Re: Laser x-y game

At 05:13 PM 5/28/97 -0400, you wrote:
>O.K. Let me add another chapter to the rumor mill.
>
>While working in the game business over the last few years, I heard a story
>about this guy in town that built a widescreen asteroids.
>
>They tell me he used a small HE/NE laser and two mirrors driven by the x and
>y outputs. Surely this would be far easier as you are only dealing with one
>color.
>
>I still can't quite grasp how to do the Z intensity ????

Bill (Paul) has a small HE/NE laser and two mirrors attached to a couple of
drivers designed for this sort of thing, and I'll be damned if he can get
anything more than a fancy figure eight out of them. They're just too slow.
We put a test oscillator into the X/Y drivers and they pretty much flatline
at about 200hz.

Bill called around, and to get galvanometers(sp?) fast enough to do
"Asteroids" speeds, you're going to have to shell out quite a few $k.

Maybe some mechanical engineer/genius can come up with a better way to
deflect the beam? The hardest part doesn't seem to be getting the beam
there fast, it's stopping it once your there. Your going to need very fast,
tightly controlled servos. Bill's drivers were not working as servos, they
seem to be coils and a magnet. Current through the coil deflects the
mirror, much like a speaker.

We were driving them by simply attaching them to the output of a test
oscillator, so we were using a constant voltage source, maybe if we drove
them using a current controlled amplifier (like the amplifiers that drive
X/Y yokes) we'd have a little better luck. Still these are low end drivers
(you know less than a few hundred bucks) and they don't move fast enough to
do anything useful as far as displaying a vector image goes...

We figured if you can build mechanical drivers fast enough to display an X/Y
image, then a third driver could be used as the Z-axis by simply deflecting
the beam onto some sort of shadow mask -- like a piece of cardboard, when we
need to turn off the trace.

By calling around, Bill found drivers that max'd out at around 100khz, so it
can be done. I believe the price of these were near $20k, but I think you
can get some slower ones, that would still work, for around $6k (two axis
only, no Z-axis).

Now if we could only deflect the laser like we can deflect electrons in a
CRT, using some kind of yoke, we'd have a cool display! Maybe miniature
black holes modulated with a Voltage Controlled Worm Hole? I'll check the
local surplus stores... :^)

-Zonn
Received on Wed May 28 15:15:14 1997