Abstract
Maturing flat panel display and membrane switch technologies permit increased capability and flexibility for person-computer interfaces. A recently established Boeing product line labeled the Universal Display and Control System (UDACS) effectively exploits these increases by including as one component a large LED display that is overlayed by a transparent membrane switch. This approach provides programmable switch legends as well as a capability to display textual, tabular or limited resolution graphic data either as a complement to, or substitute for CRT displayed data.
Development of the LED panel and switch overlay from a laboratory proof of concept breadboard into a production system for a military airborne application necessitated that a variety of human engineering design and specification issues be addressed. This paper discussed selected issues in each of three categories: image quality, switch characteristics, and software considerations.
The LED display is built up of individual modules, each module being a 48 × 96 array of LEDs. The area of image quality for which quantitative guidance is notably lacking in the literature concerns the various types of uniformity-including small and large area luminance uniformity, color uniformity, and alignment within and across module boundaries. Each of these was discussed in relation to use requirements, measured uniformity, and subjective impressions.
Transparent membrane switches differ somewhat radically from more traditional switches in a number of ways. Unlike traditional switches, the optical, tactile and electrical properties are so inextricably interrelated that they cannot be considered and designed separately. For example, inclusion of a tactile positioning cue typically requires compromises in optical quality. Similarly, since there is little or no physical movement on activation, routine activation feedback must be presented in a different manner. Some of the derived switch requirements in each of the above dimensions together with their rationale were presented.
The third category addressed was software issues. Among these are operator feedback, function hierarchy and accessing schemes, and display formatting. For example, what tradeoffs must be considered in determining the utility of and necessity for labels and boundaries for groups of related switches, characteristics that are included routinely in more traditional switch panels.
The paper concluded with an attempt to delineate those issues for which reasonable design guidance is available and suggested specific research needs in some of the areas where design guidance is lacking.
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