Can anyone tell me about the history of projection, Like when projection panels were invented and hwo it evolved into seperate projectors and so on, because I searched the web without success.
ThaNKS.
ThaNKS.
Projection TV History
Work resulting in useable CRT based projection television occured in the 1930's. By the mid 1940's there were sophisticated home entertainment rear screen projection TV receivers using the same lenticular/fresnel based screen technology employed today! RCA was a forerunner in developing this stuff. RCA had a theater projector in the early 40's called the PT-100 (IIRC) that did a 15x20 foot screen. It employed a 7" CRT (7NP4) operating at 75-80 kilovolts!!!! The schmidt optical system used a 30" diameter spherical mirror.
Eidophor was the first light valve projector using an E-beam scanning a thin film of oil on a front survace mirror inside a vacuum chamber. This technology makes fantastic video pictures the size of drive-in movie screens. I have Eidophor projectors and used to own many of the high power commercial venue CRT projection systems as well. General Electric also manufactured a series of their own light valve projectors with similarities to the eidophor.
Using liquid crystal and other panels for television projection is a relatively recent advance in this art.
I collect vintage television receivers and have a few of the early home projection units. Here is a photo of a 1949 RCA set, model 9PC41. The four chassis and 41 tubes electronics package was the same and was used in models from 1946 through 1949. The light engine is a 5" 5TP4 CRT operating at 29 kV in a Schmidt optical system employing a ~10" diameter front surfaced spherical mirror and circular correction lens.
Work resulting in useable CRT based projection television occured in the 1930's. By the mid 1940's there were sophisticated home entertainment rear screen projection TV receivers using the same lenticular/fresnel based screen technology employed today! RCA was a forerunner in developing this stuff. RCA had a theater projector in the early 40's called the PT-100 (IIRC) that did a 15x20 foot screen. It employed a 7" CRT (7NP4) operating at 75-80 kilovolts!!!! The schmidt optical system used a 30" diameter spherical mirror.
Eidophor was the first light valve projector using an E-beam scanning a thin film of oil on a front survace mirror inside a vacuum chamber. This technology makes fantastic video pictures the size of drive-in movie screens. I have Eidophor projectors and used to own many of the high power commercial venue CRT projection systems as well. General Electric also manufactured a series of their own light valve projectors with similarities to the eidophor.
Using liquid crystal and other panels for television projection is a relatively recent advance in this art.
I collect vintage television receivers and have a few of the early home projection units. Here is a photo of a 1949 RCA set, model 9PC41. The four chassis and 41 tubes electronics package was the same and was used in models from 1946 through 1949. The light engine is a 5" 5TP4 CRT operating at 29 kV in a Schmidt optical system employing a ~10" diameter front surfaced spherical mirror and circular correction lens.
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Here is one of my Eidophors being projected out of the back of my video location truck being tested on a drive-in movie screen. Video source was a Pioneer laser disc player.
The light valve allows a separate high intensity light source to provide the light rather than relying on the limited light ouptut of glowing phosphors as in a CRT based projector. This Eidophor uses a 4.2 kW xenon arc lamp like a movie theater projector.
The light valve allows a separate high intensity light source to provide the light rather than relying on the limited light ouptut of glowing phosphors as in a CRT based projector. This Eidophor uses a 4.2 kW xenon arc lamp like a movie theater projector.
Attachments
ancorp said:
The Eidophors I bought surplus from the US Government in the early 90's cost them about $1/4 Million each in the early 80's.
They are incredibly complicated physical plants with on-board high vacuum pumping system, refrigeration, etc. You can change the hair pin tungsten CRT cathode while the system is at vacuum through a special interlock. The Eidophor is similar to a scanning electron microscope in build and complexity. It is very expensive to keep an Eidophor running because of the special skilled attention they require and the expensive 'consumables' such as cathodes and arc lamps which alone can be $20.00+ an hour.
Modern DLP and LCD technology has made the Eidophor obsolete.
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