Artificial lighting, huh?

I found it!
http://www.idtechex.com/products/en/presentation.asp?presentationid=219
LED's can be produced by a modified ink jet printer. I'm not
surprised at all; those things seem to be able to do anything. For
instance, they can lay down circuitry small enough for what I am about
to describe. I am assuming a slightly updated Stanford Torus, in
which one third of the inner curve is considered "the roof."

At this point I'd like to say that I used to post here as Xenophile
and that I am prepared to utterly reject my earlier advocacy of
natural sunlight piped into habitats via fiber optics. I'm sure that
FO will have many wonderful uses, but I no longer think that they are
the best option for lighting up the habitat.

I'd like to propose LED lighting, and not just any LED lighting.
Remember my earlier message in which I linked to the Fremont Street
Experience in Las Vegas?

http://en.wikipedia.org/wiki/Fremont_Street_Experience#Technical_details
http://www.youtube.com/watch?v=XM_ek4vV8vM
http://www.youtube.com/watch?v=Cok0B0y_wBE

The FSE uses three LED's (green, red, blue) inside a frosted dome for
each of their round pixels, and each of these is two inches across
(about 50 mm). The screen is seen from about 27 metres away.

I suggested that, while three LED's, each with its own wavelength and
each capable of 256 levels of brightness (total 768 levels for the
pixel), is enough to display 16.7 million colors to the human eye, we
would be using our version for more than seeing and pictures. So I
suggested twenty distinct wavelengths instead of three. It was
suggested that even that might not be enough, though most felt that it
was plenty. Well, have I got plans for this!

Looking stuff up shows that LED displays can exceed 600*600 dpi. It
can be made higher than that, but this is described as "difficult." I
have doubt but that in a decade or so it will be "easy," but I'll
stick to today's resolution for now. Now, dpi stands for dots per
inch, and an inch is (about) 25 mm. Now, if 600 * 600 LED's fit in a
square inch, then 10 * 10 LED's would fit in 1/60 inch * 1/60 inch.
Now, 1 mm is 1/25 inch, and 1/2 mm is 1/50 inch. So 0.5 * 0.5 mm
would be a fiftieth inch by a fiftieth inch. Now, this is larger than
the sixtieth by sixtieth which it takes, with today's technology, to
fit 100 LED's without being difficult. I don't think it's asking too
much of the technology of twenty or thirty years from now to do the
same in a slightly larger area. I'll assume the exact same 256 levels
of brightness per LED as used for the FSE today, thus giving each
pixel 25,600 total levels of brightness.

So I'm going to call that good enough: each pixel is a half millimetre
by a half millimetre, contains 100 LED's, each at a different
wavelength and each capable of 256 different brightnesses, and is
covered with frosted glass or plastic. It takes four pixels to cover
a square millimetre, four hundred to cover a square centimetre, and
four MILLION pixels (and thus 400 million LED's) to cover a square metre.

I am proposing that the entire 986,959 square metres of the roof be
covered in these pixels, requiring 3,947,836,000,000 pixels and
394,783,600,000,000 LED's.

About now, you are probably thinking, "Are you mad?" No, I'm feeling
quite peaceful. Remember, these LED's as well as the ungodly amount
of circuitry needed to support them can be printed, even today (yeah,
it would be an unworkably huge project today, but the basic tech is
here). Have a robot with the printer in it's belly crawl along the
roof and simply deposit it all in place.

Now remember, the pixels for the FSE are 400 times the size of these
(and round), only use three actual separate wavelengths, and are
typically viewed from 27 metres away. That is enough to create the
fantastic light shows that leave millions of people enthralled. Our
pixels are tiny by comparison, square (and thus can be packed together
without so much blank space between), and will typically be viewed
from as little as 20 metres and as much as 75 metres away. This
should be perfectly adequate for all our lighting, display,
photosynthetic, and other interior light needs.