Halogen projector bulbs

[SCHUB@xxxxxxxxxxxxxxxxxx]

     Dr. T writes:

> Finally, the size of the filament might affect the light
> output and sharpness (small filaments are usually better).

Edmund Scientific used to sell a book called "Popular Optics", written by
the founder of the company.  It has an excellent section on the design of
projectors, and the principles of condensor systems.  (At one time the projector
section of "Popular Optics" was also sold as a separate little book, but I
don't know if they do that anymore.  Anyway, the whole "Popular Optics" book
is worth getting).
    It's been a while since I thought about this, but as I recall, the object
was to put the "hot spot", that is, the brighest part of the beam of light
that comes out of the condensor lenses, right at the aperture of the projection
lens, and to make the size of the "hot spot" fill that aperture.  If you switch
to a smaller filament, I think you would have to alter the condensor system to
meet these requirements.
						Martin Schub


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