lens questions

Okay, so the topics on this forum have been very helpful and educational, but when it comes to lenses, I think I'm still pretty clueless on most things.

I've learned so far that, and please correct me if I've gotten something wrong

1) laser beam coming out of the diode has a big angle like a flashlight and a convex lens is needed to decrease the angle
Fine - tuning the distance of the lens from the diode controls the divergence of the laser beam

2) What material the lens is made from is important as some of laser's power is absorbed more or less by different lenses and more or less power is lost. Also some materials like acrylic won't work for higher power as they will melt from the amount of absorbed light.

3) anti-reflection coated lens will help loose less power. The AR coating is different for each color (nm).

have I gotten these right?

I don't think I still get the difference between the "G1", "G2" lenses and "Aixiz" and what "single element" and "three Element" means...

I don't understand beam combining stuff.

Is two convex lenses enough to first focus the different beams closer, then a second, thinner one to spread the beam out again?

is this the way you would change the beam diameter or combine close beams into one?

I see some laser modules using prisms instead. What is their difference from lenses?

From what I gather, G1 and G2 are roughly the same. Both of these are single element lenses, meaning there is one lense. 3-element lenses have multiple(3) lenses, and since anything the laser strikes will absorb some of it's energy, have greater loss than a single element lense.

AFAIK, beam combining is usually done with either a pbs cube (polerized beam splitter) or a dichroic mirror. If the beams to be combined are the same wavelength, the pbs cube is used. If they are different wavelengths, a dichroic mirror is used.

iroquois said:

3) anti-reflection coated lens will help loose less power. The AR coating is different for each color (nm).

I don't think I still get the difference between the "G1", "G2" lenses and "Aixiz" and what "single element" and "three Element" means...

I don't understand beam combining stuff.

Click to expand...

The AR coating isn't different for each color, they cover a certain range.

The G1 lens has been discontinued because of not much demand, it had a different AR coating but testing showed them to be almost equal to a G2. There are 2 different G2 lenses, in addition to the one most of us are using there is also one with an AR coating for red and IR, but I don't see anyone selling them so you would have to buy one direct from the source and buy a lens holder and assemble your own lens.

AixiZ is simply a company in Texas found here: http://www.aixiz.com
One of the good places to buy laser stuff, but for lenses they are one of the 3 places we buy our lenses from. They sell several different ones, acrylic, 3 element, and a low price single element alternative to a G2.

There is a third method of combining beams called "knife edging", it result in a much larger beam.

Alan

I have been researching the same information, started a thread asking here:

http://laserpointerforums.com/f49/a...aser-diodes-combining-all-even-one-92516.html

You might understand more viewing the diagrams I put there.

Chris

Thanks for the replies everyone.

ChaosLord said:

From what I gather, G1 and G2 are roughly the same. Both of these are single element lenses, meaning there is one lense

Click to expand...

is "G1" and "G2" name of some kind of lens standard? Or just a name of a lens from some company?

3-element lenses have multiple(3) lenses, and since anything the laser strikes will absorb some of it's energy, have greater loss than a single element lense.

Click to expand...

Okay, thanks. Then I get the question, why have 3 lenses? Are the other two maybe are used for changing the beam diameter and divergence like in my illustration?
If not, what are they for?

AFAIK, beam combining is usually done with either a pbs cube (polerized beam splitter) or a dichroic mirror. If the beams to be combined are the same wavelength, the pbs cube is used. If they are different wavelengths, a dichroic mirror is used.

Click to expand...

Yes, I read about them.
I'm interested in what to do when you need to combine beams of same polarity and wavelength. The answer seems to be knife edging,



but everywhere I looked I didn't find an answer on how to take the array of beams you get in the end of a knife edge and turn it into a single beam with reasonable diameter.
Knife edging gives something like this (if using two rosw of diodes and mirrors + polarizing cube):



This is no good.

I'm hoping there's a way to use lenses to combine them further, like in the illustration I posted.




But I can't find much info how. The lenses mentioned (g2, 3 element) seem to be meant for putting in front of a diode, but for combining several beams they are small.

Alaskan's link ( http://laserpointerforums.com/f49/an...one-92516.html ) has some illustrations he found, but I can't find the sources of those illustrations, who made them, whether its a theory or actually used, what lenses to use and stuff like that.

Looks similar to what I have in mind, except I was thinking of two convex lenses instead.

I also don't understand pros and cons of using lenses versus anamorphic prisms.

It seems to me that AR coated lenses can also change the diameter and divergence of any beam, but if that was true then I'm puzzled why many people here are choosing not to buy a $300+ diode because of the poor diameter and divergence, when they can according to this info change it to what they want with a pair of lenses.

iroquois said:

Thanks for the replies everyone.

is "G1" and "G2" name of some kind of lens standard? Or just a name of a lens from some company?

Okay, thanks. Then I get the question, why have 3 lenses? Are the other two maybe are used for changing the beam diameter and divergence like in my illustration?
If not, what are they for?

Click to expand...

G series lenses are a name given them by a company, not some standard. The genuine G lenses are made in the US and have a high quality AR coating and are a little expensive. There are also a couple of similar low priced single element lenses made elsewhere.

You will get different results from a 3 element or a single element like the G2 or from an acrylic. The results will vary depending on the diode but the divergence isn't as good with a G2 but in return you don't have much power loss.

Maybe this will answer some questions about combining beams:
http://laserpointerforums.com/f51/reference-guide-how-combine-lasers-77449.html

Alan

Interesting thread. So I have a G9 lens with a 445nm diode, what's different to G1/G2?

tttonyyy said:

Interesting thread. So I have a G9 lens with a 445nm diode, what's different to G1/G2?

Click to expand...

They are equal quality but aren't real G lenses from the same company, they were lenses that were attached to 9mm 445nm diodes in projectors, someone here gave them the name G9 because they were attached to those 9mm diodes that were harvested from projectors, they were probably made in China. It looks like they may not be available much longer, I see that DTR is clearing out the last of the ones he has.

Here is some more advanced info on combining beams:
Sam's Laser FAQ - Items of Interest

In case it wasn't understood from other info, merging more than two polarized beams or unpolarized beams of the same wavelength is not possible, no optics can fix that. Knife edging is the only way. To get a more powerful laser and still have a small diameter beam just buy a more powerful laser.

Alan

Pi R Squared said:

In case it wasn't understood from other info, merging more than two polarized beams or unpolarized beams of the same wavelength is not possible, no optics can fix that. Knife edging is the only way.

Click to expand...

Are you sure about that?
Some diagrams I found seem to indicate otherwise.








I think the last ones was posted by DTR somewhere.

The point is to shrink the parallel beams to look like one powerful but thin beam with two lenses.
How else do commercial 10W+ modules in laser projectors do it? Is there a 10W+ visible wavelength single diode?

As to what kind of optics were used, I can't find info on that.

I'm sure one could be made but it would probably be huge.

I should have mentioned I'm not thinking about using these stuff in laser pointers.

iroquois said:

Okay, so the topics on this forum have been very helpful and educational, but when it comes to lenses, I think I'm still pretty clueless on most things.

I've learned so far that, and please correct me if I've gotten something wrong

1) laser beam coming out of the diode has a big angle like a flashlight and a convex lens is needed to decrease the angle
Fine - tuning the distance of the lens from the diode controls the divergence of the laser beam

2) What material the lens is made from is important as some of laser's power is absorbed more or less by different lenses and more or less power is lost. Also some materials like acrylic won't work for higher power as they will melt from the amount of absorbed light.

3) anti-reflection coated lens will help loose less power. The AR coating is different for each color (nm).

have I gotten these right?

I don't think I still get the difference between the "G1", "G2" lenses and "Aixiz" and what "single element" and "three Element" means...

I don't understand beam combining stuff.

Is two convex lenses enough to first focus the different beams closer, then a second, thinner one to spread the beam out again?

is this the way you would change the beam diameter or combine close beams into one?

I see some laser modules using prisms instead. What is their difference from lenses?

Click to expand...

A useful link and resource http://www.edmundoptics.com/lasers/laser-optics
http://www.amazon.com/Principles-Lasers-Optics-William-Chang/dp/0521645352
Almost for got this valuable link http://www.repairfaq.org/sam/laserlir.htm

Thanks for the link.
However, linking to a book isn't very helpful. my questions could be answered by a single post here, and most of them, probably more difficult concepts than beam combining, have been. If I had time and knowledge to read actual professional books on the subject, I wouldn't ask in a hobbyist forum. I don't.
I mean look at this:


And the site link was useful to me (and thanks for that) for knowing a place where to buy optics, but not which ones and how to use them.

Please don't get this the wrong way, I give you rep for the useful links, but they don't really answer my questions.

iroquois said:

Then I get the question, why have 3 lenses? Are the other two maybe are used for changing the beam diameter and divergence like in my illustration?

Click to expand...

When only one lens is used to collimated a laser diode, it is most likely asphere type. The combination of three (spherical) lenses can achieve similar results. If you are interested start studying spherical aberrations and how to minimize them.

Most of aspherical lenses are molded. Polishing spherical lenses is the established process and can be done by "anyone".

Here's what I want to do, but it appears physics won't allow it: Have the raw output of several red, green and blue laser diodes all fall on one PCX lens to produce a mix of colors which form one fat beam, but it appears it can't be done, or can it?

I'm trying to understand if you are trying to see all the colors still separate in a small beam or just trying to combine theme for some specific color or something else? There has to be a point at which the eye can't really discern separate colors once they get too close to each other. Probably a name for something like that.
I would like to see a build with multi wavelengths aligned so you could switch them on in a triangle (like 462nm, 520nm and 638nm). I swear I saw something like that in the Predator movie but I saw that one a long time ago. While I'm at it I'll take a multicolored one that you can also press a button to make the colors spin