P3D Re: Microscope and projector filament spacing( Was white LED efficiency)

[Greg Erker <erker@xxxxxxxxxxxxxx>]

>>To get around the coil spacing problem I offset the filament. I have a
>>1.7mm x 0.5mm filament coil in a 20w, 12v Halogen lamp that I use for
>>microscope illumination. I offset the filament by 0.6mm. The reflected
>>filament and the forward filament look like a pair of side by side
>>filaments that now occupy 1.7mm x 1.2mm. I use a simple 50mm radius
>>mirror. This is nearly as good as afocal because the mirror radius is
>>much longer that the filament size.

  Our overhead projector here at work also
has an adjustment to offset the reflected
filament into the true filament's gaps.
Seems to work fine though I don't know
what percentage of light is lost.

Greg E.