[Laser] Stepper motor control of laser communication unit

Kerry Banke kbanke at qualcomm.com
Fri Oct 22 11:19:50 EDT 2004


Actually we use  the micrometers to move one  end of a 12" bar hinged at 
the other end. If I did the calculations right  the StepperMike moves our 
laser beam  about 1" per step at 10,000 feet.  There are  three reasons 
that come to mind for trying the stepper approach.  Just placing my hands 
on the manual micrometers puts tension on the mechanics no matter how 
careful I am.   I found that working on a target 4 miles out with a 12" 
spot is a problem when you try to let go of the micrometers as things move 
slightly. This maybe not a problem if one is hauling around a very heavy 
base & mechanism but that's not what we do. We use the same tripods used 
for our microwave hilltopping.   I also have found that we end up 
nearly  always  doing a manual raster scan to find the target as our scope 
and laser are never perfectly aligned after transporting & setting up.  The 
cross hairs on my 24X rifle scope are wider than the laser beam at 4 
miles.  The final reason is that since we stumbled across these 
StepperMikes, the opportunity to learn  seemed  to good to pass up. These 
units may also be useful as we move up beyond 47 GHz.
  - Kerry N6IZW -

At 07:15 PM 10/21/2004, you wrote:

>Kerry,
>
>The stepper motor approach works pretty good.
>I use a pair of "BIG" compumotor drives that were used for disk drive servo
>writing. I put a pair of mirrors (x,y) and used them for pointing the beam.
>
>The 1/10000 of a turn (0.6mR)is still a bit course.
>Typical beam divergence is about 2mR (0.1 degrees). 360 degrees = 2*PI 
>radians.
>If you run thru a 10:1 beam expander, divergence will drop by 10 to 0.2mR.
>So you might want to use some mechanical leverage to reduce movement.
>
>I ran my 1/50000 steppers into a leadscrew system that stepped it down to 
>10uR.
>
>Jim
>N9JIM/6
>
>-



More information about the Laser mailing list