Laser Collimation

[DJVege]

Guys, I can't seem to collimate this laser collimator!!

I know how to play with the screws etc... but when I turn it in a circle, it's not pointing at the same point. It's making circles, ellipses etc... And I don't know how to work towards making the circles smaller... Get what I mean?

My process is, I have a V cut into 2 bits of wood (thanks to Phil), these are held in place, and the collimator lies in the Vs, pointing at a wall. I turn on the collimator and mark on the wall, a cross where the laser is. Then, I turn the laser in the Vs (vice I guess), and if the laser stays in the same point on the wall, I'm collimated!! But this never happens. I'm always makin circles or ellipses. Sometimes I'll adjust the screws, and the circles get smaller (yay), but I'll adjust them again, and they'll get bigger (Noooo!!).

Any advice?

Thanks!!

[davewaldo]

What you are doing is correct, you may just need to perservere.

What I did was the following:

I stuck a piece of paper on the wall (10M away from collimator) and aimed the laser at this. Then I marked the points on the paper as I turned it in the V bracket. This created a series of marks which made a circle on the paper. Now adjusting the small screws on the collimator I aimed to get it to the middle of this circle.

I would then repeat the process until it didn't move at all.

One thing to keep in mind is that you should always only just turn the collimator on. By this I mean only turn the "On" screw/switch until the laser comes on and then stop. Some collimators go out of alignment if their switches are screwed on/down too much.

Hope this helps.


Dave.

[DJVege]

Yup! I've read that somewhere before, about being cautious of turning the "on screw" too much. I'm going to try your way of doing things now.

Cheers Dave.

[taminga16 (Greg)]

Dave, another good idea is to mark quadrants on the laser body ie; NSEW, it will help to keep track where you are, and make it easier to retrace your steps, oh and only make one adjustment at a time.

Regards Greg.

[DJVege]

Uh, this isn't working...I keep getting circles...no matter what I change.

[davewaldo]

Where in Brisbane are you? I could always have a look at it for you...

[taminga16 (Greg)]

Dave, Is your "vice" secure? are the "V" cut-outs exactly the same and mounted on the same axis?
Greg.

[davewaldo]

As far as I know, the V's don't need to be teribly accurate. It is the machining of the collimator which needs to be accurate. The V's could be totally out of alignment with eachother but a cilinder will still rotate on its own axis, which is all that is needed. As long as the collimator sits in the same possition each time it is put in the V's.

What is important is that the outside of the collimator is straight and true, and that the laser inside the housing is centred and pointing straight.

[davewaldo]

Your vise does need to be secure though

[davewaldo]

When I did mine, it was a tricky balancing act of slightly loosening 2 of the little screws then tightening the 3rd, depending on what direction it needed to go. I would be careful not to over tighten any of the screws.

It is possible you have over tightened them? Or perhaps loosened them so that the laser inside it moving?

All 3 little screws need to be finger tight when collimation of the collimator is complete.

[DJVege]

Dave, I'd say all of the above is probably correct!! haha.

How do I know which way it has to go? My circles are probably perfect circles. Well, perfect triangles in fact, since there are only 3 screws. I don't know which 2 to loosen, and which to tighten. I WILL get this, though.

However, if I haven't got it in a few days, you'll have to come over, Dave, or I'll come to yours...LOL!

[davewaldo]

HA HA! Not a problem, you will get it though I'm sure.

Greg had a good idea to mark positions on your collimator. This way once you make an adjustment you can put it back in the V's in the same orientation and check you have moved it in the right direction.

Either this or... make your circle, then move the collimator until the switch is faceing up (dont take it out of the V's yet). Now check which direction you need to move the laser... up down left or right within your circle. Now look at your screws to determain which ones you should move. Now take it out and make a slight adjustment, loosen the 2 opposite screws from the one you think you need to move then tighten the one you neeed to adjust. I would imagine only doing 1 turn of the screws to start with. Now you can replace the collimator into the V's with the switch facing up again and see if you moved in the right direction.

If it has moved how you expected great! If not, keep trying different adjustments until you learn how the adjustments effect the laser movments.

Remember that everything needs to stay finger tight, so you will either loosen 2 and tighten one screw or, loosen 1 and tighten 2.

Hope this helps.... ENJOY!

Dave.

Also its worth unscrewing your collimator so you can see how the laser is mounted inside. This will give you a better understanding how it works.

[DJVege]

Yeah, I've given the collimator a good "undoing"! I had to change the batteries!!! I'm doing as you say, using the switch as my point of reference. I'm still unsure of what adjustments affect what direction the laser will go, but I'm going to test this now!!!

[DJVege]

OK!!! When I tighten, I tighten in the direction I want the laser to move!!! I'm about 2 mm off now, over 3.5 - 4 metres!

[DJVege]

OH YEAH! Guess who's laser collimator is collimated to under 0.5mm over 4 metres??? Yeah!

Thanks heaps Dave! Cheers Greg! Owe ya'll a drink!

[davewaldo]

No problem, I'm glad it worked out.

[DJVege]

And guess who's scope is now collimated??? Yeh, that's right...MINE! LOL!

Ok, now for some polar alignment!

[taminga16 (Greg)]

Wel done Dave, Regards Greg.

P.S. If we ever have the opportunity for that drink remind me to tell you about the testing of some cylindrical mirrors that I was involved with some years ago.