Projection Apparatus, about 1880
During the 1870s, the French optician Jules Duboscq devised this elegant instrument to project images from a horizontal surface onto a vertical screen. When the projector was illuminated, listeners could see iron filings arranged around an electromagnet, properties of polarized light and similar phenomena. The costly apparatus, used at the United States Military Academy at West Point, would not have been operated by students. A similar overhead projector, on the design of Henry Morton of the Stevens Institute of Technology in Hoboken, New Jersey, sold in this period as a "vertical lantern."
Transparency for Teaching Biology, about 1963
By the early 1960s, Minnesota Mining and Manufacturing Company (3M) had developed new ways to copy documents. To encourage wider classroom use of their products, they distributed transparencies like this one. It shows the glands of the human endocrine system in both men and women. Some transparencies appeared in textbooks, and others were displayed using overhead projectors. Traditional manufacturers of teaching devices, textbook publishers, and teachers also made transparencies for educational purposes.
Visual Cast Overhead Projector at the U.S. Military Academy, 1961
Overhead projectors were introduced into U.S. military training during World War II, and used at schools like the U.S. Military Academy after the war. This photograph of a West Point mathematics classroom includes an overhead projector on the right. In the 1960s, technical improvements, government funds, advertising, and the experience of teachers combined to make these projectors a popular teaching aid.