An Evaluation of the Effect of Spot Wobble Upon Observer Performance with Raster Scan Displays

摘要

A television image is formed by a series of parallel luminous lines called a raster. The visual prominence of the raster structure has been shown to interfere with the extraction of information from the image. However, the raster may be suppressed experimentally by a deflection process called spot wobble. Experiments were conducted to determine the effects of raster structure suppression on visual sine-wave contrast sensitivity thresholds, dynamic target acquisition performance using noise-free and noise-degraded imagery, and alphanumeric recognition performance using noisy and noise-free static displays. Results of the dynamic experiment indicate raster structure suppression and improvements in sine-wave threshold sensitivity are correlated and that a suppressed raster significantly improves target acquistion performance for noise-free conditions. Results of the static experiment were inconclusive, as no spot wobble effect was obtained, although display noise had a significant effect upon search time. Significant correlations with the modulation transfer functions area (MTFA) image quality metric were obtained, although the correlations were neither large nor consistent enough to be strongly advocated for detailed design evaluations.