New Projector Throws Illustrations Behind Speaker’s Back (Apr, 1935)
New Projector Throws Illustrations Behind Speaker’s Back
FACING the audience as he talks, a speaker may now illustrate his lectures on a screen behind him without turning around with the aid of a novel optical projector recently perfected by a well known German firm.
The speaker, directly facing his audience, illustrates his talk by writing or drawing horizontally on a sheet of cellophane lying on a glass table before him, and the script is projected, ten to fourteen times enlarged, on the wall screen behind him.
Underneath the glass table, the light of a 500-watt bulb is condensed and reflected through the transparent cellophane. The lines then pass through a lens to the mirror and -are projected onto the screen.
good one !
I was once told that the over-head projector was invented by the military so that instructors could keep an eye on sleepy GI’s.
You were told wrong.
1939 Principle used in bowling alleys http://www.google.com/p…
1941 same inventor http://www.google.com/p…
1944 civilian http://www.google.com/p…
1948 (filed) civilian http://www.google.com/p…
1948 another civilian http://www.google.com/p…
1963 The one we all grew up with http://www.google.com/p…
Very informative, thank you.
And yes I do remember the last one quite well. Right down to the trapezoid door to access the bulb.
Wow 500Watt bulb. Must have cost a fortune back then to keep that thing going.