In the late 1950s and early 1960s, schools and businesses started to use overhead
projectors. The first overhead projector was used in 1945 by U.S. Army for wound down
of World War II. Slide projectors of 35 mm photographic positive film became popular
among family entertainments from 1950s to the 1990s but by the early 2000s it was
replaced by digital images.