John J wrote:
David Nebenzahl wrote:
On 11/11/2008 5:18 PM John J spake thus:

The scanner thread pinged my imagination. Didn't come up with a
response but reminded me...

8x10 enlarger light source - what about an intense tube light moved by
a scanner (stepper) motor close to the negative? It would make a low
profile head, be cool (temp), is programmable (motion rate), and just
fill my weeks with an excuse not to shoot!
Lemme see if I understand this: this would be a light source that would
be "scanned" across the negative (I assume in just one axis, not an x/y
scan) while the exposure is being made? So the stepper would have to
complete its run in the time of the exposure? Hmmmmm ... verrrrry
eenteresting.

If the idea came to my mind, then it is certain that someone smarter has
already considered, then discarded it. But I'll sleep on it.

It has been done in various ways for a very long time.

In 1927 or thereabouts, my grandfather made one of the first television
systems at Bell Labs. They did not have image orthocon tubes, or even
iconoscopes in those days. He invented a way to make sensitive photocell
tubes. They placed these around the studio (which was illuminated with
subdued lighting. They had a carbon arc light that went through a spinning
Nipkow disk (a disk with a spiral of holes in it) and an optical system so
the beam of light scanned the scene and the photocells picked up the light.

This actually worked, and was a lot cooler than if the entire scene were
illuminated to the level the arc light put out.

This link shows a little of how it worked, but important details seem to be
missing:

http://www.earlytelevision.org/bell_labs.html

This link shows my grandfather holding one of the photocells he made:

http://movingimage.us/site/calendar/...7/1987_dec.pdf

This one is a bit easier to read:

http://www.corp.att.com/history/television/ives.html
http://www.corp.att.com/history/tele...witworked.html

Since they did not have CRTs yet that would show to a crowd, they made a
monitor that was a huge neon sign tube that went back and forth to make up
the image area, with lots of electrodes that could control the brightness of
each picture element. There was a big synchronous motor (had to be
synchronized with that in the "camera") to select which picture element
would be illuminated.

We have come a long way in less than 100 years.

Later, devices called flying spot scanners were made, that generally used a
CRT as the light source. But when my grandfather started out, no one had put
a phosphor at the front of a crt before, and they generally deflected the
beam only along one axis.


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