抄録
The nighttime visibility of LED type outdoor display gets deteriorated due to the glare in the case of high luminance, while in the case of low luminance the visibility is enhanced, but not very conspicuous. The glare is caused by the high contrast. Therefore we inferred that the visibility may be improved by lowering the excessively high contrast. We can control the contrast by feeble lighting of the LED’s of the background part which are usually unlighted. We conducted a series of experiments to investigate the effect of the background lighting on the visibility. We found that the visibility is improved for a certain range of contrast, 4:1 through 100:1. It is suggested that for the above range of contrast, the glare is suppressed and yet the displays conspicuous.
