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.

5 comments
  1. iswandoyo says: August 9, 20071:51 am

    good one !

  2. Timmay says: August 18, 20105:10 pm

    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.

  3. Firebrand38 says: August 18, 20105:56 pm

    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…

  4. Timmay says: August 19, 20108:06 am

    Very informative, thank you.
    And yes I do remember the last one quite well. Right down to the trapezoid door to access the bulb.

  5. M.S.W. says: August 20, 20108:05 am

    Wow 500Watt bulb. Must have cost a fortune back then to keep that thing going.

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