WTB 6x cylindrical lens set

[RedCowboy]

Well do me a favor and let me know, I will put in on this or buy the others but once this gets organized and I commit then I will have to wait or buy both, hell I will buy one pair of the others too, this 44 diode deserves correction and an expander, and I still want to knife edge a few more, I'm looking every day at the projectors, they were down to 599 one week but now 639 is the best I can find.

Either way we need the 6X cylindrical pair.


This place says they can make any lens you want, I have not asked how much.
http://www.globalspec.com/FeaturedProducts/Detail/TowerOptical/264721/Custom_Cylindrical_Lenses

 

[Glutton]

Well I really doubt we will be able to get anywhere near 100 lenses spoken for unless someone who owns a store decides to jump in and buy a whole lot of these. Opt did say that if I were to get 100 then he would also get 100 for himself which I think was part of the reason the price was 40 per set.

It really blows my mind how unpopular corrective optics are considering how much they improve these multimode diodes. Maybe people just think its too difficult to even attempt or bother with...?

Anyhow I would be in for 2 or 3 so only like 90 to go.

 

[logsquared]

I know this is a 6x specific thread but I think it worth mentioning.. An adjustable cylindrical beam expander can be made of 2X concave and 1 convex lens. like this... C-C==D===> The greater the distance between the "C's" gives higher power. The the distance between C and D needs to be adjusted for focus. A benefit of this arrangement besides adjustability is a more compact arrangement.

 

[logsquared]

Sorry for got to add "cylindrical" before beam expander. I edited the post.

 

[RedCowboy]

So is this like I was thinking of using a 2x cylindrical concave followed by a 3x cylindrical concave for the aggressive axis in place of a single 6x cylindrical concave then focus with the flat sided convex? " cylindrical "
We are not adjusting the shape of the slower diverging axis at all with these lenses.
Is that correct?

The other method would be to use a plano convex cylindrical lens to expand the slower axis to attempt to match the fast diverging axis then use a standard round lens "PCX" to bring it all down and then a double concave " round " followed by a round doublet to set the diameter and focal point?

Now where to buy the 3 lens set, or do we have to buy two pairs, a 2x and a 3x and not use the 4th lens, i.e. the 2nd cylindrical convex.
Unless we can find these lenses loose, and I have, they are very expensive, they we have to cannibalize 2 pairs.

 

[logsquared]

We are not adjusting the shape of the slower diverging axis at all with these lenses.
Is that correct?

Yes. Cylinder lenses only act on one axis.

2X, 3X, etc is just the ratio of the focal length of the lenses used. It is also the magnification of the system when using only 2 lenses. It is also possible to use 2 positive lenses, plano convex for example. The drawbacks of 2 positive lenses are a longer total system and possible higher spherical aberration.

In your previous post I thought you meant you wanted to put 2 expanders in series. --C---D---C---D--->. This will work and the magnification is the product of the 2 systems. You will end up with a long optical train and double the cost. That is why I mentioned the 3 lens approach.

The currently available lens pairs available for cheap are only 2X and 4X that I know of. The lenses available from edmunds are ridiculous in price. Also, I think the smallest -FL cylinder lens from EO is -12.5mm. So, to make a 6X system you would need a +75mm lens. That make the total system just over 60mm. If you use a -6mm FL and a 36mm +lens you have 6X in just 30mm.

The other method would be to use a plano convex cylindrical lens to expand the slower axis to attempt to match the fast diverging axis then use a standard round lens "PCX" to bring it all down and then a double concave " round " followed by a round doublet to set the diameter and focal point?

This is hard because the cylinder makes the system astigmatic. Therefore its hard to focus both axis at the same time with the PCX round (spherical) lens or any lens after.

Also note: the slow diverging axis after the collimating lens is actually the "fast axis" in diode terminology.

Another option for higher magnification with a given set of lenses, say 4x was mentioned above by someone I think. This is done by moving the corrective set of lenses further away from the diode.

What happens here is taking advantage of the rapidly diverging beam in the slow axis (diode terms). The further away from the diode the wider the beam is when it enters the corrective optics. So, the shorter the FL on the collimation lens the faster the beam diverges making the effect more noticeable. A 3 element lens will not give a noticeable effect unless you are some inches away.

.

Unless we can find these lenses loose, and I have, they are very expensive, they we have to cannibalize 2 pairs.

Unfortunately yes still cheaper than edmunds and shorter system than 2 in series.

 

[RedCowboy]

Yes. Cylinder lenses only act on one axis.

2X, 3X, etc is just the ratio of the focal length of the lenses used. It is also the magnification of the system when using only 2 lenses. It is also possible to use 2 positive lenses, plano convex for example. The drawbacks of 2 positive lenses are a longer total system and possible higher spherical aberration.

In your previous post I thought you meant you wanted to put 2 expanders in series. --C---D---C---D--->. This will work and the magnification is the product of the 2 systems. You will end up with a long optical train and double the cost. That is why I mentioned the 3 lens approach.

The currently available lens pairs available for cheap are only 2X and 4X that I know of. The lenses available from edmunds are ridiculous in price. Also, I think the smallest -FL cylinder lens from EO is -12.5mm. So, to make a 6X system you would need a +75mm lens. That make the total system just over 60mm. If you use a -6mm FL and a 36mm +lens you have 6X in just 30mm.



This is hard because the cylinder makes the system astigmatic. Therefore its hard to focus both axis at the same time with the PCX round (spherical) lens or any lens after.

Also note: the slow diverging axis after the collimating lens is actually the "fast axis" in diode terminology.

Another option for higher magnification with a given set of lenses, say 4x was mentioned above by someone I think. This is done by moving the corrective set of lenses further away from the diode.

What happens here is taking advantage of the rapidly diverging beam in the slow axis (diode terms). The further away from the diode the wider the beam is when it enters the corrective optics. So, the shorter the FL on the collimation lens the faster the beam diverges making the effect more noticeable. A 3 element lens will not give a noticeable effect unless you are some inches away.

.
Unfortunately yes still cheaper than edmunds and shorter system than 2 in series.

Ahh so the rapidly diverging axis is the slow axis, I thought I had that term backwards, thanks.

Yea I understand expanders and focal length, now beam shaping makes sense.
So many technical people are not technical writers, they don't explain things in layman's terms.
I understand them not wanting to make things easy for carless people but the masses just want's to click buy now and put batteries in....often backwards. lol
Not many want to build an optical train, that's why we are having trouble finding affordable parts, they have not caught up with the new more divergent diodes yet.
One thing that would improve simple use would be to start with a wider housing for the diodes with a wider lens and a longer focal length.
Beams will be more like flat cones but burning distance would be better.
I basically do that myself anyway but reining in the slow axis :thanks: is what we want to do, so we can have the pretty beam and the longer working range.

I'm a leaf burner, from the 2nd story into my own yard, with safety glasses on of course and I would like to make better use of these new diodes.

I have thought of gutting a projector and repurposing its optical train rather than pulling each diode and trying to knife edge them all after correcting the beam.

I have seen it done with the old A series but if I want to see what's inside a new V unit I suppose I will just buy one.

rep you again when it will let me, Thanks for the straight answers.

 

[Alaskan]

I could go for at least three sets.

 

[RedCowboy]

I could go for at least three sets.

So is it the faster diverging axis that's fast or slow.
I have also read it's how it's focused but that didn't make sense.


I just read this:

Fast and slow refers to the alignment or propagation direction (plane) of the
light. Fast axis aligns the internal stress rods in a horizontal fashion, while slow axis aligns stress rods in a vertical fashion.

It may have more to do with the substrate in the PN junctions, that is it's strained lattice structure.

I'm just going to say wider diverging and lesser diverging lol.

 

[Alaskan]

If you look at the spot, whichever axis of the spot is longer is the fast axis.

 

[RedCowboy]

If you look at the spot, whichever axis of the spot is longer is the fast axis.

That's what I always thought, but others have said the opposite, the definition I quoted was Wikipedia.....just to avoid confusion I will probably say faster diverging and slower diverging just so nobody is confused.

I know on C-mounts the FAC fast axis correction/columniation lens corrects the wider faster diverging axis, yet many people have said it's opposite and one site I read that fast was near focus and slow was far focus....what ever the heck they mean by that. lol

 

[Alaskan]

Maybe Cyparagon can help out, or some other veteran member, I study optics as a hobby, still learning.

 

[RedCowboy]

Maybe Cyparagon can help out, or some other veteran member, I study optics as a hobby, still learning.

Yes I am still learning as well.
One definition said faster after the lens, and our blue diodes cross over when focused to infinity.
That is the wide stripe from the raw output becomes the sharper line while the shorter part of the raw output is wider at distance.
I would like to know the technical definition of fast and slow axis.
logsquared seems to know what he's talking about, I think we are missing 1 critical detail and that is if the definition can change after passing through several lenses.
Perhaps there is a NATURAL fast axis that is always apparent in the raw output.
Anyway I know what I want to do, I want to be able to concentrate the energy onto a given spot at a variable distance.
I don't want too much power, just enough to write my name on the moon...permanently.:eg:

 

[Alaskan]

Yea, the fast axis is always referencing the diode output; the wider divergence output. If you get the specifications sheet for a diode, if available, they always show how many degrees wide the two individuals axis outputs are.

 

[Glutton]

Another option for higher magnification with a given set of lenses, say 4x was mentioned above by someone I think. This is done by moving the corrective set of lenses further away from the diode.

What happens here is taking advantage of the rapidly diverging beam in the slow axis (diode terms). The further away from the diode the wider the beam is when it enters the corrective optics. So, the shorter the FL on the collimation lens the faster the beam diverges making the effect more noticeable.

If my understanding of beam expander theory is correct then unfortunately this actually won't work. The best a set of 4x lenses can do is improve divergence by 4x no matter how close or far away from the source they are. Makes sense if you think about it tho because once the beam exits the collimating lens the divergence is going to be the same across the entire beam so no matter where along that beam you place the set of 4x cylinders they will still only reduce divergence by. . . 4x.

EDIT: Hmm seems I was actually wrong here which is very nice to know indeed : )

 

[logsquared]

I could go for at least three sets.

This image is correct.

If you look at the spot, whichever axis of the spot is longer is the fast axis.

This is true before the beam hits a collimation lens.

Here is what is happening...

The emitter of the diode is being imaged after the collimation lens at a distance. So, after collimation, you basically see a projected image of the laser emitter on the wall. For MM diodes is a large bar shape.

If you look at the illustration Alaskan posted and imagine placing a collimation lens at the point where the beam looks elliptical you can see what is happening. We have all seen the output right after the lens on these MM diodes, its also a long elliptical shape ( at least with 4mm and longer FL collimators). We know that its the narrower direction that expands the fastest after the collimation lens on our MM set-ups. But we can see from the illistration that its the "slow axis" that is more narrow when it strikes the lens.

It is the slow axis of the diode that we usually need to optically correct with lenses or prisms. This make sense becuase the beam of the longest side of the bar shaped emitter has to expand to be imaged at a distance.

I am not the best writter, but I hope this helps explain what is happening.