411 REFERENCE · Wiktionary
Hermann grid
Reference material by Wiktionary contributors. This retains its source identity and is not 411 news reporting.
English
thumb|The Hermann grid illusion.
Grid illusion
Etymology
en Ludimar Hermann = German physiologist (1870).
Noun
An optical illusion where ghostly grey blobs are perceived at the intersections of a light-coloured grid on a black background.
en Optical illusions