J. P. Gilliver (John) <
G6JPG@255soft.uk> wrote:
On Sun, 15 Aug 2021 at 18:45:10, Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote (my responses usually follow
points raised):
J. P. Gilliver (John) <G6JPG@255soft.uk> wrote:
On Sun, 15 Aug 2021 at 09:25:25, "Brian Gaff (Sofa)"
[...]
, My parents had a back projection model with what I now know was a
fresnell screen which tended to go yellow as it got older,
I'm curious to know what you mean by "back projection", especially if
used with a Fresnel lens.
It was a development by Philips/Mullard using the MW6-2 projection tube. >This looked like a long, slim hand torch with a 2" screen and a whacking >great glass connector on the side of the flare to handle the 25 kV EHT.
The tube stuck through a hole in a plane mirror angled at 45-degrees.
It faced into a spherical mirror which threw the light back at the
angled mirror and out of the housing at 90-degrees to the tube.
Sounds like a reflector telescope used in reverse, as it were.
I've just discovered that the optics were based on an infra-red
telescope that Philips were developing in 1939. They hid this research
from the Germans throughout WWII and then used it as the basis for their projection television system in the 1950s.
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
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