"Focusing tio infinity, and evaluating divergence".
I didn't want to waste a thread for this ... this seems like a good spot for a simple question.
Yesterday morning, at about *4:00 A.M.*, I took out my new 200mw Green Gatlin, and my binoculars (10x50), both mounted to a heavy duty camera tripod with something I rigged.
My apartment complex is divided into 2 "phases" separated by an open field (don't ask me why, I don't know, it's weird).
My apartment is at the southern edge of the complex. I targeted the Gatlin on a building WAY across the complex near the northern edge; spot was towards the TOP of the building, AWAY from windows. Then I worked the focus knob for the SMALLEST spot possible.
I have some maps of my apartment complex / area, that I printed off of TerraServer some time ago; accurate scales, grids (this was for certain amateur radio uses).
The beam path was almost exactly *250 meters* in length.
After that, I CAREFULLY moved the laser around a bit to compare the size of the spot to some objects.
The now-focused spot, at that distance, SEEMS to be *slightly* larger than the width of an automobile license plate; say, about a > foot/30cm or so. It's possible that is under-estimated, because even the TEM00 spot isn't perfectly/sharply defined, but it looks pretty good with this laser.
I marked the Gatlin with "index" marks, on the case / focus knob for this point (permanent marker covered with small squares of transparent cellophane tape).
I realize that quality varies from laser to laser, and probably even among instances of the same model... but GENERALLY, is that pretty good? Or can I / "should I be able to" do better?
Thanks.
EDIT:
Actually I just found this:
mRad:
http://www.pseudonomen.com/lasers/calculators/mRadCalculator.html
diam:
http://www.pseudonomen.com/lasers/calculators/diameterCalculator.html
... and I plugged some numbers into it. I had to guess on some things, the O-Like website doesn't provide many tech details for this laser, but I used some typical values for other green lasers.
The results seem to imply that my divergence / focus is pretty good/average for a "typical" green DPSS.