LASERS! && Freemont Street LED array (was Re: Cray J932SE (was Re: Straight 8 up on Ebay just now))

Mouse mouse at Rodents-Montreal.ORG
Tue Jul 19 15:46:54 CDT 2016

>> You'd probably know, then - what's the fastest way to deflect a
>> laser beam?  In particular, I'm wondering how practical it might be
>> to take a laser and turn it into a vector display on a handy blank
>> wall [...]
> What bandwidth (deflection rate) do you need?  Full scale in a
> microsecond?  In 10 microseconds?

Well, if it takes longer than 100ms to replot the display, it will
flicker visibly, and the more under 100ms the better.  In that time I'd
like to draw at least a couple hundred lines, though most of them will
be short (line length maybe 1-15% of corner-to-corner distance).  What
kind of radians/second deflection rates this means depends on how far
from the wall you put the projector.

But, in terms of the bandwidth on the X and Y axis signals?  If we say
200 lines at 25 ms replot (I get 20ms frame rate out of the cg6 for
displays significantly more complex than that - ie, with the cg6 the
actual limitation is the video signal vertical frequency), that's
125us/line.  Turning sharp corners is the hard part with mechanical
deflectors like mirrors, as it means very high acceleration of the
mechanical parts.  I haven't done the math to be sure, but,
until/unless taught otherwise by testing, I'd feel dubious about
clipping the X and Y signal bandwidths at anything lower than ~1MHz.

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