how to focus?

Ok, today I received phr in aixiz module from HTD. I hooked it up on driver and battery. It is powerful and it burns but I just cant focus it. You know I want it focused as all normal 5mw lasers. When I focus it, let say to 10 m, and I point it at 20 meters the dot gets oval, big, and hard to be seen. I have 5mw green which is nothing special, but its dot is not that big at distance, its dot can be seen on about 200 m. I wonder if I can set my bluray to be focused like that?

What you see from a few meters away is not the real dot, it's a sort of ghost. That's because for light near the low-wavelength limit of visibility, normal eyes are effectively quite shortsighted, so you can't focus on it (unless you're farsighted). Also the eyes sensitivity for that light is quite low - unlike green which is near the sensitivity maximum (the apparent intensity difference between BR and green is on the order of 1:100).

How I focus a BR: point the beam at a wall a few meters distant. Out-of-focus, you'll see a hazy blob. Focusing in, it'll become smaller. When reaching the focus point, it will NOT contract to a point (as with green or red), instead it will change appearance and appear to develop a rather well-defined boundary with some internal structure, looking quite different from the out-of-focus picture. Try it.

Put your laser down on a table then and walk towards the wall and have a close-up look at the dot - you'll see it really is just a few mm's across, but you have to be pretty close to really see it like that (less than a meter or so, depending on your eyes).

So i cant uSe this blu ray to point in far distance?

Not really. The dot will appear very dim, and it won't even look like a dot. Red and green are much better for that. It's a bit better if you use the BR for star pointing: here, the lesser visibility due to the wavelength is partly compensated for by the higher backscattering. Still, again the beam won't be a needle line as with red and green.

so, the blu ray in fact is best for burning, not pointing?

Yep. Or for making things fluoresce.

but I cant even focus it on few meters, I focus it on some object at 1m and on 2m dot is large about 1cm, I cant get it focused well, at least for indoor usage. Can it be focused so the dot is closer, then it is smaller, and further, bigger, but not so big(1-2cm) in distance difference of 1m

Some people report that they can't focus a BR with the knurled focusing ring attached to the Aixiz - the lens can't be screwed in sufficiently. Try removing it. It may also be that the diode hasn't been pressed into the housing fully.

also get sun glasses that block 100% of uv light. it will eliminate the ghosting that the doc described above and give you adjust for the best posible burning and infinity setting too. although for setting to infinity it will be extremely difficult. the glasses block out all ghosting in close range and you see a tiny dot. this tiny dot gets harder to see the farther out you try to focus.

Good idea. What you see with these glasses will be just the longer-wavelength fluorescence light, not the laser light itself. Nearly everything gives off at least some fluorescence when illuminated with 405nm light.

Are lasers that are unfocusable, you know, some 5mw greenies penstyle or something like that focused to infinity?

If the manufacturers have done their job right, yes.

so I, focusing to infinity is what I want, right?

and what's the divergence of laser which is focused to infinity? 1mRad?
IMHO focusing the Aixiz to infiniy is almost impossible job... I tryed it :thinking:

1mrad is a good all-around first approximation. I once measured my LPC red with VirtualVillage AR acrylic lens at <0.5mrad, but you'll lose that just by shaking the laser, due to the loose-fitting lens housing (even more loose than the Aixiz one). Still, you should easily be able to focus it down to 1mrad, where the dot will look like a (fat) point on anything more than a few meters distant - visually, you gain little by a lesser divergence. Also, I have no problems focusing. Dealing with astronomy since childhood may help :yh:

So if I build 20x dvd burner red laser, should I be able to focus it to infinity for pointing at long distance? Because this bluray cant even get close to infinity, if I focus it to long distance, at small distance dot is big oval, if I focus it to close at any further distance dot goes oval, and that also happens if I focus it on medium Distance. I just cant focus it so when i point closer, the dot is smaller, and when I point further, to get bigger dot but not too big.