Visual characteristics of LED displays pushbuttons for avionic applications

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Visual characteristics of LED displays pushbuttons for avionic applications

Vanni, P. / Isoldi, F.

Programmable LED matrix display pushbuttons may greatly increase the performances of the computer based avionic systems. Switches' number in a control panel can be reduced by a factor of 10 or more. This leads to a reduction in weight and size of the control instrumentations and in shorter response time of pilots. This work deals with the study and the optimization of visual performances of these displays in a configuration requiring a low power consumption and Night Vision Goggles (NVG) Compatibility. Considering displays for avionic applications is important taking into account sunlight readability. Visibility problems may raise in high ambient illumination, up to now the only contributions usually considered for reduction of visibility are the diffused and specular reflected luminances, that predominate with the sun behind the pilot. But there is another critical condition, the sun in front of the pilot, in this case the equivalent veiling glare predominates. Display performances and contrast enhancement filter characteristics must be optimized to find a compromise between these two extreme ambient conditions. Considering a keyboard with 10 pushbuttons, with two lines of four characters each and a power consumption less than 14 W with 40 % of LED's on, good sunlight readability has been obtained choosing an optimized combination of NVG and contrast enhancement filter and LED matrix display.