Abstract— The visual performance of TFT‐LCDs and CRT displays with different pixel densities were measured using task‐oriented tests and subjective measures of visual comfort and preferences. The effect of resolution on displayed letter legibility was measured. The legibility of letters increases with increasing pixel resolution. At a viewing distance of 50 cm, no significant differences were obtained in letter‐counting rates of capital letters 24 arcmin high, or reading rates of mixed‐case letters with 16 arcmin x‐height. In a second study for small letters, differences in letter‐counting and reading speeds were obtained for the different display conditions. For capital letters about 1.5 mm high, the letter‐counting speed was about 6% faster for a 157‐ppi TFT‐LCD than for a CRT. On 83‐ppi TFT‐LCD, letters this small could not be adequately rendered and were unrecognized. At a 50‐cm viewing distance, some subject preference and improved visual comfort was obtained for the high‐resolution TFTLCD.

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The authors measured the light-distribution patterns and the decay in light output of three mobility lights that visually impaired persons can use for night travel: the Wide-Angle Mobility Light (WAML), the Streamlight, and the Mag-Lite. The WAML had a wide beam with a medium-bright central region. The beam of the Streamlight had the brightest central region and a moderately wide surround of lower illumination. The Mag-Lite had the narrowest light distribution about a bright central spot. Both the Streamlight and the Mag-Lite maintained near-maximum brightness before undergoing rapid decay, while the WAML showed a gradual decay changing from near-maximum brightness to near extinction in almost a linear fashion 40 to 80 minutes after being turned on.

Abbildung 1 | Herkömmliche Realisierung von Intrusion Detection und BeweissicherungAUFSÄTZE DuD • Datenschutz und Datensicherheit 12 | 2009 737