OverheadProjektoren
OverheadProjektoren, commonly known as overhead projectors (OHPs) in English, are optical devices used to display content printed or handwritten on transparent sheets. The transparency, placed on a flat glass stage, is illuminated from beneath by a bright light source, usually a halogen lamp. The light passes through the transparency and is focused by a lens to form an enlarged image that is projected onto a screen in front of the presenter. A small mirror may be used to redirect the image toward the screen, depending on the model.
Users can write on the transparencies with dry-erase or other erasable markers, allowing on-the-fly annotations during
Overhead projectors became common in classrooms and meeting rooms from the 1960s through the 1990s as a
Safety and maintenance considerations include proper ventilation to dissipate heat from the lamp, careful handling of