A human performance evaluation of a large-screen light-valve display system was performed to determine character legibility requirements for four viewing distances (6-15 ft. ) and a viewing angle of 45 degree off-axis, under medium ambient illumination. Other independent variables included dot-matrix size and contrast polarity. Results indicated that both dot-matrix size and viewing distance, and their interaction, significantly influenced legibility measures. The only character configurations that fulfilled legibility criteria over the entire range of viewing distances were the 10 multiplied by 14 dot-matrix formats for both positive and negative contrasts. Negative contrast was significantly better than positive contrast. Visual angle was correlated with performance, but the relationship was nonlinear. The extent to which a stimulus of a given visual angle exceeded legibility criterion depended on the combination of its dot-matrix format, contrast polarity, and viewing distance. Results for off-axis viewing indicated that only the 10 multiplied by 14 dot-matrix format was legible through 45 degree . Thus, the results of this study indicate that several legibility requirements (e. g. , visual angle) specified for other display media are inappropriate for light-valve projection display technology.
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