanics cal package

A complete quantum mechanics CAL package for the TRS-80 microcomputer is presented. This includes a Teacher's Guide, Program Documentation, a Student's Workbook and a full Program Listing. Two STUDIES are incorporated. In the first, the computer program solves the time-independent Schrödinger equation for a particle trapped in a finite, rectangular potential energy well. Students are able to define the well depth and half-width, particle mass, wavefunction parity, and total particle energy. Both the potential energy well and the particle wavefunction corresponding to the selected parameters are automatically plotted on the TRS-80 VDU screen. In the second STUDY students explore a simple model of the deuteron which assumes that the proton and neutron interact via a rectangular potential energy well. The deuteron wavefunction and the potential energy well are plotted on the VDU screen. The package has been fully tested and evaluated in a second year undergraduate physics laboratory.

VIRUS — A Laboratory Information System for Clinical Virology

A system covering request registration, analytical orders, printing of worksheets, result reporting, result control and printing of patient reports is presented. Additionally, interim reports can be produced; accounting is automatic, and group requests and requests for new analyses of old samples can be handled. The system meets the demand for retrospective analysis which arises when acute intermediate and convalescent sera have to be analyzed simultaneously. Consequently, results from the same type of analysis performed on the same sample on different occasions can be handled and presented in a clear way on the VDU and on the report.All work is performed on-line in real time via VDU screens. All data are stored on a 3 x 100 Mbyte disk chive which can accommodate approximately 6 years’ work.The system has been implemented as a terminal system with 5 VDU: s and one line printer connected to an IBM 370/158 computer. The IMS data base management system has been utilized.