The Readability of Various Color Vacuum Fluorescent Displays Under High Brightness Ambient Conditions

The evaluation was made on phosphors of seven different colors in current use under high brightness ambient conditions. As the result, the use of an appropriate filter (e.g. Neutral Density Filter of 3.4% transmittance) allows the 3-digit numbers in the display of about 400cd/m² to be read correctly under an ambient illuminance of 50,000 lx, regardless of colors used. On the contrary, when a filter of high transmittance, such as Neutral Density Filter of 10%, is used, the required display luminance in the same ambient differs depending on phosphors; 300cd/m² for reddish orange to 1,600cd/m² for greenish yellow.