A subjective appraisal of the effects of reflected images of dispersed small sources on the readability of characters on the display screen with a specular surface was previously reported in 1987.
It was suggested that the luminous pattern of the external light source reflected on the screen also has a major effect on display readability. If a reflected image is separated into many pieces with a non-luminous grid and every piece is small compared with a displayed letter, they might overlap on the letters randomly, then the letters would be recognized to be different ones, and readability of them would be disturbed.
On the other hand, if reflected image is relatively large and continuous compared with a letter, interference of the image to readability of letters might be reduced.
Therefore, influence of luminous pattern of the reflected source such as size and arrangement on a permissible luminance of them was studied. One large continuous source and many dispersed small ones are compared.
The results are as follows:
Permissible luminance for reflected images of relatively large-area source is slightly higher than that for many dispersed small sources.
However, in actual lighting designs, this is not so significant as to cause a change of the permissible luminance for light sources of various size and arrangement.
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