Proposed evaluation method concerning numerical display device visibility

The authors describe the clarity and legibility of characters on numerical display devices of the luminous type (light-emitting diode, vacuum fluorescent display, and liquid crystal display of the negative type, which is regarded as being of the luminous type) and nonluminous type (liquid crystal display of the positive type). The brightness, luminance contrast, indication numerals, illuminance on the display device faceplate surface, and angle of the inclination of the display device faceplate, affecting both the clarity and legibility of the characters, were measured to make the cross-correlation of these parameters clear from the viewpoints of both the clarity and legibility of the characters. Significant differences were observed between the illuminances and indication numeral when the clarity and legibility of the characters were measured on the luminous display devices. Based on the measurements described, a method for testing the visibility of the characters on the numerical display devices is proposed