Aspheric collimators for red and blue laser diodes

[planters]

Fair enough. I will need to order this lens and test it in my own set up. I will expand the order for additional lenses if it performs as I hope. I will post the specifics of the set up and the beam specs to let others judge for them selves as to whether it might work for them.

At the risk of being critical, I think you might be able to simplify this issue. I believe it is fair and useful to consider the near field to be "within the projector" so 10 to 20 cm might be a reasonable starting point. Because it splits the two distances and is typical of most indoor applications, let me specify the far field at 15M. The telescope would be placed at an arbitrary point prior to a scanner and so somewhat less than 10 to 20 cm. The type of telescope weather prism or cylinder I do not believe is significant, however your choice is fine, theoretically.

I present the comparison in this way in order to bypass the issue of terminology. In my experience EVERY TIME I have manipulated a laser beam in the near field by reducing or enlarging its collimated diameter with refractive optics its far field spot size has enlarged or decreased to an extent that is inversely proportional and linear,

Looking over your plots carefully, I would say the the average power density of the aspheric lens is 3X that of the O-like even ignoring any difference in overall power throughput! The power density at 5M is slightly higher for the aspheric as well. Do you see what I am getting at?

Andy,

We are assuming the lens used does not introduce any aberrations such as when a short FL sphere introduces significant spherical aberration. And that is my question. Do we pursue ever shorter and shorter FL aspheres because they will somehow better correct the asymmetries of these high aspect emitters?

[dsli_jon]

I think the only real 'issue' for us is the cost-to-benefit ratio between these and the O-Likes. For those that are, say, making a 4-banger, getting *maybe* + a Watt (..calculatedly, at-least.. ) to play with, w/O having to add more diodes / mounts, etc, for only an additional $105.-ish, is not a bad proposition. But, for those who are, indeed, doing 5 - 10+up bangers, we are less-likely going to appreciate the 'cost-to-benefit ratio'... especially given the accessability of the M-series diodes, now, and the additional-cost necessary for prism-pairs, to, in the end-result, get something akin to the O-like-beam. I think if we could get these lenses for like, $25. US a pop (instead of $30-33.) we might see a more 'wholesale interest' from PL'ers... For now, I'm betting that a better 'ROI' will be realized with migrating to those prisms (TBD) and, perhaps, putting all M-series diodes in... We'll see...

..Again, not a 'criticism of this offering', I know you don't set the base-price, etc but, I'm just laying this perspective out there, for you, to posture why there is not a 'gold rush' of buyers, here.. I think, for *most peoples apps* the O-likes, or even Optimas, still present the 'best overall-value'... But, again - thanks for putting this info out there..

What if we looked at a 'GB'? (..oh god, not another one! Is there any 'reasonable-point' at-which we could get these to, say, ~18 € / ea.? Seems unlikely with just a 100-pc. order.. but, ??.. I mean, we, alone, would be 50 pcs., Sir Eric (possibly another 10-12, etc.. that's most of the way to a 100-pcs. order, right off the bat... Or, would this have to be, like, a '1000 pc-order' to get 'down that-far'? I mean, 25 € > 18 € is a pretty-substantial drop.. Thoughts?

[lasertack]

@Jon

I think to get the price to 18€ I´ll need to order 1000pcs at least.

[planters]

Lasertack,

Could you present the plots you posted in #8 with a single, normalized intensity for both lenses? Can you somehow overlay the plots for the two lenses to show the RELATIVE intensity for the two lenses?

[lasertack]

@planters

What do you mean with "single, normalized intensity"? The intensity plots are shown in post #31. Or did I misunderstood your question?

[planters]

Again, I may not have been clear.
Each plot is normalized to a 100% maximum intensity, FOR THAT DIODE. The maximum intensity in absolute units such as mW/um squared should be very different for these two plots. If the same vertical scale were used for the two plots they should appear quite different from each other. It would be useful to show that difference.

I am enthusiastic about these lenses because I think I see a significant difference. I am frustrated because I don't understand why this excitement is not broadly shared.

In post #37 you pointed out the relationship between certain values that you used to support the divergence calculations. I think you unintentionally crossed the relevant axises. The 3mm far field measurement for the O-like derives from the 4.5mm near field dimension not the 2mm near field dimension. Likewise, the aspheric 2mm far field value comes from the 4mm value ( and after looking at your plot, I contend more like 3.0mm) . It is this axis and not the smaller near field axises of these two lenses that I am enthusiastic about. The aspheric is 50% tighter in the near field and then rather than 50 % larger in the far field it is 50% SMALLER. This is 2X the performance.

[lasertack]

@planters

you can calculate the power density (mW/mm^2) from the plot.

Aspheric lens: 3x1=3mm^2 ; 1060mW/3mm^2 = 353,3mW/mm^2
O´Like lens : 4,5x2=9mm^2 ; 1060mW/9mm^2 = 117,8mW/mm^2

So the power density of the aspheric lens is three times higher as of the O-Like´s.

Regarding the divergence, your´re right. I crossed them for keeping it simple. But as the axes are crossed for both measurements (O-Like and aspheric lenses) it doesnt matter.

[planters]

Thanks for the response. I will go ahead and order the lens. Although consistent it matters because the divergence of the lens is more clearly understood when properly expressed. It was for this reason that no one has been all that enthusiastic about this lens and have been focused on the power through put relative to the O-like when this is the lesser of its advantages. Oh well. I look forward to working with it.

[LaNeK779]

It would also be interesting to see this lens versus the 405-g-2 or even the optima 4mm for red
I think it is a more "relevant" comparison

i am really "jealous" of your equipment Alex, but i am also very happy with the effort you put in this, sharing your research with all of us, with pictures, explanations and all. thanks man!

[Solarfire]

Thanks for the response. I will go ahead and order the lens. Although consistent it matters because the divergence of the lens is more clearly understood when properly expressed. It was for this reason that no one has been all that enthusiastic about this lens and have been focused on the power through put relative to the O-like when this is the lesser of its advantages. Oh well. I look forward to working with it.

Not quite correct.. First a lens doesn’t have a divergence a diode has a divergence which the lens is intended to correct, but here correction is actually only applied to the fast axis. The resulting divergence depends on the wavelength and the initial divergence of the raw beam of the diode. The discussion began with the comparison of the Rochester lens vs. the O-Like lens which is a comparison of apples and oranges, 2 totally different lenses. The O-Like (405/445nm) has proven to be the unbeatable economy lens @ <6€, giving low loss of ≈7%, easy to correct with prisms to a 4.5mm x4.5mm beam @ <0.7mrad. The 405-G-2 is the lens to be beaten here with a loss of <2%, with cylinder correction a 3.5mm x 3.5mm beam @ <0.7mrad. In the category of red the optima has proven to be an excellent lens of choice for collimating reds with ultra-low loss, beam data depends on the diodes used. The 405-G-2 and the optima are 4mm fl lens ≈NA0.5 giving a smaller beam with higher divergence than the Rochester. There is absolutely no doubt that the Rochester is an excellent lens, in the end, it’s a question of what you need and what you are willing to pay for it.