Displaying method adapted to visual acuity and brightness under viewing environment

The given time to gaze at an on-board display is very short from the viewpoint of safe driving. Therefore, the visibility of the on-board display should be more excellent than the general display. This report describes a method for improving display visibility. In this method, character size is decided, based on the spatial frequency properties, and the brightness of the display screen is selected using the adaptation properties. In the decision of character size, the two-dimensional frequency of the character (linear density) is calculated. Next, appropriate character size is determined from correspondence of this frequency and the spatial frequency (visual acuity). In a car-navigation display under low illuminance at night-time, the background luminance of the display screen is decided by the adaptation properties. Besides that, the character luminance is determined by the appropriate contrast with the background. Some experiments have shown that these methods were very effective in improving the display visibility.