An early 20th-century optical device used to project enlarged images of photographs, slides, or documents onto a screen for viewing or demonstration.
From Greek balon (throw) + opticon (relating to sight/vision). This is a portmanteau created around 1900 for an educational projection device.
The balopticon was basically the PowerPoint projector of the 1910s-1920s—teachers would use it to show pictures to whole classrooms before slides, film strips, and eventually digital projectors made it obsolete!
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