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I think this is the first
projector lamp I've actually catalogued in my collection - though I
know that there are another couple in there. Though I'm
meaning slide projector here, as I know there's one in this section
from an overhead transparency projector as well.
This
really does show that lamps come in all shapes and sizes, this one
appearing more like something The Doctor would pull out from behind a
panel in the TARDIS than a light bulb...fact of the matter is, is that
it's a very specialised lamp.
Very
early film projectors used carbon rods to produce their light, which
while very bright required continual attention, made a horrendous
amount of noise, used even more horrendous amounts of power, and
produced enough UV to cook anyone nearby who wasn't protected against
it. Needless to say, when filament lamps capable of filling
the same role, then followed by discharge lamps, these were innovations
very quickly picked up. It's only since 2004 or so that
relatively affordable (LCD) projectors have started to appear in the
home, using ultra-high-pressure mercury discharge lamps to produce
their light. Before that, the lamp in a home based projector
would almost exclusively have been incandescent.
You
couldn't just pick a high wattage incandescent up and stuff it in front
of a mirror though. Projectors need a very precisely focused
light source to "inject" the light correctly into their optical system,
otherwise you'll end up with one part of the image brighter than
another, or just no light at all being apparent on the
screen. Higher wattage lamps (generally for movie projectors)
tended to use lamps with a carefully designed filament with a very
tightly packed zigzag shape to present a square uniform area of
light. Smaller lamps used a bit more varied methods though,
such as this lamp which uses a very small filament for the wattage and
a specially designed, highly reflective reflector to deliver a
precisely focused beam of light into the projectors optical
system. Of course, having the reflector built into the lamp
means that a nice new, clean one is installed with each new
lamp. Especially important in an application such as this
where one stray fingerprint could be a real problem. The key
in the base on this lamp would align with one in the socket for the
lamp, meaning that it will always slot in in the correct position for
operation.
This is
a lovely made piece of lighting technology. Everything about
it is very precise, and the reflector is very, very highly polished
indeed.
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