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[photo-3d] projection using tru-beam lamps
- From: John Toeppen <toeppen@xxxxxxxx>
- Subject: [photo-3d] projection using tru-beam lamps
- Date: Mon, 16 Apr 2001 09:56:59 -0700
Don wrote:
>bulbs a large percentage of this light escapes
>from the sides and is not captured by the
>projector optics.
Tru beam lamps have reflectors that gather the light going out to the
sides. It is worth noting that such parabolic reflectors do not reimage
the filament into the projecting lens. These lamps produce a "beam
waist" about 2 1/2" in front of the reflector that is typically about
3/4" in diameter. The beam waist is then reimaged into the pupil of the
projecting lens. One down side of these lamps is that the center of the
light lobe has a dark spot where the blub is. While these sources can
reduce cos4 losses, it often leads to a dark spot in the center of the
image. The longer track length is often difficult to enclose as well.
The halogen color temp is better and the reflector only reflects the
visible light thereby reducing film plane temperture. Correct
conversion to this kind of light is a bit difficult.
John Toeppen
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