Artykuł porusza kwestie pomiaru równomierności oświetlenia oraz parametrów związanych z tym zjawiskiem: współczynnika kontrastowości, nierównomierności kontrastu, luminancji i jej nierównomierności. Przedstawia powody, dla których te parametry są istotne pod względem użytkowym, oraz opisuje metody, jakimi można badać wymienione powyżej parametry. Przedstawia wyniki badań wykonanych na próbie pięciu monitorów tego samego modelu.
The illumination uniformity in LCD monitors is analyzed in the paper. The phenomenon is described and explained by taking into consideration the following parameters: contrast ratio, luminance, uniformity of display contrast, and luminance. No defined measurement method of these values exists (except partially different standards by ISO, VESA, ANSI). The method which unify and minimize measurements is described in the paper. The same measurement points are used to measure all parameters under consideration. Luminance measurements are made in a dark room, on center of a screen surface emitting white color. The same is also used in uniformity measurement (Eq. 1). It describes luminosity difference values in different places of monitor. Contrast ratio (Eq. 2) measurements were made using electronic set of photodiode and transimpedance amplifier in one structure (Fig. 2). Uniformity measurement of display contrast have been made in few points, defined by VESA organization (Figs. 3, 4, 5, 6). 5 monitors of the same model were tested (Tab. 1). Contrast ratio show significant difference for each monitor and between each other. Similar results are for luminance and luminance uniformity (Tab. 4) where difference in uniformity reached almost 40%. Type of monitor backlight is main cause of poor uniformity, but also quality of LCD matrices may have influence on overall comfort of using such moni-tors. The results show that luminance and contrast uniformity should be given in technical specification of products.