parabolic mirrors and fresnel lens

[zxn474l]

Can you combine multiple lasers using a parabolic mirror to collect the laser light and redirect it to a common focal point? Could a fresnel lens combine multiple lasers energy and put it to a common burning point? IF anyone has experienc in this area let me know please!

 

[Jimmymcjimthejim]

Fresnel lenses are not ideal as they are low quality, a normal lens would work better. Using lenses and parabolic mirrors will work for combining beams.

 

[Benm]

You can combine any number of beams onto a focal point with a normal lens... as long as they are coming in paralel, and fit the lens.

It is not possible to make a low-divergence beam with the combined power of all lasers this way, but the point where each beam has its narrowst point will be equal to the point where all the beams cross.

 

[HIMNL9]

Anyway, is THEORICALLY possible to obtain a thin beam including all the combined beams, using a custom-made beam expander principle, as in the draw

With an output beam of 0,5mm or less of diameter, the resulting beams after the corrector are just so thin and "compressed" together, to look as a single beam ..... the only problem can be the price ..... order something similar custom-made for your specifications, i guess, can be anything, except cheap

 

[dr-ebert]

Unfortunately the resulting beam would have terrible divergence.

 

[Benm]

It wouldnt work well - in fact, the outgoing beam would eventually diverge back into the same number of beams that entered on the left side. As a method of combining a beam with high power, it is not suitable (hardly anything is, really).

What you -can- do with this approach is combine the power of, say, 10 laser diodes and focus that on a very small spot for burning. It wouldn't be useful for anything else, but if maximum burning power on a small spot is your goal, this is a feasible way to do it!

 

[HIMNL9]

If you get a custom made set of expander/corrector, you can also get as result a pseudo-beam that looks as a single one, where in fact it's made with all the beams paralleled and tightened as the more possible ..... but is for this reason, that i said theorically and high cost .....

Let me try to explain what i mean.

First of all, you need to align perfectly (and i mean literally perfectly) all the incoming beams, parallele and with the less space between them (this can be made with a set of independent alignment mirrors, or a prismatic lens, but is not easy ..... enough to drive you so frustrated to bite the first one that say you "hello", and i talk for direct experience )

Then the beam expander (that in reality is a compander) can left you enlarge the beam array or compress it, NOT combining together the beams, but reducing the size, so that the beams "look" so close that resemble a single one, but ofcourse, they are not combined ..... the only exception, as you said, is focusing them in a single point, where in this point (and only in this point), they become one (and before someone ask, no, is not so easy just reconvert this single point in a beam, LOL)

maybe the image is more clear than my bad english

 

[Benm]

I suppose the easiest is to keep in mind that optical systems always work identically in both directions. There would be no optical system that takes in 1 beam, runs it only through lenses, and then outputs 10 disinct beams going to wherever you wanted the lasers to be in the first place.

The bottom part of the first drawing illustrates what happens well - and it should be noticed that the thin combination of beams would have very large divergence here... since this system is actually a beam expander working in reverse.

 

[nikokapo]

It wouldnt work well - in fact, the outgoing beam would eventually diverge back into the same number of beams that entered on the left side. As a method of combining a beam with high power, it is not suitable (hardly anything is, really).

What you -can- do with this approach is combine the power of, say, 10 laser diodes and focus that on a very small spot for burning. It wouldn't be useful for anything else, but if maximum burning power on a small spot is your goal, this is a feasible way to do it!

THIS

And you have to be sure that all the beams enter the lens perpendicular to its vertical axis or else you'll miss some beams when focusing them to a pinpoint.


You'd be better off using a fresnel + sun if you want power.

 

[Benm]

Oh, sure.. i've got a couple of almost A4 size fresnel lenses... you can light a bbq with those on a sunny day. But focus neednt be that good - the sun provides up to a whopping 1 kW/m2 in a sunny afternoon. A lens the size of a printer page catches over 50 watts, focusses it down to a spot of about 1 cm2, which is enough to light almost anything - similar to the output of CO2 lasers.

 

[Laser_Ben]

The output beam would consist of the individual beams diverging away from the center. You would need an output correction lens with the exact same characteristics of the input lens to make this feasible.