STUDIES OF DISPLAY SYMBOL LEGIBILITY PART Ⅱ THE EFFECTS OF THE RATIO OF WIDTHS OF INACTIVE TO ACTIVE ELEMENTS WITH A TV SCAN LINE AND THE SOAN PATTERN USED IN SYMBOL CONSTRUCTION

摘要

The purpose of the present study was to- investigate" the effects on legibility of several factors characteristic of linear scan methods (TV raster) of symbol construction and display. These factors were: (1) The ratio of the widths of inactive to active elements within a TV scan line, (2) the scan pattern (the path of the scan element over the symbol) used in symbol construction. This study represents a continuation of an earlier study in which the effects on legibility tyof the number of linear scan constructions per symbol height were examined, purpose of the study was to determine whether the method of symbol illumination (reflected light vs. transilluminated light) had an effect on legibility. Two groups of subjects viewed tachistoscoplcally trans-illuminated capital letters at a 03 sec. exposure for each of three different ratios of me widths of inactive to active elements within a TV scan line. Each group viewed letters constructed by a different scan pattern. The results showed that both accuracy and speed of response in letter identifications decreased as the ratio of the widths of inactive to active elements increased. The scan pattern used in the construction of letters had a progressively greater effect on response accuracy as the ratio of the widths of inactive to active elements within a TV scan line was increased. The method of symbol illumination bad no effect on either response accuracy or speed.