Abstract
Seven segments numerical light emitting display devices installed in cars have been used at night and day. At that time, characters of the brightness vision have been most influenced by the illuminance.
Then various tests were carried to investigate throughly the relations between the illuminance and the point of subjective luminance equalities (hereafter called the PSE) on indicative figures with the light emitting diode (hereafter called the LED), the fluorescent light display device (hereafter called the FLD) and the negative type liquid crystal display device (hereafter called the LCD). The following results were obtained from the various tests.
(1) The light emitting display devices and LCD showed significant differences with respect to the influences with the illuminances and the indicative figures, since the differences of the figure's form and the luminance distribution in the segments.
(2) According to increase of the illuminance, the PSE with LED have gone down and kept equilibrium in 1000lx. The FLD have been slightly influenced by the illuminances. Then the PSE with LCD has decreased suddenly in the illuminance of more than 300lx.
(3) By inspection of Weber ratio, it was found that FLD, LED and LCD were ranked according to their brightness difference discriminations.
