Video Displays Research Articles

Enhancement of 3-D Video Displays by Means of Superimposed Stereo-Graphics

This paper describes a number of aspects of a display technology under development, which involves the integration of stereoscopic computer graphics and stereoscopic video displays. The background and justification for this development are discussed, based on the need of operators of remotely controlled vehicles and/or manipulators to estimate absolute sizes and locations of objects at a remotely viewed site. The basic technology involves superimposing an interactively controllable computer-generated stereographic cursor onto a stereoscopically viewed video image. Absolute measurements can be made with this system, based on relative comparison of cursor position with target object location. Experimental results are presented in which the ability of subjects to perform such tasks was investigated. In general, results were promising; subjects were able to align virtual pointers with real targets essentially as well as they were able to manipulate real objects. A number of implications of this technology for the enhancement of three dimensional video displays are discussed.

Human Electroretinogram Responses to Video Displays, Fluorescent Lighting, and Other High Frequency Sources

Time-averaged human electroretinogram (ERG) responses were determined for several workplace visual stimuli which are temporally modulated at rates exceeding the perceptual critical fusion frequency (CFF). A clearly identifiable synchronous response was in evidence for a video display terminal (VDT) stimulus operating with a refresh rate as high as 76 Hz. A directly viewed fluorescent luminaire with controllable driving frequency elicited a synchronous response at rates as high as 145 Hz. In addition, an intense stimulus created by modulating the light from a slide projector produced responses at least as high as 162 Hz. The implications of these high-frequency responses are representing a potential basis for visual symptoms are discussed.

Digital Chest Radiography

It is apparent that digital radiography holds considerable promise. Although there are some immediate advantages to be gained from using digital technology at present, such as more consistent image quality in portable radiography, most of the benefits have not been fully realized. To do so requires a completely integrated digital radiology department using high-resolution video displays throughout the hospital connected to a large digital image archiving system. This concept, referred to as picture archiving and communication systems (PACS), represents the logical culmination of the extensive research that is continuing in this area. Because of the great expense involved, it is likely that the transition from conventional to digital radiography will be evolutionary in most medical centers, with establishment of local PACS networks initially, such as between the intensive care units and the radiology department. At a more basic level, limited digital radiography systems can function in isolation and address specific needs successfully. Although the science of computer-aided diagnosis is at an early stage, it seems likely that the sensitivity and specificity of these programs will continue to improve. Their eventual utility will depend on their accuracy and ease of use. The ultimate goal would be a relatively "transparent" multifaceted program that would screen all radiographs prior to interpretation to provide the radiologist or clinician with diagnostic suggestions and quantitative data. Given the present rate of progress in this area, such a concept is not unrealistic. However, even the most ardent enthusiasts do not envision totally independent computer-based interpretation of radiographic images for some time. Although digital image processing has not greatly improved diagnostic accuracy merely by enhancing the appearance of the radiographs, there are other potential diagnostic advantages in using digital images, such as rapid retrieval of previous examinations and the ability to correlate chest radiographs with CT or MRI studies rapidly on a video display. Direct image correlation with registration and superimposition has been achieved in the case of positron-emission tomography and MRI studies of the brain. For chest radiograph examinations, superimposition and subtraction of earlier radiographs to enhance the detection of interval change is being studied. The question of when digital chest radiography will replace conventional imaging is controversial. In a recent multiauthored review of this subject, it was estimated that digital chest radiography will replace conventional film radiography in at least 50% of large teaching hospitals by the turn of the century.(ABSTRACT TRUNCATED AT 400 WORDS)

Digital chest radiography: effect on diagnostic accuracy of hard copy, conventional video, and reversed gray scale video display formats.

Observer performance tests were conducted to compare the effects on diagnostic accuracy of hard copy (film) versus video display and to determine the diagnostic merits of conventional negative ("white bone") versus positive ("black bone") video displays. Subjective preferences were elicited from each observer for each display modality, and diagnostic accuracy was determined with receiver operating characteristic analysis. Digitized chest radiographs were used, including normal and abnormal cases with a variety of subtle abnormalities. The hard copy was printed with a 1,024 X 1,024-matrix by a high-quality drum scanner in conventional white bone format only. The video images were displayed on a 1,023-line monitor (30 Hz, interlaced) in both white bone and black bone formats with fixed window and brightness settings. Most observers preferred hard copy to video, but preferences were sharply divided between white bone and black bone video. Diagnostic accuracy was significantly greater with hard copy than with video display, and the conventional white bone format was significantly superior in accuracy to the black bone display.

Description of colours in video displays

The natural colour system (NCS) is introduced against a background of other systems for the specification of colours. Certain features of the NCS make it particularly suited to describing the colours on a video display. It is concluded that three different systems may be required to describe the colours on a video display: technical, stimulus and perceptive systems.

Visual Fatigue and Spatial Frequency Adaptation to Video Displays of Text

This article proposes that adaptation to the fundamental spatial frequency of lines of text on a video display terminal (VDT) provides a single explanation for a wide variety of reports of visual fatigue by VDT users. Reliable contrast threshold elevations at spatial frequencies of 2, 3, and 5 cycles/deg were found after subjects read single-spaced text on a VDT. This adaptation also reduces sensitivity to spatial frequencies in the range (2 to 6 cycles/deg) largely responsible for the reflexive accommodative response (Bour, 1981. Charman and Heron, 1979), and therefore could account for objective optometric measures of disturbed accommodation as well as some subjective effects of VDT viewing. Implications for video display design and for further research are discussed.

Review of: “Video and Digital Electronic Displays: A User's Guide”. By SOL SHERR (Chichester: John Wiley & Sons, 1983.)

Review of: “<i>Video and Digital Electronic Displays: A User's Guide</i>”. By SOL SHERR (Chichester: John Wiley &amp; Sons, 1983.)

Video Displays, Work and Vision

Video Displays, Work and Vision