Making an inline red laser aiming laser.

[LeonS]

The 2.x design should accommodate adding a red laser pointer add-on very easily. There is a discussion on how to make one using a ZeSn window on the FSE forums ( http://www.fullspectrumengineering.com/ ... p?f=3&t=36 ).

After checking out eBay it looks like a single ZeSn window would cost at least $55 + shipping. the windows are pricy.

I wonder if a polished silicon wafer would do just as well. There just needs to be enough reflection for the red laser to insert itself into the "big" laser's beam.

A silicon wafer should be cheaper.

Thoughts from you brainy scientist types?

Cheers,
Leon

[bdring]

As I understand it, silicon is transparent to IR, but at a much lower value than ZnSe. That might cause it to be damaged by full power on exactly the same spot for a long time.

I have been looking for a red dot pointer for a while. I bought the one mentioned in this thread (http://www.buildlog.net/forum/viewtopic ... deal#p2363), but they took 7 weeks to arrive and they had a horrible spot. They were bright and focusable, but the spot size was never focusable below about 1/8" diameter.

[cpdude]

I second. I red laser with a beam combiner would be a very nice addition to the 2.x laser. I to have been looking at some of the eBay sources.

Brian

[r691175002]

This may sound like a second rate solution, but I have added a red laser to my build for around 5$ by knife-edging the second beam next to the first.

Instead of using a beam combiner to directly place the red beam inside the cutting beam, you can carefully place a mirror right next to the beam and bounce the red laser so that it is right next to the original beam. This approach is very common in cheaper laser projectors. You can see an example here: http://laserpointerforums.com/f50/octup ... 60584.html
Eight seperate beams are being grouped together by carefully placed mirrors. As you can imagine, you are not going to get a "tight" or accurate beam, however after going through the focusing lens it doesn't really matter.

Believe it or not, I aligned my red dot using only sticky tac. Since any beam hitting the focusing lens will be directed to the focal point, you have about half a degree of play to aim the laser. It took a lot of fiddling to get everything just right, but it took me only around an hour for the entire thing.

Accuracy is not a problem, at the focal point the red dot is aligned better than I can see which is all that really matters. I can get pictures later tonight.

[LeonS]

@r....2

I don't quite get the approach you took. I haven't been involved with laser pointers and manipulating laser light. Could you provide picture and description of your implementation? I'd really like to see it.

I was hoping to use the red dot to help align the mirrors of the laser cutter without having to do a lot of zapping and adjusting. This would also help me align my air assist nozzle whenever I had to clean the lens. Would your approach support these goals?

Thanks in advance,
Leon

[r691175002]

Here is an mspaint drawing of the two methods. The principle is similar, except that if you are using a normal mirror you cannot put the mirror in the beam.

You just stick the mirror outside of the beam and let the red laser travel beside instead of inside the main beam.

You can see that there will be some innacuracy when not at the focal point but I haven't noticed anything major. At the lens the beam is probbably off by around 3mm so if you are within +-1cm of the focal point it should be near perfect.

I had some tiny front surface mirrors laying around (From a PS3 cd drive) but they aren't that hard to find. Old CD/DVD drives will have at least one mirror and a hard drive platter can be cut into small mirrors.


This method is definetly not as nice as a true beam combiner, but I was able to do it with materials on hand and am very happy with the results. Once I get home I'll post some pictures of my setup.

[LeonS]

Ah. Now I get it.

I have some front surface mirrors scavenged from scanner They should work fine.

I could see how that would work for coarse alignment of the mirrors and it would probably work fine for the nozzle alignment since the nozzle hole is near the focal point. The difference in paths would be very small at that point. sounds like it is time to get a laser pointer!

Thanks for the illuminating diagram and description. It is a lot easier and cheaper than a window, if it works for my needs.

Cheers,
Leon

[lasersafe1]

How funny. We were having the same conversation here:
http://www.lightobject.info/viewtopic.php?f=47&t=451

[cpdude]

Interesting. I've got a stack of ten old hard drive platters sitting on my desk and I've got a red dot laser in my current FSE 40W laser. I may have to try this.

Two questions...1) What would you use to cut a hard drive platter with out distorting it? 2) In practice, how do you get as close as possible to the CO2 beam without interferring with the beam?

Thanks,
Brian

[macona]

I went ahead and ordered the beam combiner / laser diode combo from the guy from Israel off ebay. Got the parts last week. Nice, quality components.