lens questions

[iroquois]

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.

Didnt even know about aspherical lenses and their purpose. Thanks.

As for the other questions in my thread... most interesting to me is, as shown in Alaskan's diagram, how small can the output combined beam size be? Can I make it the size of one of the original beams?
Or is there some optical effect which prevents to shrink the beams beyond some amount?

 

[Alaskan]

Pman: I want to be able to switch the colors on and off to produce different mixes and from that different perceived colors. I can rotate the on-off pattern of the diodes to simulate spinning, since I have so many laser diodes to work with, 42 right now, might add more. I want uber low divergence too, so having a fat beam works out in that regard too. I just haven't settled on how to do it, was hoping I could focus the raw beam of all of the diodes on to a single PCX lens to produce a single fat beam, but from what I'm finding, all of the individual laser diodes will just have individual beams coming out of the single lens at different spots, correlating to their positions behind the lens.

iroquois: I found the thread about using a laser beam compander here on LPF, but the attachments were missing, doing a google search I found them stored in the cloud, but the resolution is low. I did another search today to find that original thread, which I didn't, but I found this one with attachments!

http://laserpointerforums.com/f49/parabolic-mirrors-fresnel-lens-41803.html

 

[iroquois]

Thanks, reading the topic I just don't get one thing. How is "combining" beams with lenses, in the sense of shrinking the parallel beams so much it appears to the human eye as a single brighter beam will result in a beam with "terrible" divergence?
Can anyone explain?
There are 10W+ visible wavelength commercial single color diode laser modules today, how else would they get so much power with that beam diameters without "combining" parallel beams from individual diodes?
http://www.kvantlasers.sk/product/10w-445-460-nm-laser-module-kvant
http://www.kvantlasers.sk/product/10w-520nm-laser-module-kvant
532nm 10W laser module, View 10W laser module, CNI Product Details from Changchun New Industries Optoelectronics Technology Co., Ltd. on Alibaba.com

And isn't knife-edge-array itself useless without somehow "combining" the resulting parallel beams?
I'm just surprised I can find detailed info on just about anything laser related except this.

There are cylindrical lenses for "narrowing" the wide beams some diodes produce: Cylindrical lenses 638 nm - Opt Lasers
I don't see why that wouldn't be usable for narrowing few individual parallel beams "into one" instead.

And any reason every illustration uses one piano-concave lens and one piano convex-lens instead of just two regular convex (biconvex) lenses like in the simulation image I posted in the very first post here?

 

[iroquois]

I don't want zero divergence, nor I expect my laser beam to behave like its in a vacuum. That's not what I want and not my question.

Sorry, but reading your reply it seems you're trying to respond while not knowing enough yourself, and you seem to admit it too, so how about we just let someone else who actually knows the answer come here and respond to my question?

 

[Alaskan]

Yep, you are certainly correct, but I hope I did help some. OK, guru's and experts, this man demands better answers than I can provide, please help him.

I just want my laser to be able to do this:

Someone can surely answer the reasons why reducing beamwidth increases divergence in the same way expanding beamwidth reduces divergence, all I can do is say it is so, I've seen it but can't explain it well yet.

In the case of an expander, if the lens used to expand the diameter of coherent light wasn't a PCX, or flat on one side, the beam output would converge to a point again. I will have to think more about how to express the converse.

 

[iroquois]

Yep, you are certainly correct, but I hope I did help some.

of course you did

 

[lazeristasUVISIR]

as shown in Alaskan's diagram, how small can the output combined beam size be?

A. Can I make it the size of one of the original beams?

B. Or is there some optical effect which prevents to shrink the beams beyond some amount?

A. Most likely you can reduce to the original size if it was not too small, and there were not many beams combined.

B. A "natural" diffraction is your enemy to get small collimated beams. imho, 3-5 mm should be no problem to create.

 

[lazeristasUVISIR]

Now I know what I want for a birthday :crackup:

 

[iroquois]

In the case of an expander, if the lens used to expand the diameter of coherent light wasn't a PCX, or flat on one side, the beam output would converge to a point again.

When you have two, not one biconvex lens, with different diameters like in my illustration?

A. Most likely you can reduce to the original size if it was not too small, and there were not many beams combined.

4-8 diodes max.

B. A "natural" diffraction is your enemy to get small collimated beams. imho, 3-5 mm should be no problem to create.

Commercial several watt modules are in that range, so I guess it'll work for me.
Thanks.