how can i "break" the laser beam into 10 beams

[Tw15t3r]

Hmm.... I dunno about that... it would seem to me impossible that even if each "ray" is considered to be a beam, that it would over converge and end up diverging. Because firstly, if you follow the top "ray", and take the bottom of it to be one ray, it seems to pass through the lens only displaced, and not bent as it should be for a converging lens.

And, I managed to find this pic, although the distance is short, but I think it should say something...
After the beam is split into three, it passes through a converging lens and becomes parallel before another converging lens makes the beams cross.

 

[Switch]

Well, my diagram was just to better show my point, not to exactly simulate what would go on.

That image doesn't make sense to me at all. :-/ Either no major divergence changes can be noticed because of the short distance, or those aren't actually round lenses, but more like multi faceted prisms or something.

Every time I try this, with any of my lasers, it will make the dot bigger.2 beams perpendicular to the lens, and reaching the lens at the same radius from the center will become convergent, then divergent. :-/ Like in this diagram.
The thing is, I'm using a bicovex lens, don't have any planoconvex, but I'd imagine the same thing happens.

 

[Tw15t3r]

Hmm.... wierd. Because in theory, a beam striking the surface of the lens (from the inside that is, as in, when the beam is exiting) would be refracted away from the normal of the lens at that particular point (i.e. in mathematical terms, normal of the tangent of the surface)

It's wierd that the lens should act as a diverging lens for some of the rays...... maybe it's another phenomenon we're looking at. Because if what previously observed were to be true, then the convex lenses in the typical modules would not be able to give a near parallel beam of light coming from the laser.

Could it be the power of the lens that you use is too high?

PS, the first of the two lenses in the picture looks like a bi-convex to me. the second one is the planoconvex.

 

[Switch]

Yes, but I'm not talking about my diagrams , I'm talking about the magnifying glass I'm shining my lasers through, it's bi-convex.

I think the theory you are refering to actually refers to a beam of light 1 photon thick, with 0 divergence, like a "line" of photons (yea doesn't sound too scientific, but I hope you understand), and not a laser beam like we have that are quite thick in diameter.

No matter what the power of a lens with a round surface it's going to change divergence.Well unless it's a flat piece of glass, it's gonna make the beam converge or diverge, not just gonna change direction, like a prism would(a prism that has flat sides...).

 

[Tw15t3r]

I understand perfectly that you're not talking about the diagrams and about the real thing itself. I do hope when I said the one in the picture you did take it as the "real" picture that I posted (or real image in this case )

and, no.... I'm not really referring to a beam of light 1 photon thick. I'm refering to the beam being made of many 1 photon thick rays (which in essence is what a real beam is made out of right? ) And if you consider that, and consider what happens to each "ray" individually, then taking the whole picture, it would mean that the beam shouldn't diverge unless you wanted it to.

I know to elliminate divergence is impossible, but if it's only a slight divergence (i.e. 1mRad), it would be suitable to call the lines parallel for this guy's set-up. Moreover, a convex lens (be it biconvex, planoconvex or even a convex meniscus) optic in front of a beam shouldn't cause it to further diverge as far as what I know (I haven't done it with lasers, but the light box with lenses experiments done in school don't seem to exhibit that)

A convex lens no doubt would have light rays hitting the lens at different angles and thus are bent differently, but rays are all, no matter what angle, bent toward the focal point of the lens and never away, unless it's a concave lens.

What causes divergence is an aperture because of the wave property of light. Hence I'm rather interested in how what you have observed can happen (if it is happening as I imagine what you see it as)

I think what you observe must be some special case, if not the collimating lens in the module which is convex would not be able to focus the laser light at all to infinity (infinity is a parallel beam after all)

 

[randomlugia]

I'm wondering, could you make something like this? Have a dome'shaped relfector (like a flashlight's) and shine it through a matrix diffraction grating and onto a mirror back towards the reflector, which will aim the beams straight out.
Picture on paint:

 

[Tw15t3r]

That should work too. And won't have aberration since it makes use of mirrors. However, it may be difficult to find a suitable parabolic mirror for that purpose. I'm not sure about where you can go to get these kind of mirrors.

 

[randomlugia]

I'm wondering, could you make something like this? Have a dome'shaped relfector (like a flashlight's) and shine it through a matrix diffraction grating and onto a mirror back towards the reflector, which will aim the beams straight out.
Picture on paint:

Or even better, use a reflective diffraction grating.

 

[Switch]

Moreover, [highlight]a convex lens[/highlight] (be it biconvex, planoconvex or even a convex meniscus) [highlight]optic in front of a beam shouldn't cause it to further diverge[/highlight]

Really? :-? Well not diverge more, but converge, and then diverge.Either way divergence messes up.I'm pretty sure that shining a beam through a lens messes the divergence.Try shining any laser through any lens and see it.The only lens that's not gonna modify divergence is a flat piece of glass.

A convex lens no doubt would have light rays hitting the lens at different angles and thus are bent differently, but rays are all, no matter what angle, bent toward the focal point of the lens and never away, unless it's a concave lens.

Yes they are all going to be bent toward the focal point, thus they will all intersect in the focal point and be parallel(or almost parallel) no more => divergence messes up.

I tried to make yet another diagram and a few pictures, hope this helps, cause I still don't get what you're saying

 

[Tw15t3r]

Yep. I finally understand what you mean. Well, all I can say is that the lens that you got is too strong!
Cos if you can clearly see that it converges, then diverges, that means ur "over-converging" it.

I think u shld try bringing the lens closer to the laser. It should help, if not, the only way is to get a weaker lens (i dunno where to buy optics, sorry)

Regarding what I was saying, I'll see if i can get some diagrams to help me explain further.

 

[Tw15t3r]

ok well, what I'm basically trying to say is that the divergence only occurs after the whole beam shrinks to a tiny dot, and not directly from the lens.

I'm also trying to say that the type of beam (i.e. thick or thin), and amount of initial divergence that it has, will require different lenses for each type to ensure parallel beams. It's custom.

Also, for the beam to remain parallel after passing through the lens, the lens must be rather large compared to the beam. What I believe you are experiencing is what is illustrated in the first diagram. Note, in the second diagram, that the lens is much bigger compared to the source, and has much less power. The beam will eventually converge and diverge again, but if you choose the right lens, it should be sufficient for normal projections (like what alibaba2 was trying to do)

 

[Switch]

The lens is not powerful actually, it's a 3x or 4x magnifying glass , it's just big in diameter.And the relation between the beam diameter and the lens diameter shouldn't make any difference.The only things that will make a difference is the lens' focal point and the beam's divergence.For example: a lens with a 10cm focal point and two beams, one with 1mm diameter , one with 10mm diameter , both 1mRad, they're both gonna converge to the smallest spot ~10cm from the lens and diverge from then on.The lens diameter can be 1cm or 5cm, it will still have the same effect on both beams. :-/

The distance from the lens to the laser is pretty negligible too.At ~1mRad there won't be any noticeable difference if the laser is 50cm from the lens or stuck directly to it.

that the lens is much bigger compared to the source, and has much less power

So again, the size of the lens is irrelevant, it's the power that makes all the difference between the 2 cases.And if the lens isn't powerfull enough it might not make 2 beams parallel.

 

[Tw15t3r]

yes, true... true...

One more thing though. Have you tried adjusting your laser to give a diverging beam, then use the magnifying class to make it parallel again? I think it should give a wide parallel beam (wider at least)

That's the idea I have here, since the diffraction grating will cause a matrix of diverging beams that will become parallel after passing through a converging lens.

 

[Switch]

Yea that's what should happen.But in the case of the diffraction grating, the divergence angle between the many beams is greater than that of the individual beams, so I don't see it giving the desired result. :-/

 

[randomlugia]

Hey Switch, your camera picks up bluray really well. What company is it?

 

[Switch]

Hey Switch, your camera picks up bluray really well. What company is it?

No it doesn't, it makes it look very blue
It's some ricoh caplio....to be honest I never heard of the company before I got this camera. :-/