Re: Generation of Ultrasound in the Megahertz region

John Larkin wrote:

I've always wondered how much a regular quartz crystal would scatter a
laser beam when driven hard. Some crystals have a quartz disc with
plated electrodes in the center and a clear rim, so you could un-can
one, shoot the laser through the clear part, and build a nasty
oscillator that drives it insanely hard. These crystals mostly run
shear mode.

This is a bit OT, but hey it's Friday

Many moons ago when I was a programmer, I worked in St Louis for a stock
brokerage company. They had these bad-ass laser printers that printed on
continuous forms paper at a rate of 30"/second. No matter what size fonts
or lines/inch, the paper always moved at the same speed. Amazing machine
(Siemens 0777 Laserdrucken (sp?)), especially the stacker. At any rate,
there was some documentation laying around and it included a theory of
operation. Well how could anyone resist looking at that. ;-)

Now to the point. The laser went thru a "lens" (might have been quartz, I
don't recall). The lens was somehow vibrated/modulated by several audio
range frequencys. This had the effect of splitting the beam into multiples
that, IIRC, came out parallel. By turning a tone on or off, the beam would
reciprocate at that position. This allowed the laser to scan the drum 6
times as fast since it was drawing with multiple beams. Pretty smart IMO.
It's been 20 years so please forgive my rusty memory on the details. :-)

The fuser/stacker was a seperate module so the paper travelled several feet
in the open with the print on the paper only being held in place by static
electricity. People couldn't resist not touching it when the door was open,
but don't touch the edge. Not many places can you get a paper cut that
results in stitches. I wish I had video of it in operation. The stacker
was just incredible. Paddle wheels, flappers and air puffing jets to coax
the continuous form paper into fan-folding back up. The key to getting the
stacker to work was to feed the first two pages thru the fuser pre-folded.
That way you could tell how it had to fold back up. After the fuser
"ironed" the perforations, you couldn't tell which way it originally went.
But the paper knew. ;-) It had just enough memory that if you didn't start
it correctly it would mess up every 100 pages or so.


.

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